Tissue stem cells transplantation activates the growth of hepatic progenitor cells in recipient rat livers.

卵圆细胞和小肝细胞(SHS)分别被认为是肝脏干细胞和祖细胞。我们分别使用Thy1和CD44作为干细胞和祖细胞的标记。在本研究中，我们检测了Thy1+细胞的分化能力及其对肝脏再生的贡献。(1)Thy1+细胞可通过Thy1+/CD44+细胞向CD44+SHS分化。在胶原夹心培养条件下，Thy1+/CD44+细胞也可分化为胆管细胞。(2)移植的Thy1+细胞虽然只能形成少量病灶，但能增加小肝细胞样祖细胞(SHPC)的数量和大小。(3)将分离的SHS细胞与Thy1+细胞间接共培养，可促进SHS的增殖。这些结果提示，Thy1+细胞分泌的因子可能促进了肝祖细胞的生长。

Oval cells and small hepatocytes (SHs) are known to be hepatic stem and progenitor cells, respectively. We have used Thy1 and CD44 as markers of stem and progenitor cells, respectively. In the present study we examined the differentiation capacity of Thy1+ cells and their contribution to liver regeneration. (1) Thy1+ cells could differentiate to the CD44+ SHs through Thy1+/CD44+ cells. Thy1+/CD44+ cells could also differentiate into bile duct cells in collagen sandwich culture. (2) Although transplanted Thy1+ cells could form only a small number of foci, , they could increase the number and the size of resident small hepatocyte-like progenitor cells (SHPCs). (3) The proliferation of SHs isolated was enhanced when the cells were indirectly co-cultured with Thy1+ cells. These results suggest that growth of hepatic progenitor cells may be enhanced by factors secreted by Thy1+ cells.