Death of Axotomized Retinal Ganglion Cells Delayed after Intraoptic Nerve Transplantation of Olfactory Ensheathing Cells in Adult Rats

Abstract

Intraorbital transection of the optic nerve (ON) always induces ultimate apoptosis of retinal ganglion cells (RGCs) and consequently irreversible defects of vision function. It was demonstrated that transplanted olfactory ensheathing cells (OECs) in partially injured spinal cord have a distant in vivo neuroprotective effect on descending cortical and brain stem neurons. However, this study gave no answers to the question whether OECs can protect the central sensitive neurons with a closer axonal injury because different neurons respond variously to similar axonal injury and the distance between the neuronal soma and axonal injury site has a definite effect on the severity of neuronal response and apoptosis. In the present study, we investigated the effect of transplanted OECs on RGCs after intraorbital ON transection in adult rats. Green fluorescent protein (GFP)-OECs were injected into the ocular stumps of transected ON and a significantly higher number of surviving RGCs was found together with a consistent marked increase in the mRNA and protein levels of BDNF in the ON stump and retina in the OEC-treated group at 7 days, but not 2 and 14 days, time point when compared to the control group. Our findings suggest that OEC transplantation induces the expression of BDNF in the ocular ON stump and retina and delays the death of axotomized RGCs at a certain survival period.