Department of Stomatology, the First Medical Center of PLA General Hospital, Beijing, China.
Institute for Laboratory Animal Resources, National Institutes for Food and Drug Control, Beijing, China.
J Morphol. 2022 Jan;283(1):134-143. doi: 10.1002/jmor.21432. Epub 2021 Nov 27.
The temporomandibular joint (TMJ) is a synovial joint involved in sliding and hinge movements of lower jaw in mammals. Studies on TMJ development in embryos have been mainly performed using rodents. However, the TMJ structure in rodents differs in several aspects from that in humans. There are few studies on the embryonic development of TMJ in large mammals. In the present study, we investigated the embryonic developmental characteristics of the TMJ in pigs histologically. Embryonic day 35 (E35), E45, E55, E75, E90, and postnatal day 1(P1) embryos/fetuses from the pigs were used for the study. The results showed condensation of mesenchymal cells on E35. The inferior articular cavity was formed on E45, together with a narrow crack in the superior articular cavity region. The superior and inferior articular cavities and articular disc of the TMJ were completely formed on E55. On E75, the condyle showed an obvious conical shape and the superior and inferior joint cavities were enlarged. Furthermore, the mandibular ramus and mandibular body under the neck of the condyle were ossified from E75 to P1 day. The chondrocyte layer of the condyle was significantly thinner from E75 to P1. It is speculated that the spatiotemporal development of the TMJ in miniature pig embryos is similar to that in humans. Embryonic development of the pig TMJ is an important bridge for translating the results of rodent research to medical applications.
颞下颌关节（TMJ）是哺乳动物下颌滑动和铰链运动中涉及的滑膜关节。胚胎 TMJ 发育的研究主要在啮齿动物中进行。然而，啮齿动物的 TMJ 结构在几个方面与人类不同。关于大型哺乳动物 TMJ 胚胎发育的研究较少。本研究采用组织学方法研究了猪 TMJ 的胚胎发育特征。使用来自猪的胚胎 35 天（E35）、E45、E55、E75、E90 和出生后 1 天（P1）的胚胎/胎儿进行研究。结果表明，E35 时出现间充质细胞的凝聚。E45 时形成下颌下关节腔，同时在上关节腔区域形成狭窄的裂缝。E55 时完全形成 TMJ 的上下关节腔和关节盘。E75 时，髁突呈明显的圆锥形，上下关节腔增大。此外，E75 至 P1 天，颈下的髁突和下颌体出现骨化。E75 至 P1 时，髁突的软骨细胞层明显变薄。推测小型猪胚胎 TMJ 的时空发育与人类相似。猪 TMJ 的胚胎发育是将啮齿动物研究结果转化为医学应用的重要桥梁。
