Walker K A, Ikeda Y, Zabbarova I, Schaefer C M, Bushnell D, De Groat W C, Kanai A, Bates C M
Children's Hospital of Pittsburgh of UPMC, University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania;
Department of Medicine, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania;
Am J Physiol Renal Physiol. 2015 Apr 15;308(8):F888-98. doi: 10.1152/ajprenal.00624.2014. Epub 2015 Feb 4.
While urothelial signals, including sonic hedgehog (Shh), drive bladder mesenchyme differentiation, it is unclear which pathways within the mesenchyme are critical for its development. Studies have shown that fibroblast growth factor receptor (Fgfr)2 is necessary for kidney and ureter mesenchymal development. The objective of the present study was to determine the role of Fgfr2 in the bladder mesenchyme. We used Tbx18cre mice to delete Fgfr2 in the bladder mesenchyme (Fgfr2(BM-/-)). We performed three-dimensional reconstructions, quantitative real-time PCR, in situ hybridization, immunolabeling, ELISAs, immunoblot analysis, void stain on paper, ex vivo bladder sheet assays, and in vivo decerebrated cystometry. Compared with control bladders, embryonic day 16.5 (E16.5) Fgfr2(BM-/-) bladders had thin muscle layers with less α-smooth muscle actin and thickened lamina propria with increased collagen type Ia and IIIa that intruded into the muscle. The reciprocal changes in mutant layer thicknesses appeared partly due to a cell fate switch. From postnatal days 1 to 30, Fgfr2(BM-/-) bladders demonstrated progressive muscle loss and increased collagen expression. Postnatal Fgfr2(BM-/-) bladder sheets exhibited decreased agonist-mediated contractility and increased passive stretch tension versus control bladder sheets. Cystometry revealed high baseline and threshold pressures and shortened intercontractile intervals in Fgfr2(BM-/-) versus control bladders. Mechanistically, whereas Shh expression appeared normal, mRNA and protein readouts of hedgehog activity were increased in E16.5 Fgfr2(BM-/-) versus control bladders. Moreover, E16.5 Fgfr2(BM-/-) bladders exhibited higher levels of Cdo and Boc, hedgehog coreceptors that enhance sensitivity to Shh, compared with control bladders. In conclusion, loss of Fgfr2 in the bladder mesenchyme leads to abnormal bladder morphology and decreased compliance and contractility.
虽然包括音猬因子（Shh）在内的尿路上皮信号驱动膀胱间充质分化，但尚不清楚间充质内的哪些信号通路对其发育至关重要。研究表明，成纤维细胞生长因子受体（Fgfr）2对肾脏和输尿管间充质发育是必需的。本研究的目的是确定Fgfr2在膀胱间充质中的作用。我们使用Tbx18cre小鼠在膀胱间充质中敲除Fgfr2（Fgfr2(BM-/-)）。我们进行了三维重建、定量实时PCR、原位杂交、免疫标记、酶联免疫吸附测定、免疫印迹分析、纸上排尿染色、离体膀胱片测定和体内去大脑膀胱测压。与对照膀胱相比，胚胎第16.5天（E16.5）的Fgfr2(BM-/-)膀胱肌层薄，α-平滑肌肌动蛋白减少，固有层增厚，I型和III型胶原蛋白增加并侵入肌肉。突变层厚度的相反变化部分是由于细胞命运转换。从出生后第1天到30天，Fgfr2(BM-/-)膀胱表现出进行性肌肉丢失和胶原蛋白表达增加。与对照膀胱片相比，出生后的Fgfr2(BM-/-)膀胱片表现出激动剂介导的收缩性降低和被动拉伸张力增加。膀胱测压显示，与对照膀胱相比，Fgfr2(BM-/-)膀胱的基线压力和阈值压力高，收缩间期缩短。从机制上讲，虽然Shh表达似乎正常，但与对照膀胱相比，E16.5的Fgfr2(BM-/-)膀胱中刺猬信号活性的mRNA和蛋白质读数增加。此外，与对照膀胱相比，E16.5的Fgfr2(BM-/-)膀胱表现出更高水平的Cdo和Boc，这两种刺猬信号共受体可增强对Shh的敏感性。总之，膀胱间充质中Fgfr2的缺失导致膀胱形态异常、顺应性和收缩性降低。
