Dataset Information

The immunoregulatory role of p21 in the development of the temporomandibular joint-osteoarthritis.

ABSTRACT:

Objective

We aimed to identify the immunoregulatory role of the cyclin-dependent kinase inhibitor p21 in the homeostasis of mandibular condylar cartilage affected by mechanical stress.

Materials and methods

Ten C57BL/6 wild-type (WT) and ten p21^-/- mice aged 8 weeks were divided into the untreated and treated groups. In the treated groups, mechanical stress was applied to the temporomandibular joint (TMJ) through forced mouth opening for 3 hr/day for 7 days. The dissected TMJs were assessed using micro-CT, histology, and immunohistochemistry.

Results

Treated p21^-/- condyles with mechanical stress revealed more severe subchondral bone destruction, with thinner cartilage layers and smaller proteoglycan area relative to treated WT condyles; untreated WT and p21^-/- condyles had smoother surfaces. Immunohistochemistry revealed significant increases in the numbers of caspase-3, interleukin-1β, matrix metalloprotease (MMP)-9, and MMP-13 positive cells, and few aggrecan positive cells, in treated p21^-/- than in treated WT samples. Moreover, the number of TUNEL positive cells markedly increased in p21^-/- condyles affected by mechanical stress.

Conclusions

Our findings indicate that p21 in chondrocytes contributes to regulate matrix synthesis via the control ofm aggrecan and MMP-13 expression under mechanical stress. Thus, p21 might regulate the pathogenesis of osteoarthritis in the TMJ.

SUBMITTER: Khurel-Ochir T

PROVIDER: S-EPMC8204032 | biostudies-literature |

REPOSITORIES: biostudies-literature

ACCESS DATA

Similar Datasets

Project description:Background Extracellular matrix (ECM) protein malfunction or defect may lead to temporomandibular joint osteoarthritis (TMJ OA). Dentin sialophophoprotein (DSPP) is a mandibular condylar cartilage ECM protein, and its deletion impacted cell proliferation and other extracellular matrix alterations of postnatal condylar cartilage. However, it remains unclear if long-term loss of function of DSPP leads to TMJ OA. The study aimed to test the hypothesis that long-term haploinsufficiency of DSPP causes TMJ OA. Materials and Methods To determine whether Dspp+/- mice exhibit TMJ OA but no severe tooth defects, mandibles of wild-type (WT), Dspp+/-, and Dspp homozygous (Dspp-/-) mice were analyzed by Micro-computed tomography (micro-CT). To characterize the progression and possible mechanisms of osteoarthritic degeneration over time in Dspp+/- mice over time, condyles of Dspp+/- and WT mice were analyzed radiologically, histologically, and immunohistochemically. Results Micro-CT and histomorphometric analyses revealed that Dspp+/- and Dspp-/- mice had significantly lower subchondral bone mass, bone volume fraction, bone mineral density, and trabecular thickness compared to WT mice at 12 months. Interestingly, in contrast to Dspp-/- mice which exhibited tooth loss, Dspp+/- mice had minor tooth defects. RNA sequencing data showed that haplodeficency of DSPP affects the biological process of ossification and osteoclast differentiation. Additionally, histological analysis showed that Dspp+/- mice had condylar cartilage fissures, reduced cartilage thickness, decreased articular cell numbers and severe subchondral bone cavities, and with signs that were exaggerated with age. Radiographic data showed an increase in subchondral osteoporosis up to 18 months and osteophyte formation at 21 months. Moreover, Dspp+/- mice showed increased distribution of osteoclast in the subchondal bone and increased expression of MMP2, IL-6, FN-1, and TLR4 in the mandibular condylar cartilage. Conclusions Dspp+/- mice exhibit TMJ OA in a time-dependent manner, with lesions in the mandibular condyle attributed to hypomineralization of subchondral bone and breakdown of the mandibular condylar cartilage, accompanied by upregulation of inflammatory markers.

Project description:BackgroundsAbnormal cartilage calcification is one of the pathological changes of temporomandibular joint (TMJ) osteoarthritis (OA). Recent studies have reported that exosomes can regulate the formation of abnormal calcified nodules in diseases including atherosclerosis and chronic kidney disease. However, the influences of chondrocyte-derived exosomes on abnormal cartilage calcification in TMJ OA are still unclear.MethodsTMJ OA was induced by unilateral anterior crossbite (UAC) for 4, 8, or 12 weeks in rats to observe abnormal calcification in TMJ condylar cartilage and exosome formation. Concomitantly, GW4869, the inhibitor of exosome formation, was locally injected to the TMJ of rats under stimulation of UAC, while the exosomes extracted from primary condylar chondrocytes stimulated with fluid flow shear stress (FFSS) were locally injected to rats TMJ.ResultsAbnormal calcification was enhanced in the degenerative cartilage of TMJ OA in UAC rats, and a large number of exosome-like structures with diameters of 50-150 nm were found in the calcified cartilage together with decreased expression of matrix Gla protein (MGP) and increased expression of CD63, tissue-nonspecific alkaline phosphatase (TNAP) and nucleotide pyrophosphatase/phosphodiesterase-1 (NPP1). After FFSS stimulation, the number of exosomes secreted by chondrocytes and the numbers of calcified nodules were increased in cultured cells, and the protein levels of MGP, TNAP, and NPP1 in exosomes were changed. Inhibition of exosome formation, TNAP, and NPP1 or supplementation with exogenous MGP effectively alleviated FFSS-induced chondrocyte calcification. Local injection of GW4869, the exosome inhibitor, alleviated TMJ OA-related cartilage degeneration and calcification in UAC rats. Local injection of exosomes obtained from chondrocytes stimulated by FFSS to the TMJs of normal rats induced cartilage degeneration and calcification similar to that in TMJ OA.ConclusionsAbnormal biomechanical loading leads to enhanced formation of chondrocyte-derived exosomes, in which promoters of calcification increased and inhibitors decreased, resulting in accelerating abnormal cartilage calcification in TMJ OA. The inhibition of degenerative chondrocyte-derived exosomes is expected to be a new way to prevent and treat TMJ OA.