Secretion of Cardioprotective Factors from Cardiac Inducing Colonies (CICS) Derived from Germline Pluripotent Stem Cells (HGPSCS) to Combat Myocardial Fibrosis
Gallicano, Ian GI
Stem cell research for treating or curing myocardial fibrosis has culminated in identifying which scenario is more important; 1) stem cell differentiation into cardiomyocytes that integrate electrically with the heart, 2) stem cells that secrete paracrine factors that promote healing by preventing activation of cardiac fibroblasts and/or inducing cardiac regeneration, or 3) a combination of both scenarios. Following MI, dead cardiomyocytes are replaced by excess amounts of ECM proteins secreted by activated cardiac fibroblasts. This increase in ECM eventually forms a mature scar in the infarct area. While this process is initially reparative, its long-term effect contributes to fibrosis and myocardial dysfunction. Significant efforts have been made in the field of stem cell research to treat and cure ischemic heart disease such as differentiating stem cells into cardiac cells that are capable of inducing myocardial repair and regeneration through secretion of cardioprotective paracrine factors within the infarcted area. Previously, we consistently found that unipotent germline stem cells, when removed from their niche and cultured in the correct medium endogenously express pluripotency genes (Lin28, Oct4, Klf4, Sox2), which induce them to become human germline pluripotent stem cells (hgPSCs). Although hgPSCs grow slowly, they can be expanded quickly and indefinitely using a germline expansion media (GEM) developed in our laboratory. hgPSCs can be differentiated into cardiac inducing colonies (CiCs) that not only express cardiac genes but also express and secrete 18 cardioprotective paracrine factors that help induce protection following injury. CiCs express negative regulators of teratoma formation and when injected into nude mice do not give rise to teratomas, unlike ESCs and iPSCs. Intriguingly, we find that the cardioprotective factors affect human cardiac fibroblasts (HCFs) and human cardiomyocytes (HCMs) by suppressing activation of HCFs and their characteristic feature of myocardial fibrosis. More importantly, we find that these factors induced significant migration/proliferation of HCMs and HUVECs into the infarct zone. CiCs also seem to play a role in ECM turnover through regulation of Lysyl oxidase (LOX) enzyme, which is responsible for collagen fibrillogenesis and cross-linking that contributes to the stiffness of the scar. Moreover, CiCs help in containment of pro-inflammation, a process that is dysregulated in fibrosis by inducing timely transition of pro-inflammation to anti-inflammation. CiCs can fuse and integrate with surrounding cardiac tissue via gap junctions. One important concept we tested was to show the feasibility of CiCs to be used clinically. Cryopreserving and thawing CiCs resulted in observed continuous expression of cardioprotective factors and cardiac genes. The work shown here suggests that secreted cardioprotective factors from CiCs could help tip the balance from fibrosis towards myocardial repair.
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Federal funding for research involving human pluripotent stem cells [". . . in response to your request for a legal opinion of whether federal funds may be used for research conducted with human pluripotent stem cells derived from embryos created by in vitro fertilization or from primordial germ cells isolated from the tissue of non-living fetuses."] Rabb, Harriet S.; United States. Department of Health and Human Services. Office of the General Counsel (1999-01-15)