Therapeutic strategies for glaucoma and optic neuropathies.

Glaucoma is a neurodegenerative eye disease that causes permanent vision impairment. The main pathological characteristics of glaucoma are retinal ganglion cell (RGC) loss and optic nerve degeneration. Glaucoma can be caused by elevated intraocular pressure (IOP), although some cases are congenital or occur in patients with normal IOP. Current glaucoma treatments rely on medicine and surgery to lower IOP, which only delays disease progression. First-line glaucoma medicines are supported by pharmacotherapy advancements such as Rho kinase inhibitors and innovative drug delivery systems. Glaucoma surgery has shifted to safer minimally invasive (or microinvasive) glaucoma surgery, but further trials are needed to validate long-term efficacy. Further, growing evidence shows that adeno-associated virus gene transduction and stem cell-based RGC replacement therapy hold potential to treat optic nerve fiber degeneration and glaucoma. However, better understanding of the regulatory mechanisms of RGC development is needed to provide insight into RGC differentiation from stem cells and help choose target genes for viral therapy. In this review, we overview current progress in RGC development research, optic nerve fiber regeneration, and human stem cell-derived RGC differentiation and transplantation. We also provide an outlook on perspectives and challenges in the field.

AAV2-Mediated Expression of HspB1 in RGCs Prevents Somal Damage and Axonal Transport Deficits in a Mouse Model of Ocular Hypertension.

Purpose: Ocular hypertension is a significant risk factor for vision loss in glaucoma caused by the death of retinal ganglion cells (RGCs). We investigated whether small heat shock proteins (sHsps) expressed in RGCs protect those cells against ocular hypertension in mice. Methods: AAV2 vectors encoding genes for one of the following four human sHsps: HSPB1, HSPB4, HSPB5, or HSPB6 were constructed for RGC-specific expression. Ischemia/reperfusion was induced by elevating the intraocular pressure (IOP) to 120 mm Hg for one hour, followed by a rapid return to normal IOP. Microbeads (MB) were injected into the anterior chamber of mice to induce ocular hypertension. RGC death and glial activation were assessed by immunostaining for Brn3a, RBPMS, Iba1, and glial fibrillary acid protein in retinal flat mounts. RGC axonal defects were evaluated by anterograde transport of intravitreally injected cholera toxin-B. RGC function was assessed by pattern electroretinography. Results: Among the sHsps, HspB1 offered the best protection against RGC death from ischemia/reperfusion injury in the mouse retina. Intravitreal administration of AAV2-HSPB1 either two weeks before or one week after instituting ocular hypertension resulted in significant prevention of RGC loss. The MB-injected mice showed RGC axonal transportation defects, but AAV2-HSPB1 administration significantly inhibited this defect. AAV2-HSPB1 prevented glial activation caused by ocular hypertension. More importantly, a single injection of AAV2-HSPB1 protected RGCs long-term in MB-injected eyes. Conclusions: The administration of AAV2-HSPB1 inhibited RGC death and axonal transport defects and reduced glial activation in a mouse model of ocular hypertension. Translational Relevance: Our results suggested that the intravitreal delivery of AAV2-HSPB1 could be developed as a gene therapy to prevent vision loss on a long-term basis in glaucoma patients.