Javiera Navarrete; Francisco Mendoza; Veronica Iturriaga; Schilin Wen & Bélgica Vásquez

The temporomandibular joint (TMJ) is frequently affected by temporomandibular disorders (TMD). The selection of an animal model should be based on morphological features comparable to the human TMJ; however, few detailed comparative studies across commonly used laboratory species are available. This study aimed to compare the histological and morphometric characteristics of the TMJ in rabbit, guinea pig, rat, and mouse, to identify relevant structural differences that may guide the choice of animal models in TMD research. TMJs from four species (n = 4 joints per group) were maintained under controlled conditions. Following euthanasia, specimens were fixed, decalcified in 10 % EDTA, and processed for histology. Parasagittal sections (5 μm) were stained with toluidine blue and Picrosirius red. Histological analysis focused on the mandibular fossa (MF), articular disc (AD), and mandibular condyle (MC). A standardized morphometric protocol was applied to measure total thickness in the anterior (AR), middle (MR), and posterior (PR) regions, as well as in the tangential (TZ), transitional (TrZ), radial (RZ), and calcified cartilage (CC) zones of the condylar cartilage across the three anatomical regions. The species exhibited differences in cartilage zonation, cellular density, and structural organization. Rabbits and guinea pigs showed a well-defined zonal organization and greater cationic staining of the matrix, whereas rats and mice exhibited reduced zonal differentiation. With Picrosirius red, rabbits and guinea pigs displayed intense birefringence in the AD, while in mice it was weak and scattered. Morphometrically, rabbits generally exhibited the greatest thickness values and mice the lowest, although each species displayed a unique regional pattern. Rabbits consistently showed the highest values in the RZ and CC across all regions. The histoarchitectural and morphometric differences reflect specific biomechanical adaptations. Rabbits and guinea pigs appear to be more suitable for studies involving high mechanical load and complex fibrocartilage, rats may be useful for investigating mechanical adaptation and malocclusion due to their intermediate structure and condylar asymmetry, whereas mice are appropriate for genetic and molecular studies because of their structural homogeneity and the availability of transgenic models.

KEY WORDS: Temporomandibular joint; Histology; Morphometry; Animal models.

NAVARRETE, J.; MENDOZA, F.; ITURRIAGA, V.; WEN, S. & VÁSQUEZ, B. Morphoquantitative comparison of the temporomandibular joint in laboratory species: rabbit, guinea pig, rat and mouse. Int. J. Morphol., 43(4):1388-1401, 2025.