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D'Souza, Rena N.,Andriana Cavender,Rajita Sood,Roy Tarnuzzer,Dickinson, Douglas P.,Anita Roberts,John Letterio Korean Academy of Oral Biology and the UCLA Dental 1998 International Journal of Oral Biology Vol.23 No.3
To better understand the precise physiologic functions of TGF- β1 in odontogenesis, we have performed a detailed analysis of developing and adult dentition in mice with a targeted deletion of the TGF-β 1 gene. TGF-β1(-/-) mice derived from TGF- β1(+/-) matings receive maternally transferred TGF-β1, but die by three weeks of age from multifocal inflammation (Shull et al., 1992; Kulkarni et al., 1993). In these mice and neonates from a TGF-β1(-/-) female that did not receive maternal TGF-β1, the earlier stages of odontogenesis appeared unaltered. Furthermore, the absence of TGF-β1 did not affect the patterns and levels of expression of related isoforms TGF-β2 and TGF-β3, as shown by in-situ hybridization and competitive RT-PCR analyses. However, histopathologic analysis of adult dentition in TGF-β1(-/-)mice, whose survival was prolonged with dexamethasone, showed extensive pathlolgy in dental and paradental tissues. In addition to inflammation, we observed a marked attrition of tooth matrices in TGF-β1(-/-) molars when compared to TGF-β1(+/+) and TGF-β1(+/-) littermates. To determine whether the phenotypic changes in teeth are primarily caused by the deficiency in TGF-β1 rather than the secondary effects of inflammation, we studied dentition in TGF-β1(-/-) mice backcrossed onto immunodeficient backgrounds using histochemical, radiographic and biomechanical methods. These analyses revealed significant differences in mineral content and hardness quality in TGF-β1(-/-) molars as compared to their control littermates, implying that the impairment in formation of dental mineralized tissues is linked directly to the absence of TGF-β1. Our findings hence demonstrate the importance of TGF-β1 in cellular functions at advanced stages of odontogenesis, in particular, the biomineralization of tooth matrices. In addition these studies indicate a non-redundant, isoform-specific role of TGF-β1 in the immune homeostasis of oral tissues.