(399d) Reprogramming Stem Cell Rejuvenation for Tissue Regeneration

Cardiovascular disease is the leading cause of mortality worldwide. Regarded as the therapeutic gold standard, treatment with autologous grafts suffers from several technical and patient-related risks. Tissue engineered small diameter blood vessels may provide a promising alternative solution as replacement grafts. We employed adult and induced pluripotent stem cells to engineer fully functional vascular grafts that were implanted into the arterial circulation of a pre-clinical ovine animal model, where they remained patent and underwent successful remodeling. We also engineered cell-free vascular grafts that were implanted successfully into the arterial system of adult as well as neonatal sheep. Most notably, as the animals grew, the grafts integrated fully into the native vasculature and increased in size (length and diameter), demonstrating their potential application for treatment of congenital pediatric disorders. Interestingly, we also discovered a novel mechanism of arterial graft endothelialization via transdifferentiation of hematopoietic stem cells under the guidance of biophysical and biochemical cues from the graft lumen and the arterial microenvironment.

During the course of our studies using mesenchymal stem cells (MSC) to engineer vascular grafts, we observed MSC originating from older donors suffer from limited proliferative capacity and significantly reduced myogenic differentiation potential. Notably, we developed a strategy to reverse the proliferation and differentiation potential of MSC from adult donors as well as to restore of ECM synthesis, actin polymerization and contractile function. In addition to MSC, we demonstrated that our strategy could “rejuvenate” senescent skeletal muscle progenitor cells (SkMC) and identified molecular pathways that are involved in this process. Our strategy ameliorated important hallmarks of aging in SkMC including improvement in genomic integrity, reversal of histone epigenetic marks, increased cellular energetics and ultimately reversed muscle regeneration in vitro as well as in vivo, in a novel mouse model that we developed in our laboratory. In summary, our work demonstrates the potential of molecular engineering strategies to reverse the effects of cellular aging and restore the potential of adult stem cells for use in cellular therapies and tissue regeneration.