Involvement of mechanical stretch in the gelatinolytic activity of the fibrous sclera of chicks, in vitro.

Purpose: To investigate the role of mechanical stretch in the regulation of matrix metalloproteinase-2 (MMP-2) in scleral fibroblasts of chick embryos.

Methods: Scleral fibroblasts derived from chick embryos were seeded onto flexible bottom culture plates, and subjected to a pulsatile stretch when the cells became subconfluent. After stretching, the cells and the conditioned medium were harvested. One portion of the conditioned medium was activated by reduction, alkylation, and 4-aminophenylmercuric acetate (APMA) treatment. The conditioned medium, with and without the treatment, was subjected to gelatin zymography and quantitative assays. Total cytoplasmic RNA was extracted from the cells, and the expression of MMP-2 and the tissue inhibitor of metalloproteinase-2 (TIMP-2) mRNA was examined by Northern blot analysis.

Results: The predominant gelatinolytic enzyme secreted by scleral fibroblasts was MMP-2. The mechanical stretch increased the gelatinolytic activities significantly in the conditioned medium with reduction, alkylation, and APMA treatment. Mechanical stretch also enhanced the expression of MMP-2 and TIMP-2 mRNA in scleral fibroblasts significantly.

Conclusions: These results suggest that mechanical stretch may be involved in the regulation of the extracellular matrix in the fibrous sclera of chicks in vivo.