[An immunohistochemical study on fetal mouse condylar cartilage].

Mandibular condylar cartilage is considered as one of the growth cartilages, but it represents many distinct features. Collagens in cartilage matrix consist mainly of type II collagen but lack type I collagen. Recently it is reported that condylar cartilage contained both type I and type II collagens, while type I collagen was lacking in growth plate cartilages of adult rat tissue. In order to investigate whether such difference in matrix collagen exists in the embryonic period, an immunohistochemical study of type I and type II collagen was performed on fetal mouse condylar cartilage and compared to the limb bud cartilage (tibial anlage). When the first appearance of condylar cartilage was recognized at the 15th day of gestation, reaction to anti-type I collagen was detected in the cartilage matrix, while reaction to anti-type II collagen was very faint. After the 16th day, the pattern of immunohistochemical reaction was almost the same as that after birth. These observations of fetal condylar cartilage were completely different from those of limb bud cartilage. These results suggest that the abilities of the condylar cartilage and the limb bud to synthesize matrix collagen are different from the embryonic period.