238 The Roles of Oxygen and Vascular Growth Factors in Pathogenesis of Retinopathy of Prematurity in a Murine Model

Abstract

Purpose: To investigate the changes of VEGF°¢FGF-2°¢IGF-1 and ER mRNA and protein levels in mice retinae of normal retinal vascular development and retinopathy of prematurity to elucidate risk factors and pathogenesis of retinopathy of prematurity (ROP). Methods: Four hundred and seventy-four 7-day-old (P7) C57BL/6J mice, half female and half male, were assigned to four groups according to oxygen therapy and the gender. Total RNA was extracted from 2 mice for one sample. VEGF, FGF-2 and ER mRNA expression were determined by reverse transcription-polymerase chain reaction (RT-PCR). The protein levels of VEGF, FGF-2, IGF-1 and ER were determined by immunohistochemistry. Results: Gender and oxygen therapy couldn't affect the expression of VEGF, bFGF, IGF-1 and ER (P0.05). However, the age was the independent factor which could affect their expression (p<0.05). While hyperoxia and age were integrated, they obviously affected these factors expression (p<0.0001). The level of VEGF mRNA increased since P7, peaked at P9, and declined since P11 to a low level and maintained to P17 in nomoxic groups. In hyperoxic groups, it declined since P8 and remained declining during oxygen exposure; while it increased slowly since mice were taken back to room air and increased rapidly since P15 which is significant compared to the controls, indicating a close relationship with changes of O2 concentration. The level of FGF-2 mRNA maintained low in normoxia; while in hyperoxic groups it had no change during the hyperoxia exposure and increased since 3 days after back to room air and maintained to P21. The level of ER mRNA increased since P7, peaked at P9, declined since P11 and maintained to P17 in nomoxic group. In hyperoxic groups, it had no change during the hyperoxic period and rised since 5 days after back to room air and maintained to P21. The changes of protein levels of these three factors were later than that of their mRNA, but had the same trend. The protein of IGF-1 declined since P7 and maintained low since P11, while in hyperoxic group, it had no change during the hyperoxic exposure, increased since mice were back to room air and declined since P16 to a low level. Conclusion: Our study suggested that hyperoxia followed by hypoxia was very important in the pathogenesis of ROP. VEGF, FGF-2, IGF-1 and ER played important roles in the development of normal retina vascularization and the pathogenesis of ROP. VEGF may be the most important factor.