Analysis of liver regeneration : A study using c-kit mutants

我们研究了在肝再生过程中骨髓（BM）细胞是否可以定向为肝组成细胞。将绿色荧光蛋白（GFP）转基因小鼠的BM细胞移植到全身照射后的W/W^v c-kit突变小鼠中。在得到的W/W^v（BMT-W/W^v）小鼠中，在门静脉周围区域观察到GFP阳性细胞。当给BMT-W/W^v小鼠注射CCl_4或抗Fas抗体时，GFP阳性细胞沿肝窦沿着生长。最近的研究表明，c-kit受体酪氨酸激酶（KIT）在幼鼠肝脏中有表达，在胆总管结扎（BDL）后，其在胆汁上皮细胞（BEC）中的表达上调。为了阐明KIT在BEC中的作用，我们研究了Ws/Ws c-kit突变大鼠BEC是否可以在BDL后胆汁淤积中增殖。2周龄正常（+/+）和Ws/Ws大鼠行BDL后，Ws/Ws大鼠门脉野仅出现少量BEC，而+/+大鼠门脉野出现大量BBC。Ki-67免疫组化显示2周龄Ws/Ws大鼠BEC增殖活性明显低于同龄+/+大鼠。相反，当6周龄+/+和Ws/Ws大鼠进行BDL时，BEC在+/+和Ws/Ws大鼠的肝脏中类似地增殖，并且BEC的增殖活性相当。这是可能的机制，BEC增殖响应胆汁淤积后BDL 2周龄和6周龄大鼠之间是不同的，KIT介导的信号转导在未成熟的BEC在年轻大鼠的增殖中起着至关重要的作用。

We examined whether bone marrow (BM) cells can commit to liver-consisting cells during liver regeneration. BM cells of green fluorescent protein (GFP) transgenic mice were transplanted into W/W^v c-kit mutant mice after whole-body irradiation. In the resulting W/W^v (BMT-W/W^v) mice, GFP positive cells were observed at the periportal region. When CCl_4 or anti-Fas antibody was administered to BMT-W/W^v mice, GFP positive cells developed along liver sinusoid. These results suggest that BM cells differentiate to sinusoid endothelial cells during liver regeneration.Recently, it has been shown that the expression of c-kit receptor tyrosine kinase (KIT) is seen in the liver of young rats, and its expression is up-regulated in bile epithelial cells (BEC) after ligation of the common bile duct (BDL). To clarify a role of KIT in BEC, we examined whether BEC of Ws/Ws c-kit mutant rats could proliferate in response to bile stasis after BDL. When 2-week-old normal (+/+) and Ws/Ws rats underwent BDL, only a few BEC were found in the portal field of livers of Ws/Ws rats, whereas many BBC were found in that of +/+ rats. Furthermore, Ki-67 immunostaining showed that the proliferative activity of BEC in 2-week-old Ws/Ws rats was much lower than that of +/+ rats of the same age. In contrast, when 6-week-old +/+ and Ws/Ws rats underwent BDL, BEC similarly proliferated in the livers of +/+ and Ws/Ws rats, and the proliferative activity of BEC was comparable. It is likely that the mechanism whereby BEC proliferate in response to bile stasis after BDL is different between 2-week-old and 6-week-old rats, and KIT mediated-signal transduction plays a crucial role in the proliferation of immature BEC in young rats.