Anti-angiogenic effect of adiponectin in human primary microvascular and macrovascular endothelial cells

Neovascularization in retina and choroid involves interplay of many cytokines and growth factors. Vascular endothelial growth factor (VEGF) being a pro-angiogenic molecule has been found to be high in aqueous and vitreous humour of patients with proliferative diabetic retinopathy (PDR). VEGF is also found in the fibroblast and retinal pigment epithelial cells (RPE) of choroidal neovascular (CNV) membranes isolated from patients. Though anti-VEGF agents cause regression of clinically visible new vessels, there is evidence that they increase the occurrence of retinal tractional detachment and other adverse effects in PDR and CNV treatments. Adiponectin (APN) is a cytokine, found to be involved in the pathobiology of PDR. It is unclear whether APN plays a reparative or pathological role in the disease condition. In this study, we explored the effect of APN on tube formation in the primary culture of human umbilical vein macrovascular endothelial cells (HUVEC), human retinal microvascular endothelial cells (hREC) and human choroidal endothelial cells (hCEC). Anti-VEGF agent, bevacizumab (avastin) was used as a control. Full-length pAc-APN transfected in HUVEC, hRECs and hCECs inhibited basal tube formation and migration comparable to bevacizumab (Avastin™). In hRECs, full length pAc-APN reduced VEGF or PDR vitreous mediated migration. In a similar way, rAPN significantly disrupted VEGF and PDR vitreous induced tube formation in HUVEC and hREC. Moreover, rAPN significantly reduced VEGF influenced proliferation and phosphorylation of ERK1/2 in hREC. Altogether, our study suggests that APN may be effective in the treatment of retinal neovascularization.