Diewert V M, Shiota K
Department of Clinical Dental Sciences, Faculty of Dentistry, University of British Columbia, Vancouver, Canada.
Teratology. 1990 Jun;41(6):663-77. doi: 10.1002/tera.1420410603.
Normal developmental events during human primary palate formation and alterations associated with cleft lip remain poorly defined. The purpose of this study was to analyze serially sectioned human embryos to identify morphological changes during normal palatal closure and alterations associated with failure of palatal formation. Normal and cleft embryos from the histological collection at the Congenital Anomaly Research Center at the University of Kyoto were studied and photographed for detailed evaluation. Seven serially sectioned cleft lip embryos of stages shortly after primary palate formation (Streeter-O'Rahilly stages 19, 20, and 22) with unilateral or bilateral clefts with varying degrees of clefting were studied. In the normal Kyoto embryos, initial nasal fin (epithelial seam) formation was observed between the medial nasal process and the lateral nasal and maxillary processes at stage 17. During stages 18 and 19, the nasal fin epithelium was replaced by an enlarging mesenchymal bridge, as the maxillary processes united with the medial nasal processes to form the primary palate. The most prominent features observed in the cleft embryos were a reduced thickness of mesenchymal bridging between the medial nasal and maxillary processes, with an excessive amount of epithelium at the junctions between these processes. With ingrowth of the maxillary processes, greater cell dispersion and apparent extracellular matrix accumulation were observed in the medial nasal region. During closure of the primary palate, terminal branches of the maxillary nerve crossed the mesenchymal bridge to the medial nasal region. The partial clefts had reduced maxillary ingrowth and smaller union areas with the medial nasal process. Detailed studies of experimental animal models are required to identify regional growth required for contact between the facial prominences, to clarify the mechanisms of mesenchymal ingrowth and epithelial displacement during palatal formation, and to identify local and/or general factors causing alterations that lead to primary palatal clefting.
人类原发腭形成过程中的正常发育事件以及与唇裂相关的改变仍未明确界定。本研究的目的是分析连续切片的人类胚胎，以确定正常腭部闭合过程中的形态变化以及与腭部形成失败相关的改变。对京都大学先天性异常研究中心组织学收藏的正常和唇裂胚胎进行了研究并拍照，以进行详细评估。研究了7个在原发腭形成后不久阶段（斯特里特-奥赖利阶段19、20和22）的连续切片唇裂胚胎，这些胚胎有单侧或双侧唇裂，唇裂程度各异。在正常的京都胚胎中，在第17阶段观察到内侧鼻突与外侧鼻突和上颌突之间最初形成鼻鳍（上皮缝）。在第18和19阶段，随着上颌突与内侧鼻突联合形成原发腭，鼻鳍上皮被扩大的间充质桥取代。在唇裂胚胎中观察到的最显著特征是内侧鼻突和上颌突之间的间充质桥厚度减小，且这些突之间的连接处上皮过多。随着上颌突向内生长，在内侧鼻区域观察到更大的细胞分散和明显的细胞外基质积累。在原发腭闭合过程中，上颌神经的终末分支穿过间充质桥到达内侧鼻区域。部分唇裂的上颌突向内生长减少，与内侧鼻突的联合区域较小。需要对实验动物模型进行详细研究，以确定面部突起之间接触所需的区域生长，阐明腭部形成过程中间充质向内生长和上皮移位的机制，并确定导致原发腭裂的改变的局部和/或一般因素。
