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Sauparnika Vijay, Annegret H. Dahlmann-Noor, Richard Foxton, Peter Munro, Peng T. Khaw; Olfactory Ensheathing Cells Promote Retinal Ganglion Cell Growth, Survival and Neurite Bundling. Invest. Ophthalmol. Vis. Sci. 2011;52(14):3089.
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© ARVO (1962-2015); The Authors (2016-present)
Olfactory ensheathing cells (OEC) are glia residing in the olfactory mucosa and bulb, where they allow continuous regeneration of axons of olfactory receptor neurons. OEC support regeneration of axons in spinal injury models with functional regain. OEC promote regeneration of retinal ganglion cell (RGC) axons in-vitro; however, myelination or synapse formation have not been described. The aim of our study was to examine interactions between OEC and RGC in-vitro.
We isolated OEC and RGC from postnatal rats. We selected primary RGC from a retinal cell suspension by magnetic sorting and cultured cells on glass coverslips in neurobasal medium enriched with neurotrophins. We maintained cells separately for five days. We characterized OEC and RGC by immunocytochemistry (ICC) and RT-PCR for specific markers. We added OEC to RGC cultures and co-cultured both for 14 days. We fixed the co-cultures and carried out ICC and transmission electron microscopy (TEM). We studied a subset of co-cultures with time-lapse phase microscopy.
We identified OEC on ICC by expression of p75 neurotrophin receptor, and RGC by neurofilament (NF). On TEM, OEC have large amounts of glycogen deposits; neurites have evenly spaced neurofilaments. RGC survival is enhanced by 204% in the presence of OEC, and neurites express more presynaptic puncta. TEM images show that OEC processes engulf synapses (figure). In the presence of RGCs OEC express synatotagmin protein, but not in monoculture. OEC organize RGC neurites into bundles with parallel fibres.
OECs support RGC regeneration and may facilitate formation of functional synapses in-vitro. We have demonstrated for the first time that RGC synapses are enhanced by the physical presence of OEC processes, and that OEC organize RGC neurites into parallel bundles. Induction of RGC synpaptotagmin may indicate that OEC can modulate neuronal synaptic activity.
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