Accelerated Repair of Vascular Injury in Diabetes by TGF-β1 Modified Hematopoietic Stem Cells (HSC).

Previously, we demonstrated that a transient blockade of endogenous transforming growth factor-beta type 1 (TGF-β1) in murine and human HSC accelerates bone marrow engraftment while dramatically reducing the number of HSC needed for long-term reconstitution. CD34+ cells give rise to endothelial progenitor cells (EPC) and have been shown to participate in the repair of damaged vasculature. CXCR4 is the receptor for stromal derived factor (SDF-1), a chemoattractant released by ischemic tissue that guides EPCs to damaged sites. In this study, we examined levels of TGF- β1 mRNA in CD34+ blood and bone marrow (BM) cells of diabetic and non diabetic individuals. We also treated CD34+ cells of diabetic and nondiabetic origin with antisense phosphorodiamidate morpholino oligomers (PMOs) to TGF-β1 and examined surface expression of CXCR-4, migratory response to SDF-1 as well as in vivo reparative function in a model of retinal ischemic injury. Our results show that CD34⁺ EPC from the blood of diabetic patients are markedly defective in their ability to repair damaged retinal vessels compared to control cells in contrast to CD34+ cells from the diabetic BM. Diabetic CD34+EPC from blood express elevated levels of TGF-β1 mRNA and have a blunted migratory response to SDF-1 compared to controls (p<0.05 and p<0.01 respectively). Transient (2–4 days) blockade of endogenous TGF-β1 using PMOs to TGF- β1 in diabetic CD34+/EPC increases CXCR-4 expression in these cells, enhances their migratory prowess and restores their ability to repair damaged retinal vessels. This approach is an enhanced autologous stem cell therapy based on a well studied, rapid and reversible modification of bone marrow CD34+EPCs derived from the diabetic patient.