Changes of palatal shelf in the teratogen-induced cleft palate in the rats
구개열의 발생기전을 규명하기 위하여 백서를 같은 환경에서 임신시켜 임신 14일에 최기형 물질인 triamcinolone acetonide 1 mg/kg을 대퇴부 근육내로 주사하여 구개형성에 가장 중요한 시기인 임신 15일, 16일, 17일에 각각 그 태자를 얻었다.
실험군과 대조군의 태자는 24시간 동안 Bouin씨 용액에 고정한 후 체중을 측정하고 하악과 혀를 제거한 후 구개판(palatal shelf)의 위치와 접합상태를 관찰하였다.
또한 일부의 태자는 정중시상절단면과 중간부위의 관상절단면을 hematoxylin-eosin염색과 Masson's trichrome염색을 하여 두개 안면의 형태학적 변화를 계측하였으며 모든 계측치는 YAP-1 program을 이용하여 컴퓨터로 처리하였다.
이 결과 대조군에서는 구개열이 발생되지 않았으나 실험군의 태자에서는 93%에서 구개열이 발생되었으며, 실험군은 대조군에 비해 구개판의 거상이 점차적으로 지연되었고 구개접합의 정도도 약화되었다.
구개판의 거상과 접합에 결정적 시기인 임신 15일과 16일에 실험군은 하악후퇴가 뚜렷하였고 안면의 폭과 구개관의 폭은 동시에 감소하였다. 혀의 폭과 높이는 실험군과 대조군에서 변화가 없었으며 구개판 내의 골 형성은 실험군에서 지연되었다.
Cleft palate is one of the most prevalent congenital anomalies seen in human. but the pathogenesis of cleft palate is poorly understood. Walker and Fraser(1957) postulated that for the palatal shelves to fuse they must become elevated by the time the size of the head and oral cavity enables them to come into contact with each other. Regardless of the means by which palatal shelves become elevated, a possible mode of cleft palate formation is delay or prevention of this process. Mandibular retrognathia was considered to be a contributing factor in induction of cleft palate in rats by Chamberlain and Nelson(1973), and in mice by Jelinek and Peterka(1977). But Shih et al. (1974) concluded the teratogen did net cause cleft palate in mice by reducing the length of the mandible at palate closure time. It appears, however, that palatal closure is mere complex than this and also involves synchronized interactions of various parts, including shelves, tongue, mandible, and cranium. Since the discovery (Baxter and Fraser, 1950) that cortisone can produce cleft palate in mice, corticosteroids have been perhaps the most widely used agents in the experimental production of this defect.
This study was undertaken to evaluate palatal development and the relation between ante-red craniofacial growth and development of palatal defects in rata treated with triamcinolone acetonide.
Maternal treatment with triamcinolone acetonide was Performed on day 14 of gestation in Sprague-Dawley rats. On day 15, 16, 17 of gestation, which, was critical period in palatal development, the status of palatal development was grossly observed after removal of the tongue and the mandible. After fetal heads were sectioned in the midsagittal or the coronal plane and stained with hematoxylin-eosin and Masson's trichrome, the morphometric Changes of craniofacial structure were measured and the YAP-1 computer program was used for analysis of the data.
The results were as follows: (1) Cleft palate was induced in 93% of the experimental fetuses, but was not produced spontaneously in the control fetuses.
The elevation of the palatal shelf was delayed from a vertical to a horizontal plane, and the fusion between the palatal shelves was also delayed in the experimental fetuses. (2) Mandibular retrognathia was noticed on day 15 & 16 of gestation in the experimental fetuses. (3) The widths of face & palatal shelf were
decreased simultaneously in the experimental fetuses. (4) The width & height of the tongue were not decreased in the experimental fetuses in comparison with the control fetuses. (5) The bone formation in the palatal shelf was delayed in the experimental fetuses.