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Alpa Ahir, Li Guo, Ali A. Hussain, John Marshall; Expression of Metalloproteinases from Human Retinal Pigment Epithelial Cells and Their Effects on the Hydraulic Conductivity of Bruch’s Membrane. Invest. Ophthalmol. Vis. Sci. 2002;43(2):458-465.
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purpose. To evaluate the expression pattern of matrix metalloproteinases (MMPs)
from retinal pigment epithelial (RPE) cells in culture, and to
determine their ability to alter the transport properties of human
methods. Human RPE cells from either primary cultures or a cell line were
maintained under culture conditions. At different time intervals after
subculturing of cells the presence of MMPs in the bathing medium was
determined by zymography. Cellular MMP activity was determined in a
similar series of experiments where serum was omitted from the culture
medium. Cultured cells were introduced onto Bruch’s membrane, mounted
in a modified Ussing chamber, to assess entry of MMPs into the
membrane. Fluid flow across Bruch’s membrane was determined by
hydraulic conductivity for different ages of donor tissue, before and
after 24 hours’ incubation with active MMPs from the RPE-conditioned
medium or after incubation with purified activated MMPs. Latent
(inactive) MMPs from medium containing serum were used in control
results. Cultured RPE cells expressed both MMP-2 and -9, with active MMP-2
becoming detectable from 4 days after subculture through to confluence
and activated MMP-9 becoming abundant up to 24 hours after subculture.
Both active MMPs significantly increased hydraulic conductivity of
Bruch’s membrane, with the increase after MMP-9 incubation being far
greater than that for MMP-2. Both enzymes showed a trend in hydraulic
conductivity change with age such that, MMP-2 produced a relatively
constant change, whereas MMP-9 showed a greater increase in older eyes.
conclusions. Activation of both MMP-2 and -9 by cultured RPE cells appeared to show
a temporal relationship with the growth cycle of the cells. The
activated enzymes increased fluid flow of Bruch’s membrane, and the
marked effect observed with MMP-9 in older eyes suggests a mechanism
that may allow debris removal.
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