Barros E J, Santos O F, Matsumoto K, Nakamura T, Nigam S K
Department of Medicine, Harvard Medical School, Boston, MA 02115, USA.
Proc Natl Acad Sci U S A. 1995 May 9;92(10):4412-6. doi: 10.1073/pnas.92.10.4412.
At least two kidney epithelial cell lines, the Madin-Darby canine kidney (MDCK) and the murine inner medullary collecting duct line mIMCD-3, can be induced to form branching tubular structures when cultured with hepatocyte growth factor (HGF) plus serum in collagen I gels. In our studies, whereas MDCK cells remained unable to form tubules in the presence of serum alone, mIMCD-3 cells formed impressive branching tubular structures with apparent lumens, suggesting the existence of specific factors in serum that are tubulogenic for mIMCD-3 cells but not for MDCK cells. Since normal serum does not contain enough HGF to induce tubulogenesis, these factors appeared to be substances other than HGF. This was also suggested by another observation: when MDCK cells or mIMCD-3 cells were cocultured under serum-free conditions with the embryonic kidney, both cell types formed branching tubular structures similar to those induced by HGF; however, only in the case of MDCK cells could this be inhibited by neutralizing antibodies against HGF. Thus, the embryonic kidney produces growth factors other than HGF capable of inducing tubule formation in the mIMCD-3 cells. Of a number of growth factors examined, transforming growth factor alpha (TGF-alpha) and epidermal growth factor (EGF) were found to be tubulogenic for mIMCD-3 cells. Whereas only HGF was a potent tubulogenic factor for MDCK cells, HGF, TGF-alpha, and EGF were potent tubulogenic factors for mIMCD-3 cells. Nevertheless, there were marked differences in the capacity of these tubulogenic factors to induce tubulation as well as branching events in those tubules that did form (HGF >> TGF-alpha > EGF). Thus, at least three different growth factors can induce tubulogenesis and branching in a specific epithelial cell in vitro (though to different degrees), and different epithelial cells that are capable of forming branching tubular structures demonstrate vastly different responses to tubulogenic growth factors. The results are discussed in the context of branching morphogenesis during epithelial tissue development.
至少有两种肾上皮细胞系，即犬肾Madin-Darby细胞（MDCK）和小鼠肾内髓集合管系mIMCD-3，当在I型胶原凝胶中与肝细胞生长因子（HGF）加血清一起培养时，可被诱导形成分支管状结构。在我们的研究中，虽然MDCK细胞在仅存在血清的情况下仍无法形成小管，但mIMCD-3细胞形成了具有明显管腔的令人印象深刻的分支管状结构，这表明血清中存在特定因子，这些因子对mIMCD-3细胞具有促管生成作用，但对MDCK细胞没有。由于正常血清中HGF含量不足以诱导小管形成，这些因子似乎是HGF以外的物质。另一项观察也表明了这一点：当MDCK细胞或mIMCD-3细胞在无血清条件下与胚胎肾共培养时，两种细胞类型都形成了类似于HGF诱导的分支管状结构；然而，只有MDCK细胞的这种情况可被抗HGF中和抗体抑制。因此，胚胎肾产生了HGF以外的能够诱导mIMCD-3细胞形成小管的生长因子。在检测的多种生长因子中，发现转化生长因子α（TGF-α）和表皮生长因子（EGF）对mIMCD-3细胞具有促管生成作用。虽然只有HGF是MDCK细胞的有效促管生成因子，但HGF、TGF-α和EGF是mIMCD-3细胞的有效促管生成因子。然而，这些促管生成因子在诱导小管形成以及已形成的小管中的分支事件的能力上存在显著差异（HGF >> TGF-α > EGF）。因此，至少三种不同的生长因子可以在体外诱导特定上皮细胞形成小管和分支（尽管程度不同），并且能够形成分支管状结构的不同上皮细胞对促管生成生长因子表现出截然不同的反应。将在上皮组织发育过程中的分支形态发生背景下讨论这些结果。
