慢性颈脊髓压迫症大鼠髓内基膜超微结构变化及其与MMP-9表达的相关性

Ultrastructural changes of microvascular basement membrane and correlationship with MMP-9 expression in rat model with chronic cervical cord compression

中文关键词:  基膜  慢性脊髓压迫  超微结构  基质金属蛋白酶-9  大鼠

英文关键词:Basement membrane  Chronic spinal cord compression  Ultrastructure  MMP-9  Rat

中文摘要:

  【摘要】 目的：观察慢性颈脊髓压迫症大鼠模型髓内基膜（basement membrane，BM）、基膜与星形细胞接触面（basement membrane-astrocyte contacts，BM-AC）的超微结构变化，并探讨其与基质金属蛋白酶-9（matrix metalloproteinase-9，MMP-9）表达的相关性。方法：72只雄性SD大鼠随机分为对照组（n=36）和实验组（n=36），对照组仅切除C5左侧椎板；实验组在切除C5左侧椎板后将吸水可膨胀聚氨酯薄板置入C6水平左侧椎板下硬膜外，建立慢性颈脊髓压迫模型，应用BBB（Basso Beattie Bresnahan）评分评价大鼠脊髓神经功能，并分别于造模后1d、14d、21d、28d、42d、70d取C5~C6段脊髓组织制备标本，用HE染色观察脊髓形态学变化、用MMP-9免疫组化染色检测脊髓MMP-9表达量，用透射电镜观察脊髓BM及BM-AC的变化。结果：对照组各时间点间BBB评分和实验组造模后1d的BBB评分无显著性差异，实验组造模后14d~70d的5个时间点BBB评分均显著性低于同时间点对照组（P<0.05）。HE染色显示对照组各时间点及实验组造模后1d的脊髓未见受压，脊髓形态结构正常；实验组造模后1d可见脊髓白质区轻度水肿；造模后14d脊髓受压变形，灰质区血管增生，灰质、白质水肿，神经元细胞核碎裂；造模后21d和28d损伤逐渐加重；造模后42d脊髓水肿减轻，髓内空泡化，前角大运动神经元数目减少、胞浆稀少、胞核萎缩，突触减少，神经纤维稀疏，髓鞘层变薄；造模后70d仍见白质区水肿、神经元细胞核碎裂，灶性胶质细胞增生等退行性变，神经元数目增多。MMP-9免疫组化显示对照组各时间点及实验组造模后1d、70d脊髓MMP-9均呈弱表达，实验组造模后14d 呈较强表达，21d呈强表达，28d呈较强表达，42d呈中度表达。对照组各时间点及实验组压迫后1d的BM电子密度及BM-AC均正常，实验组造模后14d~28d BM电子密度、BM-AC比率与对照组比较显著性降低（P<0.05）；实验组造模后42d、70d两者较前升高（P<0.05），但仍显著低于对照组水平（P<0.05）。MMP-9表达与BM电子密度及BM-AC变化呈负相关，相关系数分别为-0.892（P<0.001）和-0.664（P<0.001）。结论：慢性颈脊髓压迫性损伤后早期髓内BM降解、BM-AC分离，后期部分修复。MMP-9可能通过降解BM及BM-AC影响脊髓压迫后血脊髓屏障的完整性。

英文摘要:

  【Abstract】 Objectives: To investigate the temporal ultrastructural changes of microvascular basement membrane(BM) and basement membrane astrocyte contacts(BM-AC) in rat model with chronic cervical cord compression, and to explore their correlation with the expression of matrix metalloproteinase-9(MMP-9). Methods: 72 SD rats were randomly divided into the control group(n=36) and the experimental group(n=36). In the control group, C5 left semi-laminectomy was performed in each rat. In the experimental group, a water-absorbable polyurethane polymer was implanted into C6 left epidural space after C5 left semi-laminectomy. The Basso Beattie Bresnahan(BBB) score was used to evaluate the neurological function. HE staining, immumohistochemical staining and transmission electron microscopy(TEM) were performed at 1 day, 14 days, 21 days, 28 days, 42 days and 70 days after modeling to observe the changes of morphology, MMP-9 expression and ultrastructural changes of BM and BM-AC. Results: According to the BBB score, there was no significant difference between each time point in the control group and one day after modeling in the experimental group, neurological function in the experimental group showed an obvious decline from 14 days to 70 days after modeling(P<0.05). HE staining showed intact spinal cords at each time point in the control group. In the experimental group, a mild edema in white matter without spinal cord compression was shown at 1 day after modeling. The compressive deformation of spinal cord, vascular proliferation in grey matter, edema in white and grey matter and the fragmetation of nucleus in neurons were showen at 14 days after modeling. The damage was aggravated at 21 days and 28 days after modeling. At the 42th day after modeling, decreasing of edema in the spinal cord, intramedullary cavity, reducing number of motor neurons in the front foot of spinal cord, sparse cytoplasm, shrinking nucleus, reducing number of synapsis, sparse nerve fibers, the thinner layer of myelin were found. At the 70th day in the experimental group, edema in the white matter, the fragmetation of nucleus in neurons, focal hyperplasia of glial cells, increasing number of neurons were shown. The immunohistochemical staining displayed that MMP-9 was weakly expressed in the control group, and the same results were found at 1 day and 70 days after modeling in the experimental group. Strong expression of MMP-9 was found at 14 days and 28 days after modeling in the experimental group, strongest expression at 21 days after modeling, and moderate expression at 42 days after modeling in the experimental group. The proportion of BM-AC and electron density of BM in the experimental group decreased significantly at 14-28 days after modeling, and improved since the 42nd day after modeling(including the 70th day), but were still significantly lower than those in the control group(P<0.05). There was no significant difference between each time point in the control group and 1 day after modeling in the experimental group. MMP-9 expression was negatively correlated with the proportion of BM-astrocyte contacts(r=-0.664, P<0.001) and the BM density(r=-0.892, P<0.001). Conclusions: The BM and BM-AC are damaged after chronic cervical cord compression and rehabilitated incompletely at late stage. MMP-9 may affect the integrity of blood-spinal cord barrier by de?鄄grading the BM and BM-AC after spinal cord compression.