Age-Dependent Physiological Changes in the Histoarchitecture of the Articular Cartilage of the Rabbit Mandibular Condyle: A Morphological and Morphometric Study

Abstract

Mandibular condyle articular cartilage participates in condylar postnatal growth and is responsible for adaptations to anatomical and/or biomechanical alterations throughout life. In a preliminary study in rabbits, differences were observed in the thickness of the layers of articular cartilage in control animals at 5 and 6 months (generally considered adults for this purpose). This study aimed to describe sagittally sectioned condylar cartilages stained with Picrosirius-hematoxylin in rabbits at 40 days and 5, 6, 8, 13, and 18 months to determine when histological maturity is reached. At 40 days, 5 layers were seen: fibrous, proliferative, transition, maturation, and hypertrophic. Older animals (5–18 months) lacked the transition layer. Fibrous, proliferative, and hypertrophic regions were considered for morphometric analysis. The thickness of the fibrous region did not change during the analyzed period (p = 0.1899). When proliferative and hypertrophic regions and the total thickness of the cartilage were compared, a difference was detected (p < 0.001). The thickness of the proliferative region was greatest at 40 days and decreased at 5 months; however, it increased at 6 months, when it was significantly thicker than at 5, 8, 13, and 18 months. Both the hypertrophic region and the total thickness were thickest at 40 days, intermediate at 5, 6, and 8 months, and thinnest at 13 and 18 months. In summary, our data suggest a physiological period of increased cartilage growth at 6 months. Additionally, rabbits at this age should be avoided in experiments involving condylar cartilage. Finally, 13-month-old rabbits have reached histological maturity of the condylar cartilage.

Bone and cartilage changes in rabbit mandibular condyles after 1 injection of botulinum toxin

“…This result differs from the growth stasis reported at these ages elsewhere, 30 but that study measured thickness in the anterior condyle rather than the apex. The thicker condylar cartilage in the older animals is probably not associated with condylar growth, for reasons given above and the fact that there was no indication of increasing replication rate over time.…”

“…The continued cartilage proliferation and endochondral ossification, and the fine trabecular structure observed in the subchondral region, imply that condylar growth might not have been complete in our sample, and others have noted histological changes in the rabbit condyle until even older ages. 30 Nevertheless, because 12-week endpoint condyles were similar in size to 4-week endpoint condyles, 15 reduction in growth is an unlikely explanation for the loss of bone on the BoNT/A-injected side.…”

Glycosylation of DMP1 Is Essential for Chondrogenesis of Condylar Cartilage

“…It is also known that the ALK1/ALK5 ratio is increased in regular osteoarthritis models. In our study, the smad signals and ALK1/ALK5 ratio were dramatically increased in the S89G-DMP1 mice, which is consistent with the age-related osteoarthritis changes in the MCC (van der Kraan et al 2010;Galhardo et al 2012;Ryan et al 2013;van Caam et al 2016). Thus, an S89G substitution leads to cartilage defects by downregulating TGF-β signaling molecules and related ECM macromolecules.…”

Implications of zonal architecture on differential gene expression profiling and altered pathway expressions in mandibular condylar cartilage

“…Beside its unique histomorphological zonal organization, MCC is distinguished from growth and articular cartilages in the embryonic origin, biochemical and biomechanical properties 14,[21][22][23] . Functionally, MCC has a dual role; one as an articular fibrocartilage responsible for load distribution and disc articulation, and the other one as a major site responsible for mandibular growth 24 .…”

“…to validate the MAA data by qRT-PCR. Seven genes out of 10 showed expression patterns in real-time PCR comparable to those of the MAA (Supplementary Figs [14][15][16][17][18][19][20][21][22][23]…”