Histological and biochemical evaluation of temporomandibular joints of BALB/c-bm/bm mouse that spontaneously induces anterior transverse crossbite

Abstract

Murine brachymorphism (bm) has cartilage with glycosaminoglycans (GAGs) undersulfated. The phenotype is inherited as an autosomal recessive. Anterior transverse crossbite sometimes spontaneously occurs in BALB/c-bm/bm mouse (bm homozygotes) inbred. Temporomandibular joints of BALB/c-bm/bm mouse were histologically and biochemically evaluated.
We used BALB/c mice (control), BALB/c-bm/bm mice with normal occlusion (bm-Norm), and BALB/c-bm/bm mice with crossbite (bm-Mal). Coronal sections of control and bm-Norm groups aged 8 weeks were made and stained with hematoxylin-eosin, with the methods of alcian blue critical electrolyte concentration, and with sensitized high iron diamine methods after treatment of testicular hyaluronidase (bovine testis). After extracting condylar cartilage of control, bm-Norm, and bm-Mal groups aged 3 weeks and 13 weeks, sulfated GAGs were also measured using demethylmethylene blue assay.
Compared with the control group, condylar cartilage of the bm-Norm group was thinner and had an unclear zone of hypertrophic cells. Keratan sulfate and chondroitin sulfate were weakly stained in the bm-Norm group. The concentration of sulfated GAGs in cartilage of condyle in each group aged 13 weeks was lower than that in each group aged 3 weeks. The concentration of sulfated GAGs in cartilage of condyle in the bm-Norm and bm-Mal groups aged 3 weeks was lower than that in the control group. The concentration of sulfated GAGs in cartilage of condyle in the bm-Mal group aged 13 weeks was significantly lower than those in the control group and bm-Norm group. There was no significant difference between the concentration of sulfated GAGs in TMJ of mandibular shift sides and that in TMJ of non-shift sides of the bm-Mal group.