TSPAN12 – a novel target for the treatment of vaso-proliferative retinopathy

Abstract

Purpose : Insufficient responders to anti-VEGF therapy and potential long-term side-effects necessitate the development of novel anti-angiogenic therapeutics for the treatment of vasoproliferative retinopathy. Tetraspanin 12 (TSPAN12) - a transmembrane protein that is specifically expressed in the retinal vasculature – has been shown to be involved in retinal vascular development. This study examines the role of TSPAN12 in vasoproliferative retinal disease modelled by the mouse model of oxygen-induced retinopathy (OIR) and evaluates its potential as therapeutic target.

Methods : Murine pups were exposed to 75% oxygen from postnatal day 7 (P7) to P12 and subsequently transferred to room air. Retinal tissue was collected at different time-points during OIR to examine expression levels of TSPAN12 and downstream targets on RNA and protein level. A human monoclonal antibody against the extra-cellular domain of TSPAN12 was developed through the screening of antibody libraries. The effect of the TSPAN12-antibody (2D10) on endothelial cells was tested in vitro using the wound healing and tube-formation assay. In vivo, the TSPAN antibody 2D10 or IgG1 control were injected intra-vitreally at OIR P12 and quantification of vaso-obliteration (VO) and neovascularization (NV) performed at OIR P17.

Results : TSPAN12 was significantly upregulated in response to retinal hypoxia during OIR on RNA (1.7 fold, p=0.01, N=4) and protein (1,5 fold, p=0.047, N=4) level. The TSPAN12 antibody 2D10 inhibited endothelial migration (p=0.03) and tube formation (p=0.05) in vitro. When injected intra-vitreally at OIR P12, the TSPAN12 antibody 2D10 significantly reduced the area of vaso-obliteration and neovascularization by 28% and 33%, respectively, (p<0.05, N=14) at OIR P17. Injection of the TSPAN12 antibody 2D10 induced a 40% downregulation of b-catenin (p=0.007, N=8) in vivo suggesting that the anti-angiogenic effect is associated with the inhibition of b-catenin dependent signaling.

Conclusions : Our data suggest that TSPAN12 may be an important mediator for pathologic angiogenic processes in hypoxia-driven proliferative retinopathy. Its selective expression in retinal endothelial cells make TSPAN12 an attractive target for anti-angiogenic therapies due to its low risk for off-target side-effects. In vitro and in vivo data provide strong support for the therapeutic potential of the newly developed Tspan12 antibody 2D10 for proliferative retinopathy.

This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.