Abstract： Background Latanoprost,a prostaglandin F2a analog,has been shown to be an effective intraocular pressure lowering agent which acts by inducing ciliary muscle cells to synthesise matrix metalloproteinases.However,the response of ciliary melanocytes to latanoprost has never been reported.This research has investigated the ability of latanoprost to induce matrix metalloproteinase-1 expression in human ciliary melanocytes,and thereby advance the understanding of the mechanism of PGF2a in decreasing Intraocular pressure.Methods In vitro human ciliary melanocytes were treated for 48 hours with five different concentrations of latanoprost (100,150,200,500,and 1000 nmol/L).Ciliary melanocytes treated with 0.01% ethanel(vehicle)were used as a control.The expression of matrix metalloproteinase-1 in ciliary melanocytes was determined by Western blotting and immunofluorescent staining.Results Western blotting showed that the expression of matrix metalloproteinase-1 in ciliary melanocytes was induced by latanoprost,and the level of expression was dependent on the concentration of latanoprost in the culture medium.Immunofluorescent staining showed that matrix metalloproteinase-1 was confined to the ciliary melanocyte cytoplasm.Conclusions Latanoprost induced the expression of matrix metalloproteinase-1 in human ciliary melanocytes in a dose-dependent manner.Ciliary melanocytes,as well as ciliary muscle cells,may also play an important role in uveoscleral outflow modulation.