|M.Sc Student||Khimovich Leonid|
|Subject||Regeneration of Functional Myocardium using Human Embryonic|
Stem Cells Derived Cardiomyocytes
|Department||Department of Medicine||Supervisor||Professor Lior Gepstein|
Adult heart tissue has limited regenerative capacity and hence any significant cell loss or dysfunction may result in the development of mechanical (heart failure) or electrophysiological (abnormal electrical impulse initiation or conduction) dysfunction resulting in significant morbidity and mortality. Cell therapy is emerging as a novel therapeutic approach for restoration of the electromechanical functions of the heart but has been significantly hampered by the paucity of cell sources for transplantation and by the lack of evidence supporting electromechanical integration of host and transplanted tissues.
Human embryonic stem cells (ES) are continuously growing stem cells lines of embryonic origin isolated from the inner cell mass of human blastocyst. These unique cells are characterized by their capacity to be maintained in an undifferentiated state indefinitely in culture, while retaining their potential to develop into derivatives of all three germ layers. Following cultivation in suspension the ES cells tend to spontaneously create aggregates of differentiating tissue known as embryoid bodies (EBs). Among other cell types cardiomyocytic tissue appears within this multi-cellular arrangement, in the form of spontaneously contracting areas. Therefore, each spontaneously contracting area has its own pacemaker.
The experiments were performed on domestic pigs. Using intravenous catheter, 3D electroanatomical map of the pig’s heart was obtained, and the location of the His bundle was identified. Then, electrical current was applied to the endocardium to induce complete AV-block. The chest was opened, and a number of contracting EBs (previously labeled with vital fluorescent dye) were injected to the lateral wall of the heart. A pacemaker was implanted in order to keep the heart rate above 50 bpm. Following the operation, animal were treated with daily Cyclosporin A, to prevent rejection of the EB’s by the swine immune system.
Two weeks following the transplantation, additional electroanatomical maps were made for each pig. The earliest activation now originated not from the septal area, but from the lateral wall of the left ventricle, where the EB’s were implanted. After sacrificing the animals, the presence of the EB’s at the injection sites was confirmed by fluorescent microscopy and H&E staining.
These results suggest the capability of spontaneously contracting transplanted EB’s to survive in a host’s heart and integrate with it, forming a biological pacemaker.