Purpose: To determine the role of matrix metalloproteinases (MMP)‑1, ‑2, and ‑9 in directing the behavior
of human retinal pigment epithelial (HRPE) cells during contraction of three‑dimensional collagen gels.
Materials and Methods: The effect of HRPE cells on collagen gel invasion and contraction were quantified
by using phase contrast microscopy. Immunohistochemistry of the gel using monoclonal antibodies against
MMP‑1, ‑ 2, and ‑9 was performed. The effects of MMP inhibitor, Batimastat (BB‑94) on cultured HRPE cells,
and gel contraction were observed. Results: HRPE cells mostly proliferated as sheets of cells on the surface
of the collagen gel and only minimally invaded the gel. However, some HRPE cells were seen to invade the gel
as single cells detaching from the surface sheets. Surface‑located sheets of cells exerted a dose‑dependent
contraction on the gel and generally failed to express MMPs. Single cells invading the gel expressed MMP‑2
and ‑9. No expression of MMP‑1 was observed by HRPE cells. BB‑94, at a dose of 500 nM and 5 μM, reduced
the amount of gel contraction. Conclusions: These data indicate that MMPs are selectively involved in HRPE
invasion and collagen gel contraction. Both these processes may be implicated in the pathogenesis of similar
conditions in vivo in which contraction of collagen gel is a feature, for example, proliferative vitreoretinopathy.