Stem cell therapy for retinal ganglion cell degeneration

The prospects of stem cell therapy for retinal ganglion cell (RGC) degeneration in human: RGC degeneration is a common pathologic cause of glaucoma and optic neuropathies, which are the leading cause of irreversible blindness and visual impairment in developed countries, currently affecting more than 100 million people worldwide. Intraocular pressure lowering can slow down glaucoma progression in a proportion of patients. Also, there is still no effective therapy for optic neuropathies. Besides, the degenerated RGCs in glaucoma cannot be repaired, and human retina has limited regenerative potential. Therefore, the development of new therapeutic treatments against RGC degeneration is needed. Cell replacement and neuroprotection are the principle strategies for glaucoma and optic neuropathy treatment. Replacing the diseased or degenerated cells by stem cell-derived RGCs should provide effective therapeutic treatment. However, complex circuitry in the retina makes cell replacement challenging and difficult for functional repair. Alternatively, neuroprotection is more realistic and applicable to preserve the patients’ vision. Numerous neuroprotection strategies have been investigated, including peripheral nerve grafting, electrical stimulation, application of neurotrophic factors (brain-derived neurotrophic factor (BDNF), ciliary neurotrophic factor (CNTF), glial cell-derived neurotrophic factor (GDNF) and nerve growth factor (NGF), direct intrinsic regeneration stimulation, RNA interference and human adult stem cells. Our group recently reported that the intravitreal transplantation of human periodontal ligament-derived stem cells (PDLSCs) ameliorates RGC degeneration after optic nerve injury in rats and promotes neural repair by enhancing axon regeneration through cell-cell interaction and neurotrophic factor secretion from PDLSCs (Cen et al., 2018). At present, there are 9 clinical trials on human adult stem cells for glaucoma and optic nerve diseases (www. clinicaltrials.gov/; Table 1). An emerging role of human adult stem cell therapy for glaucoma and optic neuropathy treatments is foreseeable in the near future.