Tissues used in heart repair
Scientists already know the body uses stem cells for maintenance and repair. These special cells are present inside different types of tissue and regularly divide to produce new tissue material. Cardiac researchers utilise two distinct stem cell strategies designed to better understand heart disease and develop advanced cardiac treatments.
One option involves creating heart muscle using stem cells gathered from patients with congenital heart disease. These lab specimens behave just like the donor’s own heart muscle, which means tests and drug treatments can be safely trialled in order to develop targeted new treatments. In a second approach, scientists are developing ways to repair and replace damaged heart tissue with custom-designed stem cell tissue. This research opens the door to pro-active heart treatments which could soon replace the present symptom-driven approaches.
Current cardiac research focuses on three specific kinds of heart cell tissue:
a) Cardiomyocytes: cardiac muscle cells present in the chambers (atria) where blood enters the heart, and in the ventricles, where blood is pumped from the heart. Cardiomyocytes feature in cardiac cellular therapies targeting heart disease.
b) Cardiac pacemaker cells, whose function is to send and receive the electrical pulses which keep the heart beating regularly.
c) Endothelial cells which line the inside of all blood vessels, helping to deliver oxygen molecules to the cardiomyocytes.
Present stem-cell strategies include: the transplantation of new cell material, tissue engineering interventions to enhance the survival and/or functionality of cell transplants, and the stimulation of existent cells to create fresh cardiac muscle cells.
Lab researchers use two sources to grow and harvest cardiomyocyte cells:
i) ES cells: These are embryo-derived cells which can replicate any body cell.
ii) iPS cells: Known as ‘induced pluripotent cells’, these are lab-reprogrammed adult cells which thus acquire the potential to replicate any body cell – just like ES cells.
One vital property of stem-cell-derived cardiomyocytes is their ability to mimic living heart muscle by beating in unison. This remarkable property is spearheading current research on the transplantation of replacement tissue. Furthermore, iPS cells are used to construct lab models of human heart disease. These allow scientists to closely observe heart defects, develop and test new drugs and treatments, and investigate the possible toxic cardiac side effects of drugs prescribed for other diseases.
Both ES and iPS cells have featured in clinical trials where they have been used to create ‘patches’ made from human heart muscle cells obtained via stem-cell growth. Such patches have been successfully attached to the surface of weak human hearts. As a result, stem-cell heart therapies will now feature strongly in forthcoming rounds of cardiac clinical trials.