Bim expression modulates the pro-inflammatory phenotype of retinal astroglial cells.

Apoptosis of neurovascular cells, including astroglial cells, contributes to the pathogenesis of diseases in which neurovascular disruption plays a central role. Bim is a pro-apoptotic protein that modulates not only apoptosis but also various cellular functions such as migration and extracellular matrix protein expression. Astroglial cells act as an intermediary between neural and vascular cells facilitating retinal vascular development and remodeling while maintaining normal vascular function and neuronal integrity. We previously showed that Bim deficient (Bim -/-) mice were protected from hyperoxia mediated vessel obliteration and ischemia-mediated retinal neovascularization. However, the underlying mechanisms and more specifically the role Bim expression in astroglial cells play remains elusive. Here, using retinal astroglial cells prepared from wild-type and Bim -/- mice, we determined the impact of Bim expression in retinal astroglial cell function. We showed that astroglial cells lacking Bim expression demonstrate increased VEGF expression and altered matricellular protein production including increased expression of thrombospondin-2 (TSP2), osteopontin and SPARC. Bim deficient astroglial cells also exhibited altered proliferation, migration, adhesion to various extracellular matrix proteins and increased expression of inflammatory mediators. Thus, our data emphasizes the importance of Bim expression in retinal astroglia cell autonomous regulatory mechanisms, which could influence neurovascular function.