Transforming growth factor-β1/Thrombospondin-1/CD47 axis mediates dysfunction in CD34 cells derived from diabetic older adults.

Aging with diabetes is associated with impaired vasoprotective functions and decreased nitric oxide (NO) generation in CD34 cells. Transforming growth factor- β1 (TGF-β1) is known to regulate hematopoietic functions. This study tested the hypothesis that transforming growth factor- β1 (TGF-β1) is upregulated in diabetic CD34 cells and impairs NO generation via thrombospondin-1 (TSP-1)/CD47/NO pathway. CD34 cells from nondiabetic (ND) (n=58) or diabetic older adults (DB) (both type 1 and type 2) (n=62) were isolated from peripheral blood. TGF-β1 was silenced by using an antisense delivered as phosphorodiamidate morpholino oligomer (PMO-TGF-β1). Migration and proliferation in response to stromal-derived factor-1α (SDF-1α) were evaluated. NO generation and eNOS phosphorylation were determined by flow cytometry. CD34 cells from older, but not younger, diabetics have higher expression of TGF-β1 compared to that observed in cells derived from healthy individuals (P<0.05, n=14). TSP-1 expression was higher (n=11) in DB compared to ND cells. TGFβ1-PMO decreased the secretion of TGF-β1, which was accompanied with decreased TSP-1 expression. Impaired proliferation, migration and NO generation in response to SDF-1α in DB cells were reversed by TGF-β1-PMO (n=6). TSP-1 inhibited migration and proliferation of nondiabetic CD34 cells that was reversed by CD47-siRNA, which also restored these responses in diabetic CD34 cells. TSP-1 opposed SDF-1α-induced eNOS phosphorylation at Ser that was reversed by CD47-siRNA. These results infer that increased TGF-β1 expression in CD34 cells induces dysfunction in CD34 cells from diabetic older adults via TSP-1/CD47-dependent inhibition of NO generation.