基于MR微血管成像技术在体研究肝纤维化发展过程中血管生成的作用

Liver fibrosis is a tissue repair reaction secondary to various forms of chronic liver injury. Several studies have shown that partial liver fibrosis is reversible, and early effective intervention is helpful for improving prognosis. But noninvasive accurate diagnosis and staging of liver fibrosis is still difficult and be a hot-topic clinical problem. Variety factors contributed to the progress of liver fibrosis and among them angiogenesis is increasing more attention. Experimental and clinical study had demonstrated that angiogenesis coexisted with liver fibrosis induced by variety cause, characterized by sinusoid capillarization. Pathological study also showed that the increased vessel density and the changing of interlobular vessel diameter during the process of angiogenesis. Liver fibrosis grading has obvious positive correlation with angiogenesis. Anti-angiogenesis treatment is recognized as a potential target for liver fibrosis treatment and need further explore from the perspective of angiogenesis. Our study intend to use advanced MR vessel size imaging, to evaluate quantitatively vessel size, density and focal blood volume in vivo, discuss the microcirculation changing during the different stage of liver fibrosis. We try to provide a new noninvasive method for early diagnosis of fibrosis, and also for potential dynamic monitoring the effects of anti-angiogenesis of liver fibrosis.

肝纤维化是继发于各种形式慢性肝损伤之后的组织修复反应。研究证实部分肝纤维化是可逆的，通过有效的干预有助于改善预后。但肝纤维化的无创性诊断和分期一直是临床的难点和热点问题。在肝纤维化发展过程中，多种因素对肝脏病变的持续发展起作用，其中血管生成（Angiogenesis）越来越受到重视。实验和临床研究均证实在各种病因导致的肝纤维化中都存在血管生成过程，以肝窦毛细血管化为特征，病理上证实存在着新生血管数量增加和肝内小叶间血管管径大小的变化。血管生成的程度同肝纤维化分级有明显的正相关性。已有研究表明，抗血管生成可作为肝纤维化治疗的潜在靶标，值得深入研究。本项目拟采用先进的MR微血管成像技术（VSI），通过实验研究，在体量化评估微血管大小和密度以及局部组织血容量的变化，探讨不同程度肝纤维化的微循环改变，有望为肝纤维化无创性早期诊断提供新的方向，也为潜在的抗血管生成疗效动态监测提供理想的手段。

肝纤维化进程中存在着以肝窦毛细血管化为特征的肝脏微循环改变。本研究通过建立不同阶段肝纤维化动物模型，联合肝窦形态学定量、电镜观察、免疫组化技术观察肝窦毛细血管化动态演变。结果显示，肝窦面积（SA）、肝窦周长（SP）、肝窦面积百分比（SA%）与纤维化分期呈显著负相关（r=-0.817、-0.820和-0.836），肝细胞面积肝窦周长指数（HA/SP index）与纤维化分期呈显著正相关（r=0.827），肝窦面积肝窦周长指数（SA/SP index）与纤维化分期呈轻度负相关（r=-0.364），肝窦内皮细胞（LSEC）窗孔数目、直径与纤维化分期呈显著负相关（r=-0.825和-0.911，P＜0.0001），MVDdensity、MVDarea均与纤维化分期呈中等正相关（r=0.623、0.590, P=0.000）。. 通过IVIM-DWI及DCE-MRI检查，得到定量参数D、D*、f值、Ktrans、Kep、Ve和iAUC，证实其与纤维化分期及血管生成指标具有相关性；通过MRI 血管大小成像（VSI）及二维剪切波弹性成像（SWE）获得Q、VVF、Nu、mVD值及肝硬度（LS）值。VVF值与SA、SA%、SP值呈显著正相关（r=0.627~0.642, P=0.000），与HA/SP呈中等负相关（r=-0.467, P=0.004），其诊断F2和F3期纤维化的敏感度为91.30%、73.68%，特异度为80.00%、85.71%，AUROC为0.917、0.857，与SWE比较无统计学差异（P=0.6368和0.3672），但不能诊断F4期肝纤维化。Nu值与SA、SP、HA/SP值呈中等负相关（r=-0.490~-0.418, P=0.002~0.01），其诊断F2~F4期纤维化的敏感度为86.96%、63.16%、85.71，特异度为80.00%、85.71%、69.23%，AUROC为0.765、0.767、0.764，与SWE比较无统计学差异（P= 0.2495、0.5949、0.4943、0.8302）。表明VSI可以反映肝纤维化过程中肝窦微血管变化，可用于肝纤维化诊断分期，从而建立了基于微血管解剖及血流动力学特征的多模态MRI灌注成像无创性定量评估肝纤维化的诊断体系，为临床转化应用提供了实验依据。