Tissue Factor Pathway Inhibitor-2 is Induced by Fluid Shear Stress in Vascular Smooth Muscle

Results: Microarrays identified tissue-pathway inhibitor-2 (TFPI-2) as the most differentially expressed gene by FSS in cultured SMCs. The regulatory effect of FSS on the expression of TFPI-2 was confirmed by RT-PCR and immunobloting demonstrating a more than 400-fold increase in TFPI-2 expression in SMCs exposed to FSS compared to static controls and a consistent upregulation at the protein level. Functionally, SMC proliferation was decreased by FSS and recombinant TFPI-2 was found to inhibit SMC proliferation and induce SMC apoptosis as indicated by activation of caspase-3. In vivo, TFPI-2 expression was found to be up-regulated 5, 10 and 20 h after rat carotid balloon-injury and immunohistochemistry demonstrated TFPI-2 protein in luminal SMCs exposed to FSS in rat carotid intimal hyperplasia 10 days after balloon-injury. Conclusion: FSS strongly influence gene expression in cultured SMCs and induce TFPI-2 expression, which is also expressed after rat carotid balloon injury in luminal SMCs exposed to FSS. Functionally, TFPI-2 may play an important role in vessel wall repair by regulating SMC proliferation and survival. Further studies are needed to elucidate the mechanisms by which TFPI-2 control SMC function.结果：基因芯片（Microarrays）鉴定显示，组织通路抑制剂2（TFPI-2）是培养的平滑肌细胞（smooth muscle cells, SMCs）中经FSS作用后差异表达最显著的基因。经逆转录聚合酶链式反应（RT-PCR）与免疫印迹实验验证，FSS对TFPI-2的表达具有调控作用：与静态培养对照组相比，暴露于FSS的SMCs中TFPI-2的mRNA表达量上调超过400倍，且蛋白水平亦呈现一致的上调趋势。功能层面，FSS可抑制SMCs增殖；重组TFPI-2同样能够抑制SMCs增殖，并通过激活半胱氨酸天冬氨酸蛋白酶3（caspase-3）诱导SMCs凋亡。体内实验结果表明，大鼠颈动脉球囊损伤后5、10、20小时，TFPI-2的表达均出现上调；免疫组化检测显示，球囊损伤后10天的大鼠颈动脉内膜增生模型中，暴露于FSS的管腔SMCs内可检测到TFPI-2蛋白。结论：FSS可显著调控培养的SMCs的基因表达，并诱导TFPI-2的表达；该基因在球囊损伤后暴露于FSS的大鼠颈动脉管腔SMCs中同样存在表达。功能层面，TFPI-2或可通过调控SMCs的增殖与存活，在血管壁修复过程中发挥重要作用。未来仍需开展进一步研究，以阐明TFPI-2调控SMCs功能的具体分子机制。