Abstract
Purpose: :
To investigate the effect of hypoxia on crystallin gene expression in two models: (1) hypoxia induced by cobalt chloride in human fetal retinal pigment epithelial cells (fRPE) and (2) hyperoxia–hypoxia induced retinopathy in the mouse.
Methods: :
Crystallin gene family expression was examined by PCR in mouse retina from two strains (C57BL/6J and 129S3/SvIM) and human fRPE. Only the crystallin genes that showed high expression in pilot studies were selected for further experimentation. For hypoxia studies, human RPE in early passages (2–4) were starved in 1% FBS–containing DMEM for overnight and treated with 100µM cobalt chloride up to 24 hours. Induction of hypoxia was verified by Hif1α expression. Crystallin gene expression was quantified by using real time RT–PCR from harvested RNA at each time point. Expression of corresponding crystallin proteins was confirmed by Western blot analysis. Expression profile of crystallin genes and the effect of hypoxia were also examined in the murine model of retinopathy of prematurity (ROP).
Results: :
Human fRPE express a selected number of crystallins, the prominent ones being αB, ßa1, γD, and γS. Exposure to hypoxia resulted in an alteration of their mRNA levels. In mouse retina, both C57BL/6J and 129S3/SvIM strains expressed the following crystallin genes: αA, αB; ßa2, ßa3, ßa4; ßb3; γa, γd, γe, γf, γs. However, the magnitude of expression of the crystallin gene family members was higher in C57BL/6J retinal samples than in 129S3/SvIM. Hypoxia caused an overall decrease in the studied genes compared to normoxic controls.
Conclusions: :
The regulation by hypoxia of members of α, ß, γ–crystallin family that are expressed in the mouse retina and RPE may be important in the development of ROP. The underlying mechanism needs to be elucidated.
Keywords: hypoxia • retinopathy of prematurity • retinal pigment epithelium