Abstract
Purpose:
Retinal ganglion cells (RGCs) have been shown to play important roles in retinal vascularization. For example, RGCs can express angiorepulsive factors like Sema3A. Neuroprotection could therefore be used as a new therapeutic approach to ameliorate vasoproliferative retinal diseases. This study examines the effect of ciliary neuroprotective factor (CNTF) on physiological and pathological vascularization in the mouse-model of oxygen-induced retinopathy (OIR-model). Ciliary neurotrophic factor (CNTF) is a well known neuroprotective agent that is currently investigated in multiple clinical trials for treatment of retinitis pigmentosa, ischemic neuropathy and macular teleangiectasia.
Methods:
In the OIR model, newborn pups together with their nursing mother are exposed to hyperoxia (75% oxygen) from postnatal day 7 (P7) to P12. Following P12, pups are returned to room air. CNTF (500ng/µl) is administered intravitreally on P7 or P12 in one eye. The opposite eyes receive carrier-injections with PBS/BSA for intra-individual controls. The size of the vaso-obliterated area (VO) and the amount of neovascularization (NV) is determined on P17. To analyze the direct effect of CNTF on endothelial cell sprouting, CNTF is used in a spheroid-assay using human umbilical vein endothelial cells (HUVECS) in collagen with and without VEGF-stimulation.
Results:
Intravitreal injections of CNTF on P12 (n=25 mice) but not on P7 (n=9 mice) results in a significant reduction of NV on P17 (P 12-injected: p= 0,021, P07-injected: p=0,59). In contrast, the size of the VO area at P17 remains unchanged in both groups, suggesting a selective anti-angiogenic effect of CNTF treatment on pathologic vessel formation. In the spheroid-assay, CNTF does not show any direct pro- or anti-angiogenic effect on endothelial cells. This can be explained by a lack of CNTF-receptor expression on both HUVECS as well as human retinal microvascular endothelial cells and suggests an indirect anti-angiogenic effect of CNTF in the OIR in vivo model.
Conclusions:
CNTF potently reduces pathological NV in the OIR-model. According to our in vitro experiments, this effect cannot be attributed to a direct anti-angiogenic effect of CNTF on endothelial cells but is rather mediated by a third cell type.
Keywords: 706 retinopathy of prematurity •
700 retinal neovascularization •
531 ganglion cells