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Alessia Tassoni, Natalie D. Bull, Keith R. Martin; Enhancement Of Stem Cell Integration Into The Retina By Modulating Glial Reactivity In An In-vitro Stem Cell Transplantation Model. Invest. Ophthalmol. Vis. Sci. 2012;53(14):6612.
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There has been much recent interest in the potential use of intraocular stem cell transplantation to slow or reverse visual loss in glaucoma. However, migration and integration of stem cells into the retina is limited by reactive gliosis, a major barrier to retinal engraftment. Our aim was to identify glial modulators of low toxicity and measure their potential to facilitate stem cell entry into the host retina.
An explant organotypic culture system was used as a stem cell transplantation model and screening tool for candidate drugs. GFP+ Rat Mesenchymal Stem Cells (rMSCs) were co-cultured on the surface of the explants for 7 days. Minocycline and Propentofylline were used to inhibit microglia activation. Stat3 inhibitor VI was used to suppress Glial Fibrillary Acidic Protein (GFAP)expression. The efficacy of each drug to overcome the barrier was evaluated by immunohistochemistry for glial markers including GFAP, Nestin and Vimentin. rMSC integration was assessed by simultaneous immunostaining for GFP.
Co-culture of retinal explants with rMSCs caused a 1.5±0.4 fold increase in GFAP expression. Microglia activation and proliferation was not markedly affected by the presence of grafted rMSCs on retinal surface. Pharmacological inhibition of resident microglia does not alter glial reactivity and does not induce stem cell entry into the retina. In contrast, interfering with the JAK/STAT pathway successfully disrupted GFAP expression and facilitated rMSCs integration into the host tissue.
The results show that microglia do not play a dominant role in the barrier to retinal engraftment, but the JAK/STAT pathway may represent a promising pharmacological target. Different concentrations of STAT3 inhibitor VI are currently being tested and retinal ganglion cell viability after drug treatment explored. Targeting modulators of glia reactivity to promote stem cell integration in the host tissue may facilitate stem cell therapy in glaucoma and other neurodegenerative diseases.
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