Abbott B D, Pratt R M
Experimental Teratogenesis Section, National Institute of Environmental Health Sciences, Research Triangle Park, NC 27709.
J Craniofac Genet Dev Biol. 1987;7(3):241-65.
Reports of adverse human pregnancy outcomes including cleft palate have increased as the clinical use of isotretinoin (13-cis-retinoic acid) and other retinoic acid (RA) derivatives have increased, but the mechanisms by which their effects are exerted are not understood. Research in craniofacial development is generally performed in rodents, and mouse palatal shelves exposed in organ cultures to retinoids and epidermal growth factor (EGF) display altered medial epithelial cell morphology blocking normal union of apposing shelves. In the present study, precontacting human palatal shelves were maintained in organ culture for 2, 3, or 6 days and exposed to labeled thymidine (3H-TdR) during the last 16 hr. Retinoids and EGF were included in the media so that each shelf was exposed to one of the following: control, EGF, trans-RA at 10(-5)M, cis-RA at 10(-7) or 10(-9) M, or RA + EGF. After exposure of cultured human embryonic palatal shelves to 13-cis-RA and trans-RA with or without EGF, medial epithelial cells do not degenerate, cell surface morphology shifts toward a nasal type, glycogen deposits decrease, smooth endoplasmic reticulum (SER) increases, and basal lamina appear altered. In shelves exposed to EGF and trans-RA early in their development, DNA synthesis appears to terminate prematurely as compared to shelves cultured in control media, and this effect is accompanied by excessive mesenchymal extracellular space expansion. Exposure of shelves to EGF alone is sufficient to block degeneration and induce hyperplasia of the medial epithelial cells but does not induce other ultrastructural changes seen with both EGF and RA. The observed alterations in medial cell morphology could interfere with adhesion of the palatal shelves and may play a role in retinoid-induced cleft palate in the human embryo.
随着异维甲酸（13 - 顺式维甲酸）和其他维甲酸（RA）衍生物在临床上的使用增加，包括腭裂在内的不良人类妊娠结局的报告也有所增加，但其作用机制尚不清楚。颅面发育的研究通常在啮齿动物中进行，在器官培养中暴露于维甲酸和表皮生长因子（EGF）的小鼠腭板显示内侧上皮细胞形态改变，阻碍了相对腭板的正常愈合。在本研究中，将预接触的人类腭板在器官培养中维持2、3或6天，并在最后16小时暴露于标记的胸腺嘧啶核苷（³H - TdR）。培养基中加入维甲酸和EGF，使每个腭板暴露于以下之一：对照、EGF、10⁻⁵M的反式维甲酸、10⁻⁷或10⁻⁹M的顺式维甲酸，或维甲酸 + EGF。将培养的人类胚胎腭板暴露于含或不含EGF的13 - 顺式维甲酸和反式维甲酸后，内侧上皮细胞不会退化，细胞表面形态向鼻型转变，糖原沉积减少，滑面内质网（SER）增加，基膜出现改变。与在对照培养基中培养的腭板相比，在发育早期暴露于EGF和反式维甲酸的腭板中，DNA合成似乎过早终止，并且这种效应伴随着间充质细胞外空间过度扩张。单独将腭板暴露于EGF足以阻止退化并诱导内侧上皮细胞增生，但不会诱导与EGF和维甲酸共同作用时所见的其他超微结构变化。观察到的内侧细胞形态改变可能会干扰腭板的黏附，并可能在人类胚胎维甲酸诱导的腭裂中起作用。
