The Role Of MMP-1 And TIMP-1 In The Pathogenesis Of Pterygium

Objective: Pterygium is a common, frequently recurring ocular surface lesioncharacterized by tissue remodeling, cellular proliferation, angiogenesis, andinflammation. The increased incidence of pterygium in persons exposed to excessivesolar radiation suggests that ultraviolet (UV) light may play a critical role in thepathogenesis of this disease. The mechanism of pterygium formation is stillincompletely understood. Although recently, a lot of investigations were focused onthe essential roles of matrix metalloproteinases (MMPs) in remodeling theextracellular matrix (ECM), the correlation between UV-irradiation and theoverexpression of MMPs in pterygium has been poorly understood. Our investigationswere focused on the expression of collagenase-1 (matrix metalloproteinase-1, MMP-1)and tissue inhibitor of metalloproteinase-1 (TIMP-1) in pterygium and culturedconjunctival epithelial cells (CECs), to determine whether the expression of theseproteases could be modified after exposure to UVB.Methods:1. In this study, pterygium and normal conjunctival specimens were processedfor immunohistochemistry and RT-PCR to detect the expression of MMP-1 andTIMP-1.2. Conjunctival epithelial cells were cultured and exposed to various amounts ofUVB to determine both the protein and mRNA expression of MMP-1 and TIMP-1.Results:1. Intense MMP-1 immunoreactivity was identified predominantly in thepterygium epithelium. In contrast, significantly no MMP-1 staining was observed inthe normal conjunctival epithelium. The difference between their positive rates hadmarkedly statistical significance. The expression of TIMP-1 in pterygium andconjunctival epithelium had no distinct difference. MMP-1 and TIMP-1 mRNA expression in them correspond with the results of immunohistochemistry.2. Adult conjunctival epithelial cells and pterygium epithelial cells had beensuccessfully cultured in primary cell culture and passage culture by tissue inoculation.The cells were positive in pan-Keratin staining.3. Exposure of CECs to UVB resulted in a dose-dependent induction ofMMP-1. No expression of MMP-1 was observed in nonirradiated and 10 mJ/cm~2irradiated cells. Both the protein and mRNA expression of MMP-1 graduallyincreased after 20 to 60 mJ/cm~2 UVB exposure and reached the maximum level whenCECs were exposed to 60 mJ/cm~2 UVB. The difference between the level ofexpression in 40 mJ/cm~2 and 60 mJ/cm~2 irradiated cells had statistical significance.But MMP-1 expression at dose of 60 mJ/cm~2 was lower than that in pterygiumepithelial cells and the difference between them had statistical significance. However, CECs exposed to 80 mJ/cm~2 UVB changed from a flattened, cuboidal appearance tospindly and irregular cells, most of which detached from their substratum andgradually died. Notably, the protein and mRNA expression of TIMP-1 was shown notto be influenced by UVB. The results demonstrated relatively unaltered TIMP-1expression levels in pterygium epithelial cells compared with CECs irradiated with 0to 60 mJ/cm~2 UVB.Conclusions:1. Both the protein and mRNA expression of MMP-1 was increased in pterygium, but the expression of TIMP-1 in pterygium and conjunctiva had no distinct difference.These data imply a possible imbalance between MMP-1 and TIMP-1 activity that maybe one of the main pathogenesis of pterygium.2. UVB regulates the expression of MMP-1 at the level of transcription andtranslation. Of interest, although MMP-1 was increased in a dose-dependent mannerin cultured CECs, the same could not be said for its counter regulatory molecules, the TIMP-1.3. Adult normal conjunctival epithelial cells and pterygium epithetlial cells hadbeen cultured in primary cell culture and passage culture by using improved tissueculture method, which is simple, easy to perform, economic, practical and is worthpopularizeatoion.