Cardiomyocytes from fibroblasts: mix, but not shake
Molecular cocktail transforms skin cells into contracting heart cells
LifeSciencesToday by Gladstone Institutes:
Gladstone Scientists Develop New Molecular “Cocktail” to Transform Skin Cells into Beating Heart CellsThe reprogramming of skin cells into cells very close to the contracting heart cells confirms that regenerative medicine has turned science fiction into scientific reality.
However, the methods used for reprogramming are complex, and cell transformation is often incomplete. But scientists from the Gladstone Institutes have managed to develop a new method that allows reprogramming skin cells into cells that are practically indistinguishable from heart muscle cells, more efficiently and, importantly, more completely. The results of their study conducted on animal models and described in the journal Cell Reports (Haixia Wang et al., Small Molecules Enable Cardiac Reprogramming of Mouse Fibroblasts with a Single Factor), return scientists to optimism in search of a way to regenerate heart muscle that dies as a result of myocardial infarction.
Heart disease remains the leading cause of death worldwide, but recent scientific and medical advances increase the patient's chances of survival after a myocardial infarction. In the United States alone, about 1 million people have suffered a heart attack, but now these people are forced to live with heart failure – a chronic disease in which the heart, having lost part of the myocardium as a result of a heart attack, cannot contract at full strength. Therefore, scientists turned to reprogramming cells, seeing in it a way to restore the affected heart muscle.
Reprogramming skin cells into heart cells, an approach pioneered by Gladstone Institute researcher Deepak Srivastava, MD, requires the use of several genetic factors that stimulate the reprogramming process. However, scientists recognize the potential challenges of translating a gene-based strategy into successful therapeutic methods. Therefore, some experts, including senior researcher at the Gladstone Institute Sheng Ding, PhD, turned to a slightly different approach.
"Previously, scientists have proven that the introduction of four to seven genetic factors can lead to direct reprogramming of skin cells into contractile heart cells," explains senior author Dr. Dean, professor of pharmaceutical chemistry at the University of California, San Francisco (UCSF). "But in my lab, we're trying to figure out if a similar transformation can be done without relying on this kind of genetic manipulation, or at least by reducing the number of genes."
To this end, the researchers used the skin cells of adult mice to identify chemical compounds, so-called "small molecules" that could replace genetic factors. Dr. Dean and his colleagues have previously used the capabilities of small molecules in reprogramming skin cells into neurons and, more recently, into insulin-producing pancreatic cells. Scientists reasonably assumed that a similar method could be used for heart cells.
"After testing various combinations of small molecules, we narrowed the list down to a "cocktail" of four molecules, called SPCF, which could direct the transformation of skin cells into cells similar to heart cells," says Haixia Wang, PhD, postdoctoral fellow at the Gladstone Institute, lead author of the article. "These newly reprogrammed cells showed muscle fibrillar contractions normally seen in mature heart cells, but the transformation was not quite complete."
Therefore, Dean and Wang decided to add one genetic factor to the low–molecular cocktail - Oct4. As a result, the researchers were able to create fully reprogrammed contracting heart cells.
"By adding Oct4 to the mixture, we observed clusters of contracting cells after just 20 days," Dr. Dean comments. "It is worth noting that additional analysis showed that these cells showed the same patterns of gene activation and patterns of electrical signaling that are usually observed in the ventricles of the heart."
As recently shown, mouse fibroblasts can be reprogrammed into cardiac line cells by induction of expression of several transcription factors and microRNA molecules. For the most effective application of such a reprogramming strategy in cell therapy or in vivo regeneration of the heart, it is highly desirable to reduce the number or complete elimination of genetic manipulations and the use of low-molecular compounds. Scientists from the Gladstone Institute have developed a low-molecular cocktail that transforms mouse fibroblasts into heart cells with high efficiency, containing only one transcription factor (Oct4), without any signs of the cells entering a pluripotent state. Cardiomyocytes induced by low molecular weight compounds spontaneously contract and exhibit ventricular phenotype. In addition, these induced cardiomyocytes go through the stage of cardiac precursors. The study lays the foundation for future pharmacological approaches to reprogramming. (Fig. Cell Reports)Professor Dean and his colleagues believe that their results represent a more desirable way of reprogramming, since the cells of the ventricles of the heart are the type of cells that usually die as a result of myocardial infarction.
These data give scientists new hope that this study will open the way to a completely pharmacological method of restoring heart muscle.
"The fact that the combination of Oct4 and small molecules seems to create contracting heart cells in an accelerated way is encouraging," says Joseph Wu, MD, PhD, director of the Stanford Cardiovascular Institute, who was not involved in this study. "The future achievements of Dr. Dean and other researchers are likely to be associated with increasing the efficiency of reprogramming, as well as with reproducing the data obtained on adult human cells."
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