| Objective:1. To observe changes of neuropathology and function in the retinas of rats in early diabetic stage.2. To observe protective effects of CNTF against retinal neurons damage on diabetic rats in early diabetic stage.Methods:1. 60 male SD were randomly divided into 40 SD rats of DM model rats, and 20 SD rats of control model rats. The DM model rats were aged 8 weeks (weight between 250g and 280g ).The DM model rats were injected streptozotocin peritoneanouly at a dose of 60mg/kg body weight. Rats were diagnosed as diabetes when blood glucose concentration exceeded 16.7mmol/L after streptozotocin treatment 48 hours.2. At weekO, 4, 8, 12, 24, we observed diabetic rats and control model rats retinal structure, measured thickness of the inner plexiform layer, inner nuclear layer, and outer nuclear layer by light microscope. Apoptosis of RGCs was measured by TUNEL assay and apoptotic RGCs were counted. At week 4,12, 24, we observed retinal ultrastructure by transmission electron microscopy.3. We recorded the scotopic electroretinograph, oscillatory potentials O2-wave (OPS) and photopic electroretinograph (phot-ERG) response at OW, 4W, 8W, 12W, 24W in diabetic rats induced by streptozotocin and control model rats.4. 40 DM model rats were randomly divided into 2 groups: CNTF—treated group (DM+CNTF)and diabetes control group(DM+BSS). Ciliary neurotrophic factor were intravitieal injected in the eyes for CNTF—treated group, balanced satis solution were intravitieal injected in the eyes for diabetes control group. We recorded the ERG response at OW, 4W, 8W, 12W in two groups. Apoptosis of RGCs was measured by TUNEL assay and retinal ultrastructure was observed at 4W, 12W.Results:1. The diabetic rats which were induced by STZ in SD rats have a relatively high rate of success and steady processs. All eligible rats had the diabetic symptoms of polydipsia, polyphagia and polyuria after STZ administration. Blood glucose in diabetic rats was 28.01 ±2.04 mmol/ L and control model rats were normal. The control model rats had increased weight with its week age and the diabetic rats had a significantly reduced weight(p<0.01).2. The retinal consititutions in sections for general hematoxylin-eosin staining in diabetic rats were not different changes between control rats at 4W and 8W .And Different degree of lesion was found in diabetic rats of 12W and 24W group, including retinal edema (especially outer nuclear layer and nerve fiber layer) , disorder of cell structure and decrease of cells number. The thickness of the inner plexiform layer inner nuclear layer and outer nuclear layer were reduced(P<0.01) . And the thickness of the inner nuclear layer and outer nuclear layer were increased at 4W and 12W. The positive apoptotic RGCs were measured in ganglion cell layer by TUNEL assay. The number of apoptotic RGCs in diabetic rats was significantly higher than in control rats after 4W (P<0.01) . The retinal electron microphotographs in diabetic rats showed degenerative changes in neurons. Membrane disks were obscured and their spaces were distinctly enlarged, dividing and dissolving locally. Photoreceptor nuclei showed pykosis and chromatin condensation. The condrocyte in the inner segments of the rods swelled and even denatured.3. The results indicated that at the before onset of diabetes, the ERG of diabetic rats did not differ form control ones. At the 4W, the diabetic rats had changes of amplitudes and latency of oscillatory potentials. In addition, the change occurred earlier than another waves. The ERG of diabetic rats was different significantly from that of control rats during our observation.4. The Blood glucose and weight in CNTF—treated group (DM+CNTF)and diabetes control group(DM+BSS) were not changes (P > 0.05 ) . The number of apoptotic RGCs in CNTF—treated group was significantly lower than in diabetes control group at 12W by TUNEL assay (P<0.05) . From the 4 week on, we observed that the neurons of two groups had degenerative changes bytransmission electron microscopy. With the treatment of CNTF , the abnormalities were improved, such as the membrane disks spaces shrinked, photoreceptor nuclei were little swelled and chromatin condensation. The ERG of CNTF—treated group did differ form control ones, amplitudes and latency of ERG b-wave did significantly change at 12W. And the latency of oscillatory potentials delayed in diabetes control group than those in CNTF—treated group at 4W ( P<0. 01 ) .The amplitudes of ERG a-wave was lower in diabetes control group than those in CNTF-treated group at 12W (P<0. 05 ) .Conclusions:1. The result suggested that in early diabetic rats, there were some pathomophology changes in the ganglion cells, photoreceptors and membrane disks. The ERG changes which was characterized by significant elongated latency and declined amplitude had been detected in early diabetic rats. The positive apoptotic RGCs were measured in ganglion cell layer by TUNEL assay. And the thickness of the inner plexiform layer inner nuclear layer and outer nuclear layer were reduced.2. CNTF has no significant effects on the CNTF—treated group rats and diabetes control group such as blood glucose and weight. But treatment of CNTF showed a protective effects on RGCs and photoreceptors, and it could prevent the changes of ERG by decreasing the elongated latency and rising the descented amplitude. |
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