Direct optic nerve sheath (DONS) application of Schwann cells prolongs retinal ganglion cell survival in vivo.

Cell-based therapies are increasingly recognized as a potential strategy to treat retinal neurodegenerative disease. Their administration, however, is normally indirect and complex, often with an inability to assess in real time their effects on cell death and their migration/integration into the host retina. In the present study, using a partial optic nerve transection (pONT) rat model, we describe a new method of Schwann cell (SC) delivery (direct application to injured optic nerve sheath, SC/DONS), which was compared with intravitreal SC delivery (SC/IVT). Both SC/DONS and SC/IVT were able to be assessed in vivo using imaging to visualize retinal ganglion cell (RGC) apoptosis and SC retinal integration. RGC death in the pONT model was best fitted to the one-phase exponential decay model. Although both SC/DONS and SC/IVT altered the temporal course of RGC degeneration in pONT, SC/DONS resulted in delayed but long-lasting effects on RGC protection, compared with SC/IVT treatment. In addition, their effects on primary and secondary degeneration, and axonal regeneration, were also investigated, by histology, whole retinal counting, and modelling of RGC loss. SC/DONS was found to significantly reduce RGC apoptosis in vivo and significantly increase RGC survival by targeting secondary rather than primary degeneration. Both SC/DONS and SC/IVT were found to promote RGC axonal regrowth after optic nerve injury, with evidence of GAP-43 expression in RGC somas and axons. SC/DONS may have the potential in the treatment of optic neuropathies, such as glaucoma. We show that SC transplantation can be monitored in real time and that the protective effects of SCs are associated with targeting secondary degeneration, with implications for translating cell-based therapies to the clinic.

Effect of the Aß aggregation modulator MRZ-99030 on retinal damage in an animal model of glaucoma.

Several lines of evidence suggest that there are similarities in the pathomechanisms of glaucoma and Alzheimer's disease, and that amyloid-beta (Aß) could be a new, promising target for neuroprotective therapy of glaucoma. In the present study, we evaluated the effect of the Aß aggregation modulator MRZ-99030 in the Morrison model of glaucoma based on increased intraocular pressure (IOP) in rats. MRZ-99030 provided dose-dependent neuroprotection and at the highest dose (240 mg/kg) reduced the degree of RGC apoptosis to 33 % of that seen after vehicle (P < 0.05; one-way ANOVA). No significant effect on IOP was observed. Pharmacokinetic experiments showed that following systemic injection of MRZ-99030, concentrations above affinity for Aß were reached. Hence the present results are consistent with the notion that Aß is a promising target for neuroprotective intervention in glaucoma and that MRZ-99030 may be a good drug candidate for further development.

Imaging multiple phases of neurodegeneration: a novel approach to assessing cell death in vivo.

Nerve cell death is the key event in all neurodegenerative disorders, with apoptosis and necrosis being central to both acute and chronic degenerative processes. However, until now, it has not been possible to study these dynamically and in real time. In this study, we use spectrally distinct, well-recognised fluorescent cell death markers to enable the temporal resolution and quantification of the early and late phases of apoptosis and necrosis of single nerve cells in different disease models. The tracking of single-cell death profiles in the same living eye over hours, days, weeks and months is a significant advancement on currently available techniques. We identified a numerical preponderance of late-phase versus early-phase apoptotic cells in chronic models, reinforcing the commonalities between cellular mechanisms in different disease models. We showed that MK801 effectively inhibited both apoptosis and necrosis, but our findings support the use of our technique to investigate more specific anti-apoptotic and anti-necrotic strategies with well-defined targets, with potentially greater clinical application. The optical properties of the eye provide compelling opportunities for the quantitative monitoring of disease mechanisms and dynamics in experimental neurodegeneration. Our findings also help to directly observe retinal nerve cell death in patients as an adjunct to refining diagnosis, tracking disease status and assessing therapeutic intervention.