Effect of hepatocyte growth factor/scatter factor on the development and metabolism of bone tissue : relation of regulation on fetuin gene expression.

为了研究肝细胞生长因子/分散因子（HGF/SF）是否以及如何参与骨组织的发育，我们采用逆转录-聚合酶链反应分析了胚胎第10天小鼠前肢、后肢、体部和第一鳃弓中HGF/SF和HGF/SF受体c-Met的mrna，发现HGF/SF和c-Met在这些组织中均有表达。我们还利用RNA探针进行原位杂交，证实了HGF/SF和c-Met在E10 ~ E16小鼠这些组织中的表达，发现c-Met在骨化部位的表达特别高。提示HGF/SF可能调控成骨细胞向骨组织的分化。虽然我们无法在任何阶段检测到fetuin的表达，但上述结果也提示HGF/SF可能参与了舌头的发育。因此，我们接下来用无血清EGJb培养基体外培养E10小鼠第一鳃弓120小时，发现c-Met在下颌骨发育的位置表达。我们还发现肌肉特异性转录因子myoD、myogenin和myf5在上述培养的第一鳃弓舌部表达。在培养液中加入浓度为50 ng/ml的重组HGF/SF，培养120小时后，舌部大小增大，舌部肌肉细胞的高增殖位置与c-Met对应。提示HGF/SF在发育阶段抑制舌肌分化，同时以旁分泌方式刺激舌成肌细胞增殖。在本课题的研究过程中，我们还发现并报道了在甲状旁腺激素存在的情况下，大鼠胎儿激素对骨吸收的促进作用，以及大鼠胎儿激素参与了胎鼠大脑新皮质的发育。

In order to study whether and how hepatocyte growth factor/scatter factor (HGF/SF) is involved in development of bone tissue, we analyzed mRNAs for HGF/SF and c-Met, the receptor for HGF/SF, in the forelimb, hindlimb, somite and first branchial arch from mice of embryonic day 10 (E10) by reverse transcription-polymerase chain reaction and found that HGF/SF and c-Met were expressed in these tissues. We also confirmed the expression of HGF/SF and c-Met in these tissues from E10 to E16 mice by whole-mount in situ hybridization using RNA probes and found that expression of c-Met was especially high at the position of ossification. This finding suggested that HGF/SF may regulate the differentiation of osteoblasts ht bone tissue. Although we could not detect the expression of fetuin at any stages, above results also suggested that HGF/SF may involved in the development of tongue. Therefore, we next cultured the first branchial arch from E10 mice with serum-free EGJb medium for 120 hr in vitro and found that c-Met expressed at the position where mandible will develop. We also found that muscle specific transcription factors, such as myoD, myogenin and myf5, expressed in the cultured first branchial arch described above at the position of tongue. Addition of recombinant HGF/SF to the medium at the concentration of 50 ng/ml enlarged the size of tongue after 120 hr incubation, and the position of high proliferation of muscle cells of tongue was corresponding with that of c-Met was expressed. These findings suggested that HGF/SF suppressed the differentiation muscle of tongue during developing stage and at the same time, HGF/SF stimulated proliferation of myoblasts of tongue by paracrine mode.During this project was processing, we also found and reported that rat fetuin stimulated bone resorption in the presence of parathyroid hormone and that rat fetuin was involved development of neocortex in fetal rats.