A role for endothelial cells in regenerative and personalized medicine

Abstract

REGENERATIVE MEDICINE: VASCULARIZED SKELETAL MUSCLE Tissue engineering is a compelling strategy to create replacement tissues and in this study, skeletal muscle. One major hurdle in the field is how to vascularize large tissue-engineered constructs exceeding the nutrient delivery capability of diffusion. Endothelial colony forming cells and mesenchymal progenitor cells form blood vessels de novo and were co-injected with satellite cells in Matrigel, an extracellular matrix, or PuraMatrix, a synthetic hydrogel. Our approach focused on the ability of bioengineered vascular networks to induce murine and human satellite cells to differentiate and form organized skeletal muscle when injected. We found that perfused human blood vessels were formed in both Matrigel and PuraMatrix and that murine satellite cells differentiated and formed organized myotubes with striations, indicative of adult skeletal muscle. Mesenchymal progenitor cells also induced differentiation of satellite cells in vitro. Human Satellite cells, however, did not show signs of differentiation in either Matrigel or Puramatrix. These data have provided a proof of concept of engineering vascularized skeletal muscle using murine satellite cells.

INDUCTION OF CARDIOMYOGENESIS The heart's regenerative capabilities are not robust enough to repair the amount of damaged tissue from myocardial infarction. A novel approach to relieve the ischemia is to deliver cells with vasculogenic ability, endothelial colony forming cells and mesenchymal progenitor cells, to assemble de novo blood vessels and support recovery of cardiomyocytes. In our study, we used an in vitro transwell system that prevent cell contact, but allow diffusion of soluble factors to investigate if endothelial colony forming cells or mesenchymal progenitor cells secrete factors that induce cardiomyogenesis. We found that neonatal rat cardiomyocyte proliferation is enhanced in the presence of endothelial colony forming cells and mesenchymal progenitor cells; however, presence of these cells without fetal bovine serum is not sufficient to initiate cardiomyogenesis.

PERSONALIZED THERAPY FOR RENAL CELL CARCINOMA TESTING IN AN ENDOTHEIAL CELL MODEL Sunitinib and Pazopanib are both tyrosine kinase inhibitors with high specificity for vascular endothelial growth factor receptor 2 and are used in the treatment of Renal Cell Carcinoma to inhibit angiogenesis. Recent clinical findings suggest that a subset of the population with a single nucleotide polymorphism in vascular endothelial growth factor receptor 2 respond better to Pazopanib treatment. We used a standard in vitro angiogenesis assay, endothelial cell proliferation, to test the effects of the single nucleotide polymorphism on responsiveness to Sunitinib and Pazopanib. We found that cells containing the polymorphism are more sensitive to Pazopanib than Sunitinib, confirming the clinical finding. We also analyzed the inhibition of phosphorylated vascular endothelial growth factor receptor 2 and confirmed drug activity on the phosphorylated protein. These findings could have personalized clinical implications for the 3% of the population with the polymorphism.