MESENCHYMAL STEM CELLS AND CELLULAR TRANSPLANTATION

J. Luo¹, B.P.J. Van biber², M.A. Laflamme², M.D. Allen^1
1Hope Heart Program, Benaroya Research Institute at Virginia Mason, Seattle/WA/UNITED STATES OF AMERICA, ²Department Of Pathology, University of Washington, Seattle/WA/UNITED STATES OF AMERICA

Body: Introduction: Cell therapy for myocardial infarct (MI) repair requires a donor cell population that can both differentiate reliably into cardiomyocytes and proliferate after in vivo delivery. Human embryonic stem cell-derived cardiomyocytes (huESC-CMs) are one cell source that meets these criteria. However, a major limitation is that up to 90% of injected cells die soon after implantation. We examined whether induction of pro-survival factor heme oxygenase-1 (HO-1) might improve the tolerance of injected cells to the hypoxic environment of the ischemic infarct bed. Methods: Human embryonic stem cells were differentiated into nascent cardiomyocytes using previously described protocols. HO-1 expression was induced in huESC-CMs by culturing cells for 24 hours with 25µM cobalt protoporphyrin (CoPP), a transcriptional activator of HO-1. For in vitro studies, cells were then exposed to 5 hours hypoxia and 16 hours reoxygenation, and surviving cells counted. For in vivo experiments, acute MI was produced in 17 athymic rats by coronary ligation, followed by peri-infarct injection of 1x10⁷ CoPP-treated or untreated huESC-CMs. At 1 week, surviving huESC-CMs were quantified by qPCR for the human-specific Alu gene and graft size measured as ß-myosin heavy chain-containing areas on immunohistochemistry. Results: CoPP-pretreatment of huESC-CMs resulted in significantly higher surviving cell numbers following in vitro hypoxia/reoxygenation (P<0.05). One week after in vivo huESC-CM implantation, human DNA levels were higher in hearts receiving CoPP-treated vs. untreated cells (P<0.001, Fig. 1). Graft areas were 100-fold larger in hearts receiving CoPP-treated cells (P<0.001, Figs. 2, 3); hearts receiving untreated cells had only small surviving grafts. Conclusions: These findings show that pharmacologic induction of pro-survival factor HO-1 in huESC-CMs can improve graft survival under ischemic conditions, both in vitro and in vivo.

Disclosure: All authors have declared no conflicts of interest.