Latanoprost and matrix metalloproteinase-1 in human choroid organ cultures

Purpose. Latanoprost, a prostaglandin F-2 alpha analogue and ocular hypoten sive agent, alters extracellular matrix and matrix metalloproteinases (MMPs ), including MMP-1, within tissues of the uveoscleral outflow pathway. In a ddition to these tissues, the anterior choroid also is exposed to fluid wit hin the uveoscleral outflow pathway. The present study was undertaken to co mpare MMP-1 expression in the choroid with other uveoscleral pathway tissue s and to determine the effect of latanoprost on MMP-1 expression in human c horoid organ cultures. Methods. Choroid tissue explant cultures were generated and incubated with PhXA85, the biologically active form of latanoprost, or vehicle for 12 or 1 8 hours. Explant cultures from iris and ciliary body also were generated an d exposed to PhXA85. Protein extracts of theses cultures, as well as from f resh tissues, were then probed for MMP-1 by Western blotting. All samples w ere normalized for protein content and reletive expression was evaluated by densitometry. Also, total RNA was harvested from fresh tissues or from cul tures treated with PhXA85. The amount of MMP-1 mRNA in these samples was me asured using real time polymerase chain reaction. These results were normal ized according to simultaneous measurements of glyceraldehyde-3-phosphate d ehydrogenase mRNA within the same samples. Results. Compared to the ciliary body, in which specific MMP-1 concentratio n (/total mg protein) was greatest, the specific MMP-1 concentrations withi n iris, anterior choroid, and posterior choroid were less by 24.7 +/- 0.69% , 40.7 +/- 1.04%, and 64.5 +/- 0.52%, respectively (mean +/- SD). The order of MMP-1 mRNA expression among these tissues from fresh eyes was ciliary b ody > anterior choroid > posterior choroid > iris. Treatment of ciliary bod y explant cultures with 200 nM PhXA85 for 12 hours increased MMP-1 protein content by 154 +/- 34% (P = 0.004, students t test, N = 3). In contrast, si milar treatment of anterior choroid, posterior choroid or iris explant cult ures minimally changed MMP-1 protein content (23 +/- 22%, P = 0.124; 14 +/- 8%, P = 0.462; 27 +/- 16%, P = 0.037, respectively). Increased MMP-1 was o bserved in choroid cultures incubated for 18 hrs with 200 nM or 500 nM PhXA 85. MMP-1 mRNA in 12 hour PhXA85-treated choroid cultures was the same or l ess than vehicle-treated cultures from 7 of 9 donors. In contrast, MMP-1 mR NA was increased in PhXA85-treated ciliary body cultures from 2 of 2 donors . Conclusions. These results suggest that the capacity for latanoprost-mediat ed induction of MMP-1 within the choroid is less than within the ciliary mu scle. Hence, it is unlikely that induction of MMP-1 in choroid plays as imp ortant a role in uveoscleral outflow modulation as induction of MMP-1 in th e ciliary muscle.