Abstract
Purpose::
Protein kinase CK2 is highly expressed in retinal astrocytes and is important for retinal neovascularization in the mouse oxygen-induced retinopathy (OIR). The purpose was to examine the effects of CK2 inhibition on the incorporation of bone marrow-derived endothelial progenitor cells (EPC) into sites of retinal neovascularization in OIR.
Methods::
8-day old C57BL mouse pups received one intravitreal injection into the right eye of 5,000 Ska-1- and c-kit-positive bone marrow-derived EPC from green fluorescent protein (gfp) transgenic mice. Left eye was left as a control. On days 12 to 17, pups received intraperitoneal injections of a specific CK2 inhibitor, 4,5,6,7-tetrabromobenzotriazole (TBB) twice daily at 100 mg/g/day or vehicle (20% PEG 400 + 2% Tween-80, pH 7.4). On day 17, animals were sacrificed, retinas perfused with rhodamine-dextran and flat mounts analyzed by confocal microscopy. Some eyes were fresh-frozen and cryostat sections examined by immunohistochemistry.
Results::
At day 17, distinct retinal neovascularization developed. In EPC-injected eyes gfp+ cells incorporated into neovascular tufts. Noninjected contralateral eyes had no fluorescent cells present. Labeled EPC showed similar distribution in retinas from untreated and vehicle-treated animals. In contrast, retinas from TBB-treated animals demonstrated a significant decrease of gfp+ cells including areas of retinal neovascularization. Flat mounts data were confirmed on cryostat sections using antibody to gfp.
Conclusions::
The data show that EPC participate in pathologic retinal neovascularization in the OIR model by incorporating into neovascular tufts. Marked inhibition of this process by a specific CK2 blocker suggests a distinct mechanism of CK2 participation in angiogenesis by facilitating EPC incorporation into retinal neovessels, possibly by stimulating cell migration and proliferation.
Keywords: retinal neovascularization • enzymes/enzyme inhibitors • drug toxicity/drug effects