In addition to studying the pathophysiology of glaucoma, we are also interested in any potential treatments. Glaucoma is associated with impairment in retrograde transport of neurotrophic factors to retinal ganglion cell (RGC) bodies. Previously we demonstrated that bone marrow-derived MSC (BMSC) transplantation is protective in a rat model of glaucoma and that factors secreted by BMSC are essential for neuroprotection. To elucidate the nature of neuroprotective factors we used exosomes produced by BMSC and tested them in a rat optic nerve crush (ONC) model. Treatment of primary retinal cultures with BMSC-exosomes demonstrated significant neuroprotective and neuritogenic effects. In vivo, intravitreal injection of BMSC-derived exosomes, but not fibroblast-derived exosomes, provided statistically significant RGC neuroprotection, regeneration of their axons while partially preventing RGC axonal loss and RGC dysfunction. Exosomes successfully delivered their cargo into inner retinal layers after intravitreal injection and the effects were reliant on miRNA, demonstrated by the diminished therapeutic effects of exosomes derived from BMSC after knockdown of Argonaute-2, a key miRNA effector molecule. RNAseq identified 43 miRNAs upregulated in BMSC exosomes in comparison to fibroblast exosomes. The role of individual miRNA in neuroprotection and identification of their targets in RGCs are under investigation. BMSC-derived exosomes promote similar therapeutic effects in two tested rat models of glaucoma. This study supports the use of BMSC-derived exosomes as a cell-free therapy for traumatic and degenerative ocular disease. Using the same ONC model as above, intravitreal injection of adeno-associated viral vectors to express a number of candidate proteins is being explored to provide neuroprotection and/or axon regeneration to injured RGC. Expression of some of these proteins led to a profound neuroprotective and partial restoration of visual functions and the molecular mechanisms are currently under investigation. We continued our investigations of the molecular mechanisms involved in the protection of retinal ganglion cells by PDGF-AA. Our data indicate that the neuroprotective effect of PDGF-AA in a rodent model of glaucoma could be mediated by astrocytes and/or a sub-population of amacrine cells. We suggest that after intravitreal injection of PDGF-AA, these cells respond by secreting factors that protect RGCs. The characterization of molecular changes in astrocytes and sub-population of amacrine cells expressing PDGFR is under investigation.
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