Vascular endothelial growth factor receptor-1 (VEGFR-1) expression in human corneal fibroblast decreased with age

PURPOSE Mechanisms by which fibroblast networks between stromal lamellae are laid in the corneal stroma are far from clear. We have investigated the role of vascular endothelial growth factor receptors (VEGFRs) by in vitro studies in the human corneal network formation obtained from donors whose ages ranged from 19 to 89 years. METHODS Corneal fibroblasts were prepared from cornea donations. The functional properties of these cells to form networks were analyzed using a semi solid matrix (substratum) of Matrigel. The presence of VEGF receptor-1 (VEGFR-1) and the functionality in these fibroblasts were investigated using immunofluorescence, molecular analysis (gene microarray, reverse transcription polymerase chain reaction [RT-PCR] and VEGFR siRNA transfections), and cell culture. RESULTS Corneal fibroblasts from 61 donors were classified into two groups according to whether they formed (82%) a reticulum on Matrigel or not (18%). By RT-PCR and immunofluorescence analysis, we showed that corneal fibroblasts expressed VEGFR-1 (mRNA and protein). Further, cell culture analysis revealed that only the network (reticulum) forming corneal fibroblast expressed VEGFR-1 in contrast to non network-forming fibroblasts. Use of inhibitors such as VEGFR-1 siRNA transfection or neutralizing antibody (Avastin) indicated that VEGFR-1 was essential to the formation of the corneal network in vitro. CONCLUSIONS The cell reticulum formation seemed to be directly related to the expression of VEGFR-1 in the corneal fibroblast, and this expression decreased with age. The decrease in VEGFR-1 expression is probably related to the diminution of autocrine functions, which may alter the overall tissular homeostasis. This may culminate in the gradual development of poor vision, which is observed in certain pathologies and in aging individuals.