Treatment With Nitric Oxide (NO) Donors or Pioglitazone Improves CD34+ Cell Dynamics on Advanced Glycation End Product (AGE) Modified Basement Membrane

Abstract

Purpose: : We investigated whether reduced bio-available NO and diabetes-induced accumulation of AGE adducts on vascular basement membrane (BM) was responsible for abnormal function of CD34⁺ cells in diabetes and contribute to vasodegeneration observed in diabetic retinopathy (DR).

Methods: : CD34⁺ cells were isolated from healthy controls and diabetic individuals. AGE-modified substrates (AGE-BM) were prepared by incubating the dicarbonyl methylglyoxal with either Matrigel or fibronectin for 24 and 72 hr respectively. CD34⁺ cells propagated on AGE-BM were studied for attachment and tubule formation. Phosphorylation of the pro-survival, attachment-dependent signaling factor FAK^{Tyr 397} and endothelial NO synthase (eNOS ^{Ser 1176}) was measured using ‘In Cell Westerns’. Healthy or diabetic CD34⁺ cells were also treated with the NO donor or Pioglitazone and then assessed for migration along a stromal derived factor-1 (SDF-1) gradient using a modified Boyden chamber assay.

Results: : Non-diabetic CD34⁺ cells demonstrated a dose-dependent reduction of attachment while diabetic CD34⁺ cells showed a 35 % increase in attachment. Despite this increase, these diabetic cells failed to form proper focal adhesion contacts (10 % reduction in FAK phosphorylation; p<0.05) on AGE-BM. Non diabetic CD34⁺ cells formed vascular tubules which were significantly attenuated on AGE-BM (p<0.001). In both CD34⁺ cell-populations phosphorylation of eNOS was reduced upon exposure to AGE-BM. Treatment with NO donor improved adhesion of diabetic CD34⁺ cells and restored matrigel tube formation (p<0.001). Pioglitazone treatment of diabetic CD34⁺ cells corrected their migratory defects towards SDF-1 as compared to untreated cells.

Conclusions: : Diabetic CD34⁺ cells have enhanced adherence to AGE-BM compared to non diabetics, but possess defects in adhesion associated signaling and tubule formation, which is possibly linked to inherent cytoskeletal damage. NO donor and pioglitazone treatment may improve this deficit and may have therapeutic implications for correcting CD34⁺ cell dysfunction in diabetic patients.

Keywords: diabetic retinopathy • extracellular matrix