Altered expression of growth factors and cytokines in keratoconus, bullouskeratopathy and diabetic human corneas

The purpose of this study was to identify the growth factors and cytokines present in normal and diseased corneas, Total RNA was isolated from normal and diseased corneas. cDNA was synthesized from individual corneas and semi quantitative reverse transcription-polymerase chain reaction (RT-PCR) was p erformed with primers to IL-1 alpha, IL-8, PDGF-B, BMP-2, BMP-4, IGF-I, TGF -beta2, FGF-2, and VEGF. After normalization to beta (2)-microglobulin, sev eral factors were identified that were significantly different from normal. Antibodies to IGF-I, BMP-2, VEGF and TGF-beta2 were used for immunohistoch emistry. A total of 93 corneas were used for this study including 31 normal , 20 keratoconus, 19 bullous keratopathy (pseudophakic and aphakic, PBK/ABK ), and 23 diabetic corneas. The VEGF RNA levels were significantly decrease d in the keratoconus and PBK/ABK corneas but increased in the diabetic corn eas. BMP-2 gene expression was lower than normal in the PBK/ABK and diabeti c corneas. IGF-I and BMP-4 RNA levels were increased in PBK/ABK. In the imm unohistochemical studies, the protein patterns paralleled those found at th e mRNA level. The only exception was IGF-I in diabetic corneas that showed increased staining in the epithelium and its basement membrane without a si gnificant increase in mRNA levels. TGF-beta2 mRNA and protein levels were s imilar to normal in all diseased corneas. Thus, no alterations in the teste d growth factors/cytokines were unique to keratoconus corneas. In contrast, PBK/ABK corneas had specific significant elevations of BMP-4 and IGF-I. Di abetic corneas were unique in their increased VEGF mRNA levels. These data suggest that while some growth factor/cytokine alterations are non-specific and can be found in multiple corneal diseases, there are others that are u nique to that disease. (C) 2001 Academic Press.