Robey, Helen Louise; (1994) Retinal pigment epithelial cells in vitro: Behaviour and the cytoskeleton with particular emphasis on cytokeratins. Doctoral thesis (Ph.D), UCL (University College London).

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Abstract

Under certain pathological conditions the retinal pigment epithelium (RPE) undergoes changes in shape and behavioural activities, such as phagocytosis, proliferation and mobility. Changes in any of these processes influences the cytoskeleton, which is a cytoplasmic matrix of filaments, consisting of actin microfilaments (AMFs), microtubules (MTs) and intermediate filaments (IFs). The role of AMFs and MTs in these activities is better known than the role of IFs. In the present study immunohistochemical staining techniques were used to identify the cytoskeletal elements, visualise their arrangement in normal and diseased RPE in vitro and examine the possible role of the IFs in RPE phagocytosis, proliferation and migration. Bovine RPE were used as control cells, RCS rat RPE provided a source of diseased RPE and human RPE provided test cells to study proliferation and migration. Immunohistochemical labelling established that mammalian RPE in vivo and in vitro contained well developed systems of AMFs, MTs and co-expressed vimentin and cytokeratin IFs. The reactivity of cytokeratin monoclonal antibodies used in this study varied both in vivo and in vitro and between neighboring cells. Moreover a sub-population of RPE cells expressed cytokeratin 18 (K18) and cytokeratin 19 (K19) and this sub-population did not appear to be linked to phagocytosis in control rat RPE, but could have an association with phagocytosis in dystrophic cells. K18 fialments showed tortuous arrangements that were unique to dystrophic RPE and this may be the first documentation of a structural difference between control and dystrophic rat RPE. Using proliferation markers (BrdU & PCNA) it appeared that K18 and KI9 were not related to cell proliferation, but were involved in cell migration. Investigations using microchemotaxis chambers showed that human RPE, caught in the process of active migration through the pores of permable membranes, always expressed K18 and K19. The findings demonstrated for the first time a possible functional role for subtypes of cytokeratin IFs in the change of RPE from stationary to motile cells. Antibodies to K18 and K19 may have value as markers for migrating RPE so providing information about the RPE population from sections of ocular pathological material

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