Growth factors/chemokines in diabetic vitreous and aqueous alter the function of bone marrow-derived progenitor (CD34⁺) cells in humans

Ocular ischemic microenvironment plays a critical role in the progression of diabetic retinopathy (DR). In this study, we investigated the effect of vitreous and aqueous obtained from proliferative DR patients on the function of CD34⁺ cells derived from healthy humans. Human CD34⁺ cells were incubated with vitreous or aqueous of subjects with PDR. After incubation, cell migration of CD34⁺ was evaluated with CXCL12. Intracellular levels of nitric oxide (NO) were measured with DAF-FM. Tube formation assay was used to evaluate the effect of treated CD34⁺ cells on in vitro angiogenesis. Angiogenic protein array and mass spectrometry (MS) were performed to ascertain the factors secreted by healthy nondiabetic CD34⁺ cells exposed to diabetic vitreous or aqueous. PDR vitreous/aqueous reduced migration of CD34⁺ cells (672.45 ± 42.1/736.75 ± 101.7 AFU; P < 0.01) and attenuated intracellular NO levels (182 ± 1.4/184.5 ± 6.3 AFU, P = 0.002). Pretreatment with PDR vitreous suppressed tube formation of human retinal endothelial cells (64 ± 1.6 vs. 80 ± 2.5). CD34⁺ exposed to PDR vitreous resulted in the increased expression of CXCL4 and serpin F1, whereas CD34⁺ exposed to PDR aqueous showed increased expression of CXCL4, serpin F1, and endothelin-1 (ET-1). MS analysis of CD34⁺ (exposed to PDR vitreous) expressed J56 gene segment, isoform 2 of SPARC-related modular calcium-binding protein 2, isoform 1 of uncharacterized protein c1 orf167, integrin α-M, and 40s ribosomal protein s21. Exposure of healthy nondiabetic CD34⁺cells to PDR vitreous and aqueous resulted in decreased migration, reduced generation of NO, and altered paracrine secretory function. Our results suggest that the contribution of CD34⁺ cells to the aberrant neovascularization observed in PDR is driven more by the proangiogenic effects of the retinal cells rather than the influence of the vitreous.