Sonic hedgehog regulates morphogenesis, cell proliferation and and differentiation in developing tooth germs.

Sonic hedgehog(Shh)在牙齿发育过程中以特定的时空模式表达，但该信号效应因子的具体作用尚不清楚。为了解决这个问题，来自E11和E14小鼠胚胎的磨牙胚胎被保持在器官培养条件下，以便在没有或存在反义Shh寡核苷酸的情况下继续发育。RT-PCR和免疫组织化学分析表明，反义寡核苷酸处理后，内源性Shh的表达显著和选择性降低，而正义、随机或突变的反义寡核苷酸处理对内源性Shh表达无影响。抑制培养的E11板层阶段牙胚中Shh的表达阻止了它们发展到与伴生对照牙胚相同的帽状阶段，并伴随着上皮细胞和间充质细胞的增殖急剧减少，以及Hedgehog信号中介分子Patched-1、Patch-2和Gli-1的下调。同样，抑制E14胚胎的Shh不仅会导致严重的生长迟缓，还会导致形态发生和细胞分化的严重异常。对照组E14帽期的细菌进入钟状期，可见明显的牙尖、成釉细胞和成牙本质细胞，而反义处理组的牙尖和分化细胞均缺失。这些结果表明，Shh是牙齿正常发育所必需的一个因素，似乎是包括形态发生、细胞增殖和细胞分化在内的多个事件所必需的。

Sonic hedgehog (Shh) is expressed in specific spatio-temporal patterns during odontogenesis, but the specific roles played by this signaling effector are not clear. To address this question, molar tooth germs from E11 and E14 mouse embryos were maintained in organ culture conditions, which allow continuation of their development, in the absence or presence of antisense Shh oligonucleotides. RT-PCR and immunohistological analyses showed that a marked and selective reduction of endogenous Shh expression was caused by antisense oligonucleotide treatment, whereas sense, random or mutated antisense oligomers had no effect. Inhibition of Shh expression in cultured E11 lamina stage tooth germs prevented their progression to the cap stage seen in companion control germs and was accompanied by a sharp reduction of proliferation in both epithelial and mesenchymal cells and down-regulation of hedgehog signal-mediating molecules Patched-1, Patched-2 and Gli-1. Likewise, Shh inhibition in E14 germs led not only to a severe growth retardation but also severe abnormalities in morphogenesis and cytodifferentiation. Control E14 cap stage germs advanced to the bell stage and displayed conspicuous cusps, ameloblasts and odontoblasts, whereas the antisense-treated germs lacked both cusps and differentiated cells. These results show that Shh is an essential factor for normal tooth development is appeared to be required for multiple events, including morphogenesis, cell proliferation and cytodifferentiation.