Altered proliferation of retinal microvascular cells on glycated matrix

To investigate the effect of nonenzymatic glycosylation (glycation) of basement membranes (BM) and isolated BM proteins on the growth of retinal pericytes and retinal endothelial cells.

Type IV collagen, laminin, Engelbreth-Holm-Swarm tumor basement membrane (EHS-BM) and bovine retinal basement membrane (RBM), after incubation in the presence of reducing sugars to induce glucose-mediated modifications, or in the absence of any sugar (control), were used as a substrate to culture bovine retinal microvascular cells. Cell growth on the nonenzymatically glycosylated and the corresponding control substrates was measured daily, using an automated cell counter.

Retinal pericytes seeded on glycated type IV collagen proliferated consistently more slowly than on control type IV collagen (P = 0.02), showing a 20% to 33% decrease throughout most of the growth curve, whereas on glycated laminin the difference from control was not significant. In contrast, proliferation increased by 16% to 25% for retinal endothelial cells on glycated laminin compared with control substrate (P = 0.025), whereas on glycated type IV collagen the growth curve was not significantly different from the curve for the control. When seeded on whole glycated EHS-BM or RBM, proliferation of pericytes decreased by 20% to 30% (P = 0.04); the endothelial cells showed no difference on glycated EHS-BM, however, the growth rate increased on glycated RBM by 25% to 30% more than it did for the control (P = 0.01).

Nonenzymatic glycosylation of intact BM or individual BM macromolecules resulted in reduced proliferation of retinal pericytes and increased proliferation of retinal endothelial cells. These in vitro observations resemble some of the pathologic changes of the retinal microvascular cells observed in situ, when diabetic retinopathy develops.