正常及先天性肛门直肠畸形大鼠消化道末端平滑肌发育的研究

Comparison of development of smooth muscle at the bottom of alimentary tract in normal rats and rats with anorectal malformations

目的观察乙烯硫脲致畸的肛门直肠畸形（ARMs）大鼠模型后肠平滑肌的发育过程及演变规律。方法实验分为正常组和ARMs组，ARMs组为以乙烯硫脲制作的肛门直肠畸形大鼠模型，取不同胎龄（E13．5、E14、E14．5，E15、E16、E17、E18和E21）的正常组和ARMs组胚胎，经常规处理制成蜡块，行矢状面切片，以ccSMA作为平滑肌的标志物，进行免疫组化染色，观察正常和肛门直肠畸形大鼠胚胎肛门内括约肌和直肠纵肌在发育过程中的形态学变化过程。结果从胚胎E15开始，可在正常组和ARMs组观察到在后肠壁内出现α-SMA阳性细胞组成的环肌层，并有轻微的末端膨大，表现出肛门内括约肌的特点；E15、E16时，正常组与ARMs组的环肌发育无明显差异，E17～21，ARMs组的后肠末端环肌膨大部分在到达后肠末端漏斗样过渡区后逐渐变薄弱，并形成一个锐角末端，而在正常组这一末端膨大是以钝圆性的末端结束的，且ARMs组的肌束界限较模糊，排列略紊乱；这一趋势一直持续到胚胎的末期。从E17开始纵肌层片段在后肠间断出现，到E21时，后肠的纵肌层才完全连续，ARMs组的直肠纵肌同样在E17时出现，在近段后肠发育与正常组相似，在后肠末段发育较差。结论正常组及ARMs组的肛门内括约肌在E15开始出现于后肠末端，直肠纵肌在E17开始出现，ARMs组的肛门内括约肌和直肠纵肌较正常组发育差。

Objective To investigate the development of smooth muscle at the hind gut in the embryos of rats with ARMs induced by ethylene thiourea （ETU） and normal rats. Methods The model of rat embryos with ARMs was established by administration of ETU to pregnant rats. Normal rat embryos and embryos with ARMs were taken out at E 13.5, E14, E14. 5, E15, E16, E17, E18 and E21 and made into paraffin blocks. Sections in sagittal plane were made and stained with specific anti body to α-SMA which was a marker for smooth muscles. During the development of hind gut, the morphological change of internal anal sphincter （IAS） and the longitudinal muscle of the rectum were observed in both groups. Results From E15 to E21, the circular muscle layer with positive staining of α-SMA could be observed in the hind gut with slightly dilated terminus in both groups, which was the characteristic of IAS. On E15 and E16, no significant difference could be noted in the development of the circular muscle layer in both groups. From E17 to E21, the dilated musculature in the ARMs groups gradually became thinner at the transitional zone of the funnel-shaped terminus of hind gut and formed a sharp angle extremity, while the dilated terminus formed a relatively semi-round shaped extremity in the normal group. The musculature with vague outline and disordered arrangement persistently existed in the ARMs group. From E17, longitudinal muscles gradually appeared in the hind gut, and continuous longitudinal muscles could be observed on E21. Similar developmental progress could be noted in the ARMs group, while with poor development in the terminus of hind gut. Conclusions IAS began to appear at the terminal segment of hind gut on E15. The longitudinal muscles appeared on E17 in both groups. IAS and the longitudinal muscles had poorer development in the ARMs group than that in the normal group.