Exosomes derived from osteoclasts under compression stress inhibit osteoblast differentiation

Orthodontic tooth movement is triggered by orthodontic force loading on the periodontal ligament and is achieved by alveolar bone remodeling,which is regulated by intimate crosstalk between osteoclastogenesis and osteoblast differentiation.Whether the communication between osteoclasts and osteoblasts is influenced by orthodontic compression stress requires further clarification.In this study,osteoclasts were differentiated for 10 days.On day 4 of differentiation,the number of pre-osteoclasts peaked,as determined by the increased expression of RANK and the number of multinucleated cells.After 24 h of compression stress loading,on day 4,the number of osteoclasts increased,and the optimal magnitude of stress to promote osteoclastogenesis was determined as 1 g/cm2.Moreover,the results of RNA-sequencing analysis showed that the miRNA expression profile changed markedly after compression loading and that many of the altered miRNAs were associated with cell communication functions.A series of indirect co-culture experiments showed an inhibitory effect of osteoclasts on osteoblast differentiation,especially after compression.Next,we added osteoclast-derived exosomes to hPDLSCs during osteoblast differentiation.Exosomes derived from osteoclasts under compression(cEXO)showed a greater inhibitory effect on osteoblast differentiation,compared to exosomes from osteoclasts without compression(EXO).Therefore,we analyzed differentially expressed miRNAs associated with bone development functions in exosomes:miR-223-5p and miR-181a-5p were downregulated,whereas miR-133a-3p,miR-203a-3p,miR-106a-5p,and miR-331-3p were upregulated;these altered expressions may explain the enhanced inhibitory effect of compression stress.

Long non-coding RNAMIR22HG inhibits the adipogenesis of human bone marrow mesenchymal stem cells with the involvement of Wnt/β-catenin pathway

Osteoporosis is a frequently occurring bone remodeling disorder worldwide with one characteristic being decreasing bone mineral density and a predisposition to bone fracture,which diminishes patients’quality of life.Several studies showed that imbalance between the osteogenesis and adipogenesis of bone marrow mesenchymal stem cells(BMSCs)took part in the development of osteoporosis.In previous study,we found MIR22HG regulated the osteogenesis of human BMSCs positively.In this study,we found that MIR22HG was decreased during the adipogenesis of human BMSCs and exerted negative effects on adipogenesis with the involvement of Wnt/β-catenin signaling pathway both in vitro and in vivo.Nitazoxanide could inhibit Wnt signaling and relieve MIR22HG’s suppression on adipogenesis.These findings indicated that MIR22HG had great potential in clinical application for osteoporosis treatment and prevention.

Compression loading of osteoclasts attenuated micro RNA-146a-5p expression,which promotes angiogenesis by targeting adiponectin

Osteoclastogenesis in alveolar bone induced by compression stress triggers orthodontic tooth movement.Compression stress also stimulates angiogenesis,which is essential for osteoclastogenesis.However,the effects of osteoclastogenesis induced by compression on angiogenesis are poorly understood.In vivo,we found the markers of angiogenesis increased during orthodontic bone remodeling.In vitro,osteoclast-derived exosomes increased proliferation,migration,and tube formation of human umbilical vein endothelial cells(HUVECs),as well as expression of vascular endothelial growth factor and CD31.The promotive effects of exosomes derived from compressed osteoclasts were greater than those derived from osteoclasts without compression.Next,we analyzed changes in the micro RNA transcriptome after compression stress and focused on micro RNA146 a-5 p(mi R-146 a),which was significantly decreased by compression.Transfection of an inhibitor of mi R-146 a stimulated angiogenesis of HUVECs while mi R-146 a mimics repressed angiogenesis.Adiponectin(ADP)was confirmed to be a target of mi R-146 a by dual luciferase reporter assay.In HUVECs treated with exosomes,we detected increased ADP which promoted angiogenesis.Knockdown of ADP in HUVECs reduced the promotive effects of exosomes.Our results demonstrate that the decreased mi R-146 a observed in osteoclasts after compression promotes angiogenesis by targeting ADP,suggesting a novel method to interfere with bone remodeling induced by compression stress.

Loss of cathepsin C enhances keratinocyte proliferation and inhibits apoptosis

Papillon-Lefevre Syndrome is a rare autosomal recessive disorder characterized by rapidly progressive periodontitis and confined palrnoplantar hyperkeratosis resulting from genetic mutations in cathepsin C （CTSC）. The present study investigated the effect of CTSC on keratinocyte proliferation and apoptosis. HaCaT keratinocytes were transfected with wild-type CTSC and CTSC-targeted siRNAs to investigate the effects of CTSC expression on cell keratosis. Real-time PCR and Western blot analyses showed that the levels of loricrin and keratin （KRT）-I, but not KRT9, was correlated with CTSC expression. Loricrin was increased in the CTSC-overex- pression group and downregulated in the CTSC-silenced group. A positive association between loricrin expression and cell apoptosis was detected in HaCaT keratinocytes. KRT1 was decreased in the CTSC-overexpression group and increased in the CTSC-silenced group. Prominent, punctuate KRT1 aggregates were present in CTSC-knockdown HaCaT cells. This study suggested that loss of CTSC contributes to keratinocyte hyperkeratosis via downregulation of loricrin and enhanced cell proliferation.