Abstract
Purpose: :
Pericyte-endothelial cell (EC) interactions are critical to both vascular development and vessel stability in the adult. Using cocultures we have previously shown that TGF-β1 signaling between EC and mural cells may mediate vessel stabilization. These studies were undertaken to assess the role of TGF-ß1 in retinal vascular structure and function in the adult.
Methods: :
TGF-β1 signaling was inhibited by intravenous injection of an adenovirus expressing soluble endoglin (sEng), a TGF-β1 co-receptor. Effects of TGF-ß1 neutralization in the retina were assessed by examining retinal perfusion with high molecular weight fluorescein dextran, light and transmission electron microscopic (TEM) examination, TUNEL staining, western blot analysis of caspase and electroretinogram (ERG). Coculture of EC and 10T1/2 cells (as pericyte precursors) was used to assess the effect of TGF-ß1 neutralization in vitro.
Results: :
The efficacy of systemic TGF-β1 inhibition was demonstrated by reduced retinal phospho-smad2. There was increased vascular and neural cell apoptosis in the inner retina as determined by TUNEL staining, TEM and analysis of cleaved caspase 3, concomitant with a decrease in inner retinal visual function as measured by ERG. The perfusion of the inner retinal vasculature was impaired, and was associated with retinal capillary collapse and defective autoregulation of peripheral blood flow in response to acetylcholine (ACh). Fundus angiography and Evans blue permeability assays revealed a breakdown of the blood-retinal-barrier, with a decreased association of tight junction proteins zo-1 and occludin. Coculture of EC and 10T1/2 cells in Transwell or in 3-D matrigel led to local TGF-β1 activation and signaling. Inhibition of TGF-β1 in the cocultures led to EC but not 10T1/2 cell death and dissociation of EC and 10T1/2 cells.
Conclusions: :
Endogenous TGF-β1 signaling plays a central role in the integrity and function of the retinal vasculature and has important implications for understanding both vasoproliferative and vascular degenerative retinal diseases.
Keywords: retina • apoptosis/cell death • blood supply