AIM: To evaluate the protective effects of ciliary neurotrophic factor(CNTF)against retinal neurons damage in a rat model of diabetes mellitus(DM).

METHODS: Forty Sprague Dawley rats(weighing 250g-280g)received an intraperitoneal injection of streptozotocin(60mg/kg). The rats were then randomly divided into two groups: the treatment(DM+CNTF)or control(DM+BSS)group. The CNTF(0.5μg/μL)or balanced salt solution(2μL)was injected into the vitreus of the rats. Apoptosis of retinal ganglion cells(RGCs)was measured and retinal ultrastructure was assessed 4 and 12 weeks after establishing the model and performing the injections.

RESULTS: No difference in blood glucose or body weight was noted between the two groups. There were significantly fewer apoptotic RGCs in DM+CNTF group(8.56±1.22, P<0.05). From week 4, the neurons in the two groups of rats had degenerative changes(i.e., shrunken membrane disk spaces, swollen photoreceptor nuclei, and chromatin condensation)were noted on transmission electron microscopy. In DM+CNTF group, these abnormalities were improved by week 12.

CONCLUSION: CNTF has no significant effects on blood glucose levels or body weight in either group. CNTF shows protective effects on RGCs and photoreceptors based on apoptosis and transmission electron microscopy. Additional studies to establish the optimal time of administration and dosage of neurotrophic factors to achieve the greatest protective effects on retinal nerve tissue are warranted.