The Neuroprotective Effect of Human CD 34 Positive Stem Cells on the Survival of Injured Retinal Ganglion Cells

Purpose: To assess the neuroprotective effect of CD 34+ stem cells on retinal ganglion cell (RGC) survival after optic nerve compression injury (ONCI). Methods: The optic nerve compression injury was obtained through exerting pressure on the optic nerve 1 mm behind the eye globe for duration of 60 seconds. This compression was conducted using a stereotactic device attached to small forceps after good exposure to optic nerve. Treatment of ONCI model was done through intravenous administration of 3,000,000 CD34+ stem cells intravenous through rat tail was done six hours after the onset of the nerve crush injury. Evaluation of the effect of CD34 positive stem cells on injured retinal cells was obtained 6 days after ONCI through the following: (1) immunohistochemistry through Brn-3b labelled RGCs and, (2) electrophysiological changes was studied using F-VEPS after dark adaptation period. Results: Brn-3b labeled RGCs density was found with an average of 1490 /70074 µm² in the normal retina of adult female Wistar rat animal, in compared to 366 / 70074 µm² in the retina of non treated ONCI. Flash–Visual Evoked potentials (f-VEPs) were prolonged from 50 msec in control rats to 110 msec in experimental rats after treatment with stem cells, there was an increase in the number of RGCs with an average of 999 / 70074 μm² and reduction in the latency of F. VEPs to 91 msec in the CD 34 + treated group. Conclusion: Intravenous administration of 3,000,000 human umbilical cord blood CD 34+ stem cells may have a potential neuroprotective effect on damage/injured retinal ganglion cells manifested by an increase in the survival of retinal ganglion cells (56%)and an improvement in the latency period of f-VEPs in the optic nerve compression injury model treated with stem cells (33%).