Recombinant TIMP-1 and -2 enhance the proliferation of rabbit corneal epithelial cells in vitro and the spreading of rabbit corneal epithelium in situ

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Abstract
PURPOSE. The repair of the corneal epithelium is modulated by matrix metalloproteinases. The present study examined the effects of recombinant (r-) tissue inhibitors of metalloproteinases-1 and -2 (TIMP-1 and -2) on the proliferation of cultured epithelial cells from rabbit cornea, and on the spreading of a sheet of squamous epithelium of rabbit cornea placed in an organ culture system. METHODS. DNA synthesis of the cells, with or without r-TIMPs, was determined by an immunoassay for BrdU incorporation. Cell proliferation was assayed by measuring MTT mitochondrial activity. Epithelial spreading was evaluated by culturing small corneal blocks for 24 h in the presence or absence of each agent. Cryosections were prepared and the epithelial growth on the cut stromal surface was measured. RESULTS. Each agent, r-TIMP-1 (at 50 and 100 ng/ml) and r-TIMP-2 (at 50 ng/ml) significantly enhanced the DNA synthesis and MTT activity of the corneal epithelial cells in vitro. Relative to the untreated control cells, DNA synthesis was increased 2.4-fold by r-TIMP-1 and 2.3-fold by r-TIMP-2. r-TIMP-1 (at 100 and 200 ng/ml) and r-TIMP-2 (at 10 and 50 ng/ml) each significantly enhanced the spreading of the corneal epithelium. Relative to the untreated control tissue, spreading of the epithelial sheet was increased 1.7-fold by r-TIMP-1 and 1.4-fold by r-TIMP-2. Higher concentrations of r-TIMP-1 and r-TIMP-2 did not further enhance either the DNA synthesis of the cultured cells or the spreading of the epithelium. CONCLUSIONS. Exogenous TIMPs enhanced the spreading of the corneal epithelium and proliferation of cultured corneal epithelial cells. Findings suggest that endogenous TIMPs may influence the healing of corneal epithelium in vivo.