Characterization of a new murine retinal cell line (MU-PH1) with glial, progenitor and photoreceptor characteristics

Unlike fish and amphibians, mammals do not regenerate retinal neurons throughout life. However, neurogenic potential may be conserved in adult mammal retina and it is necessary to identify the factors that regulate retinal progenitor cells (RPC) proliferative capacity to scope their therapeutic potential. Muller cells can be progenitors for retinal neuronal cells and can play an essential role in the restoration of visual function after retinal injury. Some members of the Toll-like receptor (TLR) family, TLR2, TLR3 and TLR4, are related to progenitor cells proliferation. Muller cells are important in retinal regeneration and stable cell lines are useful for the study of retinal stem cell biology. Our purpose was to obtain a Muller-derived cell line with progenitor characteristics and potential interest in regeneration processes. We obtained and characterized a murine Muller-derived cell line (MU-PHI), which proliferates indefinitely in vitro. Our results show that (i) MU-PHI cells expresses the Muller cell markers Vimentin, S-100, glutamine synthetase and the progenitor and stem cell markers Nestin, Abcg2, Ascl1, alpha-tubulin and beta-III-tubulin, whereas lacks the expression of CRALBP, GFAP, Chx10, Pax6 and Notch1 markers; (ii) MU-PHI cell line stably express the photoreceptor markers recoverin, transducin, rhodopsin, blue and red/green opsins and also melanopsin; (iii) the presence of opsins was confirmed by the recording of intracellular free calcium levels during light stimulation; (iv) MU-PHI cell line also expresses the melatonin MT1 and MT2 receptors; (v) MU-PH1 cells express TLR1, 2, 4 and 6 mRNA; (vi) MU-PHI express TLR2 at cell surface level; (vii) Candida albicans increases TLR2 and TLR6 mRNA expression; (viii) C albicans or TLR selective agonists (Pam(3)CysSK(4), LPS) did not elicit morphological changes nor TNF-alpha secretion; (ix) C. albicans and Pam(3)Cy5SK(4) augmented MU-PHI neurospheres formation in a statistically significant manner. Our results indicate that MU-PHI cell line could be of great interest both as a photoreceptor model and in retinal regeneration approaches and that TLR2 may also play a role in retinal cell proliferation. (C) 2012 Elsevier Ltd. All rights reserved.