Adam Lerman Date: May 11
Ghrelin promotes the differentiation of human embryonic stem cells in infracted cardiac microenvironment

Reference: Meijuan Gao, Jin Yang, Guoqiang Liu, Rui Wei, Lin Zhang, Haining Wang, Guang Wang, Hongwei Gao, Guian Chen, Tianpei Hong, Ghrelin promotes the differentiation of human embryonic stem cells in infarcted cardiac microenvironment, Peptides, Volume 34, Issue 2, April 2012, Pages 373-379, ISSN 0196-9781, 10.1016/j.peptides.2012.02.006.
Background:
Human embryonic stem cells (hESC’s) are derived from inner cell mass of blastocyst of embryos, which are used for in vitro fertilization and embryonic donations. hES cells are used because of their self renewing ability and their pluripotency to differentiate into germ layers. hESC’s are used for regeneration of and organ regeneration of tissues, like for myocardial regeneration to treat irreversible heart injuries. Ghrelin is an endogenous ligand for the growth hormone secretagogue receptor to promote the release of growth hormone. It is unclear is hESC’s can induce myocardial generation by ghrelin after in vivo engraftment into the myocardium.

What was done: Adult male Sprague-Dawley rats that were eight weeks old were used. The hESC’s were cultured on y-irradiated mouse embryonic fibroblast feeder layers. The rats were induced with myocardial infarction (MI) by the ligation of the left anterior descending coronary artery (LAD). They used one millions undifferentiated hESC’s and injected them into the hearts. The Mi animals transplanted with hESC’s were put into two treatment groups: the subcutaneous injections of ghrelin or the phosphate buffered solution (PBS). The control group was the sham ligation and PBS. Transthoracic echocardiography was done 4 weeks after cell transplantation before the rats were sacrificed to measure the maximal left ventricular end-diastolic (LVDd, mm), the end-systolic diameter (LVSd, mm), the correction left ventricular mass (LV mass, mg) and the fractional shortening (FS). Histochemical staining was done 4 weeks after the rats were sacrificed and after the cells were injected. The macro sections were embedded with freezing media and were kept frozen at –80 Celsius. Myocardial sections were sectioned at 8 micrometers on a cryosection.

What was learned: The undifferentiated hESC’s were grown on a feeder cells that were compact, and were tested positive for the pluirpotent marker alkaline phosphate (AKP). The sections that were stained for hematoxylin and eosin (HE) showed that myocardial cells in an irregular shape and arrangement with myocardial fibrosis was observed in the infracted area 4 weeks after coronary ligation. The histological tests showed that the sections were positive for grafted cells. In the ghrelin-treated group, there were 58.3% of grafted cells that was positive for human nuclear antigen (HNA), and in the PBS treated group there were 33.3% of grafts positive for HNA. This shows that ghrelin was beneficial to hESC’s survival and in the differentiation in into cardiac progenitors in infracted cardiac microenvironment. The heart function was evaluated 4 weeks after hESC transplantation. This showed that MI experimental groups differed with the control groups to the changes in measures of FS and LVSd. There was no significant changes were found in the left ventricular correction mass in the hESC-transplanted group when compared to the control group. The article suggests that the ventricular weight were not affected by the MI model or cell injection.
What is means: The data shows that hESC’s can survive and form stable intra cardiac grafts in infracted cardiac microenvironment. The heart function by using echocardiography showed that the engrafted cells and the ghrelin administration were not enough to restore heart function. There is evidence that ghrelin may play a role in the regulation of cell differentiation during development. Gherlin functions as inhibiting cardiomyocyte and endothelial cell death, improving LV dysfunction in humans, and attenuation the development of cardiac cachexia by decreasing systemic vascular resistance in rats with chronic heart failure. This study showed the potential benefit of ghrelin on hESC differentiation into cardiac progenitors in infracted cardiac microenvironments.