Intravitreally transplanted dental pulp stem cells promote neuroprotection and axon regeneration of retinal ganglion cells after optic nerve injury

Purpose To investigate the potential therapeutic benefit of intravitreally implanted dental pulp stem cells (DPSC) on axotomised adult rat retinal ganglion cells (RGCs) using in vitro and in vivo neural injury models. Methods Conditioned media collected from cultured rat DPSC and bone marrow-derived mesenchymal stem cells (BMSC) were assayed for nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF) and neurotrophin-3 (NT-3) secretion using ELISA. DPSC or BMSC were co-cultured with retinal cells, with or without Fc-TrK inhibitors, in a transwell system and the number of surviving βIII-tubulin+ retinal cells and length/number of βIII-tubulin+ neurites were quantified. For the in vivo study, DPSC or BMSC were transplanted into the vitreous body of the eye after a surgically-induced optic nerve crush injury. At 7, 14 and 21 days post-lesion (dpl), optical computerized tomography (OCT) was used to measure the retinal nerve fibre layer thickness as a measure of axonal atrophy. At 21 dpl, numbers of Brn-3a+ RGCs in parasagittal retinal sections and growth associated protein-43+ axons in longitudinal optic nerve sections were quantified as measures of RGC survival and axon regeneration, respectively. Results Both DPSC and BMSC secreted NGF, BDNF and NT-3, with DPSC secreting significantly higher titres of NGF and BDNF than BMSC. DPSC, and to a lesser extent BMSC, promoted statistically significant survival and neuritogenesis/axogenesis of βIII-tubulin+ retinal cells in vitro and in vivo where the effects were abolished after TrK receptor blockade. Conclusion Intravitreal transplants of DPSC promoted significant neurotrophin-mediated RGC survival and axon regeneration after optic nerve injury.