Activation of β-catenin signaling in aggrecan-expressing cells in temporomandibular joint causes osteoarthritis-like defects

β-Catenin plays a critical role in cartilage formation and development. To further understand the role of β-catenin in osteoarthritis（OA） development in temporomandibular joint（TMJ）, we have generated β-catenin conditional activation mice（β-cat（ex3）^Agc1CreER）by breeding Agc1-CreER mice with β-catenin^flox（ex3/＋）mice. Results of histologic analysis showed the progressive TMJ defects in 3-and 6-month-old β-cat（ex3）^Agc1CreERmice（tamoxifen induction was performed at 2 weeks of age）, including decreased chondrocyte numbers in the superficial layer associated with less Alcian blue staining, increased numbers of hypertrophic chondrocytes in deep layers, and rough articular surface. Compared to the TMJ phenotype of β-cat（ex3）^（Col2CreER）mice, β-cat（ex3）^（Agc1CreER）mice showed much severe morphological defects in the superficial layer of TMJ. This may reflect that Agc1-CreER mice could efficiently target cells in the superficial layer of TMJ. Results of immunostaining showed significantly increased expression of MMP13, Col-X, Adamts4,and Adamts5 in TMJ of β-cat（ex3）^（Agc1CreER）mice. Results of proliferating cell nuclear antigen（PCNA）, Ki67, and terminal deoxinucleotidyl transferase-mediated d UTP-fluorescein nick end labeling（TUNEL） staining further demonstrated that cell proliferation was decreased and cell apoptosis was increased in condylar cartilage of β-cat（ex3）^Agc1CreERmice. Our findings indicate that abnormal upregulation of β-catenin in TMJ leads to defects assembling to OA-like phenotype, further demonstrating that β-catenin plays a critical role in TMJ pathogenesis.

Disturbed bone remodelling activity varies in different stages of experimental, gradually progressive apical periodontitis in rats

Bone remodelling keeps going through the lifespan of human by bone formation and bone resorption.In the craniofacial region,mandibles act as the main force for biting and chewing,and also become susceptible to a common bone-loss disease,namely,apical periodontitis,once infected dental pulp is not treated timely,during which bone resorption occurs from the apical foramen to the apical bone area.Although conventional root canal treatment(RCT)can remove the most of the infection,chronical apical periodontitis due to incomplete removal of dental pulp and subsequent microleakage will become refractory and more challenging,and this process has scarcely been specifically studied as a bone remodelling issue in rat models.Therefore,to study chronical and refractory apical periodontitis owing to incomplete cleaning of infected dental pulp and microleackage in vivo,we establish a modified rat model of gradually progressive apical periodontitis by sealing residual necrotic dental pulp and introducing limited saliva,which simulates gradually progressive apical periodontitis,as observed in the clinical treatment of chronical and refractory apical periodontitis.We show that bone-loss is inevitable and progressive in this case of apical periodontitis,which confirms again that complete and sound root canal treatment is crucial to halt the progression of chronical and refractory apical periodontitis and promote bone formation.Interestingly,bone remodelling was enhanced at the initial stage of apical periodontitis in this model while reduced with a high osteoblast number afterwards,as shown by the time course study of the modified model.Suggesting that the pathological apical microenvironment reserve its hard tissue formation ability to some degree but in a disturbed manner.Hopefully,our findings can provide insights for future bone regenerative treatment for apical periodontitisassociated bone loss.

Concentrated growth factor regulates the macrophage-mediated immune response

Concentrated growth factor(CGF)is a promising regenerative material that serves as a scaffold and adjunct growth factor for tissue engineering.The host immune response,particularly macrophage activity,plays a critical role in injury repair and tissue regeneration.However,the biological effect of CGF on the immune response is not clear.To enrich the theoretical groundwork for clinical application,the present study examined the immunoregulatory role of CGF in macrophage functional activities in vitro.The CGF scaffold appeared as a dense fibrin network with multiple embedded leukocytes and platelets,and it was biocompatible with macrophages.Concentrated bioactive factors in the CGF extract enhanced THP-1 monocyte recruitment and promoted the maturation of suspended monocytes into adherent macrophages.CGF extract also promoted THP-1 macrophage polarization toward the M2 phenotype with upregulated CD163 expression,as detected by cell morphology and surface marker expression.A cytokine antibody array showed that CGF extract exerted a regulatory effect on macrophage functional activities by reducing secretion of the inflammatory factor interleukin-1b while inducing expression of the chemokine regulated on activation,normal T cell expressed and secreted.Mechanistically,the AKT signaling pathway was activated,and an AKT inhibitor partially suppressed the immunomodulatory effect of CGF.Our findings reveal that CGF induces a favorable immune response mediated by macrophages,which represents a promising strategy for functional tissue regeneration.