African-Americans Receive Heart Transplants at Hospitals With Poor Performance Track Records

About five million people in the US suffer from heart failure, and approximately half of them die within five years of being diagnosed. Only about 2,500 people a year receive a heart transplant – the treatment of last resort. A new heart can be life-saving, but it is also life-changing. Even under the best conditions, the surgery is complex, and recovery carries a heavy physical and emotional burden.

And not all heart transplant recipients fare equally well after the surgery. Researchers have found that black heart transplant patients are more likely to die after surgery than white or Hispanic patients.

While many different factors contribute to the disparity, the research indicates that where patients received their heart transplants played a big role. Black patients were more likely to have their transplants performed at the worst-performing centers.

Patient with his family and physician (via Shutterstock)
Patient with his family and physician (via Shutterstock)


This is merely one of many examples of health disparities faced by black Americans. But as a cardiologist, I find this finding especially troubling because many of the heart failure patients I treat are black.

So how do patients decide where to have their heart transplants performed? And wouldn’t a person who needs a heart transplant choose to go to a top center?

Quality is obviously a major factor. But there is another big consideration in deciding where to get a transplant: accessibility.

Not all transplant centers have the same results

Researchers at Ohio State University reviewed the records of heart transplants performed at 102 transplant centers in the US from 2000 to 2010. The researchers focused on the rate of death during the first year after the transplant in over 18,000 heart transplant recipients.

They found that black patients had a higher rate of dying within one year of receiving a new heart (15.3%) than either Hispanics (12.5%) or whites (12.8%).

To find out why this was happening, the researchers used a mathematical model to predict the risk of dying within a year after the transplant for every patient based on the severity of their disease and complicating risk factors such as advanced age or reduced kidney function. They then compared the calculated risk with the actually observed death rates. The difference between the prediction and reality allowed them to determine the quality of a transplant center.

Care doesn’t end when surgery does.
Heart via

It turned out that a greater proportion of blacks received their heart transplant at centers with higher-than-expected mortality as compared with whites and Hispanics (56.4% versus 47.1% versus 48.1%, respectively).

The contrast was even starker between the top- and worst-performing centers. Blacks had the lowest rate of being transplanted at centers with excellent performance (blacks: 18.5%; whites: 25.3%; Hispanics 28.3%). They also had the highest likelihood of undergoing their transplant surgery at the worst-performing centers.

It turns out that where a person has their transplant is critical. Only 8.7% of black patients died during the first year after the transplant if they were fortunate enough to undergo surgery at a top center. But this number was more than twice as high (18.3%) for blacks at the worst-performing centers.

The study didn’t provide any definitive explanations as to why the majority of blacks underwent heart transplantation at centers with lower than expected outcomes.

Choosing a transplant center isn’t much of a choice

Patients do not “choose” a transplant center by simply looking it up in a catalog or on a website. While performance statistics for each organ transplant center in the United States are publicly available in the Scientific Registry of Transplant Recipients, those statistics are only part of the decision for where a patient will get their transplant. The “choice” is often made for the patients by the doctors who refer them to a transplant center and by the accessibility of the center.

I’m a cardiologist, and in the Chicago area, where I practice, there are five active heart transplant centers. We can show the numbers for the centers to our patients when discussing the possibility of a heart transplant and also provide some additional advice based on our prior experiences with the respective transplant teams. Because our patients are nearly all based in the Chicagoland area, most of these programs are reasonable options for them. However, patients and doctors in cities or regions that don’t have as many transplant centers, or who live in more remote areas may not have the luxury of choice.

Far from home?
Hospital bed via

Accessibility matters because care doesn’t end with the surgery

Unless you’ve had a heart transplant, or know someone who has, it’s hard to understand just how life-changing the surgery is. I’ve noticed that many people are unprepared for the emotional and physical toll from the surgery and recovery. And it’s this toll that can makes accessibility such an important factor when choosing a transplant center.

After surgery, patients spend a couple of weeks recovering in the hospital. Even when they can go home, their health is closely monitored with frequent lab tests and check ups.

After transplant, patients will start taking medications to suppress their immune systems and keep their body from rejecting the new heart. And they have to stay on these medications for their rest of their lives. This means a lifetime of close monitoring to make sure that their heart is functioning well and that there aren’t any complications from the immune suppression.

For instance, during the first couple of months after surgery, patients have heart biopsies, where a small piece of the heart is removed to check for signs of rejection, every one to two weeks. As recovery progresses, biopsies may become monthly. The heart sample is so small that it does not damage the heart, but the biopsy is still an invasive procedure requiring hospitalization. And waiting for results can be stressful.

All of this means heart recipients spend a lot of time during the first year after their transplant seeing doctors and waiting for test results. Being close to a transplant center is important – it’s just easier to get to appointments. But accessibility isn’t just about the patient. It’s also about their support network. Imagine going through all of that alone.

On a practical level, family members and friends provide rides to the hospital, keep track of medications and doctor’s appointments and help with household chores during the recovery period. But what is most important is the emotional support that they provide.

So why do black transplant patients tend to wind up in transplant centers that don’t perform as well? Right now, we don’t know. Is it because they were referred to these centers by their cardiologists despite other feasible alternatives? What role does the health insurance of patients play in determining where they receive the heart transplant? Why are centers with a high percentage of black transplant recipients performing so poorly? And most importantly, what measures need to be taken to improve the quality of care?

These are important questions that physicians, public health officials and politicians need to ask themselves in order to address these disparities.

The Conversation

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Kilic, A., Higgins, R., Whitson, B., & Kilic, A. (2015). Racial Disparities in Outcomes of Adult Heart Transplantation Circulation, 131 (10), 882-889 DOI: 10.1161/CIRCULATIONAHA.114.011676

When can you have sex after a heart attack? Most doctors do not talk about it.

Each year in the United States about 720,000 people have heart attacks and about 124,000 people in the UK and 55,000 people in Australia will have them as well. Since the 1980s, survival rates from heart attacks have improved – a lot of people get them, but more and more people are surviving. A recent study of patients in Denmark showed that in 1984-1988 31.4% of patients died within a month of having a heart attack. From 2004-2008 this was down to 14.8%.

Once a patient has made it through a heart attack and begins to recover, they get advice from their doctors on what to do to stay healthy and get back to normal. That includes a lot of things – when to go back to work, when they can start traveling again and what to eat. But there is an important item that a lot of doctors don’t talk about: sex.

There are no universal guidelines for getting back to ‘normal’

Providing advice about lifestyle can be more challenging than prescribing standardized medications or smoking cessation because “normal” life differs widely among patients and requires individualized counseling.

For instance, scientific evidence from large-scale clinical trials isn’t always available to help the cardiologist decide the ideal time for when an individual patient should return to work. A software engineer might get different advice than a butcher or construction worker who has to lift heavy objects all day long. Physicians have to carefully estimate the patient’s capacity for physical activity as well as the physical demands of the job and be pragmatic about how long a patient can take time off from work.

Sex also requires this kind individualized counseling. New research shows that patients want to talk about sexual activity with their doctors, but that all too often that conversation never takes place.

Time for a heart-to-heart with your doctor.
Heart via Syda Productions/Shutterstock


Let’s talk about sex

A recent study conducted in 127 hospitals in the United States and Spain suggests that doctors are not very good at broaching the topic of sexual activity after a heart attack.

Researchers studied 2,349 women and 1,152 men who had suffered from a myocardial infarction (the medical term for a heart attack). This study focused on younger heart attack patients (ages 18-55) and asked them whether they had discussed sexual activity with their doctors. With younger patients talking about life after a heart attack is especially important. The loss of sexual activity or function is a major quality of life issue, and can affect intimate relationships, reproduction and lead to depression.

In the month following the heart attack, only 12% of women and 19% of men had some discussion with a doctor about sex. In the US, most patients reported that they initiated the discussion, whereas in Spain, most discussions were initiated by the doctor. This means that more than 85% of patients received no advice from their doctors regarding if and when they could resume sexual activity.

The study found that the vast majority of patients were sexually active in the year before their heart attacks, and they valued sexuality as an important part of life. They also felt it was appropriate for physicians to initiate the discussion about having sex again.

It is interesting that in the US, patients were more likely to bring up sex and men were given more restrictive advice, while in Spain, physicians were more likely to bring up the topic and more restrictive recommendations were given to women.

The study did not specifically study the motivations of the physicians but these differences suggest that cultural differences and gender affect the counseling in regards to sexual activity. Future research could potentially also study the physicians and help uncover how culture and gender influence the counseling process.

This lack of communication between doctors and patients was not due to the patients’ unease: 84% of women and 91% of men said that they would feel comfortable talking to their doctors about sex. What is even more concerning is that the 15% or so of patients who received counseling often got inaccurate recommendations.

Sex is exercise. But doctors don’t talk about it that way

Two-thirds of those who talked about sex with their doctors were told that they could resume sexual activity with restrictions like limiting sex, taking a “passive role” or keeping their heart rate down during sex. But here’s the thing: sex is exercise. And after a heart attack doctors routinely ask patients whether they can tolerate mild to moderate physical activity such as mowing the lawn or climbing up two flights of stairs without chest pain or other major symptoms.

The Scientific Statement of the American Heart Association (AHA) on sexual activity states that it is reasonable to resume sexual activity as early as one week after an uncomplicated heart attack. If there are complications after the heart attack such as feeling out of breath or experiencing persistent chest pain then these problems need to be addressed first. And in the AHA guidelines there is no mention of “passive roles” or keeping heart rates down during sex. These restrictions are also quite impractical. How are patients supposed to monitor their heart rates and keep them down during sex?

The kind of restrictions recommended by doctors in the study – and presumably by medical practitioners who weren’t polled – are not backed up by science and place an unnecessary burden on a patient’s personal life. Hopefully, after reading the results of this study, doctors will take a more pro-active role and address the topic of sex with their heart attack patients with proper recommendations instead of leaving patients in a state of uncertainty. If a patient can handle moderate exercise, they can probably handle sex.

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Fixing ‘Leaky’ Blood Vessels in Severe Respiratory Ailments and Ebola

When you get an infection, your immune system responds with an influx of inflammatory cells that target the underlying bacteria or viruses. These immune cells migrate from your blood into the infected tissue in order to release a cocktail of pro-inflammatory proteins and help eliminate the infectious threat.

During this inflammatory response, the blood vessel barrier becomes “leaky.” This allows for an even more rapid influx of additional immune cells. Once the infection resolves, the response cools off, the entry of immune cells gradually wanes and the integrity of the blood vessel barrier is restored.

But if the infection is so severe that it overwhelms the immune response or if the patient is unable to restore the blood vessel barrier, fluid moves out of the blood vessels and begins pouring into the tissue. This “leakiness” is what can make pneumonia turn into acute respiratory distress syndrome. ARDS, by my estimate affects hundreds of thousands of people each year worldwide. In the US around 190,000 people develop ARDS each year and it has a mortality rate of up to 40%. In people with Ebola, this leakiness is also often deadly, causing severe blood pressure drops and shock.

New therapies to fix the leakiness of blood vessels in patients suffering from life-threatening illnesses, such as acute respiratory distress syndrome and Ebola virus infections, have the potential to save many lives.

Green fluorescent staining for of the junction protein VE-cadherin in a layer of lung blood vessel endothelial cells
Green fluorescent staining for of the junction protein VE-cadherin in a layer of lung blood vessel endothelial cells – Image Malik Lab

What is ARDS?

Severe pneumonia can lead to acute respiratory distress syndrome (ARDS), a complication in which the massive leakiness of blood vessels in the lung leads to the fluid build-up, which covers the cells that exchange oxygen and carbon dioxide. Patients usually require mechanical ventilators to force oxygen into the lungs in order to survive.

Pneumonia is one of the most common causes of ARDS but any generalized infection and inflammation that is severe enough to cause massive leakiness of lung blood vessels can cause the syndrome.

For people with ARDS treatment, options other than ventilators and treating the underlying infection are limited. And suppressing the immune system to treat this leakiness can leave patients vulnerable to infection.

A new treatment option

But what if we specifically target the leakiness of the blood vessels? Our research has identified an oxygen-sensitive pathway in the endothelial cells which line the blood vessels of the lungs. The leakiness or tightness of the blood vessel barrier depends on the presence of junctions between these cells. These junctions need two particular proteins to work properly. One is called VE-cadherin and is a key building block of the junctions. The other is called VE-PTP and helps ensure that VE-cadherin stays at the cell surface where it can form the junctions with neighboring cells.

When the endothelial cells are inflamed, these junctions break down and the blood vessels become leaky. This prompts the cells to activate a pathway via Hypoxia Inducible Factors (HIFs), which are usually mobilized in response to low oxygen stress. In the heart, HIF pathways are activated during a heart attack or long-standing narrowing of the heart blood vessels to improve the survival of heart cells and initiate the growth of new blood vessels.

We found that a kind of HIF (called HIF2α) was protective in lung blood vessel cells. When it was activated, it increased levels of the proteins that support the junctions between lung cells and strengthened the blood vessel barrier. But in many patients, this activation may not start soon enough to prevent ARDS.

The good news is that we can activate this factor before the lung fluid accumulates and before low oxygen levels set in. Using a drug, we activated HIF2α under normal oxygen conditions, which “tricked” cells into initiating their protective low-oxygen response and tightening the blood vessel barrier. Mice treated with a HIF2α activation drug had substantially higher survival rates when exposed to bacterial toxins or bacteria which cause ARDS.

Similar drugs have already been used in small clinical trials to increase the production of red blood cells in anemic patients. This means that activating HIF2α is probably safe for human use and may indeed become a viable strategy in ARDS. However, the efficacy and safety of drugs which activate HIF2α still have to be tested in humans with proper placebo control groups.

Could this treat Ebola?

The Ebola virus is a hemorrhagic virus and is also known to induce the breakdown of blood vessel barriers. In fact, it is these leaks in the blood vessels that make the disease so deadly. Due to the leakage of fluid and blood from the blood vessels into the tissue, the levels of fluid and blood inside the blood vessels decrease to critically low levels, causing blood pressure drops and ultimately shock.
A group of researchers in Germany recently reported the use of an experimental drug (a peptide) developed for the treatment of vascular leakage in a 38-year-old doctor who had contracted Ebola in Sierra Leone and was airlifted to Germany. The researchers received a compassionate-use exemption for the drug and the patient recovered.

This is just a single case report and it is impossible to know whether the patient would have recovered similarly well without the experimental vascular leakage treatment, but it does highlight the potential role of drugs which treat blood vessel leakiness in Ebola patients.

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Gong, H., Rehman, J., Tang, H., Wary, K., Mittal, M., Chatturvedi, P., Zhao, Y., Komorova, Y., Vogel, S., & Malik, A. (2015). HIF2α signaling inhibits adherens junctional disruption in acute lung injury Journal of Clinical Investigation DOI: 10.1172/JCI77701

Builders and Blocks – Engineering Blood Vessels with Stem Cells

Back in 2001, when we first began studying how regenerative cells (stem cells or more mature progenitor cells) enhance blood vessel growth, our group as well as many of our colleagues focused on one specific type of blood vessel: arteries. Arteries are responsible for supplying oxygen to all organs and tissues of the body and arteries are more likely to develop gradual plaque build-up (atherosclerosis) than veins or networks of smaller blood vessels (capillaries). Once the amount of plaque in an artery reaches a critical threshold, the oxygenation of the supplied tissues and organs becomes compromised. In addition to this build-up of plaque and gradual decline of organ function, arterial plaques can rupture and cause  severe sudden damage such as a heart attack. The conventional approach to treating arterial blockages in the heart was to either perform an open-heart bypass surgery in which blocked arteries were manually bypassed or to place a tube-like “stent” in the blocked artery to restore the oxygen supply. The hope was that injections of regenerative cells would ultimately replace the invasive procedures because the stem cells would convert into blood vessel cells, form healthy new arteries and naturally bypass the blockages in the existing arteries.


Image of mouse red blood cells flowing through an engineered human blood vessel- Image from Paul and colleagues (2013), Creative Commons license.
Image of mouse red blood cells flowing through an engineered human blood vessel implanted in a mouse- Image from Paul and colleagues (2013), Creative Commons license.

As is often the case in biomedical research, this initial approach turned out to be fraught with difficulties. The early animal studies were quite promising and the injected cells appeared to stimulate the growth of blood vessels, but the first clinical trials were less successful. It was very difficult to retain the injected cells in the desired arteries or tissues, and even harder to track the fate of the cells. Which stem cells should be injected? Where should they be injected? How many? Can one obtain enough stem cells from an individual patient so that one could use his or her own cells for the cell therapy? How does one guide the injected cells to the correct location, and then guide the cells to form functional blood vessel structures? Would the stem cells of a patient with chronic diseases such as diabetes or high blood pressure be suitable for therapies, or would such a patient have to rely on stem cells from healthier individuals and thus risk the complication of immune rejection?

The complexity of blood-vessel generation became increasingly apparent, both when studying the biology of stem cells as well as when designing and conducting clinical trials. A large clinical study published in 2013 studied the impact of bone marrow cell injections in heart attack patients and concluded that these injections did not result in any sustained benefit for heart function. Other studies using injections of patients’ own stem cells into their hearts had led to mild improvements in heart function, but none of these clinical studies came close to fulfilling the expectations of cardiovascular patients, physicians and researchers. The upside to these failed expectations was that it forced the researchers in the field of cardiovascular regeneration to rethink their goals and approaches.

One major shift in my own field of interest – the generation of new blood vessels – was to reevaluate the validity of relying on injections of cells. How likely was it that millions of injected cells could organize themselves into functional blood vessels? Injections of cells were convenient for patients because they would not require the surgical implantation of blood vessels, but was this attempt to achieve a convenient therapy undermining its success? An increasing number of laboratories began studying the engineering of blood vessels in the lab by investigating the molecular cues which regulate the assembly of blood vessel networks, identifying molecular scaffolds which would retain stem cells and blood vessel cells and combining various regenerative cell types to build functional blood vessels. This second wave of regenerative vascular medicine is engineering blood vessels which will have to be surgically implanted into patients.  This means that it will be much harder to get approval to conduct such invasive implantations in patients than the straightforward injections which were conducted in the first wave of studies, but most of us who have now moved towards a blood vessel engineering approach feel that there is a greater likelihood of long-term success even if it may take a decade or longer till we obtain our first definitive clinical results.

The second conceptual shift which has occurred in this field is the realization that blood vessel engineering is not only important for treating patients with blockages in their arteries. In fact, blood vessel engineering is critical for all forms of tissue and organ engineering. In the US, more than 120,000 people are awaiting an organ transplant but only a quarter of them will receive an organ in any given year. The number of people in need of a transplant will continue to grow but the supply of organs is limited and many patients will unfortunately die while waiting for an organ which they desperately need. The advances in stem cell biology have made it possible to envision creating organs or organoids (functional smaller parts of an organ) which could help alleviate the need for organs. One thing that most organs and tissues need is a network of tiny blood vessels that permeate the whole tissue: small capillary networks. For example, a liver built out of liver cells could never function without a network of tiny blood vessels which supply the liver cells with metabolites and oxygen. From an organ engineering point of view, microvessel engineering is just as important as the building of functional arteries.

In one of our recent projects, we engineered functional human blood vessels by combining bone marrow derived stem cells with endothelial cells (the cells which coat the inside of all blood vessels). It turns out that stem cells do not become endothelial cells but instead release a molecular signal – the protein SLIT3- which instructs the endothelial cells to assemble into networks. Using a high resolution microscope, we watched this process in real-time over a course of 72 hours in the laboratory and could observe how the endothelial cells began lining up into tube-like structures in the presence of the bone marrow stem cells. The human endothelial cells were like building blocks, the human bone marrow stem cells were the builders “overseeing” the construction. When we implanted the assembled blood vessel structures into mice, we could see that they were fully functional, allowing mouse blood to travel through them without leaking or causing any other major problems (see image, taken from reference 3).

I am sure that SLIT3 is just one of many molecular cues released by the stem cells to assemble functional networks and there are many additional mechanisms which still need to be discovered. We still need to learn much more about which “builders” and which “building blocks” are best suited for each type of blood vessel that we want to construct. The fact that human fat tissue can serve as an important resource for obtaining adult stem cells(“builders”) is quite encouraging, but we still know very little about the overall longevity of the engineered vessels, the best way to implant them into patients, and the key molecular and biomechanical mechanisms which will be required to engineer organs with functional blood vessels. It will be quite some time until the first fully engineered organs will be implanted in humans, but the dizzying rate of progress suggests that we can be quite optimistic.

(An earlier version of this article was first published on


References and links (all of them are open access, so you can read them for free, including the original paper we published):

 1. A recent longform overview article I wrote for “The Scientist” in which I describe the importance of blood vessel engineering for organ engineering:

J Rehman “Building Flesh and Blood“, The Scientist (2014), 28(5):48-53


2. An unusual and abundant source of adult stem cells which promote the formation of blood vessels: Fat tissue obtained from individuals who undergo a liposuction! 

J Rehman “The Power of Fat” Aeon Magazine (2014)


3. The study which describes how adult stem cells release a protein (SLIT3) which organizes blood vessel cells into functional networks (open access – can be read free of charge):

J.D. Paul et al., “SLIT3-ROBO4 activation promotes vascular network formation in human engineered tissue and angiogenesis in vivo” J Mol Cell Cardiol (2013), 64:124-31.

Paul JD, Coulombe KL, Toth PT, Zhang Y, Marsboom G, Bindokas VP, Smith DW, Murry CE, & Rehman J (2013). SLIT3-ROBO4 activation promotes vascular network formation in human engineered tissue and angiogenesis in vivo. Journal of molecular and cellular cardiology, 64, 124-31 PMID: 24090675

The Road to Bad Science Is Paved with Obedience and Secrecy

We often laud intellectual diversity of a scientific research group because we hope that the multitude of opinions can help point out flaws and improve the quality of research long before it is finalized and written up as a manuscript. The recent events surrounding the research in one of the world’s most famous stem cell research laboratories at Harvard shows us the disastrous effects of suppressing diverse and dissenting opinions.

Cultured cells via Shutterstock
Cultured cells via Shutterstock

The infamous “Orlic paper” was a landmark research article published in the prestigious scientific journal Nature in 2001, which showed that stem cells contained in the bone marrow could be converted into functional heart cells. After a heart attack, injections of bone marrow cells reversed much of the heart attack damage by creating new heart cells and restoring heart function. It was called the “Orlic paper” because the first author of the paper was Donald Orlic, but the lead investigator of the study was Piero Anversa, a professor and highly respected scientist at New York Medical College.

Anversa had established himself as one of the world’s leading experts on the survival and death of heart muscle cells in the 1980s and 1990s, but with the start of the new millennium, Anversa shifted his laboratory’s focus towards the emerging field of stem cell biology and its role in cardiovascular regeneration. The Orlic paper was just one of several highly influential stem cell papers to come out of Anversa’s lab at the onset of the new millenium. A 2002 Anversa paper in the New England Journal of Medicine – the world’s most highly cited academic journal –investigated the hearts of human organ transplant recipients. This study showed that up to 10% of the cells in the transplanted heart were derived from the recipient’s own body. The only conceivable explanation was that after a patient received another person’s heart, the recipient’s own cells began maintaining the health of the transplanted organ. The Orlic paper had shown the regenerative power of bone marrow cells in mouse hearts, but this new paper now offered the more tantalizing suggestion that even human hearts could be regenerated by circulating stem cells in their blood stream.

Woman having a heart attack via Shutterstock
Woman having a heart attack via Shutterstock

2003 publication in Cell by the Anversa group described another ground-breaking discovery, identifying a reservoir of stem cells contained within the heart itself. This latest coup de force found that the newly uncovered heart stem cell population resembled the bone marrow stem cells because both groups of cells bore the same stem cell protein called c-kit and both were able to make new heart muscle cells. According to Anversa, c-kit cells extracted from a heart could be re-injected back into a heart after a heart attack and regenerate more than half of the damaged heart!

These Anversa papers revolutionized cardiovascular research. Prior to 2001, most cardiovascular researchers believed that the cell turnover in the adult mammalian heart was minimal because soon after birth, heart cells stopped dividing. Some organs or tissues such as the skin contained stem cells which could divide and continuously give rise to new cells as needed. When skin is scraped during a fall from a bike, it only takes a few days for new skin cells to coat the area of injury and heal the wound. Unfortunately, the heart was not one of those self-regenerating organs. The number of heart cells was thought to be more or less fixed in adults. If heart cells were damaged by a heart attack, then the affected area was replaced by rigid scar tissue, not new heart muscle cells. If the area of damage was large, then the heart’s pump function was severely compromised and patients developed the chronic and ultimately fatal disease known as “heart failure”.

Anversa’s work challenged this dogma by putting forward a bold new theory: the adult heart was highly regenerative, its regeneration was driven by c-kit stem cells, which could be isolated and used to treat injured hearts. All one had to do was harness the regenerative potential of c-kit cells in the bone marrow and the heart, and millions of patients all over the world suffering from heart failure might be cured. Not only did Anversa publish a slew of supportive papers in highly prestigious scientific journals to challenge the dogma of the quiescent heart, he also happened to publish them at a unique time in history which maximized their impact.

In the year 2001, there were few innovative treatments available to treat patients with heart failure. The standard approach was to use medications that would delay the progression of heart failure. But even the best medications could not prevent the gradual decline of heart function. Organ transplants were a cure, but transplantable hearts were rare and only a small fraction of heart failure patients would be fortunate enough to receive a new heart. Hopes for a definitive heart failure cure were buoyed when researchers isolated human embryonic stem cells in 1998. This discovery paved the way for using highly pliable embryonic stem cells to create new heart muscle cells, which might one day be used to restore the heart’s pump function without  resorting to a heart transplant.


Human heart jigsaw puzzle via Shutterstock
Human heart jigsaw puzzle via Shutterstock

The dreams of using embryonic stem cells to regenerate human hearts were soon squashed when the Bush administration banned the generation of new human embryonic stem cells in 2001, citing ethical concerns. These federal regulations and the lobbying of religious and political groups against human embryonic stem cells were a major blow to research on cardiovascular regeneration. Amidst this looming hiatus in cardiovascular regeneration, Anversa’s papers appeared and showed that one could steer clear of the ethical controversies surrounding embryonic stem cells by using an adult patient’s own stem cells. The Anversa group re-energized the field of cardiovascular stem cell research and cleared the path for the first human stem cell treatments in heart disease.

Instead of having to wait for the US government to reverse its restrictive policy on human embryonic stem cells, one could now initiate clinical trials with adult stem cells, treating heart attack patients with their own cells and without having to worry about an ethical quagmire. Heart failure might soon become a disease of the past. The excitement at all major national and international cardiovascular conferences was palpable whenever the Anversa group, their collaborators or other scientists working on bone marrow and cardiac stem cells presented their dizzyingly successful results. Anversa received numerous accolades for his discoveries and research grants from the NIH (National Institutes of Health) to further develop his research program. He was so successful that some researchers believed Anversa might receive the Nobel Prize for his iconoclastic work which had redefined the regenerative potential of the heart. Many of the world’s top universities were vying to recruit Anversa and his group, and he decided to relocate his research group to Harvard Medical School and Brigham and Women’s Hospital 2008.

There were naysayers and skeptics who had resisted the adult stem cell euphoria. Some researchers had spent decades studying the heart and found little to no evidence for regeneration in the adult heart. They were having difficulties reconciling their own results with those of the Anversa group. A number of practicing cardiologists who treated heart failure patients were also skeptical because they did not see the near-miraculous regenerative power of the heart in their patients. One Anversa paper went as far as suggesting that the whole heart would completely regenerate itself roughly every 8-9 years, a claim that was at odds with the clinical experience of practicing cardiologists.  Other researchers pointed out serious flaws in the Anversa papers. For example, the 2002 paper on stem cells in human heart transplant patients claimed that the hearts were coated with the recipient’s regenerative cells, including cells which contained the stem cell marker Sca-1. Within days of the paper’s publication, many researchers were puzzled by this finding because Sca-1 was a marker of mouse and rat cells – not human cells! If Anversa’s group was finding rat or mouse proteins in human hearts, it was most likely due to an artifact. And if they had mistakenly found rodent cells in human hearts, so these critics surmised, perhaps other aspects of Anversa’s research were similarly flawed or riddled with artifacts.

At national and international meetings, one could observe heated debates between members of the Anversa camp and their critics. The critics then decided to change their tactics. Instead of just debating Anversa and commenting about errors in the Anversa papers, they invested substantial funds and efforts to replicate Anversa’s findings. One of the most important and rigorous attempts to assess the validity of the Orlic paper was published in 2004, by the research teams of Chuck Murry and Loren Field. Murry and Field found no evidence of bone marrow cells converting into heart muscle cells. This was a major scientific blow to the burgeoning adult stem cell movement, but even this paper could not deter the bone marrow cell champions.

Despite the fact that the refutation of the Orlic paper was published in 2004, the Orlic paper continues to carry the dubious distinction of being one of the most cited papers in the history of stem cell research. At first, Anversa and his colleagues would shrug off their critics’ findings or publish refutations of refutations – but over time, an increasing number of research groups all over the world began to realize that many of the central tenets of Anversa’s work could not be replicated and the number of critics and skeptics increased. As the signs of irreplicability and other concerns about Anversa’s work mounted, Harvard and Brigham and Women’s Hospital were forced to initiate an internal investigation which resulted in the retraction of one Anversa paper and an expression of concern about another major paper. Finally, a research group published a paper in May 2014 using mice in which c-kit cells were genetically labeled so that one could track their fate and found that c-kit cells have a minimal – if any – contribution to the formation of new heart cells: a fraction of a percent!

The skeptics who had doubted Anversa’s claims all along may now feel vindicated, but this is not the time to gloat. Instead, the discipline of cardiovascular stem cell biology is now undergoing a process of soul-searching. How was it possible that some of the most widely read and cited papers were based on heavily flawed observations and assumptions? Why did it take more than a decade since the first refutation was published in 2004 for scientists to finally accept that the near-magical regenerative power of the heart turned out to be a pipe dream.

One reason for this lag time is pretty straightforward: It takes a tremendous amount of time to refute papers. Funding to conduct the experiments is difficult to obtain because grant funding agencies are not easily convinced to invest in studies replicating existing research. For a refutation to be accepted by the scientific community, it has to be at least as rigorous as the original, but in practice, refutations are subject to even greater scrutiny. Scientists trying to disprove another group’s claim may be asked to develop even better research tools and technologies so that their results can be seen as more definitive than those of the original group. Instead of relying on antibodies to identify c-kit cells, the 2014 refutation developed a transgenic mouse in which all c-kit cells could be genetically traced to yield more definitive results – but developing new models and tools can take years.

The scientific peer review process by external researchers is a central pillar of the quality control process in modern scientific research, but one has to be cognizant of its limitations. Peer review of a scientific manuscript is routinely performed by experts for all the major academic journals which publish original scientific results. However, peer review only involves a “review”, i.e. a general evaluation of major strengths and flaws, and peer reviewers do not see the original raw data nor are they provided with the resources to replicate the studies and confirm the veracity of the submitted results. Peer reviewers rely on the honor system, assuming that the scientists are submitting accurate representations of their data and that the data has been thoroughly scrutinized and critiqued by all the involved researchers before it is even submitted to a journal for publication. If peer reviewers were asked to actually wade through all the original data generated by the scientists and even perform confirmatory studies, then the peer review of every single manuscript could take years and one would have to find the money to pay for the replication or confirmation experiments conducted by peer reviewers. Publication of experiments would come to a grinding halt because thousands of manuscripts would be stuck in the purgatory of peer review. Relying on the integrity of the scientists submitting the data and their internal review processes may seem naïve, but it has always been the bedrock of scientific peer review. And it is precisely the internal review process which may have gone awry in the Anversa group.

Just like Pygmalion fell in love with Galatea, researchers fall in love with the hypotheses and theories that they have constructed. To minimize the effects of these personal biases, scientists regularly present their results to colleagues within their own groups at internal lab meetings and seminars or at external institutions and conferences long before they submit their data to a peer-reviewed journal. The preliminary presentations are intended to spark discussions, inviting the audience to challenge the veracity of the hypotheses and the data while the work is still in progress. Sometimes fellow group members are truly skeptical of the results, at other times they take on the devil’s advocate role to see if they can find holes in their group’s own research. The larger a group, the greater the chance that one will find colleagues within a group with dissenting views. This type of feedback is a necessary internal review process which provides valuable insights that can steer the direction of the research.

Considering the size of the Anversa group – consisting of 20, 30 or even more PhD students, postdoctoral fellows and senior scientists – it is puzzling why the discussions among the group members did not already internally challenge their hypotheses and findings, especially in light of the fact that they knew extramural scientists were having difficulties replicating the work.

Retraction Watch is one of the most widely read scientific watchdogs which tracks scientific misconduct and retractions of published scientific papers. Recently, Retraction Watch published the account of an anonymous whistleblower who had worked as a research fellow in Anversa’s group and provided some unprecedented insights into the inner workings of the group, which explain why the internal review process had failed:

“I think that most scientists, perhaps with the exception of the most lucky or most dishonest, have personal experience with failure in science—experiments that are unreproducible, hypotheses that are fundamentally incorrect. Generally, we sigh, we alter hypotheses, we develop new methods, we move on. It is the data that should guide the science.

 In the Anversa group, a model with much less intellectual flexibility was applied. The “Hypothesis” was that c-kit (cd117) positive cells in the heart (or bone marrow if you read their earlier studies) were cardiac progenitors that could: 1) repair a scarred heart post-myocardial infarction, and: 2) supply the cells necessary for cardiomyocyte turnover in the normal heart.

 This central theme was that which supplied the lab with upwards of $50 million worth of public funding over a decade, a number which would be much higher if one considers collaborating labs that worked on related subjects.

 In theory, this hypothesis would be elegant in its simplicity and amenable to testing in current model systems. In practice, all data that did not point to the “truth” of the hypothesis were considered wrong, and experiments which would definitively show if this hypothesis was incorrect were never performed (lineage tracing e.g.).”

Discarding data that might have challenged the central hypothesis appears to have been a central principle.


Hood over screen - via Shutterstock
Hood over screen – via Shutterstock

According to the whistleblower, Anversa’s group did not just discard undesirable data, they actually punished group members who would question the group’s hypotheses:

In essence, to Dr. Anversa all investigators who questioned the hypothesis were “morons,” a word he used frequently at lab meetings. For one within the group to dare question the central hypothesis, or the methods used to support it, was a quick ticket to dismissal from your position.

The group also created an environment of strict information hierarchy and secrecy which is antithetical to the spirit of science:

“The day to day operation of the lab was conducted under a severe information embargo. The lab had Piero Anversa at the head with group leaders Annarosa Leri, Jan Kajstura and Marcello Rota immediately supervising experimentation. Below that was a group of around 25 instructors, research fellows, graduate students and technicians. Information flowed one way, which was up, and conversation between working groups was generally discouraged and often forbidden.

 Raw data left one’s hands, went to the immediate superior (one of the three named above) and the next time it was seen would be in a manuscript or grant. What happened to that data in the intervening period is unclear.

 A side effect of this information embargo was the limitation of the average worker to determine what was really going on in a research project. It would also effectively limit the ability of an average worker to make allegations regarding specific data/experiments, a requirement for a formal investigation.

This segregation of information is a powerful method to maintain an authoritarian rule and is more typical for terrorist cells or intelligence agencies than for a scientific lab, but it would definitely explain how the Anversa group was able to mass produce numerous irreproducible papers without any major dissent from within the group.

In addition to the secrecy and segregation of information, the group also created an atmosphere of fear to ensure obedience:

“Although individually-tailored stated and unstated threats were present for lab members, the plight of many of us who were international fellows was especially harrowing. Many were technically and educationally underqualified compared to what might be considered average research fellows in the United States. Many also originated in Italy where Dr. Anversa continues to wield considerable influence over biomedical research.

 This combination of being undesirable to many other labs should they leave their position due to lack of experience/training, dependent upon employment for U.S. visa status, and under constant threat of career suicide in your home country should you leave, was enough to make many people play along.

 Even so, I witnessed several people question the findings during their time in the lab. These people and working groups were subsequently fired or resigned. I would like to note that this lab is not unique in this type of exploitative practice, but that does not make it ethically sound and certainly does not create an environment for creative, collaborative, or honest science.”

Foreign researchers are particularly dependent on their employment to maintain their visa status and the prospect of being fired from one’s job can be terrifying for anyone.

This is an anonymous account of a whistleblower and as such, it is problematic. The use of anonymous sources in science journalism could open the doors for all sorts of unfounded and malicious accusations, which is why the ethics of using anonymous sources was heavily debated at the recent ScienceOnline conference. But the claims of the whistleblower are not made in a vacuum – they have to be evaluated in the context of known facts. The whistleblower’s claim that the Anversa group and their collaborators received more than $50 million to study bone marrow cell and c-kit cell regeneration of the heart can be easily verified at the public NIH grant funding RePORTer website. The whistleblower’s claim that many of the Anversa group’s findings could not be replicated is also a verifiable fact. It may seem unfair to condemn Anversa and his group for creating an atmosphere of secrecy and obedience which undermined the scientific enterprise, caused torment among trainees and wasted millions of dollars of tax payer money simply based on one whistleblower’s account. However, if one looks at the entire picture of the amazing rise and decline of the Anversa group’s foray into cardiac regeneration, then the whistleblower’s description of the atmosphere of secrecy and hierarchy seems very plausible.

The investigation of Harvard into the Anversa group is not open to the public and therefore it is difficult to know whether the university is primarily investigating scientific errors or whether it is also looking into such claims of egregious scientific misconduct and abuse of scientific trainees. It is unlikely that Anversa’s group is the only group that might have engaged in such forms of misconduct. Threatening dissenting junior researchers with a loss of employment or visa status may be far more common than we think. The gravity of the problem requires that the NIH – the major funding agency for biomedical research in the US – should look into the prevalence of such practices in research labs and develop safeguards to prevent the abuse of science and scientists.


Note: An earlier version of this article was first published on

Does Human Fat Contain Stem Cells?

Aeon Magazine recently published my longform essay on our research with human liposuction samples and our attempts to use fat for regenerative and therapeutic purposes. Many research groups, including our own group, have been able to isolate stem cells from human fat. However, when it came to using this cells for treating cardiovascular disease, the cells behaved in a manner that we had not anticipated.

Undifferentiated mesenchymal stem cells (left) and their fat neighbors (right)
Undifferentiated mesenchymal stem cells (left) and their fat neighbors (right) – From our PLOS One paper

We were unable to convert them into heart muscle cells or blood vessel endothelial cells, but we found that they could help build large networks of blood vessels by releasing important growth factors. Within a few years of our initial publication, clinical trials with patients with blocked arteries or legs were already being planned, and are currently underway.

We decided to call the cells “adipose stromal cells” because we wanted to emphasize that they were acting as a “stroma” (i.e. supportive environment for blood vessels) and not necessarily as stem cells (i.e. cells that convert from an undifferentiated state into mature cell types). In other contexts, these same cells were indeed able to act like “stem cells”, because they could be converted into bone-forming or cartilage-forming cells, thus showing the enormous versatility and value of the cells that reside within our fat tissues.

The answer to the question “Does Human Fat Contain Stem Cells?” is Yes, but these cells cannot be converted into all desired tissues. Instead, they have important supportive functions that can be used to engineer new blood vessels, which is a critical step in organ engineering.

In addition to describing our scientific work, the essay also mentions the vagaries of research, the frustrations I had as a postdoctoral fellow when my results were not turning out as I had expected, and how some predatory private clinics are already marketing “fat-derived stem cell therapies” to paying customers, even though the clinical results are still rather preliminary.


For the readers who want to dig a bit deeper, here are some references and links:


1. The original paper by Patricia Zuk and colleagues which described the presence of stem cells in human liposuction fat:

Zuk, P et al (2001) “Multilineage Cells from Human Adipose Tissue: Implications for Cell-Based Therapies


2. Our work on how the cells can help grow blood vessels by releasing proteins:

Rehman, J et al (2004) “Secretion of Angiogenic and Antiapoptotic Factors by Human Adipose Stromal Cells


3. Preliminary findings from ongoing clinical studies in which heart attack patients receive infusions of fat derived cells into their hearts to improve heart function and blood flow to the heart:

Houtgraf, J et al (2012) “First Experience in Humans Using Adipose Tissue–Derived Regenerative Cells in the Treatment of Patients With ST-Segment Elevation Myocardial Infarction


4. Preliminary results from an ongoing trial using the fat-derived cells in patients with severe blockages of leg arteries:

Bura, A et al (2014) “Phase I trial: the use of autologous cultured adipose-derived stroma/stem cells to treat patients with non-revascularizable critical limb ischemia


5. Example of how “cell therapies” (in this case bone marrow cells) are sometimes marketed as “stem cells” but hardly contain any stem cells:

The Largest Cell Therapy Trial in Heart Attack Patients Uses Hardly Any Stem Cells


6. The major scientific society devoted to studying the science of fat and its cells as novel therapies is called International Federation for Adipose Therapeutics and Science (IFATS).

I am not kidding, it is I-FATS!

Explore their website if you want to learn about all the exciting new research with fat derived cells.


7. Some of our newer work on how bone marrow mesenchymal stem cells turn into fat cells and what role their metabolism plays during this process:

Zhang, Y et al (2013) “Mitochondrial Respiration Regulates Adipogenic Differentiation of Human Mesenchymal Stem Cells

Zuk PA, Zhu M, Mizuno H, Huang J, Futrell JW, Katz AJ, Benhaim P, Lorenz HP, & Hedrick MH (2001). Multilineage cells from human adipose tissue: implications for cell-based therapies. Tissue engineering, 7 (2), 211-28 PMID: 11304456

Rehman J, Traktuev D, Li J, Merfeld-Clauss S, Temm-Grove CJ, Bovenkerk JE, Pell CL, Johnstone BH, Considine RV, & March KL (2004). Secretion of angiogenic and antiapoptotic factors by human adipose stromal cells. Circulation, 109 (10), 1292-8 PMID: 14993122

The Largest Cell Therapy Trial in Heart Attack Patients Uses Hardly Any Stem Cells

One of the world’s largest clinical cell therapy trials has begun to enroll 3,000 heart attack patients, some of whom will have bone marrow cells extracted with a needle from their hip and fed into their heart using a catheter in their coronary arteries.


The BAMI trial has €5.9m in funding from the European Commission and will be conducted in ten European countries. Enlisted patients will be randomly assigned into two groups: one group will receive the standard care given to heart attack patients while the other will get an added infusion of bone marrow cells.

A number of studies, including one in the New England Journal of Medicine and another in the European Heart Journal, have suggested that bone marrow cells could be beneficial to patients with heart disease. However, because these studies were too small to work out whether cell infusions affected patients’ survival, they instead focused on the extent of scar formation after a heart attack or the ability of the heart muscle to contract after cell infusion.

One commonly used surrogate measure is the cardiac ejection fraction, which measures the fraction of blood squeezed out by the heart during a contraction. A healthy rate ranges from 55% to 65%. Bone marrow cell infusion has been associated with a modest but statistically significant improvement in heart function. In 2012, a comprehensive analysis of 50 major studies with a combined total of 2,625 heart disease patients showed that cardiac ejection fraction in patients receiving these infusions was 4% higher than in control patients.

While the results were encouraging, the study was a retrospective analysis with patients who had varying treatments and endpoints. There also remain questions over 400 patients included in the analysis from trials showing benefits of bone marrow cell infusions that were conducted by controversial German cardiologist Bodo Strauer, who some scientists have accused of errors in research.

The new large-scale BAMI trial will be able to provide a more definitive answer to the efficacy of bone marrow cell infusions and address the even more important question: does this experimental treatment prolong the lives of heart attack patients?

A hard cell

Despite the impressive target of enrolling 3,000 patients, there is a problem with how the trial is being framed. The underlying premise of why bone marrow cells are thought to improve heart function is that the bone marrow contains stem cells which could potentially regenerate the heart. In media reports, the BAMI trial is portrayed as a study which will test whether stem cells can heal broken hearts, and a press release by Barts Health NHS Trust, which is leading on the trial, described the study as “the largest ever adult stem cell heart attack trial”. But the scientific value of the BAMI trial for stem cell research is questionable.

In 2013, a Swiss study reported the results of treating heart attack patients with bone marrow cells. Not only did the study find no significant improvement of heart function with cell therapy, the researchers also reported that only 1% of the infused cells had clearly defined stem cell characteristics. The vast majority of the infused bone marrow cells were a broad mixture of various cell types, including immune cells such as lymphocytes and monocytes.

Scientific studies have even cast doubts about whether any of the scarce stem cells in bone marrow can convert into beating heart muscle cells. A study published in 2001 suggested bone marrow cells injected into mouse hearts could differentiate into heart muscle cells, but the finding could not be replicated in a subsequent study published in 2004.

If there are so few stem cells in the bone marrow and if the stem cells do not become cardiac cells, then how does one explain the improvements observed in the smaller studies? Researchers have proposed a variety of potential explanations, including the release of growth factors or proteins by bone marrow cells that are independent of their stem cell activity.

The disease machine

The success of modern medicine lies in its ability to isolate causal mechanisms of disease and design therapies which specifically target these mechanisms using rigorous scientific methods. Instead of using nebulous “fever tinctures” or willow bark, physicians now prescribe therapies with well-defined active ingredients such as paracetamol (acetaminophen) or aspirin.

Infusing heterogeneous bone marrow cell mixtures into the hearts of patients seems like a throwback to the era of mysterious herbal extracts containing a variety of active and inactive ingredients.

Even if the BAMI trial succeeds in demonstrating that infusion of bone marrow cell mixtures can prolong lives, then the scientific value of the results will still remain doubtful. We will not know whether the tiny fraction of stem cells contained in the bone marrow was responsible for the improvement or whether this effect was due to one of the many other cell types contained in the cell mixtures.

One could argue that it is irrelevant to know the mechanism of action as long as the infusions can prolong patient survival. But for any evidence-based therapy to succeed, it is essential for physicians to know how to dose or modify the therapy according to the needs of an individual patient. This won’t be possible if we don’t even understand how the treatment works.

We should also consider the impact of a negative result. If the BAMI trial fails to show improved survival, will the lack of efficacy be interpreted as a failure of stem cell therapy for heart disease? An alternate explanation would be that a negative result was due to infusing numerous cell types, most of which were not stem cells.

The ultimate test of a treatment’s efficacy is how it fares in controlled, large-scale trials. And these trials need to be grounded in solid scientific data and provide answers that can be interpreted in the context of scientifically sound mechanisms. The BAMI trial might provide an answer to the question of whether or not bone marrow cell infusions are efficacious in heart disease, but it will not teach us much about stem cells.

Jalees Rehman has received research funding from the National Institutes of Health (NIH).

The Conversation

This article was originally published on The Conversation.
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Rehman, J. (2013). Bone Marrow Tinctures for Cardiovascular Disease: Lost in Translation Circulation, 127 (19), 1935-1937 DOI: 10.1161/CIRCULATIONAHA.113.002775


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