Accelerated Repair of Vascular Injury in Diabetes by TGF-beta Modified Stem Cells

Betastem Therapuetics, Inc., San Francisco CA

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Abstract

DESCRIPTION (provided by applicant): Accelerated Repair of Vascular Injury in Diabetes by TGF-beta Modified Stem Cells Abstract: Stem cells of hematopoietic origin (HSC) have been described that have the potential to repair vascular injury (CD34+ stem cells). We have recently demonstrated that a blockade of endogenous transforming growth factor-beta type 1 (TGF-21) in murine and human hematopoietic stem cells accelerates bone marrow engraftment while dramatically reducing the number of HSC needed for long-term reconstitution. CD34+ stem cells can give rise to endothelial progenitor cells (EPC), which have been shown to repair damaged blood vessels. CXCR4 are homing receptors expressed on EPC. Stromal derived factor (SDF)-1 is a chemoattractant released by damaged blood vessels that helps guide EPCs to these damaged sites. TGF-21 has been shown not only to downregulate SDF-1 in damaged blood vessels but also downregulate its receptor (CXCR4) on CD34+/EPC leading to detrimental effects on vessel repair. Importantly, we have recently demonstrated that CD34+/EPC from diabetic patients are markedly defective in their ability to repair damaged vessels and that their migratory response to SDF-1 is markedly reduced. Overall Hypothesis: Transient blockade of endogenous transforming growth factor- beta type 1 (TGF-21) using antisense phosphorodiamidate morpholino oligomers (PMOs) to TGF- 21 in diabetic EPC will restore their ability to repair cardiac damage. The clinical significance of this hypothesis is further supported by observations in the African-American population: 1) HSC isolated from African-Americans with diabetes produce more TGF-21 than normal controls, suppressing their ability to repair damaged vessels. 2) Serum TGF-2 levels are markedly elevated in African-Americans, further suppressing their ability to repair damaged vessels and 3) As a group, African-Americans have a markedly increased risk of cardiovascular disease as compared to Caucasians. This proposal utilizes these novel observations to test these hypotheses applicable to the repair of diabetes-induced vascular injury mediated by CD34+/EPCs. Furthermore, current cellular therapies as well as mechanical therapies such as stents may not benefit this at risk population because of high TGF-21 levels, which can lead to CD34+/EPC dysfunction. The ability to reverse this defect by transient blockade of TGF-2 expression in these CD34+/EPC cells could be sufficient to improve vascular repair of infarcted coronary tissue in not only diabetic African- Americans but also the population as a whole. PUBLIC HEALTH RELEVANCE: This research proposal aims to treat diabetic patients with damaged blood vessels using adult bone marrow-derived stem cells. Endothelial cells line the blood vessels and can be injured during chronic diabetes. We recently demonstrated that an important normal regulator of bone marrow-derived stem cells is TGF-21 but overproduction can naturally slow vessel repair by stem cells through a negative regulatory pathway. Here we hypothesize that blocking the gene expression of TGF-21 in human HSC will accelerate vascular repair, especially after heart attacks. Importantly, we recently showed that HSC from diabetic patients are defective in their ability to repair damaged vessels compared to normal individuals. Furthermore, other studies have now shown that African- Americans with diabetes can have high levels of TGF-21, which can exacerbate their diabetic vascular damage. Our focus is to demonstrate proof of principle that adult HSC can be effectively used to repair infarcted coronary vessels and eventually greatly improve the quality and duration of these patient's lives.