Distribution of Mucopolysaccharides and Glycoproteins in the Articular Discs of Temporomandibular Joints in Human Fetuses

Aims: To evaluate the distribution of mucopolysaccharides and glycoproteins in the articular discs of temporomandibular joints (TMJs) in human fetuses at different stages of development in order to test the hypothesis that the development and histological maturation of the articular disc has already begun by the 12th week of gestation. Methods: Eighteen human fetuses at gestational ages 12, 14, and 16 weeks were used (6 fetuses of each age). Sections (6 µm wide) of the articular discs were stained with trichromic stain for collagen fibers, Mayer's mucicarmine for mucopolysaccharides, and Schiff's periodic acid reaction for glycoproteins. The densities of the stained zones were measured by means of Image J software. The nonparametric Kruskal-Wallis test was used to evaluate the differences among stained zones in the 3 fetus groups. Results: TMJ tissues of four of the six 12-week-old fetuses were stained positive for collagen fibers, mucopolysaccharides, and glycoproteins. In these fetuses the stain was localized to the articular posterior area and was denser in that area than in the middle and anterior areas. The stained areas in the 14-week-old fetuses were distributed throughout the articular discs, with isolated clear unstained areas. The stained areas of all the articular discs of the 16-week-old fetuses were more compact than those of the 12-and 14-week-old fetuses. In all the fetuses examined, the collagen fibers along the articular disc had a wavy appearance. The fossa of the temporal bone was observed in all the fetuses as a straight structure that was similar in the 3 fetus groups. The densities (mean ± SD) of the stained zones were 38.36% ± 3.39%, 59.5% ± 1.56%, and 94.04% ± 2.04% for 12, 14, and 16 weeks of gestation, respectively; these densities were significantly different (x2 = 15.16; df = 2, P .001). Conclusion: This study indicates that mucopolysaccharides and glycoproteins as well as collagen fibers are present at 12, 14, and 16 weeks of gestation. This suggests that the histological maturation of the articular disc has already begun at the 12th week and is complete by the 16th week of gestation. Keywords: articular disc, collagen, human fetuses, mucopolysaccharides, temporomandibular joint