Endothelial cells and basement membrane : a co-regulatory unit for fibroblast growth factor-2 in hyperglycemic stress

Abstract

Endothelial cells and basement membrane interact as a biochemical and mechanical co-regulatory unit. The wide spectrum of manifestations of diabetic vascular disease could be related to altered kinetics of vasoactive compounds within this regulatory unit. We hypothesized that hyperglycemic stress mediates storage, release, and function of fibroblast growth factor-2 (FGF-2) through changes in interaction between endothelial cells and basement membrane. We discovered that basement membrane associated FGF-2 increased linearly with culture glucose concentration. Using novel assays, we demonstrated that FGF-2 binding kinetics were surprisingly unchanged over a range of basement membrane culture glucose. Instead, the combination of increased endothelial cell apoptosis-associated FGF-2 release and enhanced endothelial cell permeability allowed more FGF-2 to bind into the basement membrane. Such high levels of basement membrane FGF-2 abrogated the effects of hyperglycemia on proliferation but not apoptosis. An FGF-2 stimulus returned endothelial cell proliferation close to euglycemic levels, but increased apoptosis was still evident as FGF-2 signaling down an intracellular survival pathway was inhibited by glucose.

(cont.) These same findings were confirmed in vivo where FGF-2 levels were elevated in the aortic subendothelial space of diabetic animals. This thesis suggests a new paradigm for active cellular control of basement membrane and indicates the complexities of growth factor signaling in endothelial cells. Characterization of the interaction between endothelial cells and basement membrane in health and disease may advance our understanding of diabetic vascular disease and lead to development of novel biomimetic materials for therapeutic intervention.