Purpose: This study investigates the possibility that prostaglandins (PGs) induce changes in extracellular matrix (ECM) adjacent to ciliary muscle cells.
Methods: Human ciliary smooth muscle cells were grown to confluence in monolayer cultures and were treated with PGF2alpha, 11-deoxy-PGE1, or PhXA85 (the nonesterified analogue of PhXA41) for 12 to 72 hours. The amount of collagens type I, III, and IV in the cultures was determined, using sandwich enzyme immunoassays. The distributions of these collagens were assessed in the PG-treated cultures by immunocytochemistry.
Results: Twenty-four-hour treatment with 20 nM PGF2alpha, 11-deoxy-PGE1, or PhXA85 reduced the amount of collagen type I in extracts of the cell layer by 65+/-10%, 56+/-7%, and 46+/-7%, respectively, when compared with levels of those substances in vehicle-treated cultures. In similar fashion, collagen type III in cell layer extracts was reduced by 41+/-5%, 33+/-9%, and 3+/-5%, respectively. When the concentration of PGs was increased to 200 nM, the amount of type III collagen in the cell layer extracts was reduced by 93+/-7%, 99+/-1%, and 99+/-1%, respectively. Changes in type IV collagen in cell layer extracts after treatment with 20 nM PGs were not statistically significant. When the concentration of PGF2alpha, 11-deoxy-PGE1, or PhXA85 was increased to 200 nM, the amount of collagen type IV in the cell layer extract increased by 101+/-16%, 14+/-5%, and 89+/-11%, respectively. There were minimal changes in the staining pattern for collagen type I after 24-hour treatment with 20 nM PGs. When the PG concentration was increased to 200 nM, there were reductions in the density of collagen type I fibrils and clumping of collagen type III immunoreactive elements. The delicate lacework of collagen type IV immunoreactivity was replaced by bundles or clumps of heavy immunoreactive strands, separated by areas without immunoreactivity. These changes were present in cultures exposed to 20 nM PGs and were marked when PG concentration was increased to 200 nM.
Conclusion: These results indicate that PGs can induce substantial changes in the ECM around ciliary smooth muscle cells in vitro. These data support the possibility that changes in ciliary muscle ECM may contribute to increased uveoscleral outflow facility after topical PG administration.