Van Hul Noémi K M, Abarca-Quinones Jorge, Sempoux Christine, Horsmans Yves, Leclercq Isabelle A
Laboratory of Gastroenterology, Faculty of Medicine, Université Catholique de Louvain, Brussels, Belgium.
Hepatology. 2009 May;49(5):1625-35. doi: 10.1002/hep.22820.
In chronic liver injury, liver progenitor cells (LPCs) proliferate in the periportal area, migrate inside the lobule, and undergo further differentiation. This process is associated with extracellular matrix (ECM) remodeling. We analyzed LPC expansion and matrix accumulation in a choline-deficient, ethionine-supplemented (CDE) model of LPC proliferation. After day 3, CDE induced collagen deposits in the periportal area. Expansion of LPCs as assessed by increased number of cytokeratin 19 (CK19)-positive cells was first observed at day 7, while ECM accumulated 10 times more than in controls. Thereafter, LPCs and ECM increased in parallel. Furthermore, ECM not only accumulates prior to the increase in number of LPCs, but is also found in front of LPCs along the porto-venous gradient of lobular invasion. Double immunostaining revealed that LPCs are embedded in ECM at all times. Moreover, LPCs infiltrating the liver parenchyma are chaperoned by alpha-smooth muscle actin (alpha-SMA)-positive cells. Gene expression analyses confirmed these observations. The expression of CK19, alpha-fetoprotein, E-cadherin, and CD49f messenger RNA (mRNA), largely overexpressed by LPCs, significantly increased between day 7 and day 10. By contrast, at day 3 there was a rapid burst in the expression of components of the ECM, collagen I and laminin, as well as in alpha-SMA and connective tissue growth factor expression.
Our data demonstrate that, in a CDE model, ECM deposition and activation of matrix-producing cells occurred as an initial phase, prior to LPC expansion, and in front of LPCs along the porto-venous gradient of lobular invasion. Those observations may reveal a fundamental role for the established hepatic microenvironment or niche during the process of activation and differentiation of liver progenitor cells.
在慢性肝损伤中，肝祖细胞（LPCs）在门静脉周围区域增殖，向小叶内迁移，并进一步分化。这一过程与细胞外基质（ECM）重塑有关。我们在胆碱缺乏、乙硫氨酸补充（CDE）的LPC增殖模型中分析了LPC的扩增和基质积累情况。在第3天后，CDE诱导门静脉周围区域出现胶原沉积。通过细胞角蛋白19（CK19）阳性细胞数量增加评估的LPC扩增在第7天首次观察到，而ECM的积累比对照组多10倍。此后，LPCs和ECM并行增加。此外，ECM不仅在LPC数量增加之前积累，而且在沿小叶侵袭的门静脉梯度方向上LPCs的前方也有发现。双重免疫染色显示LPCs始终嵌入在ECM中。此外，浸润肝实质的LPCs由α-平滑肌肌动蛋白（α-SMA）阳性细胞陪伴。基因表达分析证实了这些观察结果。LPCs大量过表达的CK19、甲胎蛋白、E-钙黏蛋白和CD49f信使核糖核酸（mRNA）的表达在第7天至第10天之间显著增加。相比之下，在第3天，ECM成分、胶原I和层粘连蛋白以及α-SMA和结缔组织生长因子的表达迅速爆发。
我们的数据表明，在CDE模型中，ECM沉积和基质产生细胞的激活作为初始阶段发生在LPC扩增之前，并在沿小叶侵袭的门静脉梯度方向上LPCs的前方。这些观察结果可能揭示了既定的肝微环境或生态位在肝祖细胞激活和分化过程中的重要作用。
