Liver Progenitor Cells Fold Up a Cell Monolayer into a Double-layered Structure during Tubular Morphogenesis
Liver Progenitor Cells Fold Up a Cell Monolayer into a Double-layered Structure during Tubular Morphogenesis
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DOI：
10.1091/mbc.e08-02-0177
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发表时间：
2009-05-01
影响因子：
3.3
通讯作者：
Mostov, Keith E.
中科院分区：
文献类型：
--
作者：
Tanimizu, Naoki;Miyajima, Atsushi;Mostov, Keith E.
胆管是由胆管细胞排列的肝小管结构，胆管细胞是一种肝上皮细胞。胆管细胞首先在门静脉周围形成单层细胞，称为胆管板，最终形成胆管分支管状网络。胆管形态发生的过程尚不清楚：在管腔形成之前，胆管细胞增殖复制单层管板的传统模型似乎与肝母细胞（肝祖细胞）分化为胆管细胞时增殖显著减少的观察结果不一致。在这里，我们开发了一种新的培养系统，在该系统中，肝祖细胞系HPPL在覆盖含有I型胶原蛋白和基质凝胶的情况下，从单层结构重组为管状结构。我们发现单层中的一些HPPL去极化并迁移到单层折叠成双细胞层。这些形态发生过程无需细胞增殖，需要磷脂酰肌醇3-激酶和Akt活性。在后来的形态发生中，两层细胞之间产生管腔空间。这一过程，特别是根尖管腔的扩大，涉及到HNF1 β的转录活性。因此，利用这种三明治培养系统，我们可以将胆管的小管形成分为不同的步骤，并发现PI3K/Akt通路和HNF1 β调控了不同的形态发生步骤。虽然培养中的小管形成过程特别类似于早期胆管形成，但这两个关键参与者的参与表明，三明治培养可能有助于我们找到一般的小管形成的共同原则。
Bile ducts are hepatic tubular structures that are lined by cholangiocytes, a type of liver epithelial cell. Cholangiocytes first form a single layer of cells, termed the ductal plate, surrounding the portal vein, which eventually remodels into the branching tubular network of bile ducts. The process of bile duct morphogenesis is not yet clear: a conventional model where cholangiocytes proliferate to duplicate a single layer of the ductal plate before lumen formation seems inconsistent with the observation that proliferation is dramatically reduced when hepatoblasts, liver progenitor cells, differentiate into cholangiocytes. Here, we developed a new culture system in which a liver progenitor cell line, HPPL, reorganizes from a monolayer to tubular structures in response to being overlaid with a gel containing type I collagen and Matrigel. We found that some of the HPPL in the monolayer depolarized and migrated to fold up the monolayer into a double-cell layer. These morphogenetic processes occurred without cell proliferation and required phosphatidylinositol 3-kinase and Akt activity. Later in morphogenesis, luminal space was generated between the two cell layers. This process, in particular enlargement of the apical lumen, involved transcriptional activity of HNF1 beta. Thus, using this sandwich culture system, we could segregate tubulogenesis of bile ducts into distinct steps and found that the PI3K/Akt pathway and HNF1 beta regulated different steps of the morphogenesis. Although the process of tubulogenesis in culture specifically resembled early bile duct formation, involvement of these two key players suggests that the sandwich culture might help us to find common principles of tubulogenesis in general.