Growth regulation of bovine retinal pericytes by transforming growth factor-beta2 and plasmin

Abstract

Purpose: Transforming growth factor -beta2 (TGF-beta2) is a predominant isoform of TGF-betas in the eye and plasmin is a peptidase with many functions. To better understand the pathogenesis of retinal microcirculation disorders, the effects of TGF-beta2 and plasmin on cultured bovine retinal pericytes were investigated.

Methods: Exogenous TGF-beta2 or plasmin was added to some cultures, DNA synthesis during cell cycle progression was investigated using [(3)H]thymidine incorporation. Anti-TGF-beta2 antibody was added to neutralize the effects of TGF-beta2. TGF-beta2 in the culture medium was measured using enzyme-linked immunosorbent assay (ELISA).

Results: Exogenous TGF-beta2 (10 pg to 100 ng/mL) suppressed DNA synthesis. Pericytes produced TGF-beta2. Anti-TGF-beta2 antibody neutralized TGF-beta2 and accelerated DNA synthesis, which shows that pericytes regulate their own cell cycle by action of the autocrine and/or paracrine system of TGF-beta2. Plasmin (0.2 to 0.5 U/mL) accelerated DNA synthesis in a dose-dependent manner, while addition of aprotinin, a protease inhibitor, counteracted this effect of plasmin. The concentration of TGF-beta2 in the culture medium decreased with the addition of plasmin. Simultaneous addition of both plasmin and anti-TGF-beta2 antibody accelerated DNA synthesis. High and low glucose concentrations of the culture medium did not affect DNA synthesis.

Conclusions: Our results suggest that TGF-beta2 and plasmin respectively decrease and increase DNA synthesis. In a retinal microcirculation disorder, they may play competitive roles in the cell cycle of pericytes.