Chitooligosaccharide inhibits RANKL-induced osteoclastogenesis and ligation-induced periodontitis by suppressing MAPK/ c-fos/NFATC1 signaling

Chitosan-based biomaterials for bone tissue engineering

Common critical size bone defects encountered in clinical practice often result in inadequate bone regeneration,primarily due to the extent of damage surpassing the inherent capacity of the body for self-healing. Bone tissue engineering scaffolds possess the desirable characteristics of biomimetic bone structure, simulated extracellular matrix, optimal mechanical strength, and biological functionality, rendering them the preferred option for the treatment of bone defects. Chitosan demonstrates favorable biocompatibility, plasticity, and a range of biological activities, rendering it a highly appealing material. Chitosan and its derivatives have been found to exert an impact on bone repair through their ability to modulate macrophage polarization, angiogenesis, and the delicate equilibrium of bone remodeling. However, the efficacy of pure chitosan is constrained, necessitating its combination with other bioactive substances to achieve an optimal biomimetic scaffold that is compatible with the specific bone defect site. Chitosan is commonly utilized in the field of bone repair in four different application forms: rigid scaffold, hydrogel, membranes, and microspheres. In order to enhance comprehension of the benefits and constraints associated with chitosan, this review provides a comprehensive overview of the structure and biological properties of chitosan, the molecular mechanisms by which chitosan promotes osteogenic differentiation, the diverse methods of chitosan preparation for various applications, and the impacts of chitosan when loaded with bioactive substances.

LRP5 Down-Regulation Exacerbates Inflammation and Alveolar Bone Loss in Periodontitis by Inhibiting PI3K/c-FOS Signalling

AIM

To investigate the involvement of low-density lipoprotein receptor-related protein 5 (LRP5) in inflammation and alveolar bone loss in periodontitis.

MATERIALS AND METHODS

Gingival tissues were obtained from 10 periodontitis patients and 10 healthy individuals. Wild-type (WT) and osteoblast-specific Lrp5 conditional knock-out C57BL/6 (LRP5fl/fl;Oc-Cre) mice were used to establish a ligature-induced mouse model of periodontitis. Human periodontal ligament stem cells (hPDLSCs) were isolated and used to further verify the mechanism through which LRP5 mediates periodontitis in vitro. Micro-computed tomography, haematoxylin and eosin staining, immunohistochemistry, quantitative reverse transcription PCR, western blotting, enzyme-linked immunosorbent assay and RNA sequencing were performed to explore the role of LRP5 in periodontitis and the underlying mechanism.

RESULTS

LRP5 expression was down-regulated in human/mouse periodontal tissues compared to that in healthy controls. Compared to those in wild-type mice, the periodontal tissues of LRP5fl/fl;Oc-Cre mice had increased alveolar bone loss, higher proinflammatory cytokine levels, and lower osteogenesis-related factor expression. LRP5 expression was down-regulated in hPDLSCs after lipopolysaccharide treatment in vitro. LRP5 knockdown increased proinflammatory cytokine production and inhibited osteoblastogenesis by inhibiting PI3K/c-FOS signalling.

CONCLUSION

LRP5 down-regulation exacerbates inflammation and alveolar bone loss in periodontitis by inhibiting PI3K/c-FOS signalling, suggesting LRP5 as a potential therapeutic target for periodontitis.

Potential diagnostic markers and therapeutic targets for periodontitis and Alzheimer's disease based on bioinformatics analysis

BACKGROUND AND OBJECTIVE

As a chronic inflammatory disease, periodontitis threatens oral health and is a risk factor for Alzheimer's disease (AD). There is growing evidence that these two diseases are closely related. However, current research is still incomplete in understanding the common genes and common mechanisms between periodontitis and AD. In this study, we aimed to identify common genes in periodontitis and AD and analyze the relationship between crucial genes and immune cells to provide new therapeutic targets for clinical treatment.

MATERIALS AND METHODS

We evaluated differentially expressed genes (DEGs) specific to periodontitis and AD. Co-expressed genes were identified by obtaining gene expression profile data from the Gene Expression Omnibus (GEO) database. Using the STRING database, protein-protein interaction (PPI) networks were constructed, and essential genes were identified. We also used four algorithms to identify critical genes and constructed regulatory networks. The association of crucial genes with immune cells and potential therapeutic effects was also assessed.

RESULTS

PDGFRB, VCAN, TIMP1, CHL1, EFEMP2, and IGFBP5 were obtained as crucial common genes. Immune infiltration analysis showed that Natural killer cells and Myeloid-derived suppressor cells were significantly differentially expressed in patients with PD and AD compared with the normal group. FOXC1 and GATA2 are important TFs for PD and AD. MiR-23a, miR-23b, miR-23a, and miR-23b were associated with AD and PD. Finally, the hub genes retrieved from the DSigDB database indicate multiple drug molecule and drug-target interactions.

CONCLUSION

This study reveals commonalities in common hub genes and immune infiltration between periodontitis and AD, and the analysis of six hub genes and immune cells may provide new insights into potential therapeutic directions for the pathogenesis of periodontitis complicated by AD.

Changes in cuproptosis-related gene expression in periodontitis: An integrated bioinformatic analysis

Periodontitis causes inflammatory destruction of tooth-supporting tissues; however, the complex mechanism underlying its etiology remains unclear. Cuproptosis is a type of cell death caused by an imbalance in intracellular copper homeostasis that leads to excess copper. However, changes in the expression and biological function of cuproptosis-related genes (CRGs) in periodontitis are not yet fully understood. This study investigated the comprehensive effects of differentially expressed CRGs (DE-CRGs) on periodontitis via bioinformatic analysis. Nine DE-CRGs were discovered using normal and periodontitis gingival samples, and single-cell RNA sequencing data were analyzed to identify them changes in diverse cell clusters. We then detected the correlation between DE-CRGs and immune infiltration, immune factors, mitochondrial dysfunction, diagnostic efficacy, and predicted drugs. Moreover, changes of DE-CRG in whole periodontitis tissue and a human gingival fibroblast cell line (HGF-1) were confirmed and copper content changes in HGF-1 cells were investigated. Most DE-CRG expression trends were reversed between the periodontal tissues and cell clusters, which may be related to the proportion of cell clusters changes caused periodontitis. Furthermore, most DE-CRG trends in periodontitis cell clusters were inconsistent with the effects of cuproptosis. In HGF-1 cells treated with Porphyromonas gingivalis lipopolysaccharide (Pg-LPS), the intracellular copper content increased by more than threefold, indicating that although some periodontitis cells had excess copper, the amount may not have been sufficient to trigger cuproptosis. Additionally, DE-CRGs were closely associated with multiple biological functions, antibiotic drugs, and natural herbal medicines. Our findings may provide an overview of DE-CRGs in the pathogenesis and treatment of periodontitis.

Chitosan derived chito-oligosaccharides promote osteoblast differentiation and offer anti-osteoporotic potential: Molecular and morphological evidence from a zebrafish model

This study delves into the potential of chito-oligosaccharides (COS) to promote osteoblast differentiation and prevent osteoporosis, utilizing experiments with mouse MSCs and the zebrafish model. The preliminary biocompatibility study affirms the non-toxic nature of COS across various concentrations. In the osteoblast differentiation study, COS enhances ALP activity and calcium deposition at the cellular level. Moreover, COS induces the upregulation of molecular markers, including Runx2, Type I collagen, ALP, osteocalcin, and osteonectin in mouse MSCs. Zebrafish studies further demonstrate COS's anti-osteoporotic effects, showcasing its ability to expedite fin fracture repair, vertebral mineralization, and bone mineralization in dexamethasone-induced osteoporosis models. The scale regenerative study reveals that COS mitigates the detrimental effects of dexamethasone induced osteoclastic activity, reducing TRAP and hydroxyproline levels while elevating the expression of Runx2a MASNA isoform, collagen2α, OC, and ON mRNAs. Additionally, COS enhances calcium and phosphorus levels in regenerated scales, impacting the bone-healthy calcium-to‑phosphorus ratio. The study also suggests that COS modulates the MMP3-Osteopontin-MAPK signaling pathway. Overall, this comprehensive investigation underscores the potential of COS to prevent and treat osteoporosis. Its multifaceted cellular and molecular effects, combined with in vivo bone regeneration and repair, propose that COS may be effective in addressing osteoporosis and related bone disorders. Nonetheless, further research is imperative to unravel underlying mechanisms and optimize clinical applications.

IL13Rα2 as a crucial receptor for Chi3l1 in osteoclast differentiation and bone resorption through the MAPK/AKT pathway

BACKGROUND

Previous research has revealed that the 18 glycoside hydrolase gene family (GH18) member Chitinase 3-like 1 (Chi3l1) can regulate osteoclast differentiation and bone resorption. However, its downstream receptors and molecular mechanisms during osteoclastogenesis have yet to be elucidated.

METHODS

Initially, we conducted a comprehensive investigation to evaluate the effects of recombinant Chi3l1 protein or Chi3l1 siRNA on osteoclast differentiation and the RANKL-induced MAPK/AKT signaling pathways. Moreover, we used immunofluorescence and immunoprecipitation assays to identify IL13Rα2 as the downstream receptor of Chi3l1. Subsequently, we investigated the impact of IL13Rα2 recombinant protein or IL13Rα2-siRNA on osteoclast differentiation and the associated signaling pathways. Finally, we performed in vivo experiments to examine the effect of recombinant IL13Rα2 protein in an LPS-induced mouse model of cranial osteolysis.

RESULTS

Our findings highlight that the administration of recombinant Chi3l1 protein increased the formation of osteoclasts and bolstered the expression of several osteoclast-specific genes (TRAP, NFATC1, CTR, CTSK, V-ATPase d2, and Dc-STAMP). Additionally, Chi3l1 significantly promoted the RANKL-induced MAPK (ERK/P38/JNK) and AKT pathway activation, whereas Chi3l1 silencing inhibited this process. Next, using immunofluorescence and co-immunoprecipitation assays, we identified IL13Rα2 as the binding partner of Chi3l1 during osteoclastogenesis. IL13Rα2 recombinant protein or IL13Rα2-siRNA also inhibited osteoclast differentiation, and IL13Rα2-siRNA attenuated the RANKL-induced activation of the MAPK (ERK/P38/JNK) and AKT pathways, similar to the effects observed upon silencing of Chi3l1. Moreover, the promoting effect of recombinant Chi3l1 protein on osteoclastogenesis and the activation of the MAPK and AKT pathways was reversed by IL13Rα2 siRNA. Finally, recombinant LI13Rα2 protein significantly attenuated the LPS-induced cranial osteolysis and the number of osteoclasts in vivo.

CONCLUSIONS

Our findings suggested that IL13Rα2 served as a crucial receptor for Chi3l1, enhancing RANKL-induced MAPK and AKT activation to promote osteoclast differentiation. These findings provide valuable insights into the molecular mechanisms of Chi3l1 in osteoclastogenesis, with potential therapeutic implications for osteoclast-related diseases. Video Abstract.

Koumine inhibits RANKL-induced ubiquitination and NF-κB activation to prevent ovariectomy and aging-induced bone loss

Osteoporosis (OP) is a bone remodeling disease characterized by an imbalance between bone resorption and formation. Osteoclasts are the primary therapeutic targets for treating bone destruction. Koumine (KM), the most bioactive component in Gelsemium alkaloids, exhibits antitumor, immunosuppressive, anti-inflammatory, and analgesic properties. However, the effects of bone loss have not been well studied. This study conducted in vitro and in vivo verification experiments on KM. The results showed that KM inhibited bone resorption and tartrate-resistant acid phosphatase positive (TRAP+) osteoclasts development by mature osteoclasts in a dose-dependent manner. Moreover, KM prevented OVX-induced OP in vivo and potentially inhibited ubiquitination, a process closely related to various biological activities, including protein interaction, transcription, and transmembrane signal transduction regulation, especially within the nuclear factor-κB (NF-κB) pathway. Previous studies have demonstrated that several proteins ubiquitination promotes osteoclastogenesis, our study indicated that KM inhibits early NF-κB activation and receptor activator of NF-κB ligand induced ubiquitination, a critical factor in osteoclast differentiation. In conclusion, our research suggests that KM holds potential as an effective therapeutic agent for OP.

Long-chain noncoding RNA sequencing analysis reveals the molecular profiles of chemically induced mammary epithelial cells

Long noncoding RNAs (lncRNAs) were important regulators affecting the cellular reprogramming process. Previous studies from our group have demonstrated that small molecule compounds can induce goat ear fibroblasts to reprogram into mammary epithelial cells with lactation function. In this study, we used lncRNA-Sequencing (lncRNA-seq) to analyze the lncRNA expression profile of cells before and after reprogramming (CK vs. 5i8 d). The results showed that a total of 3,970 candidate differential lncRNAs were detected, 1,170 annotated and 2,800 new lncRNAs. Compared to 0 d cells, 738 lncRNAs were significantly upregulated and 550 were significantly downregulated in 8 d cells. Heat maps of lncrnas and target genes with significant differences showed that the fate of cell lineages changed. Functional enrichment analysis revealed that these differently expressed (DE) lncRNAs target genes were mainly involved in signaling pathways related to reprogramming and mammary gland development, such as the Wnt signaling pathway, PI3K-Akt signaling pathway, arginine and proline metabolism, ECM-receptor interaction, and MAPK signaling pathway. The accuracy of sequencing was verified by real-time fluorescence quantification (RT-qPCR) of lncRNAs and key candidate genes, and it was also demonstrated that the phenotype and genes of the cells were changed. Therefore, this study offers a foundation for explaining the molecular mechanisms of lncRNAs in chemically induced mammary epithelial cells.

Oligosaccharides from Sargassum thunbergii inhibit osteoclast differentiation via regulation of IRF-8 signaling

Osteoporosis (OP) is a systemic bone degenerative disease characterized by low bone mass and deteriorated microarchitecture of bone tissue, causing high morbidity and mortality rates. Bone resorption by overactivated osteoclasts (OCs) is the main cause of osteoporosis. Glucuronomannan and its oligomers (Gs) and their sulfated derivatives (SGs) were previously prepared. The anti-osteoporosis activities of these glycans were evaluated. Firstly, we determined the viability of RAW264.7 by CCK-8 test. Nextly, we investigated the inhibitory effects of Gs and SGs on the differentiation of RAW264.7 cells into OCs using tartrate-resistant acid phosphatase (TRAP) staining, F-actin ring staining, qualitative reverse-transcription polymerase chain reaction(qRT-PCR) and western blotting. TRAP staining revealed that Gs significantly blocked RANKL-induced OC generation while SGs did not exhibit this ability. F-actin staining assays demonstrated that Gs inhibits RANKL-induced actin ring formation. qRT-PCR analyses indicated that Gs dose-dependently inhibited the expression of OCs marker genes including Trap, NFATc1, c-Fos, DC-Stamp and ATP60 during the differentiation process, while SGs did not suppress. Regarding the mechanism of Gs, it was found that Gs suppressed osteoclastogenesis via inhibiting the degradation of IRF-8 and interfering with NF-κB pathway activation. Together, these results suggest that Gs have the ability to inhibit osteoclastogenesis by modulating IRF-8 signaling.

Characterization of effects of chitooligosaccharide monomer addition on immunomodulatory activity in macrophages

The present study aimed to investigate the effects of five chitooligosaccharide monomers of different molecular weights on immunomodulatory activity in macrophage-like RAW264.7 cells. The incubation of various chitooligosaccharide monomers enhanced phagocytosis and pinocytosis activity toward Staphylococcus aureus and Escherichia coli in RAW264.7 cells. The incorporation of chitooligosaccharide monomers significantly boosted the generation of reactive oxygen species and reactive nitrogen species, as well as the release of inflammatory cytokines. To further explore the mechanism of inflammation regulated by chitooligosaccharide, the activation inhibitors of NF-кB (CAPE) and TLR-4 (TAK-242) were utilized, the determination data demonstrated that chitobiose suppressed the expression of inflammatory cytokines and NF-кB p65. In addition, the investigation results revealed that the presence of the mannose receptor inhibitor (mannan) suppressed chitohexaose-induced phagocytic activity and inflammatory cytokines. These results suggested that the five distinct chitooligosaccharide monomers had inconsistent effects, the chitobiose and chitohexaose exhibiting the best biological activity in activating RAW264.7 cells, promoting cell proliferation, and increasing non-specific immunity.

Lacticaseibacillus rhamnosus MG4706 Suppresses Periodontitis in Osteoclasts, Inflammation-Inducing Cells, and Ligature-Induced Rats

Periodontitis is a chronic inflammatory disease characterized by tooth loss due to inflammation and the loss of alveolar bone. Periodontitis is closely related to various systemic diseases and is emerging as a global health problem. In this study, we investigated the anti-inflammatory effect of lactic acid bacteria (LAB) in vitro on Porphyromonas gingivalis (P. gingivalis) LPS-activated RAW264.7 and human gingival fibroblasts-1 (HGF-1) cells and the anti-osteoclastogenic effect of LAB on RANKL-induced RAW264.7 cells. All LAB strains (Lacticaseibacillus rhamnosus MG4706, MG4709, and MG4711) inhibited nitric oxide (NO)/inducible nitric oxide synthase (iNOS) in P. gingivalis LPS-activated RAW264.7 cells and pro-inflammatory cytokines (IL-1β and IL-6) and matrix metalloproteinase (MMP-8 and MMP-9) in HGF-1 cells. In addition, LAB treatment inhibited osteoclastogenesis by reducing tartrate-resistant acid phosphatase (TRAP) activity and cathepsin K (CtsK) through the downregulation of nuclear factor of activated T cells cytoplasmic 1 (NFATc1) and c-fos gene expression in RANKL-induced RAW264.7 cells. Administration of MG4706 alleviated alveolar bone loss indices and reduced the gene expression of IL-1β, IL-6, MMP-8, MMP-9, and RANKL/OPG ratio in gingival tissue. In conclusion, L. rhamnosus MG4706 has the potential to alleviate periodontitis.

Polarized Macrophages in Periodontitis: Characteristics, Function, and Molecular Signaling

Periodontitis (PD) is a common chronic infectious disease. The local inflammatory response in the host may cause the destruction of supporting periodontal tissue. Macrophages play a variety of roles in PD, including regulatory and phagocytosis. Moreover, under the induction of different factors, macrophages polarize and form different functional phenotypes. Among them, M1-type macrophages with proinflammatory functions and M2-type macrophages with anti-inflammatory functions are the most representative, and both of them can regulate the tendency of the immune system to exert proinflammatory or anti-inflammatory functions. M1 and M2 macrophages are involved in the destructive and reparative stages of PD. Due to the complex microenvironment of PD, the dynamic development of PD, and various local mediators, increasing attention has been given to the study of macrophage polarization in PD. This review summarizes the role of macrophage polarization in the development of PD and its research progress.

Anethole inhibits RANKL-induced osteoclastogenesis by downregulating ERK/AKT signaling and prevents ovariectomy-induced bone loss in vivo

Postmenopausal osteoporosis is a chronic population health hazard systemic metabolic disease caused by excessive bone resorption and reduced bone formation. The activity between osteoblast and osteoclast, with their mutual effects, influence the procedure of normal bone remodeling. Over-activated osteoclast differentiation and function play a crucial role in excessive bone resorption. Hence, therapy strategies targeting osteoclast activity may promote the bone mass preservation and delay the osteoporosis process. Natural compound (anethole) is emerging as potential therapeutics for various metabolic diseases. The purpose of this study is to investigate the potential effects of anethole on RANKL-induced osteoclast formation and function in vitro and in vivo. Here, in vitro TRAP staining assay was performed to investigate the inhibitory effect of anethole on osteoclast differentiation. Bone pits resorption assay revealed that osteoclast-mediated bone resorption was inhibited by anethole. At mRNA and protein levels, anethole significantly reduced the expression of osteoclast-specific genes expression in a concentration- or time-dependent manner, including NFATc1, MMP-9, DC-STAMP, c-F, TRAP, CTR, Cathepsin K, and V-ATPase d2. Furthermore, intracellular signaling transduction assay indicated that anethole inhibited osteoclast formation via blocking ERK and AKT signaling. GSK3β, the downstream signal of AKT, is simultaneously suppressed with anethole treatment. Based on ovariectomized (OVX) mice model, micro-CT and histological staining results suggested that anethole prevented estrogen deficiency-induced bone mass loss and increased osteoclast activity in vivo. In conclusion, our results show significant indications that anethole exhibits an osteoprotective effect and may be potential for the treatment of osteoporosis.

Oroxylin A reduces osteoclast formation and bone resorption via suppressing RANKL-induced ROS and NFATc1 activation

Excessive bone erosion by osteoclasts is associated with osteoporosis, rheumatoid arthritis, and periprosthetic osteolysis. Targeting osteoclasts may serve as an effective treatment for osteolytic diseases. Although drugs are currently available for the treatment of these diseases, exploring potential anti-osteoclast natural compounds with safe and effective treatment remains needed. Oroxylin A (OA), a natural flavonoid isolated from the root of Scutellaria baicalensis Georgi, has numerous beneficial pharmacological characteristics, including anti-inflammatory and antioxidant activity. However, its effects and mechanisms on osteoclast formation and bone resorption have not yet been clarified. Our research showed that OA attenuated the formation and function of osteoclast induced by RANKL in a time- and concentration-dependent manner without any cytotoxicity. Mechanistically, OA suppressed intracellular reactive oxygen species (ROS) levels through the Nrf2-mediated antioxidant response. Moreover, OA inhibited the activity of NFATc1, the master transcriptional regulator of RANKL-induced osteoclastogenesis. OA exhibited protective effects in mouse models of post-ovariectomy (OVX)- and lipopolysaccharide (LPS)-induced bone loss, in accordance with its in vitro anti-osteoclastogenic effect. Collectively, our findings highlight the potential of OA as a pharmacological agent for the prevention of osteoclast-mediated osteolytic diseases.

Puerarin alleviates osteoporosis in the ovariectomy-induced mice by suppressing osteoclastogenesis via inhibition of TRAF6/ROS-dependent MAPK/NF-κB signaling pathways

In this study, we investigated the mechanisms by which puerarin alleviates osteoclast-related loss of bone mass in ovariectomy (OVX)-induced osteoporosis model mice. Puerarin-treated OVX mice exhibited higher bone density, fewer tartrate-resistant acid phosphatase (TRAcP)-positive osteoclasts, and levels of lower reactive oxygen species (ROS) within bone tissues than vehicle-treated OVX mice. Puerarin suppressed in vitro osteoclast differentiation, hydroxyapatite resorption activity, and expression of osteoclastogenesis-related genes, such as NFATc1, MMP9, CTSK, Acp5 and c-Fos, in RANKL-induced bone marrow macrophages (BMMs) and RAW264.7 cells. It also reduced intracellular ROS levels by suppressing expression of TRAF6 and NADPH oxidase 1 (NOX1) and increasing expression of antioxidant enzymes such as heme oxygenase-1 (HO-1). Puerarin inhibited TRAF6/ROS-dependent activation of the MAPK and NF-κB signaling pathways in RANKL-induced RAW264.7 cells, and these effects were partially reversed by HO-1 silencing or TRAF6 overexpression. These findings suggest puerarin alleviates loss of bone mass in the OVX-model mice by suppressing osteoclastogenesis via inhibition of the TRAF6/ROS-dependent MAPK/NF-κB signaling pathway.

[Zoledronate regulates osteoclast differentiation and bone resorption in high glucose through p38 MAPK pathway]

OBJECTIVE

To investigate the effect of zoledronate (ZOL) on osteoclast differentiation and bone resorption under high glucose, and the regulation mechanism of p38 mitogen activated kinase (p38 MAPK) signaling pathway in this process.

METHODS

RAW264.7 cells were divided into four groups: low group, high group, low+ZOL group and high+ZOL group after induced into osteoclasts. Cell proliferation activity was determined by MTT assay. The migration of RAW264.7 cells were examined Optical microscopy. Immunofluorescence microscopy was used to observe the cytoskeleton and sealing zones of osteoclasts. After adding group 5: high + ZOL + SB203580 group, trap staining was used to identify the number of positive osteoclasts in each group. The number and area of resorption lacunae were observed by SEM. The mRNA and protein expression of osteoclast related factors were detected by real-time PCR and Western blotting.

RESULTS

The cells in the 5 groups showed similar proliferative activity. High glucose promoted the migration of RAW264.7 cells (P < 0.05), inhibited the clarity of cytoskeleton and the formation of sealing zones in the osteoclasts. Exposure to high glucose significantly lowered the expressions of p38 MAPK, p-p38 MAPK, NFATc1, CTSK and TRAP, and inhibited osteoclast differentiation and bone absorption (P < 0.05). Treatment with ZOL obviously suppressed the migration ability of RAW264.7 cells, further reduced the clarity of the cytoskeleton, inhibited the formation of sealing zones of the osteoclasts, lowered the expressions of p38 MAPK, p-p38 MAPK, NFATc1, CTSK, and TRAP (P < 0.05), and inhibited osteoclast differentiation and bone absorption. Treatment with SB203580 obviously inhibited osteoclast differentiation and bone resorption and the expressions of P38 MAPK, p-p38 MAPK, NFATc1, CTSK and TRAP (P < 0.05).

CONCLUSIONS

High glucose inhibits osteoclast differentiation and bone resorption. ZOL inhibits osteoclast differentiation and bone resorption in high-glucose conditions by regulating p38 MAPK pathway, which can be a new pathway for ZOL to regulate diabetic osteoporosis.

Genome-Wide Analysis Reveals Changes in Long Noncoding RNAs in the Differentiation of Canine BMSCs into Insulin-Producing Cells

Long noncoding RNAs (lncRNAs) have been extensively explored over the past decade, including mice and humans. However, their impact on the transdifferentiation of canine bone marrow mesenchymal stem cells (cBMSCs) into insulin-producing cells (IPCs) is largely unknown. In this study, we used a three-step induction procedure to induce cBMSCs into IPCs, and samples (two biological replicates each) were obtained after each step; the samples consisted of “BMSCs” (B), “stage 1” (S1), “stage 2” (S2), “stage 3” (S3), and “islets” (I). After sequencing, 15,091 lncRNAs were identified, and we screened 110, 41, 23, and 686 differentially expressed lncRNAs (p_adjusted < 0.05) in B vs. S1, S1 vs. S2, S2 vs. S3, and I vs. S3 pairwise comparisons, respectively. In lncRNA target prediction, there were 166,623 colocalized targets and 2,976,362 correlated targets. Gene Ontology (GO) analysis showed that binding represented the main molecular functions of both the cis- and trans-modes. Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis suggested that the insulin signaling pathway, Rap1 signaling pathway, tight junctions, MAPK signaling pathway, and cell cycle were enriched for these relative genes. The expression of lncRNAs was verified using qRT-PCR. This study provides a lncRNA catalog for future research concerning the mechanism of the transdifferentiation of cBMSCs into IPCs.

SLIT2 Overexpression in Periodontitis Intensifies Inflammation and Alveolar Bone Loss, Possibly via the Activation of MAPK Pathway

SLIT2, a member of neuronal guidance cues, has been reported to regulate inflammation and cancer progression. Periodontitis is an oral inflammatory disease that degenerates periodontal tissue, alveolar bone and tooth. This study aims to explore the expression pattern of SLIT2 in periodontitis and its role in disease progression and bone loss. Gingival tissue of 20 periodontitis patients and 20 healthy-controls was obtained. Ligature-induced periodontitis (LIP) mice-model was developed in Slit2-Tg and wild-type mice. The effect of SLIT2 on inflammation, immune cell infiltration, M1 macrophage polarization, and alveolar bone loss in periodontitis was analyzed extensively. In periodontitis-affected gingival-tissue, SLIT2 expression was 4.4-fold higher compared to healthy-volunteers. LIP enhanced SLIT2 expression in mice periodontitis-affected periodontal tissue (PAPT) and blood circulation of wild-type mice by 4. 6-, and 5.0-fold, respectively. In Slit2-Tg-mice PAPT, SLIT2 expression was 1.8-fold higher compared to wild-type mice. Micro-CT and histomorphometric analysis revealed a 1.3-fold higher cement-enamel-junction to the alveolar-bone-crest (CEJ-ABC) distance and alveolar bone loss in LIP Slit2-Tg-mice compare to LIP wild-type mice. Results from RNA-sequencing, RT-qPCR, and ELISA showed a higher expression of Cxcr2, Il-18, TNFα, IL-6, and IL-1β in Slit2-Tg-mice PAPT compared to wild-type-mice. Slit2-Tg-mice PAPT showed a higher number of osteoclasts, M1 macrophages, and the upregulation of Robo1 expression. Slit2-Tg-mice PAPT showed upregulation of M1 macrophage marker CD16/32 and osteoclastogenic markers Acp5, Ctsk, and Nfatc1, but osteogenic markers (Alp, Bglap) remained unchanged. Immunohistochemistry unveiled the higher vasculature and infiltration of leucocytes and macrophages in Slit2-Tg-mice PAPT. RNA-sequencing, GO-pathway enrichment analysis, and western blot analysis revealed the activation of the MAPK signaling pathway in Slit2-Tg mice PAPT. In conclusion, SLIT2 overexpression in periodontitis intensifies inflammation, immune cells infiltration, M1 macrophage polarization, osteoclastogenesis, and alveolar bone loss, possibly via activation of MAPK signaling, suggesting the role of SLIT2 on exacerbation of periodontitis and alveolar bone loss.