BACKGROUND: The pathobiology in proliferative vitreoretinopathy (PVR) is complex. The mechanism of the release of retinal cells from their cellular bond is unknown. The metalloproteinase stromelysin cleaves proteins of the extracellular matrix (ECM). This may liberate retinal cells. The expression of stromelysin in human RPE cells has been demonstrated. Here, stromelysin gene expression under all-trans-Retinal (atR) was investigated. MATERIALS AND METHODS: Human RPE-cells were used from passage 2 to 5. The expression of the human stromelysin gene was determined by reverse transcriptase-polymerase chain reaction using specific oligonucleotides. RPE-cells were incubated with 162 nmol/l tetraphorbolester (TPA) alone or simultaneous with 1 mumol/l atR. RESULTS: TPA increased the expression of stromelysin in RPE cells. Incubation with TPA and atR lowered this increase. The decrease of expression was calculated semiquantitatively. CONCLUSIONS: The expression of stromelysin in RPE cells is lowered after incubation with 1 mumol/l atR. The dedifferentiation of RPE-cells may decrease intracellular atR levels. This could turn an inhibition of stromelysin gene expression to an increase. This may then release retinal cells from their cellular bond and therefore be one of the initial steps in the development of PVR.