Imperial College London

An Atlas of the Human Heart that May Guide Development of New Therapies

/ Kevin McCormack / Leave a comment

By Lisa Kadyk, PhD. CIRM Senior Science Officer

Illustration of a man’s heart – Courtesy Science Photo

I love maps; I still have auto club maps of various parts of the country in my car.  But, to tell the truth, those maps just don’t have as much information as I can get by typing in an address on my cell phone.  Technological advances in global positioning systems, cellular service, data gathering and storage, etc. have made my beloved paper maps a bit of a relic.  

Similarly, technological advances have enabled scientists to begin making maps of human tissues and organs at a level of detail that was previously unimaginable.  Hundreds of thousands of single cells can be profiled in parallel, examining expression of RNA and proteins.  These data, in combination with new three-dimensional spatial analysis techniques and sophisticated computational algorithms, allow high resolution mapping of all the cells in a given tissue or organ.

Given these new capabilities, an international “Human Cell Atlas Consortium” published a white paper in 2017 outlining plans and strategies to build comprehensive reference maps of all human cells, organ by organ.  The intent of building such an atlas is to give a much better understanding of the biology and physiology of normal human tissues, as well as to give new insights into the nature of diseases affecting those tissues and to point the way to developing new therapies. 

One example of this new breed of cartography was published September 24 in the journal Nature, in a paper called simply “Cells of the Human Heart”.   This tour-de-force effort was led by scientists from Harvard Medical School, the Wellcome Sanger Institute, the Max Delbruck Center for Molecular Medicine in Berlin and Imperial College, London.  These teams and their collaborators analyzed about 500,000 cells from six different regions of the healthy adult human heart, using post-mortem organs from 14 donors.  They examined RNA and protein expression and mapped the distribution of different types of cells in each region of the heart.  In addition, they made comparisons of male and female hearts, and identified cells expressing genes known to be associated with different types of heart disease.  

One of the take-home messages from this study is that there is a lot of cellular complexity in the heart – with 11 major cell types (examples include atrial and ventricular cardiomyocytes, fibroblasts and smooth muscle cells), as well as multiple subpopulations within each of those types.  Also notable is the different distribution of cells between the atria (which are at the top of the heart and receive the blood) and ventricles (which are on the bottom of the heart and pump blood out): on average, close to half of the cells in the ventricles are cardiomyocytes, whereas only a third of the cells in the atria are cardiomyocytes.  Finally, there is a significantly higher percentage of cardiomyocytes in the ventricles of women (56%) than in the ventricles of men (47%).    The authors speculate that this latter difference might explain the higher volume of blood pumped per beat in women and lower rates of cardiovascular disease.  

The authors gave a few examples of how their data can be used for a better understanding of heart disease.  For example, they identified a specific subpopulation of cardiomyocytes that expresses genes associated with atrial fibrillation, suggesting that the defect may be associated with those cells.   Similarly, they found that a specific neuronal cell type expresses genes that are associated with a particular ventricular dysfunction associated with heart failure.    In addition, the authors identified which cells in the heart express the highest levels of the SARS-CoV-2 receptor, ACE2, including pericytes, fibroblasts and cardiomyocytes.  

Now that these data are accessible for exploration at www.heartcellatlas.org, I have no doubt that many scientific explorers will begin to navigate to a more complete understanding of both the healthy and diseased heart, and ultimately to new treatments for heart disease.

Researcher claims to have made first gene-edited baby. But did it really happen?

/ Kevin McCormack / Leave a comment

Raelians

Claude Vorilhorn, founder of Raelism; Photo: courtesy thoughtco.com

Remember the Raelians? Probably not. But way back in 2002 the group, some described them as a cult, claimed it had created the world’s first cloned baby. The news made headlines all around the world raising fears we were stepping into uncharted scientific territory. Several weeks later the scientist brought in by the Raelians to verify their claims called it an “elaborate hoax.”

hejiankui

He Jiankui: Photo courtesy MIT Technology Review

Fast forward 16 years and a Chinese scientist named He Jiankui of Shenzhen claims he has created the first genetically modified humans. Again, it is generating headlines around the world and alarming people. In an interview with CNBC, Hank Greely, a bioethicist at Stanford, said if it happened it was “criminally reckless and I unequivocally condemn the experiment.”

The question now is did it happen, or is this just another “elaborate hoax”?

The concerns about this story are real. The scientist claims he used CRISPR to modify embryos during fertility treatments, resulting in the birth of twin girls.

CRISPR has been making headlines all of its own in the last few years as a fast, cheap and efficient way of editing genes. CIRM supports research using CRISPR for problems such as sickle cell disease. The difference being that our research works with adults so any changes in their genes are just for them. Those changes are not passed on to future generations.

The work making headlines around the world used CRISPR on embryos, meaning a child born from one of those embryos would pass those changes on to future generations. In effect, creating a new kind of human being.

This approach raises all sorts of serious issues – scientific, ethical and moral – not the least of which is that the technique could create unknown mutations down the road that would be passed on to future generations.  That’s why in the US the editing of embryos for pregnancy is banned.

But almost as soon as the news was announced there were questions raised about it. The research was not published anywhere. A hospital that the researchers named in their ethical approval documents is denying any involvement.

If it did happen, it could open a new, and potentially frightening chapter in science. In an interview on CNN, Julian Savulescu, director of the Oxford Uehiro Centre for Practical Ethics at the University of Oxford, called the use of CRISPR in this manner as “genetic Russian Roulette.”

“If true, this experiment is monstrous. Gene editing itself is experimental and is still associated with off-target mutations, capable of causing genetic problems early and later in life, including the development of cancer.”

And in an interview on the BBC, Prof Robert Winston, Professor of Science and Society at Imperial College London, said: “If this is a false report, it is scientific misconduct and deeply irresponsible. If true, it is still scientific misconduct.”

Our best hope right now is that this is just a repeat of the Raelians. Our worst fear, is that it’s not.

Avoiding drug trial tragedies: new stem cell-based test predicts dangerous drug toxicity

/ Todd Dubnicoff / Leave a comment

In 2006 Ryan Wilson, a healthy 20 year old Londoner, volunteered for a first-in-human clinical trial to help test the safety of a new drug, TGN1412, intended to treat rheumatoid arthritis and leukemia. The cash he’d get in exchange for his time would help fund his upcoming vacation.

Instead, he nearly died.

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The TGN1412 drug trial disaster got a lot of high profile news coverage in 2006. (image credit: BBC News)

Even though the drug amount injected in his body was 500 times lower than the dose found to be safe in animals, Wilson experienced a catastrophic immune reaction, called a cytokine storm, that led to heart, kidney and liver failure, pneumonia and the loss of his toes and three fingers to dry gangrene. The other five healthy volunteers were also severely injured.

TGN1412’s devastating effect was unfortunately missed in preclinical laboratory and animal studies prior to the human trial. Unlike the pills in your medicine cabinet which are made up of synthesized chemicals, TGN1424 belongs to a growing class of medicines called biologics which come from biological sources such as proteins, DNA, sugars and cells. There is a concern that once a biologic is injected in a patient, the immune system may mount a strong attack all over the body. If that happens, too many immune cells, or white blood cells, are activated and release proteins, called cytokines, which in turn activate more immune cells and the reaction spirals into a dangerous cytokine storm like in Ryan Wilson’s case.

Clearly this tragedy begs for tests that can better predict drug toxicity in humans well before the first trial participants step into the clinic. On Monday a research team from the Imperial College London reported in the journal FASEB that they have done just that using human blood stem cells.

The team’s novel test is not so different than previous ones. Both tests are carried out in a petri dish using two human cell types: white blood cells and endothelial cells, a component of blood vessels. Both tests are also designed to mimic the human immune system’s response to biologics by measuring the release of cytokines.

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Endothelial cells grown from blood stem cells. (credit: Imperial College London)

But the Imperial College London team’s test differs from others in one important way: both the white blood cell and endothelial cell types come from the same individual. First they collect a donor’s blood stem cells and specialize them into endothelial cells. Then white blood cells are also collected from the same donor.

The prior tests, on the other hand, rely on cells from two different donors. Because the two cell types aren’t necessarily tissue-matched, the white blood cells may already be primed for an immune response even before a biologic is added to the test. In fact, these prior tests weren’t able to distinguish between a biologic known to cause a limited immune response versus TGN1424, known to cause a cytokine storm. The newly developed test, however, accurately predicts both the toxic cytokine storm caused by TGN1424 and the absence of a response by several approved biologics, such as the breast cancer drug Herceptin.

In a college news release, Jane Mitchell, the senior author on the report, sees the big picture importance of her lab’s work:

“As biological therapies become more mainstream, it’s more likely that drugs being tested on humans for the first time will have unexpected and potentially catastrophic effects. We’ve used adult stem cell technology to develop a laboratory test that could prevent another disaster like the TGN1412 trial.”

Their results also highlight the often-overlooked power of stem cells to not just deliver therapies but to help develop safer ones.

British Parliament votes to approve “three parent” baby law

/ Kevin McCormack / 1 Comment

After what is being described as “an historic debate”, the British Parliament today voted to approve the use of an IVF technique that critics say will lead to the creation of “three parent” babies.

UK Parliament

UK Parliament

Parliament voted 382 to 128 in favor of the technique known as mitochondrial donation, which will prevent certain genetic diseases being passed on from parents to children; diseases that can cause a wide range of conditions such as fatal heart problems, liver failure, brain disorders and blindness.

Mitochondrial donation involves replacing a small amount of faulty DNA from a mother’s egg with healthy DNA from a second woman. The technique involves taking two eggs, one from the mother and another from the donor. The nucleus of the donor egg is removed, leaving the rest of the egg contents, including the mitochondria. The nucleus from the mother’s egg is then placed in the donor egg. This means that the baby would have genes from the mother, the father and the female donor.

The vote makes the UK the first country in the world to endorse this process. It comes at the end of what supporters of the measure described in a letter to Parliament as “seven years of consultation and inquiry that have revealed broad scientific, ethical and public approval.”

Mitochondrial donation is a controversial process opposed by many religious and faith-based groups who say it creates “designer babies” because it involves implanting genetically modified embryos, and because it could result in genetic alterations that might be passed on to subsequent generations.

While many scientists support the technique some have raised concerns about it. Among those are Dr. Paul Knoepfler, a stem cell researcher at U.C. Davis, (CIRM is funding some of his work). In a recent blog on the process Paul wrote that while he is not opposed to the technique in theory, he thinks this move at this time is premature:

“There is no doubt that mitochondrial diseases are truly terrible and need to be addressed, but if the potential outcomes from the technology are still vague, there are safety concerns, and it raises profound ethical issues such as changing the human genome heritably as is the case here, then my view is that a careful approach is both practical and logical. We cannot at this time have a reasonable expectation that this technology would be safe and effective. That may change in coming years with new knowledge. I hope so.”

Supporters in the UK say the science is already good enough to proceed. Dame Sally Davies, Britain’s Chief Medical Officer, calls it the genetic equivalent of “changing a faulty battery in a car.”

Professor Lord Winston, a fertility expert at Imperial College, London, says:

“I think the case is self-evident and reasonable. This is about something that is unusual and will benefit a small number of patients. I know there are some people who think it is a slippery slope that the next thing will be choosing intelligence or blond hair, but I don’t think that. For 20 years, it’s been scientifically possible to have sex selection of embryos; we still don’t allow it in Britain apart from for heritable diseases.”

It’s important to point out that while the House of Commons passed the regulations they still have to be approved by the House of Lords before they become law. A vote is scheduled for the end of this month. Even then any future trial involving the technique will still require the approval of the Human Fertilisation and Embryology Authority (HFEA) before it can go ahead.

Even if the process is ultimately approved in the UK it will likely face an uphill battle to be approved here in the U.S. where the debate over the ethical, as well as the scientific and technical implications of the process, has already generated strong feelings on both sides of the divide.