Maeshima A, Zhang Y Q, Furukawa M, Naruse T, Kojima I
Department of Cell Biology, Institute for Molecular and Cellular Regulation, Gunma University, and Third Department of Internal Medicine, Gunma University School of Medicine, Maebashi, Japan.
Kidney Int. 2000 Oct;58(4):1511-22. doi: 10.1046/j.1523-1755.2000.00313.x.
The activin-follistatin system is expressed in tubular cells of the kidney. The present study was conducted to examine the role of the activin-follistatin system in tubulogenesis using Madin-Darby canine kidney (MDCK) cells as a model system.
Tubulogenesis was assessed using MDCK cells cultured in collagen gel. The effect of recombinant human activin A on tubulogenesis was examined. Blockade of the action of endogenous activin was achieved by either adding follistatin or transfection of dominant-negative mutant of the type II activin receptor. The production of activin A was examined by Northern blotting, in situ hybridization, and Western blotting.
MDCK cells expressed mRNA for the betaA subunit of activin. These cells formed spherical cysts when cultured in collagen gel. Hepatocyte growth factor (HGF) added to the spherical cysts induced branching tubulogenesis. When activin A was added together with HGF, activin A blocked the branching tubulogenesis induced by HGF, and the activin-treated cells were scattered. Conversely, follistatin, an antagonist of activin A, induced branching tubulogenesis qualitatively similar to that induced by HGF. Adenovirus vector-mediated transfer of the gene encoding truncated type II activin receptor, which acts as a dominant negative mutant, also induced branching tubulogenesis. Finally, HGF markedly inhibited the production of activin A in MDCK cells cultured in collagen gel.
Activin A produced in MDCK cells tonically inhibits branching tubulogenesis, and HGF induced branching tubulogenesis mainly by blocking the production of activin A.
激活素-卵泡抑素系统在肾的肾小管细胞中表达。本研究以Madin-Darby犬肾（MDCK）细胞作为模型系统，探讨激活素-卵泡抑素系统在肾小管形成中的作用。
使用在胶原凝胶中培养的MDCK细胞评估肾小管形成。检测重组人激活素A对肾小管形成的影响。通过添加卵泡抑素或转染II型激活素受体的显性负性突变体来阻断内源性激活素的作用。通过Northern印迹、原位杂交和Western印迹检测激活素A的产生。
MDCK细胞表达激活素βA亚基的mRNA。这些细胞在胶原凝胶中培养时形成球形囊肿。添加到球形囊肿中的肝细胞生长因子（HGF）诱导分支肾小管形成。当激活素A与HGF一起添加时，激活素A阻断了HGF诱导的分支肾小管形成，且经激活素处理的细胞分散。相反，激活素A的拮抗剂卵泡抑素诱导的分支肾小管形成在性质上与HGF诱导的相似。腺病毒载体介导的编码截短型II型激活素受体（作为显性负性突变体起作用）的基因转移也诱导了分支肾小管形成。最后，HGF显著抑制了在胶原凝胶中培养的MDCK细胞中激活素A的产生。
MDCK细胞产生的激活素A持续抑制分支肾小管形成，而HGF主要通过阻断激活素A的产生诱导分支肾小管形成。
