[Retinal cell apoptosis, microvascular changes and expression of connective tissue growth factor in experimental...

To study the cell apoptosis and the expression of connective tissue growth factor (CTGF) in the retina of diabetic rats and to explore their contributions to the changes of microcirculation.

It was a experiment study. Fifty-five adult male Wistar rats were divided into two groups, normal control group (CON, 10 rats) and diabetes mellitus group (DM, 45 rats). The 30 surviving rats in the DM group were further divided into 3 groups based on the time of observation, 2 month (DM2), 4 month (DM4) and 6 month (DM6) groups, with 10 rats in each group. Cell apoptosis was detected by TdT-mediated dUTP nick end labeling (TUNEL). Expression of CTGF was determined by immunohistochemical study. Retinal vessels were observed by retinal digest stretched periodic acid Schiff (PAS) staining.

Immunohistochemical staining and TUNEL staining revealed negative results in normal control group. Retinal cell apoptosis index increased gradually from DM2 to DM6, the differences between any two groups were statistically significant (t(2-4, 2-6, 4-6) = 21.432, 50.843, 29.410; P < 0.05). Expression of CTGF in the retina increased from DM2-DM6, the differences between any two groups were statistically significant (t(2-4, 2-6, 4-6) = 15.345, 26.316, 10.971; P < 0.05). PAS staining of retinal blood vessels obtained negative results in the CON and DM2 groups. Part of retinal capillaries were slightly stiff and narrow in DM4 group. Retinal capillaries in DM6 group were trunk stiff and were narrowed obviously. The number of pericytes was reduced in DM4, and progressed following the course of diabetes. The number of pericytes in the DM2 group did not different from that in the CON group (t = 0.875, P = 0.387). The number of pericytes in the DM4 and DM6 group were significantly decreased as compared to the CON group (t = 3.367, 6.667; P < 0.05). Retinal cellular apoptosis index had a significant positive correlation to the expression of CTGF (r = 0.958, P < 0.05). Number of pericytes was significantly correlated (negative correlation) with retinal cellular apoptosis index and the expression of CTGF (r = -0.540, -0.595; P < 0.05).

The appearances of cellular apoptosis and fibrosing factor CTGF in the retina of diabetic rats occurred earlier than the changes of microcirculation and the number of capillary pericytes.