PURPOSE:To determine the effect of latanoprost on the expression of human matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPs) in the trabecular meshwork (TM). METHODS:Total RNA was isolated, and qualitative RT-PCR was performed to detect the mRNA of MMPs and TIMPs in human TM tissue and explant cultures of TM endothelial cells. Cultures of TM cells were treated with vehicle control or latanoprost acid for 24 hours. Real-time RT-PCR of cell cultures from five different donors was performed to determine relative changes in expression. GAPDH served as an endogenous control. RESULTS:The mRNA of MMP-1, -2, -3, -11, -12, -14, -15, -16, -17, -19, and -24 and of TIMP-1 to -4 was present in TM tissue and cultures of TM cells. MMP-9 was not found. In control TM endothelial cells, the relative expression of MMP mRNA were MMP-2 and -14 > MMP-16, -19, and -24 > MMP-15 > MMP-11 and -17 > MMP-1 and -3 > MMP-12. The relative expressions of TIMP mRNA were TIMP-1 > TIMP-2 and -3 > TIMP-4. Latanoprost increased MMP-1 (in four of five cultures), MMP-3 (in four of five cultures), MMP-17 (in three of five cultures), MMP-24 (in all five cultures), TIMP-2, -3, and -4 expression (in three of five cultures); MMP-11 and -15 were downregulated. CONCLUSIONS:Contrary to the expected result, latanoprost seems to have a significant effect on TM cells. The transcription of the genes for MMP-1, -3, -17, and -24 is increased by latanoprost treatment. TIMP-2, -3, and -4 are also upregulated. The upregulation of these TIMPs may compensate for the increase of those MMPs. The absence of MMP-9 and concurrent upregulation of a greater number of TIMPs may explain the limited effect of latanoprost on TM outflow.