Trps1 deficiency enlarges the proliferative zone of growth plate cartilage by upregulation of Pthrp

详细信息	查看全文 | 推荐本文 |

• 作者：Katsuhiro Nishioka ; Shunji Itoh ; Hiroki Suemoto ; Seiji Kanno ; Zhibo Gai ; Motohisa Kawakatsu ; Hiroyuki Tanishima ; Yoshifumi Morimoto ; Ikuji Hatamura ; Munehito Yoshida ; Yasuteru Muragaki
• 关键词：Trps1 ; Growth plate ; Pthrp ; Chondrocytes ; Differentiation
• 刊名：Bone
• 出版年：2008
• 期刊代码：39_87563282
• 类别：med
• 出版时间：July 2008
• 卷：43
• 期：1
• 页码：64-71
• 文件大小：1407 K

摘要

We have reported that elongation of the columnar proliferative zone of long bone growth plates in <i>Trps1^−/−i> mice during the late fetal stage in the previous study [1]. Since expression of Trps1 protein was found to overlap with that of mRNAs for <i>Indian hedgehogi> (<i>Ihhi>), <i>PTH/PTHrP receptori> (<i>PPRi>), and <i>PTHrPi>, we hypothesized that Trps1 may inhibit the hypertrophic differentiation of chondrocytes by interacting with the Ihh/PTHrP feedback loop. To investigate whether Trps1 has a role in this Ihh/PTHrP feedback loop, we compared the growth plates of <i>Trps1^−/−i> mice and wild-type (<i>Trps1i>^<i>+/+i>) mice. Immunohistochemistry showed that Trps1 protein was strongly expressed in the periarticular and prehypertrophic zones of the fetal growth plate in wild-type mice on embryonic day 18.5 (E18.5). On the other hand, <i>Ihhi>, <i>PPRi>, and <i>PTHrPi> mRNAs were predominantly expressed in the prehypertrophic zone at this stage of development. While expression of <i>Ihhi> and <i>PPRi> by prehypertrophic chondrocytes was unaffected in the growth plates of <i>Trps1^−/−i> mice, the range of <i>PTHrPi> expression was expanded toward the proliferating zone in these mice. Quantitative real-time PCR analysis demonstrated upregulation of <i>PTHrPi> in the epiphyseal growth plates of <i>Trps1^−/−i> mice. Furthermore, promoter analysis combined with the chromatin immunoprecipitation (ChIP) assay demonstrated that direct binding of Trps1 to the <i>PTHrPi> promoter suppressed the transcription of <i>PTHrPi>. Finally, organ culture of E14.5 tibiae in the absence or the presence of Pthrp revealed that the proliferative zone of the tibial growth plate was elongated by culture with Pthrp compared to that of control tibiae. Taken together, these data provide the first genetic evidence that lack of Trps1 leads to overexpression of PTHrP, and that Trps1 is required to maintain the normal organization of chondrocytes in the growth plate.