Effect of compressive forces on extracellular matrix in rat mandibular condylar cartilage

Abstract

To reveal the effect of compressive force on the mandibular condylar cartilage, an appliance was set on 8-week-old Wistar rats to load continuous compressive force. Immunohistochemical and histochemical analyses were performed using toluidine blue, antibodies, and probes for aggrecan, hyaluronan, type II collagen, type X collagen, and 5-bromo-2"-deoxyuridine (BrdU). Histomorphometry and statistical analyses were also performed for aggrecan and BrdU immunostaining. In toluidine blue staining, tissue metachromasia was observed in the transitional zone and the hypertrophic zone of the mandibular condylar cartilage. In histomorphometry and statistical analysis, thickness of the cartilage decreased significantly in all regions in the 3-day experimental group. However, the thickness of the cartilage in the anterior region showed recovery while it decreased continuously in the posterior region. Distributional changes of aggrecan, hyaluronan, type II collagen, and type X collagen in the experimental groups were similar to those for toluidine blue staining. The immunostained area of all these molecules decreased as a result of the decrement of the cartilage area. However, enhanced immunostaining for aggrecan in the proliferative zone was observed only in the 1-day experimental group. BrdU-positive cells, observed in the proliferating zone and the transitional zone, decreased significantly in the experimental group 3 days after force was applied. These results demonstrate that continuous compressive forces on the mandibular condylar cartilage decrease the proliferation of chondrocytes and the amount of extracellular matrices.

The effects of gradually induced backward movement of the mandible by a Twin Inclined Plane Device in rats

“…Posterior condylar displacement with a continuous force can induce a decrease in the proliferation of chondrocytes and the amount of extracellular matrix. 24 Our results indicated that the areas in the most posterior and superior regions of the condylar cartilage are sensitive to microenvironment change, which is in agreement with the findings of Tang and Rabie 25 and Tang et al 26 …”

Altered mandibular growth under functional posterior displacement in rats

“…15,16 In adult rats, continuous compressive force on the mandibular condylar cartilage decreased the proliferation of chondrocytes and the amount of extracellular matrices after 7 days. 7 In young monkeys, constant retraction force applied to the mandible resulted in growth disturbance and condylar remodeling. 17 Resorption occurred at the posterior surface of the condyle and the posterior wall of the glenoid fossa, while apposition was observed at the anterior surface.…”

“…5 In contrast, posterior displacement of the mandible demonstrated a decrease in the proliferation of chondrocytes and the amount of extracellular matrix. 6,7 However, the extent to which this can be achieved and whether it has any clinical significance are topics of long-standing controversy. 2 Due to the design of these experimental studies it is often not clear whether the observed effects are temporary or long lasting, and whether these changes are restricted at the cellular level in condylar cartilage or ultimately influence mandibular length.…”

Endoplasmic Reticulum Stress Regulates Rat Mandibular Cartilage Thinning under Compressive Mechanical Stress

“…1B). This regionalization method has been extensively used in studies on mandibular condylar cartilage (12)(13)(14)(15). The thickness of each zone was measured with Image-Pro Plus software.…”