Young bone marrow Sca-1⁺ stem cells home to aged retina and protect retina from acute glaucoma injury

Abstract

Purpose : Glaucoma is a major clinical ocular disorder, especially prevalent in the aged population. Retinal ganglion cell (RGC) apoptosis and optic nerve degeneration in aged glaucoma patients typically result in blindness. Recently, we demonstrated that young bone marrow (BM) stem cells can regenerate aged tissue and enhance tissue repair. This study investigated whether BM-derived stem cell homing to the retina increased regeneration/repair mechanisms in the retina using a mouse model of this neurodegenerative disease.

Methods : Young BM stem cell antigen 1 (Sca-1⁺) and Sca-1^- cells from GFP⁺ mice (2-3 months old) were isolated by immunomagnetic cell sorting and transplanted into lethally-irradiated aged recipient mice (20-22 months old) to generate Sca-1⁺ [Y(Sca1⁺)-O] and Sca-1^- [Y(Sca1^-)-O] chimeras. Homing efficiency of Sca-1 cells in chimeric aged mice was evaluated by immunostaining. Acute ocular hypertensive glaucoma was induced 8 weeks after BM reconstitution and vision function was evaluated by the light/dark exploration and optomoter tests. Western blot and RT-qPCR were performed for mechanistic analyses.

Results : The light/dark exploration and optomoter tests showed better preservation of visual function in Sca-1⁺ than Sca-1^- chimeras (p<0.05, n=10/group) 7 days after induction of acute ocular hypertension. Sca-1⁺ cells had greater capability to home to the retina (p<0.01, n=4-6/group) than Sca-1^- cells. There was more cell differentiation into glia, microglia and neural cells in the Sca-1⁺ than Sca-1^- group (p<0.05, n=4) after retinal injury. Furthermore, Sca-1⁺ cells in the retina prevented cellular apoptosis of host retinal cells (p<0.01, n=6/group). Exploration of potential mechanisms revealed that fibroblast growth factor 2 (FGF2) expression increased significantly in Sca-1⁺ chimeras compared to Sca-1^- chimeras after acute glaucoma injury. In vitro study also demonstrated that Sca-1⁺ cells had higher expression levels of FGF2 (both mRNA and protein) than Sca-1^- cells (p<0.01). After application of an FGF2-neutralizing antibody, activation of the Akt pathway was blocked, and the beneficial effects of Sca-1⁺ cells were lost.

Conclusions : Homed BM Sca-1 cells in the retina prevented cellular apoptosis after acute glaucoma injury in aged mice. FGF2 and its signal pathway may play an important role in BM Sca-1 cell-mediated retinal neuroprotection.

This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.