Mv. Miceli et Da. Newsome, EFFECTS OF EXTRACELLULAR-MATRIX AND BRUCHS MEMBRANE ON RETINAL OUTER SEGMENT PHAGOCYTOSIS BY CULTURED HUMAN RETINAL-PIGMENT EPITHELIUM, Current eye research, 15(1), 1996, pp. 17-26
The goal of this study was to determine the effect of extracellular ma
trix components on the phagocytic function of the retinal pigment epit
helial (RPE) cell. Cultured human fetal RPE cells were established in
culture and plated on three commercially-prepared substrates: collagen
IV, fibronectin and laminin and on three native matrices: bovine corn
eal endothelial cell matrix (BCEM) denuded bovine Bruch's membrane and
denuded human Bruch's membrane. Cultured cells were allowed to become
confluent and maintained for an additional two weeks before uptake of
fluorescent bovine retinal outer segments (ROS) was measured by flow
cytometry. Morphology by phase contrast microscopy and melanization wa
s also determined as measures of differentiation. The results showed t
hat morphology, melanization and ROS uptake by cells on collagen IV, l
aminin and fibronectin were not different from control cells plated on
tissue culture plastic. However, ROS uptake by cells plated on BCEM w
as significantly less than that of cells cultured on plastic and melan
ization was greater. ROS uptake by cells plated on both types of Bruch
's membrane was also significantly less than control cells. Treatment
of cells plated on tissue culture plastic with 44 mM NaHCO3, which inc
reased melanization, also reduced ROS uptake. We conclude that native
matrices seem to contain components that significantly depress ROS upt
ake in culture. The inhibition is not mimicked by collagen, laminin or
fibronectin coated wells. The ECM may play a significant role in cont
rolling phagocytosis of ROS either by determining morphology, increasi
ng differentiation or by directly influencing intracellular metabolism
, and thus serve as another level of control for this RPE function whi
ch may not occur in cells plated on tissue culture plastic. These resu
lts may also have implications for the effects of aging or disease in
which there are changes in the ECM.