BMP/ALK pathway and pathological retinal neovascularization

Abstract

Purpose : Alk2 and Alk3 are crucial receptors in mediating bone morphogenetic protein 2 and 4 (BMP2 and BMP4) signaling through recruiting BMP receptor-II (BMPR-II). Recently, Alk2 and Alk3 were found to be expressed in the retinal vasculature and implicated in retinal vascular development. Moreover, our preliminary data show that pharmacological inhibition of Alk2 and Alk3 restores human retinal endothelial cell barrier function under high glucose or BMP2 treatment. The goal of this study was to determine the effect of BMP/ALK inhibition on pathological retinal neovascularization in a mouse model of oxygen-induced retinopathy.

Methods : We developed endothelial Alk2/3 and Alk3 knockout (eKO) mice by crossing Alk2/3 fl/fl and Alk3 fl/fl mice with vascular-endothelial-cadherin promoted Cre mice (VEC-Cre, Jackson Labs) targeted deletion in endothelial cells. Wild type (wt) (n=8) and Alk2/3-eKO (n=6) and Alk3-eKO mice (n=3) were subjected to high oxygen (75%) for 5 days (p7-p12) before room air for additional 5 days (p12-p17). We also treated an additional group with intraperitoneal (IP) injection of BMP/ALK signaling inhibitor noggin (0.048 mg/kg/day) (n=7); starting from p12 daily until p16. On P17, retinas from all groups were flat mounted and retinal vessels were labeled with Isolectin-B4. Areas of retinal neovascularization (RNV) and vaso-obliteration were measured by Image-J and normalized to total retinal area.

Results : The morphological examination of the retinas from Alk2/3 eKO mice demonstrated significant decrease in both RNV and vaso-obliteration compared to the wt control (p<0.0001). On the other hand, morphological examination of the retinas from Alk3 eKO mice and noggin treated mice demonstrated significant decrease in RNV (p<0.05). Retinas from Alk3 eKO mice and noggin-treated mice did not demonstrate significant changes in the extent of vaso-obliteration compared to the wt control (p>0.05).

Conclusions : Inhibition of BMP/ALK pathway could be a novel therapeutic approach to prevent pathological RNV.

This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.