Circular RNA SLTM as a miR-421-competing endogenous RNA to mediate HMGB2 expression stimulates apoptosis and inflammation in arthritic chondrocytes.

Osteoarthritis (OA) is the most common age-related joint disease characterized by chronic inflammation, progressive articular cartilage destruction, and subchondral sclerosis. Accumulating evidence suggests that circular RNAs (circRNAs) play key roles in OA, but the function of circSLTM in OA remains greatly unknown. Therefore, this study focused on interleukin-1ß (IL-1ß)-treated primary human chondrocytes as well as a rat model to investigate the expression pattern and functional role of circSLTM in OA in vitro and in vivo. CircSLTM and high mobility group protein B2 (HMGB2) were upregulated in IL-1ß-induced chondrocytes, whereas miR-421 was downregulated. Knockdown of circSLTM or overexpression of miR-421 ameliorated IL-1ß-induced chondrocyte apoptosis and inflammation. The regulatory relationship between circSLTM and miR-421, as well as that between miR-421 and HMGB2, was predicted by bioinformatics and then verified by the RNA immunoprecipitation experiment and dual-luciferase reporter gene assay. Furthermore, silencing of circSLTM increased cartilage destruction and decreased cartilage tissue apoptosis rate and inflammation in a rat model of OA. Taken together, our findings demonstrate the fundamental role of circSLTM in OA progression and provide a potential molecular target for OA therapy.

Cyasterone has a protective effect on steroid-induced Osteonecrosis of the femoral head.

CONTEXT: Cyasterone alleviated the apoptosis of BMSCs induced by Dexamethasone via the PI3K/AKT signaling pathway. In addition, Cyasterone had a protective effect on SIONFH model rats by reducing the percentage of empty bone lacunae. OBJECTIVE: To study the effect of Cyasterone on apoptosis of rat BMSCs and its function on the SIONFH rat model. METHODS: Rat BMSCs were cultured and divided into Control, DXM and Cyasterone (DXM+Cyasterone) groups. The apoptosis of each group was detected by flow cytometry, the expressions of Caspase-3 and Caspase-9 were detected by immunofluorescence staining, and the mRNA and protein expressions of AKT, BAX, P53, P85, Bcl-2 and Cytochrome C were detected by qPCR and WB. In animal experiments, the femoral head of rats were subjected to HE staining and Micro-CT to observe the necrosis and repair conditions. RESULTS: The apoptosis rate of DXM and Cyasterone groups increased compared with Control group, and the apoptosis rate of Cyasterone group decreased compared with DXM group. Compared with DXM group, the mRNA expression of BAX, P53, P85 and Cytochrome C in Cyasterone group were increased, while the protein expression of AKT and Bcl-2 decreased. The histopathological and morphological analysis showed that Cyasterone promoted the trabecular bone structure in rat, which evenly benefit for the repair of SIONFH. CONCLUSION: Cyasterone can reduce the apoptosis of rat BMSCs induced by Dexamethasone, and help promoting the bone repair in SIONFH rats.

Tert-butylhydroquinone attenuates osteoarthritis by protecting chondrocytes and inhibiting macrophage polarization.

AIMS: Tert-butylhydroquinone (tBHQ) has been identified as an inhibitor of oxidative stress-induced injury and apoptosis in human neural stem cells. However, the role of tBHQ in osteoarthritis (OA) is unclear. This study was carried out to investigate the role of tBHQ in OA. METHODS: OA animal model was induced by destabilization of the medial meniscus (DMM). Different concentrations of tBHQ (25 and 50 mg/kg) were intraperitoneally injected in ten-week-old female mice. Chondrocytes were isolated from articular cartilage of mice and treated with 5 ng/ml lipopolysaccharide (LPS) or 10 ng/ml interleukin 1 beta (IL-1ß) for 24 hours, and then treated with different concentrations of tBHQ (10, 20, and 40 µM) for 12 hours. The expression levels of malondialdehyde (MDA) and superoxide dismutase (SOD) in blood were measured. The expression levels of interleukin 6 (IL-6), IL-1ß, and tumour necrosis factor alpha (TNF-α) leptin in plasma were measured using enzyme-linked immunoabsorbent assay (ELISA) kits. The expression of nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) and mitogen-activated protein kinase (MAPK) signalling pathway proteins, and macrophage repolarization-related markers, were detected by western blot. RESULTS: Tert-butylhydroquinone significantly attenuated cartilage destruction in DMM-induced mice in vivo. It demonstrated clear evidence of inhibiting IL-1ß-induced chondrocyte apoptosis, inflammation, and differentiation defect in vitro. Meanwhile, tBHQ inhibited LPS-induced activation of NF-κB and MAPK signalling pathways, and also inhibited LPS-induced reactive oxygen species production and macrophages repolarization in vitro. CONCLUSION: Taken together, tBHQ might be a potential therapeutic strategy for protecting against OA development. Cite this article: Bone Joint Res 2021;10(11):704-713.

Network Pharmacology Integrated with Molecular Docking Explores the Mechanisms of Naringin against Osteoporotic Fracture by Regulating Oxidative Stress.

Naringin (NG), as the most abundant component of Drynariae Rhizoma (Chinese name: Gusuibu), has been proved to be an antioxidant flavonoid on promoting osteoporotic fracture (OF) healing, but relevant research is scanty on the underlying mechanisms. We adopted target prediction, protein-protein interaction (PPI) analysis, Gene Ontology (GO) analysis, Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis, and molecular docking to establish a system pharmacology database of NG against OF. Totally 105 targets of naringin were obtained, including 26 common targets with OF. A total of 415 entries were obtained through GO Biological Process enrichment analysis (P < 0.05), and 37 entries were obtained through KEGG pathway enrichment analysis with seven signaling pathways included (P < 0.05), which were primarily concerned with p53, IL-17, TNF, estrogen, and PPAR signaling pathways. According to the results of molecular docking, naringin is all bound in the active pockets of the core targets with 3-9 hydrogen bonds through some connections such as hydrophobic interactions, Pi-Pi stacked interactions, and salt bridge, demonstrating that naringin binds tightly to the core targets. In general, naringin may treat OF through multiple targets and multiple pathways via regulating oxidative stress, etc. Notably, it is first reported that NG may regulate osteoclast differentiation and oxidative stress through the expression of the core targets so as to treat OF.

[Pro-apoptotic effect on osteosarcoma SOSP-9607 cells by human recombinant caspase-6 fusion protein].

OBJECTIVE: To investigate the pro-apoptotic effect of Her-2 targeted recombinant caspase-6 fusion protein on osteosarcoma SOSP-9607 cells. METHODS: Recombinant immunocasp-6 was generated by sequential fusion of the genes of a signal peptide, a single-chain Her-2 antibody (e23sFv), a PEA translocation domain (PEA aa253-364) and an active caspase-6. The immunocasp-6 gene was cloned into pCMV plasmid to construct a kind of eukaryotic expression vector, i.e. pCMV-e23sfv-PE II-caspase-6 (abbr. pCMV-6) and transfected into SOSP-9607 cells. Murine xenograft models were randomly divided into two groups that received i.m. injections of liposome encapsulated pCMV-6 or pCMV alone. The tumor volume and weight of the nude mice and the tumor weight of the cured mice were observed and statistically analyzed. The morphological changes of the tumors were examined with HE staining, apoptotic morphology of the tumor was observed by TUNEL staining and the gene expression was analyzed by immunohistochemical staining. RESULTS: The tumor growth of the mice in the treatment group was significantly slower than that of the control group (P = 0.001). The weight of the nude mice in the treatment group was significantly higher than that of the control group (P = 0.0002). The tumor weight of the mice in the treatment group was significantly lower than that of the control group (P = 0.0006). HE and TUNEL staining of the tumor of nude mice in the treatment groups showed typical characteristics of apoptosis, while normal structure was found in the control group. Furthermore, caspase-6 was not found in the tumor and muscle tissues in the control group, but only in the treatment group by immunohistochemistry. CONCLUSION: Immunocasp-6 can selectively recognize and bind to and kill HER-2 positive osteosarcoma cells, therefore, to offer some foundation for the clinical treatment of osteosarcoma.

A caspase-6 and anti-HER2 antibody chimeric tumor-targeted proapoptotic molecule decreased metastasis of human osteosarcoma.

Human growth factor receptor-2 (HER2), overexpressed as a result of gene amplification, is detected in 20-40% of patients with breast, ovarian, endometrial, gastric, bladder, prostate, or lung cancers, correlated to metastasis of many tumors, and considered to be a poor prognostic indicator for these tumors. However, the data was controversial for HER2 overexpression and the prognosis of osteosarcoma, which is the most common primary malignant bone tumor, presents a therapeutic challenge in medical oncology due to its metastasis and poor response to current treatments. Previously, we reported that the immunocasp-6 gene fused by a HER2-specific single-chain antibody with domain II of Pseudomonas exotoxin A (PEA) and the 5' end of the truncated active caspase-6 could selectively suppress the HER2-positive tumor growth. In this study, we extend its application. We first confirmed the higher HER2 expression on the surface of metastatic osteosarcoma SOSP-9607(E10) cells, which then be proved specifically addicted to immunocasp-6-induced cells killing in vitro. Thereafter, the efficacy of immunocasp-6 was tested in an osteosarcoma lung metastasis mouse model using intramuscular (i.m.) injections of liposome-encapsulated vectors. Our results showed that the expression of the immunocasp-6 gene not only significantly prolonged animal's survival, but also greatly inhibited tumor metastasis. Thereby, our strategy suggests an alternative approach to treating HER2/neu-positive osteosarcoma.

Semaphorin 4A acts in a feed-forward loop with NF-κB pathway to exacerbate catabolic effect of IL-1ß on chondrocytes.

Inflammation is fundamental in osteoarthritis (OA) pathogenesis. Semaphorin 4A (Sema4A) has been implicated in immune-associated diseases, however, its role in OA remains unclear. In this study, we show that Sema4A is upregulated in knee OA articular cartilage as well as in chondrocytes exposed to IL-1ß treatment in vitro. Moreover, IL-1ß-induced Sema4A upregulation is abrogated in the presence of BAY 11-7082, a specific inhibitor of NF-κB pathway, suggesting that the activation of NF-κB is required for Sema4A upregulation under this pathological condition. Intriguingly, Sema4A in turn activates NF-κB through facilitating Rac1/AKT-dependent IκBα phosphorylation and subsequent degradation. Functionally, Sema4A aggravates the catabolic effect of IL-1ß on chondrocytes, which can be largely attributed to exacerbated NF-κB activation, since NF-κB inhibition remarkably abolishes this effect. In conclusion, our study suggests that Sema4A is a novel regulator of NF-κB-dependent catabolic events in chondrocytes, which may underlie OA pathogenesis.

Bone marrow osteoma of the tibia: A case report.

In this study, an unusual case of osteoma is presented, whereby a bone marrow osteoma was identified in the tibia. No previous cases of bone marrow osteoma have been reported. In this case, an eight-year-old male presented with discontinuous discomfort in the right distal calf for six months. Radiological examination and computed tomography revealed a radiopaque lesion within the affected bone. A technetium-99m bone scan revealed focally increased uptake in the same region. Together, these observations prior to surgery indicated that the patient may suffer from bone disease. Subsequently, a surgical excision was performed and the biopsy specimen was identified as bone marrow osteoma. Following surgery, the symptoms were eradicated and the prognosis was positive during the 24-month follow-up period. Bone marrow osteoma should be considered when a patient suffers from discontinuous and unexplained limb discomfort.

A novel recombinant immunocasp-6 fusion gene specifically and efficiently suppresses HER2-overexpressing osteosarcoma.

Osteosarcoma is the most common primary malignant tumor of bone for adolescent or children. The poor prognosis of patients, due to its remote metastasis, has led to the exploration of more effective and less toxic treatments. Immunotherapy is a promising strategy for the treatment of human epidermal growth factor receptor 2 (HER2)-overexpressing tumors. Herein, we describe experiments conducted with a fusion gene, immunocasp-6, which was generated by fusing a HER2-specific single-chain Ab, a single-chain Pseudomonas exotoxin A and an active caspase-6 which can directly cleave lamin A leading to nucleus damage inducing programmed cell death. We demonstrated that immunocasp-6 can specifically and efficiently recognize and induce apoptosis in HER2-overexpressing osteosarcoma cells in vitro. The immunocasp-6 was transferred into BALB/c athymic mice bearing human osteosarcoma by i.m. injection of liposome-encapsulated pCMV-immunocap-6. Expression of immunocasp-6 not only strongly inhibited tumor growth and significantly prolonged animal survival, but also greatly prevented tumor metastasis. Our data showed that the immuno-casp-6 can specifically recognize HER2-overexpressing osteosarcoma cells, can also promptly attack their nucleus and induce apoptotic death, suggesting the potential of this strategy for the treatment of human HER2-overexpressing tumors.