Jiang Tao, Liu Fen, Wang Wei-Guang, Jiang Xin, Wen Xuan, Hu Kai-Jin, Xue Yang
State Key Laboratory of Military Stomatology & National Clinical Research Center for Oral Diseases &Shaanxi Clinical Research Center for Oral Diseases, Department of Oral and Maxillofacial Surgery, School of Stomatology, the Fourth Military Medical University, Xi'an, P. R. China.
Department of Periodontology, School of Stomatology, the Fourth Military Medical University, Xi'an, P. R. China.
PLoS One. 2017 Jan 17;12(1):e0169857. doi: 10.1371/journal.pone.0169857. eCollection 2017.
Cathepsin K (CTSK) is a member of cysteine proteinase family, and is predominantly expressed in osteoclastsfor degradationof bone matrix proteins. Given the similarity in physical properties of bone and dental mineralized tissues, including enamel, dentin and cementum, CTSK is likely to take part in mineralization process during odontogenesis. On the other hand, patients with pycnodysostosis caused by mutations of the CTSK gene displayedmultipledental abnormalities, such as hypoplasia of the enamel, obliterated pulp chambers, hypercementosis and periodontal disease. Thereforeitis necessary to study the metabolic role of CTSK in tooth matrix proteins. In this study, BALB/c mice at embryonic day 18 (E18), post-natal day 1 (P1), P5, P10 and P20 were used (5 mice at each time point)for systematic analyses of CTSK expression in the late stage of tooth germ development. We found that CTSK was abundantly expressed in the ameloblasts during secretory and maturation stages (P5 and P10) by immunohistochemistry stainings.During dentinogenesis, the staining was also intense in the mineralization stage (P5 and P10),but not detectable in the early stage of dentin formation (P1) and after tooth eruption (P20).Furthermore, through zymography and digestion test in vitro, CTSK was proved to be capable of hydrolyzing Emdogain and also cleaving Amelogenininto multiple products. Our resultsshed lights on revealing new functions of CTSK and pathogenesis of pycnodysostosis in oral tissues.
组织蛋白酶K（CTSK）是半胱氨酸蛋白酶家族的成员，主要在破骨细胞中表达，用于降解骨基质蛋白。鉴于骨组织和牙齿矿化组织（包括牙釉质、牙本质和牙骨质）在物理性质上的相似性，CTSK可能参与牙齿发育过程中的矿化过程。另一方面，由CTSK基因突变引起的致密性成骨不全患者表现出多种牙齿异常，如牙釉质发育不全、牙髓腔闭塞、牙骨质增生和牙周疾病。因此，有必要研究CTSK在牙齿基质蛋白中的代谢作用。在本研究中，使用胚胎第18天（E18）、出生后第1天（P1）、P5、P10和P20的BALB/c小鼠（每个时间点5只小鼠）对牙胚发育后期CTSK的表达进行系统分析。通过免疫组织化学染色，我们发现CTSK在分泌期和成熟期（P5和P10）的成釉细胞中大量表达。在牙本质形成过程中，矿化期（P5和P10）的染色也很强烈，但在牙本质形成早期（P1）和牙齿萌出后（P20）未检测到。此外，通过体外酶谱分析和消化试验，证明CTSK能够水解釉基质蛋白，并将釉原蛋白切割成多种产物。我们的研究结果为揭示CTSK的新功能和口腔组织中致密性成骨不全的发病机制提供了线索。
