Phagocytosis by retinal pigment epithelium explants in culture

Philp, Nancy J.; Bernstein, Maurice H.

doi:10.1016/s0014-4835(81)80080-2

Cited by 42 publications

(15 citation statements)

References 14 publications

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“…This is because in the neonatal rat, increasing differentiation has been associated with increasing ability to ingest ROS, while non-specific phagocytosis (i.e., ingestion of latex beads) remained constant (32). However.…”

Section: Discussionmentioning

confidence: 99%

Effects of extracellular matrix and Bruch's membrane on retinal outer segment phagocytosis by cultured human retinal pigment epithelium

Miceli

Newsome

1996

Current Eye Research

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The goal of this study was to determine the effect of extracellular matrix components on the phagocytic function of the retinal pigment epithelial (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 corneal 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 was also determined as measures of differentiation. The results showed that morphology, melanization and ROS uptake by cells on collagen IV, laminin and fibronectin were not different from control cells plated on tissue culture plastic. However, ROS uptake by cells plated on BCEM was significantly less than that of cells cultured on plastic and melanization 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 increased melanization, also reduced ROS uptake. We conclude that native matrices seem to contain components that significantly depress ROS uptake in culture. The inhibition is not mimicked by collagen, laminin or fibronectin coated wells. The ECM may play a significant role in controlling phagocytosis of ROS either by determining morphology, increasing differentiation or by directly influencing intracellular metabolism, and thus serve as another level of control for this RPE function which may not occur in cells plated on tissue culture plastic. These results may also have implications for the effects of aging or disease in which there are changes in the ECM.

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Section: Discussionmentioning

confidence: 99%

Effects of extracellular matrix and Bruch's membrane on retinal outer segment phagocytosis by cultured human retinal pigment epithelium

Miceli

Newsome

1996

Current Eye Research

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“…Other proteins, such as guanylate cyclase (Zhan et al, 1987) and a RPE-specific antigen described in newt (Klein et al, 1990), appear in the RPE upon the emergence of the outer segments. In fact, several features of the RPE cell such as binucleation (a phenomenon very frequent in rat RPE), maturation of the melanin pigmentation (Stroeva and Mitashov, 1983), and phagocytosis of significant amounts of rod outer segments develop only after birth (Philp and Bernstein, 1981;Ershov and Stroeva, 1989). It is possible that a general mechanism of maturation synchronized with the growth of outer segments occurs in the RPE cell at this time.…”

Section: Discussionmentioning

confidence: 99%

A developmentally regulated microsomal protein specific for the pigment epithelium of the vertebrate retina

Hamel

Tsilou

Harris

et al. 1993

J of Neuroscience Research

127

114

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In the vertebrate retina, the retinal pigment epithelium (RPE) performs specific functions critical to the normal process of vision. Although some of these functions are well documented, molecular data are still scarce. Using the RPE-specific monoclonal antibody RPE9, raised against human RPE cells, we have identified a novel 65 kD protein, conserved in mammals, birds, and frogs. This RPE-specific protein was found to be nonglycosylated. It was most effectively solubilized in the presence of detergent suggesting that it is associated with the RPE cell membranes. Its partitioning in the detergent phase of Triton X-114 and its solubilization in 0.75 M and 1.0 M KCl suggest that it interacts with the membrane either through a polypeptide anchor or charged amino acids. Cell fractionation by differential solubilization and differential centrifugation demonstrated that the protein was preferentially associated with the microsomal membrane fraction, where it is the major protein. Developmental expression of this 65 kD protein was examined in neonatal rats. Morphologically well-differentiated RPE cells did not express the 65 kD protein at birth. However, expression was detectable at postnatal day 4, that is, one to two days before the photoreceptors develop their outer segments, suggesting that the expression of the 65 kD protein may be coordinated with other developmental events in the intact retina. This is further supported by the fact that RPE cells in confluent culture lose the expression of this protein within two weeks, while they maintain their characteristic epithelial morphology. Because of its specificity, its evolutionary conservation, and its timing of expression, it is possible that this protein may be involved in one of the key roles of RPE and as such is an important molecular marker for RPE differentiation.

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“…At birth, rat RPE cells lack phagocytic ability (3,4). During postnatal retinal maturation, the RPE forms long, apical microvilli that ensheath developing photoreceptor outer segments.…”

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confidence: 99%

Phagocytosis of rod outer segments by retinal pigment epithelial cells requires αvβ5 integrin for binding but not for internalization

Finnemann

Bonilha

Marmorstein

et al. 1997

Proc. Natl. Acad. Sci. U.S.A.

341

374

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Phagocytosis of shed photoreceptor rod outer segments (ROS) by the retinal pigment epithelium (RPE) is essential for retinal function. Here, we demonstrate that this process requires ␣v␤5 integrin, rather than ␣v␤3 integrin utilized by systemic macrophages. Although adult rat RPE expressed both ␣v␤3 and ␣v␤5 integrins, only ␣v␤3 was expressed at birth, when the retina is immature and phagocytosis is absent. Expression of ␣v␤5 was first detected in RPE at PN7 and reached adult levels at PN11, just before onset of phagocytic activity. Interestingly, ␣v␤5 localized in vivo to the apical plasma membrane, facing the photoreceptors, and to intracellular vesicles, whereas ␣v␤3 was expressed basolaterally. Using quantitative f luorimaging to assess in vitro uptake of f luorescent particles by human (ARPE-19) and rat (RPE-J) cell lines, ␣v␤5 function-blocking antibodies were shown to reduce phagocytosis by drastically decreasing (85%) binding of ROS but not of latex beads. In agreement with a role for ␣v␤5 in phagocytosis, immunof luorescence experiments demonstrated codistribution of ␣v␤5 integrin with internalized ROS. Control experiments showed that blocking ␣v␤3 function with antibodies did not inhibit ROS phagocytosis and that ␣v␤3 did not colocalize with phagocytosed ROS. Taken together, our results indicate that the RPE requires the integrin receptor ␣v␤5 specifically for the binding of ROS and that phagocytosis involves internalization of a ROS-␣v␤5 complex. ␣v␤5 integrin does not participate in phagocytosis by other phagocytic cells and is the first of the RPE receptors involved in ROS phagocytosis that may be specific for this process.Among the vital functions performed by the retinal pigment epithelium (RPE) (1) is the phagocytosis of rod outer segments (ROS) fragments (2). At birth, rat RPE cells lack phagocytic ability (3, 4). During postnatal retinal maturation, the RPE forms long, apical microvilli that ensheath developing photoreceptor outer segments. From about PN12, stacks of ROS membranes are shed daily from the distal end of photoreceptors and become efficiently phagocytosed by RPE cells (5). The essential role of RPE phagocytosis is highlighted by the rapid degeneration of photoreceptor neurons in Royal College of Surgeons rats. Royal College of Surgeons rats carry an autosomal recessive mutation that impairs RPE phagocytosis, resulting in subretinal accumulation of ROS (3, 6, 7). Photoreceptor death is irreversible and inevitably results in blindness (8, 9). RPE phagocytosis is poorly understood, compared with the well characterized phagocytosis by monocyte macrophages. RPE and systemic phagocytosis differ in that the former follows a circadian rhythm in many species (10). Furthermore, although RPE cells express Fc receptors, they highly favor ROS binding and uptake over internalization of opsonized bacteria, yeast or inert particles (11). Of special relevance to RPE phagocytosis is the phagocytosis of apoptotic cells by circulating macrophages. Clearance of senescent cells by monocyte macro...

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Phagocytosis by retinal pigment epithelium explants in culture

Cited by 42 publications

References 14 publications

Effects of extracellular matrix and Bruch's membrane on retinal outer segment phagocytosis by cultured human retinal pigment epithelium

Effects of extracellular matrix and Bruch's membrane on retinal outer segment phagocytosis by cultured human retinal pigment epithelium

A developmentally regulated microsomal protein specific for the pigment epithelium of the vertebrate retina

Phagocytosis of rod outer segments by retinal pigment epithelial cells requires αvβ5 integrin for binding but not for internalization

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