DAPK1 Interacts with the p38 Isoform MAPK14, Preventing Its Nuclear Translocation and Stimulation of Bone Marrow Adipogenesis.

Bone marrow (BM) adipose tissue (BMAT), a unique adipose depot, plays an important role in diseases such as osteoporosis and bone metastasis. Precise control of mesenchymal stem cell (MSC) differentiation is critical for BMAT formation and regeneration. Here, we show that death associated protein kinase 1 (DAPK1) negatively regulates BM adipogenesis in vitro and in vivo. Prx1creDapk1loxp/loxp mice showed more adipocytes in the femur than Dapk1loxp/loxp mice. Further mechanistic analyses revealed that DAPK1 inhibits p38 mitogen-activated protein kinase (MAPK) signaling in the nucleus by binding the p38 isoform MAPK14, decreasing p38 nuclear activity, which subsequently inhibits BM adipogenesis. The inhibitory effect of DAPK1 against MAPK14 was independent of its kinase activity. In addition, the decreased DAPK1 was observed in the BM-MSCs of ageing mice. Our results reveal a previously undescribed function for DAPK1 in the regulation of adipogenesis and may also reveal the underlying mechanism of BMAT formation in ageing.

Impairment of APPL1/Myoferlin facilitates adipogenic differentiation of mesenchymal stem cells by blocking autophagy flux in osteoporosis.

An imbalance of human mesenchymal stem cells (hMSCs) adipogenic and osteogenic differentiation is crucial in the pathogenesis of osteoporosis, and elucidation of the underlying mechanism is urgently needed. APPL1, an adaptor protein of the adiponectin receptor, was recently shown to be closely related to bone mass. However, the role of APPL1 in the imbalance of hMSC differentiation in osteoporosis is unclear. Therefore, we aimed to explore the mechanisms by which APPL1 alters hMSCs adipogenic differentiation in osteoporosis. Here, we found that APPL1 expression was downregulated in elderly patients with osteoporosis and in mouse osteoporosis model. APPL1 negatively regulated hMSC adipogenic differentiation in vivo and in vitro. Mechanistically, by enhancing ubiquitination-mediated Myoferlin degradation, downregulated APPL1 expression increased the risk of lysosome dysfunction during hMSCs adipogenic differentiation. Lysosomal dysfunction inhibited autophagy flux by suppressing autophagosome degradation and promoted hMSC differentiation towards the adipocyte lineage. Our findings suggest that APPL1/Myoferlin downregulation promoted hMSCs adipogenic differentiation by inhibiting autophagy flux, further impairing the balance of hMSCs adipogenic and osteogenic differentiation in osteoporosis; the APPL1/ Myoferlin axis may be a promising diagnostic and therapeutic target for osteoporosis.

SMAD-specific E3 ubiquitin ligase 2 promotes angiogenesis by facilitating PTX3 degradation in MSCs from patients with ankylosing spondylitis.

Dysregulated angiogenesis of mesenchymal stem cells (MSCs) is closely related to inflammation and disrupted bone metabolism in patients with various autoimmune diseases. However, the role of MSCs in the development of abnormal angiogenesis in patients with ankylosing spondylitis (AS) remains unclear. In this study, we cultured human umbilical vein endothelial cells (HUVECs) with bone marrow-derived MSCs from patients with AS (ASMSCs) or healthy donors (HDMSCs) in vitro. Then, the cocultured HUVECs were assayed using a cell counting kit-8 (CCK-8) to evaluate the cell proliferation. A wound healing assay was performed to investigate cell migration, and a tube formation assay was conducted to determine the angiogenesis efficiency. ASMSCs exhibited increased angiogenesis, and increased expression of SMAD-specific E3 ubiquitin ligase 2 (Smurf2) in MSCs was the main cause of abnormal angiogenesis in patients with AS. Downregulation of Smurf2 in ASMSCs blocked angiogenesis, whereas overexpression of Smurf2 in HDMSCs promoted angiogenesis. The pro-angiogenic effect of Smurf2 was confirmed by the results of a Matrigel plug assay in vivo. By functioning as an E3 ubiquitin ligase in MSCs, Smurf2 regulated the levels of pentraxin 3 (PTX3), which has been shown to suppress angiogenesis through the PTX3-fibroblast growth factor 2 pathway. Moreover, Smurf2 transcription was regulated by activating transcription factor 4-induced endoplasmic reticulum stress. In conclusion, these results identify novel roles of Smurf2 in negatively regulating PTX3 stability and promoting angiogenesis in ASMSCs.

LncRNA-mRNA expression profiles and functional networks in osteoclast differentiation.

Human osteoclasts are differentiated from CD14+ monocytes and are responsible for bone resorption. Long non-coding RNAs (lncRNAs) have been proved to be significantly involved in multiple biologic processes, especially in cell differentiation. However, the effect of lncRNAs in osteoclast differentiation is less appreciated. In our study, RNA sequencing (RNA-seq) was used to identify the expression profiles of lncRNAs and mRNAs in osteoclast differentiation. The results demonstrated that expressions of 1117 lncRNAs and 296 mRNAs were significantly altered after osteoclast differentiation. qRT-PCR assays were performed to confirm the expression profiles, and the results were almost consistent with the RNA-seq data. GO and KEGG analyses were used to predict the functions of these differentially expressed mRNA and lncRNAs. The Path-net analysis demonstrated that MAPK pathway, PI3K-AKT pathway and NF-kappa B pathway played important roles in osteoclast differentiation. Co-expression networks and competing endogenous RNA networks indicated that ENSG00000257764.2-miR-106a-5p-TIMP2 may play a central role in osteoclast differentiation. Our study provides a foundation to further understand the role and underlying mechanism of lncRNAs in osteoclast differentiation, in which many of them could be potential targets for bone metabolic disease.

DEPDC1 promotes cell proliferation and tumor growth via activation of E2F signaling in prostate cancer.

DEP domain containing 1 (DEPDC1) is recently reported to be overexpressed in several types of human cancer; however the role of DEPDC1 in prostate cancer remains to be investigated. Herein, we identified that the DEPDC1 mRNA and protein expression levels were dramatically increased in prostate cancer tissues and cell lines. Overexpression of DEPDC1 promoted, but depletion of DEPDC1 inhibited cell proliferation by regulating the G1-S phase cell cycle transition. Importantly, we found that DEPDC1 was essential for the tumor growth and formation of bone metastases of prostate cancer cells in vivo. Finally, we demonstrated that DEPDC1 interacted with E2F1 and increased its transcriptional activity, leading to hyper-activation of E2F signaling in prostate cancer cells. Our findings reveal an oncogenic role of DEPDC1 in prostate cancer progression via activation of E2F signaling, and suggest DEPDC1 might be a potential therapeutic target against the disease.

Micro-invasive surgery combined with intraoperative radiotherapy for the treatment of spinal metastasis.

PURPOSE: This is a retrospective analysis of the strategy and clinical results of surgery combined with intraoperative radiotherapy (IORT) to treat spinal metastases. METHODS: We delivered tumour-conformal IORT in 40 patients with 52 metastatic vertebrae based on our surgical classification system. The strategies were evaluated with respect to neurologic function and spinal stability. The EORTC QLQ-BM22, visual analogue scale (VAS) and the Frankel Scale were used to assess quality of life, pain and neurologic function. Local control was evaluated every 3 months using X-rays and MRI. RESULTS: Micro-invasive IORT was performed in 42 vertebrae (80.8%), and open surgery with IORT was performed in 10 vertebrae (19.2%). Single-level, 2-level and 3-level IORT was performed in 30, 8 and 2 cases, respectively. The delivered dose was 9.2 ± 3.6 Gy (8-15 Gy) with a depth of 10.1 ± 2.1 mm. The actual IORT treatment time was 5 min and 16 s. The follow-up period was 6-23 months (mean: 12.5 months). The local control rate was 92.3%. The EORTC QLQ-BM22 scores showed that patients had significant improvements in pain location, degree and function after treatment (P < 0.01). Thirty-five patients (89.7%) achieved pain relief throughout the follow-up period. VAS scores were significantly reduced by 3.4 points 3 months after treatment. Neurological function was improved in 7 patients (87.5%). No radiation-related complications were observed. CONCLUSIONS: Surgery combined with tumour-conformal IORT can effectively relieve pain, achieve good local control and improve QOL.

Comparison of smith-petersen osteotomy, pedicular subtraction osteotomy, and poly-segmental wedge osteotomy in treating rigid thoracolumbar kyphotic deformity in ankylosing spondylitis a systematic review and meta-analysis.

BACKGROUND: This study aimed to compare Smith-Petersen osteotomy (SPO), poly-segmental wedge osteotomy (PWO) and pedicular subtraction osteotomy (PSO) in patients with rigid thoracolumbar kyphosis primarily caused by ankylosing spondylitis. The efficiency, efficacy and safety of these three osteotomies have not been compared systematically, and no illness-oriented surgical type selection strategy for the treatment of ankylosing spondylitis related to non-angular kyphosis has been reported. METHODS: The inclusion and exclusion criteria were defined, and 19 electronic databases were searched for eligible studies without language limitations. For the included studies, data extraction, bias analysis, heterogeneity analysis and quantitative analysis were performed to analyze the correction of kyphosiskyphosis and the incidence of complications. RESULTS: Nine comparative studies that met the standards were included with a total of 539 patients that underwent SPO (n = 120), PWO (n = 119), or PSO (n = 300). The correction of kyphosis by PSO was 8.74° [95% CI: 0.7-16.78] greater than SPO. The correction of kyphosis by PWO was 13.88° [95 % CI: 9.25-18.51] greater than SPO. For local biomechanical complications, the pooled risk ratio of PWO to PSO was 1.97 [95 % CI: 1.03-3.77]. For blood loss, PSO was 806.42 ml [95% CI: 591.72-1021.12] greater than SPO and 566.76 ml [95 % CI: 129.80-1003.72] greater than PWO. CONCLUSIONS: To treat rigid thoracolumbar kyphosis, PSO showed higher efficiency and efficacy than SPO, and PWO had a higher efficacy than SPO. The risk of local biomechanical complications was greater in PWO than PSO. Bleeding was more severe in PSO than in SPO or PWO. The incidence of neural complications and systemic complications was similar.

[Total en-bloc spondylectomy for recurrence spinal tumor].

OBJECTIVE: To evaluate the clinical outcomes of total en-bloc spondylectomy (TES) in recurrence spinal tumor. METHODS: The study was a retrospective study of recurrence spinal tumor from January 2010 to October 2013. A total of 6 patients with recurrent spinal tumor underwent TES procedures, with 5 cases located in thoracic spine and 1 case located in L1. There were 3 male and 3 female patients, with a mean age of 33.2 years. Pathological diagnosis included giant cell tumor of bone in 3 cases, breast cancer, lung cancer and nasopharyngeal carcinoma with 1 case in each. The operation time, bleeding loss, resected segments, cutting edge, spinal cord function and complications was evaluated. RESULTS: Single segment resected in 1 case, 2 segments resected in 2 cases and 3 segments resected in 3 cases. The average operation time was 8.9 hours (7.5 to 12.0 hours). The average blood loss was 3 116 ml (2 500 to 4 500 ml). The average follow-up period was 23.2 months (12 to 47 months) without recurrence. There was no spinal cord injury during operation. The neurologic function was significantly improved in 2 cases (American Spinal Injury Association (ASIA) grade C to grade D), unchanged in 1 cases (ASIA grade B) and no deteriorated case in 3 cases (ASIA grade E). There was no perioperative deaths case. Complications included 2 cases pleural rupture, 1 case dural tear and 1 case massive haemothorax. No peri-operation death case. CONCLUSION: Some of the recurrent spinal tumors are still suitable for en-bloc resection and TES procedure with the extent of its applicability under strict control.

N-Halaminated spermidine-containing polymeric coating enables titanium to achieve dual functions of antibacterial and osseointegration.

Titanium (Ti) and its alloys have been widely employed in the treatment of orthopedics and other hard tissue diseases. However, Ti-based implants are bioinert and suffer from bacterial infections and poor osseointegration in clinical applications. Herein, we successfully modified Ti with a porous N-halaminated spermidine-containing polymeric coating (Ti-SPD-Cl) through alkali-heat treatment, surface grafting and chlorination, and it has both excellent antibacterial and osteogenic abilities to significantly enhance osseointegration. The as-obtained Ti-SPD-Cl contains abundant N-Cl groups and demonstrates effective antibacterial ability against S. aureus and E. coli. Meanwhile, due to the presence of the spermidine component and construction of a porous hydrophilic surface, Ti-SPD-Cl is also beneficial for maintaining cell membrane homeostasis and promoting cell adhesion, exhibiting good biocompatibility and osteogenic ability. The rat osteomyelitis model demonstrates that Ti-SPD-Cl can effectively suppress bacterial infection and enhance bone-implant integration. Thus, Ti-SPD-Cl shows promising clinical applicability in the prevention of orthopedic implant infections and poor osseointegration.

One-Pot Construction of Articular Cartilage-Like Hydrogel Coating for Durable Aqueous Lubrication.

Articular cartilage has an appropriate multilayer structure and superior tribological properties and provides a structural paradigm for design of lubricating materials. However, mimicking articular cartilage traits on prosthetic materials with durable lubrication remains a huge challenge. Herein, an ingenious three-in-one strategy is developed for constructing an articular cartilage-like bilayer hydrogel coating on the surface of ultra-high molecular weight polyethylene (BH-UPE), which makes full use of conceptions of interfacial interlinking, high-entanglement crosslinking, and interface-modulated polymerization. The hydrogel coating is tightly interlinked with UPE substrate through hydrogel-UPE interchain entanglement and bonding. The hydrogel chains are highly entangled with each other to form a dense tough layer with negligible hysteresis for load-bearing by reducing the amounts of crosslinker and hydrophilic initiator to p.p.m. levels. Meanwhile, the polymerization of monomers in the top surface region is suppressed via interface-modulated polymerization, thus introducing a porous surface for effective aqueous lubrication. As a result, BH-UPE exhibits an ultralow friction coefficient of 0.0048 during 10 000 cycles under a load of 0.9 MPa, demonstrating great potential as an advanced bearing material for disc prosthesis. This work may provide a new way to build stable bilayer coatings and have important implications for development of biological lubricating materials.

A Versatile Sulfur-Assisted Pyrolysis Strategy for High-Atom-Economy Upcycling of Waste Plastics into High-Value Carbon Materials.

With the overconsumption of disposable plastics, there is a considerable emphasis on the recycling of waste plastics to relieve the environmental, economic, and health-related consequences. Here, a sulfur-assisted pyrolysis strategy is demonstrated for versatile upcycling of plastics into high-value carbons with an ultrahigh carbon-atom recovery (up to 85%). During the pyrolysis process, the inexpensive elemental sulfur molecules are covalently bonded with polymer chains, and then thermally stable intermediates are produced via dehydrogenation and crosslinking, thereby inhibiting the decomposition of plastics into volatile small hydrocarbons. In this manner, the carbon products obtained from real-world waste plastics exhibit sulfur-rich skeletons with an enlarged interlayer distance, and demonstrate superior sodium storage performance. It is believed that the present results offer a new solution to alleviate plastic pollution and reduce the carbon footprint of plastic industry.

The lncRNA PILA promotes NF-κB signaling in osteoarthritis by stimulating the activity of the protein arginine methyltransferase PRMT1.

Inflammatory cytokine-induced activation of nuclear factor κB (NF-κB) signaling plays a critical role in the pathogenesis of osteoarthritis (OA). We identified PILA as a long noncoding RNA (lncRNA) that enhances NF-κB signaling and OA. The abundance of PILA was increased in damaged cartilage from patients with OA and in human articular chondrocytes stimulated with the proinflammatory cytokine tumor necrosis factor (TNF). Knockdown of PILA inhibited TNF-induced NF-κB signaling, extracellular matrix catabolism, and apoptosis in chondrocytes, whereas ectopic expression of PILA promoted NF-κB signaling and matrix degradation. PILA promoted PRMT1-mediated arginine methylation of DExH-box helicase 9 (DHX9), leading to an increase in the transcription of the gene encoding transforming growth factor ß-activated kinase 1 (TAK1), an upstream activator of NF-κB signaling. Furthermore, intra-articular injection of an adenovirus vector encoding PILA triggered spontaneous cartilage loss and exacerbated posttraumatic OA in mice. This study provides insight into the regulation of NF-κB signaling in OA and identifies a potential therapeutic target for this disease.

Identification of MAP3K15 as a potential prognostic biomarker and correlation with immune infiltrates in osteosarcoma.

BACKGROUND: Osteosarcoma (OS) is a type of primary malignant tumor, and increasing evidence shows the clinical benefits of immunotherapy in treating OS. However, the lack of comprehensive studies on the complex OS immune microenvironment hinders the application of immunotherapy. Thus, this study aimed to systematically explore the immune characteristics of OS and identify novel biomarkers for OS treatment. METHODS: We systematically studied the immune score and proportions of infiltrating immune cells in OS in the Therapeutically Applicable Research to Generate Effective Treatments (TARGET) and Gene Expression Omnibus (GEO) databases using the ESTIMATE and CIBERSORT algorithms. Differential expression and functional analyses were used to identify dysregulated genes and explore their functions. Survival and Cox regression analyses were applied to establish an immune-related prognostic signature. Additionally, qPCR and immunohistochemistry were performed to validate the results. RESULTS: A total of 103 differentially expressed immune genes (DEIGs) were found in the TARGET-OS and GSE39058 databases, and these DEIGs were mainly enriched in leukocyte proliferation, leukocyte differentiation, osteoclast differentiation, natural killer (NK) cell-mediated cytotoxicity, and the adaptive immune system. A predictive signature was constructed based on the survival analysis, with an area under the receiver operating characteristic (ROC) curve (AUC) of 0.65. Moreover, we found that mitogen-activated protein kinase kinase kinase 15 (MAP3K15) can predict the prognosis of patients with OS and is closely related to CD4+ T cells and macrophages. The OS patients with high MAP3K15 expression had a significantly poorer prognosis. CONCLUSIONS: Our study found that MAP3K15, whose expression level is closely related to immune activity in tumors, is a critical immune-related biomarker, and our findings may provide a basis for OS immunotherapy.

ZIP10 drives osteosarcoma proliferation and chemoresistance through ITGA10-mediated activation of the PI3K/AKT pathway.

BACKGROUND: The zinc transporters Zrt- and Irt-related protein (ZIP/SLC39) are overexpressed in human tumors and correlate with poor prognosis; however, their contributions to carcinogenesis and chemoresistance in osteosarcoma (OS) remain unclear. METHODS: We collected 64 OS patient tissues with (n = 12) or without (n = 52) chemotherapy. The expression levels of ZIP10 were measured by immunohistochemistry and applied to prognostic analysis. ZIP10 was knocked down or overexpressed in OS cell lines to explore its effect on proliferation and chemoresistance. RNA sequencing, quantitative real-time PCR, and western blotting analysis were performed to explore ZIP10-regulated downstream target genes. A xenograft mouse model was established to evaluate the mechanisms by which ZIP10 modulates chemoresistance in OS cells. RESULTS: The expression of ZIP10 was significantly induced by chemotherapy and highly associated with the clinical outcomes of OS. Knockdown of ZIP10 suppressed OS cell proliferation and chemoresistance. In addition, ZIP10 promoted Zn content-induced cAMP-response element binding protein (CREB) phosphorylation and activation, which are required for integrin α10 (ITGA10) transcription and ITGA10-mediated PI3K/AKT pathway activation. Importantly, ITGA10 stimulated PI3K/AKT signaling but not the classical FAK or SRC pathway. Moreover, overexpression of ZIP10 promoted ITGA10 expression and conferred chemoresistance. Treatment with the CREB inhibitor 666-15 or the PI3K/AKT inhibitor GSK690693 impaired tumor chemoresistance in ZIP10-overexpressing cells. Finally, a xenograft mouse model established by subcutaneous injection of 143B cells confirmed that ZIP10 mediates chemotherapy resistance in OS cells via the ZIP10-ITGA10-PI3K/AKT axis. CONCLUSIONS: We demonstrate that ZIP10 drives OS proliferation and chemoresistance through ITGA10-mediated activation of the PI3K/AKT pathway, which might serve as a target for OS treatment.

Evaluation of a new spinal surgical robotic system of Kirschner wire placement for lumbar fusion: A multi-centre, randomised controlled clinical study.

BACKGROUND: To introduce a novel robotic system 'Orthbot' that has been developed and tested as a surgical assistant for auto-placement of the K-wire in lumbar fusion. METHODS: This is a multi-centre, randomized controlled clinical study that includes 56 patients (robot group, RG: 27, free-hand group, FG: 29). Following the pre-operative planning and intra-operative fluoroscopic images, the 'Orthbot' automatically completed registration and K-wire placement under the supervision of the surgeon. Deviation distance (DD) and deviation angle (DA) were used as the primary parameters to evaluate the accuracy of the robotic system. RESULTS: The average DD was 0.95 ± 0.377 mm and 4.35 ± 2.01 mm, respectively in the RG and FG (p < 0.001). The average DA of the K-wire in the coronal plane and the sagittal plane in X-Ray was respectively 6.80 ± 7.79° and 1.27 ± 2.32° in the RG (p < 0.001), and 22.22 ± 16.85° and 4.57 ± 3.86° in the FG (p < 0.001), which showed a higher accuracy rate in the robotic-assisted cases compared to the free-hand cases. CONCLUSIONS: The novel robotic system could achieve accurate K-wire insertions as indicated by the radiological results.

TRAF4 acts as a fate checkpoint to regulate the adipogenic differentiation of MSCs by activating PKM2.

BACKGROUND: Mesenchymal stem cells (MSCs) selectively differentiate into adipocytes or osteoblasts, and several molecules control the fate determination of MSCs. Understanding these key checkpoints greatly contributes to the ability to induce specific MSC differentiation for clinical applications. In this study, we aimed to explore whether TNF receptor-associated factor 4 (TRAF4) affects MSC adipogenic differentiation, which we previously reported that could positively regulated the osteogenic differentiation. METHODS: Western blotting and Real-time Polymerase Chain Reaction were used to detected the expression pattern of TRAF4 during adipogenic differentiation. Lentivirus was constructed to regulate TRAF4 expression, and oil red O staining and Western blotting were used to assess its role in adipogenesis, which was confirmed in vivo by implanting an MSC-matrigel mixture into nude mice. Western blotting was used to detect the activated signaling pathways, and a specific inhibitor and agonist were used to clear the roles of the key signaling pathways. Additionaly, Co-Immunoprecipitation was conducted to find that Pyruvate kinase isozyme type M2 (PKM2) interacts with TRAF4, and to further explore their binding and functional domains. Finally, an RNA-binding protein immunoprecipitation assay and Western blotting were used to detect whether N6-methyladenosine mediates the decreased TRAF4 expression during adipogenic differentiation. FINDINGS: The results demonstrated that TRAF4 negatively regulates MSC adipogenesis in vitro and in vivo. Mechanistically, we revealed that TRAF4 binds to PKM2 to activate the kinase activity of PKM2, which subsequently activates ß-catenin signaling and then inhibits adipogenesis. Furthermore, TRAF4 downregulation during adipogenesis is regulated by ALKBH5-mediated N6-methyladenosine RNA demethylation. INTERPRETATION: TRAF4 negatively regulates the adipogenesis of MSCs by activating PKM2 kinase activity, which may act as a checkpoint to fine-tune the balance of adipo-osteogenic differentiation, and suggests that TRAF4 may be a novel target of MSCs in clinical use and may also illuminate the underlying mechanisms of bone metabolic diseases. FUNDING: This study was supported by the National Natural Science Foundation of China (81871750 and 81971518) and the Science and Technology Project of Guangdong Province (2019B02023600 and 2017A020215070).

Pantoprazole (PPZ) Inhibits RANKL-Induced Osteoclast Formation and Function In Vitro and Prevents Lipopolysaccharide- (LPS-) Induced Inflammatory Calvarial Bone Loss In Vivo.

Bone remodeling is a process delicately balanced between osteoclastic bone resorption and osteoblastic bone formation. Osteoclasts (OCs) are multinucleated giant cells formed through the fusion of monocytic precursors of the hematopoietic stem cells lineage. OCs are the exclusive cells responsible for the resorption and degradation of the mineralized bone matrix. Pantoprazole (PPZ), a proton pump inhibitor (PPI), is commonly prescribed to reduce excess gastric acid production for conditions such as gastroesophageal reflux disease and peptic ulcer disease. Studies have found contradictory effects of PPI therapy on bone metabolism due to the lack of understanding of the exact underlying mechanism. In this study, we found that PPZ inhibits receptor activator of nuclear factor-κB (NF-κB) ligand- (RANKL-) induced osteoclastogenesis from bone marrow monocytic/macrophage (BMMs) precursors and the bone-resorbing activity of mature OCs. Correspondingly, the expression of OC marker genes was also attenuated. At the molecular level, PPZ treatment was associated with reduced activation of the ERK MAPK signaling pathways crucial to OC differentiation. Additionally, the in vivo administration of PPZ protected mice against lipopolysaccharide- (LPS-) induced inflammatory calvarial bone erosion, as a result of the reduced number and activity of OCs on the calvarial bone surface. Although PPI use is associated with increased risk of osteoporosis and bone fractures, our study provides evidence for the direct inhibitory effect of PPZ on OC formation and bone resorption in vitro and in vivo, suggesting a potential therapeutic use of PPZ in the treatment of osteolytic disease with localized bone destruction.

Enhanced Osteogenic Differentiation of Human Bone Marrow Mesenchymal Stem Cells in Ossification of the Posterior Longitudinal Ligament Through Activation of the BMP2-Smad1/5/8 Pathway.

Ossification of the posterior longitudinal ligament (OPLL) is characterized by ectopic OPLL. To date, the specific molecular pathogenesis of OPLL has not been clearly elucidated. In this study, bone marrow-derived mesenchymal stem cells obtained from healthy donors (HD-MSCs) and patients with OPLL (OPLL-MSCs) were cultured in osteogenic differentiation medium for 21 days. The osteogenic differentiation capacity was determined by alizarin red S (ARS) and alkaline phosphatase (ALP) assays. Gene expression levels of osteoblastic markers were measured by quantitative reverse transcription-polymerase chain reaction. Protein levels of related genes and the activation of related signaling pathways were measured by western blotting. LDN193189 was used to inhibit the Smad1/5/8 pathway, and small interfering RNA was used to regulate BMP2 expression. Our results showed that the OPLL-MSCs had stronger ARS staining and ALP activity and higher expression of RUNX2, Osterix, and OCN than the HD-MSCs. During osteogenic differentiation, the Smad1/5/8 pathway was overactivated in the OPLL-MSCs, and LDN193189 inhibition reversed the enhanced osteogenic ability of these cells. Besides, BMP2 was upregulated in the OPLL-MSCs. After BMP2 knockdown, the abnormal osteogenic differentiation of OPLL-MSCs was rescued. Thus, abnormal activation of the BMP2-Smad1/5/8 pathway induces enhanced osteogenic differentiation of OPLL-MSCs compared with HD-MSCs. These findings reveal a mechanism of pathological osteogenesis in OPLL and provide a new perspective on inhibiting pathological osteogenesis by regulating BMP2.

Aberrantly Expressed lncRNAs and mRNAs of Osteogenically Differentiated Mesenchymal Stem Cells in Ossification of the Posterior Longitudinal Ligament.

Ectopic bone formation is the chief characteristic of ossification of the posterior longitudinal ligament (OPLL). Emerging evidence has revealed that long non-coding RNAs (lncRNAs) can regulate the osteogenic differentiation of mesenchymal stem cells (MSCs), which are the main cells responsible for bone formation. However, the role of lncRNAs in the pathogenesis of OPLL remains unclear. In this study, 725 aberrantly expressed lncRNAs and 664 mRNAs in osteogenically differentiated MSCs from OPLL patients (OPLL MSCs) were identified by microarrays and confirmed by qRT-PCR assays. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses showed that the most enriched pathways included the p53, JAK-STAT, and PI3K-Akt signaling pathways. The co-expression network showed the interactions between the aberrantly expressed lncRNAs and mRNAs in OPLL MSCs, and the potential targets and transcription factors of the lncRNAs were predicted. Our research demonstrated the aberrantly expressed lncRNA and mRNA and the potential regulatory networks involved in the ectopic bone formation of OPLL. These findings imply that lncRNAs may play a vital role in OPLL, which provides a new perspective on the pathogenesis of OPLL.

A Study of the Immunoregulatory Function of TLR3 and TLR4 on Mesenchymal Stem Cells in Ankylosing Spondylitis.

The pathogenesis of ankylosing spondylitis (AS), an immune-mediated inflammatory disease, remains largely unknown. We previously reported that the immunoregulatory function of mesenchymal stem cells (MSCs) was dysfunctional in AS. Furthermore, it has been demonstrated that TLR3 and TLR4 could regulate the immunoregulatory function of MSCs. Therefore, this study aimed to investigate the effect of TLR3 and TLR4 activation on the immunoregulatory function of AS-MSCs. By gene expression and western blot analyses, we found that both TLR3 and TLR4 in AS-MSCs to be downregulated when compared with MSCs derived from healthy donors (HDs). Despite the lower basal expression of TLRs, AS-MSCs were as sensitive or more sensitive to TLR agonists as compared with HD-MSCs in terms of activation of p38 and ERK MAPK signaling pathways. Furthermore, TLR4-primed AS-MSCs were observed to possess enhanced immunoregulatory effects against the proliferation of naive CD4+ T cells than HD-MSCs due to elevated IL-10 production. However, TLR activation or the source of MSCs did not affect MSC-induced differentiation of naive CD4+ T cells to Th17 cells. Similarly, the MSC-induced inhibition of Treg cell differentiation of naive CD4+ T cells was not affected by TLR activation or MSC source. MSC-induced Th17 differentiation was likely mediated by the elevated secretion of proinflammatory cytokines, IL-6 and IL-17, and reduced expression of IL-2, IL-4, and IFN-γ, which were not affected by TLR activation. Taken together, our results suggest that TLR3 and TLR4 may play an important role in the immunoregulatory function of MSCs in AS patients.