Molecular switch between cell proliferation and differentiation in the craniofacial development

热休克蛋白（Hsps）是由热休克和其他生理应激诱导产生的，作为分子伴侣保护细胞免于死亡。在非应激条件下，热休克蛋白在细胞中组成性表达。27kDa热休克蛋白（Hsp27）被认为在增殖、分化和细胞死亡的关键细胞检查点起作用。提示Hsp27具有调节腺泡细胞分化和保护腺泡细胞凋亡的作用。在本研究中，我们检测了大鼠颌下腺导管结扎释放后再生腺泡细胞中Hsp27的时间顺序免疫定位。8周龄雄性Wister大鼠麻醉后，用小夹子结扎右侧颌下腺主排泄管，左侧为对照。1周后，取出夹子以解除导管结扎。取夹后0、1、3、5、7、10、14、28 d，用4%多聚甲醛溶液固定颌下腺，进行Hsp27和PCNA免疫组化。在对照组和正常颌下腺中，hsp27在神经和血管中有免疫反应，而在腺泡和导管细胞中无免疫反应。取夹3天后，再生腺泡部分远端出现少量hsp27免疫阳性细胞。hsp27的免疫反应性强烈地局限于小圆形上皮细胞的细胞质中。hsp27阳性细胞数量增加至7天后，但14天后腺泡中未发现阳性细胞。组织学上，14天后识别出正常的腺泡细胞。在腺泡再生过程中，hsp27阳性上皮细胞未与pcna免疫反应性共定位。这些结果表明，腺泡细胞分化发生在去夹后3-7天，Hsp27调节了颌下腺再生过程中腺泡细胞的初始分化。少

Heat shock proteins (Hsps) are induced by heat shock and other physiological stresses, and protect cells from cell death through their roles as molecular chaperone. Hsps are constitutively expressed in the cells under unstressed conditions. The 27kDa Hsp (Hsp27) has been suggested to work at crucial cellular checkpoints for proliferation, and differentiation, and cell death. Hsp27 was suggested to regulated the acinar cell differentiation and protect them from apoptosis.In the present study, we have examined the chronological immunolocalization of Hsp27 in the regenerating acinar cells after release of duct ligation in the rat submandibular gland.Male Wister rats of 8 weeks old were anesthetized and the right main excretory duct of submandibular gland were ligated by small clips and the left is control. After 1 week, clips were removed to release the duct ligation. Submandibular glands were fixed with 4% paraformaldehyde solution after 0, 1, 3, 5, 7, 10, 14 and 28 days after clip remov … More al. They were treated for immunohistochemistry of Hsp27 and PCNA.In the control and normal submandibular glands, Hsp27-immunoreactivity was observed in the nerves and blood vessels but not in the acinar and duct cells. Three days after the clip removal, small number of Hsp27-immunopositive cells was found in the distal end of regenerating acinar portion. Hsp27-immunoreacitvity was intensely localized in the cytoplasm of small and round-shaped epithelial cells. Hsp27-positive cells were increased in number until 7 days after clip removal, but no positive cells were recognized in the acini after 14 days of clip removal. Histologically, normal acinar cells were recognized after 14 days. Hsp27-positive epithelial cells were not colocalized with PCNA-immunoreactivity during the acinar regeneration.These results suggest that differentiation of acinar cells occur during 3-7 days after clip removal, and Hsp27 regulates the initial differentiation of acinar cells during submandibular gland regeneration. Less