Contribution of Endothelial Progenitor Cells in Murine Retinopathy of Prematurity Model

Abstract

Purpose:: In pathological retinal vascular development cause in murine retinopathy of prematurity (ROP), the contribution of bone marrow (BM) derived endothelial progenitor cells (EPCs) remains to be elucidated, although already described in pathological retinal neovascularization of adult mammals.In the present study, we investigated that in murine ROP model, BM-derived EPCs play a role in pathological retinal vascular development through mobilization from BM and recruitment to retinal neovasculature.

Methods:: ROP was induced in C57 BL6/J mice exposed 75% oxygen from postnatal day 7 (P7) to P12, followed by returning to room air.On P12 and P17, BM and peripheral blood (PB) were obtained from ROP± mice. EPCs producing potential of BM derived Sca-1⁺/Lin^- cells (immature EPC fraction) was estimated methylcellulose colony assay.To asses the recruitment of BM derived EPCs into retina of ROP , bone marrow transplantation (BMT) was performed on newborn mice.Recipient mice were conditioned just before delivery, and then received Sca-1⁺/Lin^- cells isolated from eGFP-transgenic C57BL/6J donors mice BM within 48 hours after birth (eGFP/BMT mice). The retinal wholemounts of ROP± eGFP/BMT mice were immunohistochemically examined at P12 and P17.

Results:: The frequency of Sca-1⁺/Lin^- cells in BM of ROP+ mice gradually decreased from P12 to P17, as compared with ROP- (P12:P=0.33 , P17:P<0.01). To the contrary, the frequency of Sca-1⁺/CD31⁺ cells in PB increased in ROP+ mice at P12 (P<0.05), which means the enhanced mobilization of EPCs from BM. Sca-1⁺/Lin^- cells isolated from BM of ROP+ disclosed the predominant number of differentiating EPC colonies vs immature EPC colonies in vasculogenic colony assay. Immunostaining of retinal flatmounts showed that GFP⁺/CD31⁺cells were significantly incorporated in retinal neovasculature of ROP+ vs ROP- eGFP/BMT mice at P17 (P< 0.01).

Conclusions:: BM derived EPCs significantly contribute to the pathological retinal vascular development in murine ROP model by the differentiation and mobilization, recruitment.

Keywords: retinopathy of prematurity • vascular cells • transplantation