Role of endothelial progenitor cells in optic nerve injury of rats

Abstract

To investigate the role of endothelial progenitor cells (EPC) in the injury of rat optic nerve. An experimental study. The rat model of optic nerve injury was created by fluid percussion brain injury device (FPI). On hundred and eight rats (108 eyes) were divided into 2 groups randomly. Each group was further divided into 9 subgroups by the time of injury (24 h before and 3, 12, 24, 48, 72 h, 1, 2 and 3 weeks after the injury). The number of circulating EPCs was measured, HE staining of the optic nerve, immunohistochemistry study of CD31 (markers of vascular endothelial cells) and flash-visual evoked potential (F-VEP) were observed at every time point. Two independent sample t-test was used for the comparison between the control group and the optic nerve injury groups at the same time point. The correlation between different items was analyzed by Pearson test. P value less than 0.05 was considered significant. The number of EPCs in normal rats was 46-52/200 000 monocytes. After traumatic optic nerve injury, the number of EPCs was (34 ± 4, 34 ± 5, 69 ± 9, 76 ± 6, 107 ± 9, 69 ± 7, 58 ± 6 and 56 ± 4)/200 000 monocytes at 3, 12, 24, 48, 72 h, and 1, 2 and 3 weeks. The difference of number of EPCs between the experiment and control groups was significant at 3, 12, 24, 48, 72 h and 1 and 2 weeks after the injury (t = 5.29, 2.90, -4.30, -7.61, -14.17, -5.74 and -2.79; P < 0.05). The number of CD31(+) cell in the optic nerve and surround tissues in normal rats was (7-9)/5 high magnification field. After the injury, the number of CD31(+) cell was 8.36 ± 1.52, 7.17 ± 1.10, 10.41 ± 1.92, 11.43 ± 1.58, 14.29 ± 2.03, 17.33 ± 1.47, 17.86 ± 1.22 and 18.13 ± 1.40 at different time points. The difference of number of CD31(+) cell between the experiment and control groups was significant at 48, 72 h, and 1, 2, and 3 weeks after the injury (t = 4.31, -7.61, -8.17, -10.08, and -10.79; P < 0.05). The number of microvessels in the optic nerve and surround tissues in normal rats was 6-9/5 high magnification field. After traumatic optic nerve injury, the number of microvessels was 7.54 ± 2.01, 8.52 ± 2.21, 11.02 ± 1.62, 15.40 ± 2.04, 18.39 ± 1.96, 23.21 ± 1.50, 22.78 ± 2.40 and 24.13 ± 2.51 at different time points. The difference of number of microvessels between the experiment and control groups was significant at 48, 72 h, 1, 2, and 3 weeks after the injury (t = 4.25, -7.74, -8.26, -10.28 and -11.49; P < 0.05). The latency period of P waves was decreased at 3 h and increased to above basic level at 24 h, and then tend to be stable. The difference of latency period of P waves between the experiment and control groups was significant at 3, 12, 24, 48, 72 h, 1, 2 and 3 weeks after the injury (t = 4.15, 3.74, 5.84, 6.08, 6.40, 6.52, 6.53 and 6.61; P < 0.05). The amplitude of F-VEP was decreased at 3 h and increased to the basic level at 12 h, then decreased to below the basic level gradually. The difference of the amplitude of F-VEP between the experiment and control groups was significant at 3, 24, 48, 72 h, 1, 2 and 3 weeks after the injury (t = 3.95, 4.14, 5.26, 5.78, 6.49, 6.72 and 6.23; P < 0.05). The number of EPCs was correlated with the number of CD31(+) cell, microvessels and F-VEP (r = 0.43, 0.41 and 0.43; P < 0.01). The present study showed that the number of EPCs in the blood increases significantly after traumatic optic nerve injury, and the cells can arrive the traumatic area to repair injured tissue and enhance angiogenesis.