CXCR4-FAK信号通路在低氧预处理骨髓间充质干细胞向大鼠脊髓缺血再灌注损伤组织迁移和粘附中的作用

Role of CXCR4-FAK signaling pathway in migration and adhesion of hypoxia-preconditioned bone marrow mesenchymal stem cells towards damaged tissues resulting from spinal cord ischemia-reperfusion injury in rats

目的探讨CXC趋化因子受体4-粘着斑激酶（CXCR4．FAK）信号通路在低氧预处理骨髓间充质干细胞（BMSC）向大鼠脊髓缺血再灌注损伤组织迁移和粘附中的作用。方法第一部分重组腺病毒介导绿色荧光蛋白基因转染成功的大鼠原代BMSC，以1×106个／ml密度接种于24孔培养板（1ml／μL），采用随机数字表法，将其分为5组（n=18）：对照组（C组）、常氧培养组（N组）、低氧预处理组（H组）、低氧预处理＋CXCR4拮抗剂AMD3100组（HA组）和低氧预处理＋FAK抑制剂粘着斑相关非激酶组（HF组）。N组BMSC在常氧环境中培养36h；H组BMSC在低氧环境中培养24h后在常氧环境中继续培养12h；HA组和HF组于低氧预处理前分别加入5μg／mlAMD3100和10μg／ml粘着斑相关非激酶。测定BMSC中基质细胞衍生因子-1α（SDF-1α）、CXCR4和磷酸化FAK（p-FAK）表达、BM-sc向SDF—1α迁移能力和BMSC与纤维粘连蛋白（FN）粘附能力。第二部分雄性SD大鼠216只，体重300～350g，其中210只采用阻断胸主动脉合并体循环低血压的方法制备脊髓缺血再灌注损伤模型。取脊髓缺血再灌注大鼠36只，分别于模型制备前、再灌注12h、1、3、5、7d（T0-5）时处死6只大鼠，取腰段脊髓组织，检测SDF—1α含量。其余脊髓缺血再灌注大鼠180只，采用随机数字表法，将其分为5组（n=36），于再灌注即刻分别鞘内注射C组DMEM培养液300μl和N组、H组、HA组、HF组1×10^6个／mlBMSC悬液300μl。分别于T0-5时取6只大鼠，进行神经行为学评分，然后取腰段脊髓组织，测定BMSC聚集度。结果与c组比较，N组BMSC的SDF—1α、CXCR4、P—FAK表达及其向SDF-1α迁移能力、与FN粘附能力、神经行为学评分和脊髓组织BMSC聚集度差异无统计学意义（P〉0．05）；与N组比较，H组BMSC的SDF—1α、CXCR4和p-FAK表达上调，向SDF-1α迁移能力、与FN粘附能力、神经行为学评分和脊髓组织BMSC聚集度升高（P〈0．05），HA组和HF组BMSC的p-FAK表达及其向SDF-1α迁移能力、与FN粘附能力、神经行为学评分和脊髓组织BMSC聚集度差异无统计学意义（P〉0．05）；与H组比较，HA组和HF组BMSC的p-FAK表达下调，向SDF-1α迁移能力、与FN粘附能力、神经行为学评分和脊髓组织BMSC聚集度降低（P〈0．05）。与T0时比较，T2-3时脊髓组织SDF-1α含量升高（P〈0．05）。结论低氧预处理通过CXCR4-FAK信号通路促进BMSC向大鼠脊髓缺血再灌注损伤组织迁移，并与之粘附，从而发挥脊髓保护作用。

Objective To investigate the role of CXC chemokine receptor 4-focal adhesion kinase （CXCR4-FAK） signaling pathway in migration and adhesion of hypoxia-preconditioned bone marrow mesencbymal stem cells （BMSCs） towards damaged tissues resulting from spinal cord ischemia-reperfusion （I/R） injury in rats. Methods Part I Rat BMSCs transfected with recombinant adenovirus-mediated green fluorescent protein gene 3 were seeded in 24-well plates and randomly divided into 5 groups （ n = 18 wells each） ：control group （group C）, normoxia-incubated group （group N）, HP group （group H）, HP ＋ CXCR4 antagonist AMD3100 group （group HA） and HP ＋ FAK inhibitor FAK-related nonkinase group （group HF）. In group C, BMSCs were incubated in DMEM culture medium. In group N, BMSCs were exposed to 21% 02-74% N2-5% CO2 for 36 h. In group H, BMSCs were exposed to 0. 5 % 02-94.5 % N2 -5.0 % CO2 for 24 h followed by 12 h exposure to normoxia. In groups HA and HF, 5 μg/ml AMD3100 and 10 ptg/ml FAK-related nonkinase were added to the culture medium before HP, respectively. The expression of stromal derived factor-1α （SDF-1α）, CXCR4 and phosphorylated FAK （p- FAK） in BMSCs was determined by Western blot. The migratory capability and adhesive ability of BMSCs were measured by Transwell invasive assay and fibronectin adhesive assay, respectively. Part II Two hundred and six- teen male Sprague-Dawley rats weighing 300-350 g were used and 210 out of the 216 rats underwent spinal cord ischemia by occlusion of the thoracic aorta combined with controlled hypotension. Thirty-six rats were chosen and sacrificed before spinal cord I/R and at 12 h and 1, 3, 5 and 7 days of reperfusion （T0-5 ） and the lumbar segment of spinal cord was removed for detection of the content of SDF-1α. The left 180 rats with spinal cord I/R were ran- domly divided into 5 groups （ n = 36 each）. IT DMEM medium 300μl was injected in group C and BMSC suspen- sion 300 tzl （1 x 106/ml） was injected in groups N, H, HA and HF immediately after onset of reperfusion. Neurological function was scored at T0-5 . The animals were then sacrificed and the lumbar segment of spinal cord was removed for detection of the degree of BMSC aggregation. Results There was no significant difference in the expres- sion of SDF-1α, CXCR4 and p-FAK, migratory capability and adhesive ability of BMSCs, neurological function scores and degree of BMSC aggregation between groups C and N （ P 〉 0. 05）. Compared with group N, the ex- pression of SDF-1α, CXCR4 and p-FAK was significantly up-regulated, and migratory capability and adhesive ability of BMSCs, neurological function scores and the degree of BMSC aggregation were increased in group H, while no significant change was found in the expression of p-FAK, migratory capability and adhesive ability of BM- SCs, neurological function scores and degree of BMSC aggregation in HA and HF groups （ P 〉 0.05 ）. Compared with group H, the expression of p-FAK was down-regulated and the migratory capability and adhesive ability of BMSCs, neurological function scores and degree of BMSC aggregation were decreased in groups HA and HF （ P 〈0. 05）. The content of SDF-1 a was significantly higher at T2.3 than at TO . Conclusion HP can promote migration and adhesion of BMSCs towards damaged tissues resulting from spinal cord I/R injury through CXCR4-FAK signaling pathway in rats; thus CXCR4-FAK signal pathway provides the protective effect on spinal cord.