Dynamic expression of bone morphogenetic protein 2 and its clinical significance after spinal cord injury in rat

English Keywords:Spinal cord injury  Bone morphogenetic protein 2  Rat

English Abstract:

  【Abstract】 Objective：To observe the dynamic expression of bone morphogenetic protein 2（BMP2） after spinal cord injury in rat，especially the changes on different time point and in different site，and to investigate the optimal time point and site for inhibiting BMP2 expression.Method：A total of 40 Sprague Dawley rats were randomly assigned into 5 groups：1-day-after-impact group，3-day-after-impact group，7-day-after-impact group，14-day-after-impact group and sham operation group with 8 rats in each group.After making skin incision centered as T10，the whole T10 and T9 and T11 partial laminar were removed to expose the spinal cord.Spinal cord injury models were created by NYU impactor.After that，behavior testing of all rats was assessed by using the Basso-Beattie-Bresnahan（BBB） locomotor rating scale before and after the perfusion.Each group of rats were perfused with 4% paraformaldehyde in heart on the 1st，3th，7th，14th day-after-impact，and then HE staining was used to observe the difference between the sham operation group and test groups.Meanwhile，immunohistochemistry was used to evaluate the level of BMP2 in the injuried region.Result：BBB score showed no significant difference among the spinal cord injury groups at the same time point（P＞0.05）.By HE staining， the tissue structure of sham operation group showed clear and orderly，on the contrary，it was disorderly in rest groups.According to the result of immunohistochemistry，significant difference was detected between the model group and sham operation group（P<0.05）.Compared with the sham operation group，the mean number of BMP2 positive cells in 1-day-after-impact group was 13.70±4.81 and 7.23±3.14 for the gray and white matter respectively，9.37±3.61 and 5.63±2.23 in 3-day-after-impact group，6.17±1.81 and 4.17±1.24 in 7-day-after-impact group，and 4.36±1.60 and 1.87±1.13 in 14-day-after-impact group.The BMP2-positive cells in gray matter increased more significantly than white matter（P<0.01）.Conclusion：The number of BMP2-positive cells increase after SCI，and reach peak at 14d，the specific inhibition of BMP2 should be performed in gray matter at 1d after SCI.