Dexamethasone-induced cytotoxicity in human osteoblasts is associated with circular RNA HIPK3 downregulation

Taxifolin-mediated Nrf2 activation ameliorates oxidative stress and apoptosis for the treatment of glucocorticoid-induced osteonecrosis of the femoral head

Glucocorticoid-induced osteonecrosis of the femoral head (GIONFH) is the main complication secondary to long-term or excessive use of glucocorticoids (GCs). Taxifolin (TAX) is a natural antioxidant with various pharmacological effects, such as antioxidative stress and antiapoptotic properties. The purpose of this study was to explore whether TAX could regulate oxidative stress and apoptosis in GIONFH by activating the nuclear factor erythroid 2-related factor 2 (Nrf2) pathway. We conducted qRT-PCR, Western blotting, TUNEL assays, flow cytometry, and other experiments in vitro. Microcomputed tomography analysis, hematoxylin-eosin staining, and immunohistochemical staining were performed to determine the therapeutic effect of TAX in vivo. TAX mitigated the overexpression of ROS and NOX gene expression induced by DEX, effectively reducing oxidative stress. Additionally, TAX could alleviate DEX-induced osteoblast apoptosis, as evidenced by qRT-PCR, Western blotting, and other experimental techniques. Our in vivo studies further demonstrated that TAX mitigates the progression of GIONFH in rats by combating oxidative stress and apoptosis. Mechanistic exploration revealed that TAX thwarts the progression of GIONFH through the activation of the Nrf2 pathway. Overall, our research herein reports that TAX-mediated Nrf2 activation ameliorates oxidative stress and apoptosis for the treatment of GIONFH.

Role of non-coding RNAs in osteoporosis

Osteoporosis, a prevalent bone disorder influenced by genetic and environmental elements, significantly increases the likelihood of fractures and bone weakness, greatly affecting the lives of those afflicted. Yet, the exact epigenetic processes behind the onset of osteoporosis are still unclear. Growing research indicates that epigenetic changes could act as vital mediators that connect genetic tendencies and environmental influences, thereby increasing the risk of osteoporosis and bone fractures. Within these epigenetic factors, certain types of RNA, such as microRNAs (miRNAs), long non-coding RNAs (lncRNAs), and circular RNAs (circRNAs), have been recognized as key regulatory elements. These RNA types wield significant influence on gene expression through epigenetic regulation, directing various biological functions essential to bone metabolism. This extensive review compiles current research uncovering the complex ways in which miRNAs, lncRNAs, and circRNAs are involved in the development of osteoporosis, especially in osteoblasts and osteoclasts. Gaining a more profound understanding of the roles these three RNA classes play in osteoporosis could reveal new diagnostic methods and treatment approaches for this incapacitating condition. In conclusion, this review delves into the complex domain of epigenetic regulation via non-coding RNA in osteoporosis. It sheds light on the complex interactions and mechanisms involving miRNAs, lncRNAs, and circRNAs within osteoblasts and osteoclasts, offering an in-depth understanding of the less explored aspects of osteoporosis pathogenesis. These insights not only reveal the complexity of the disease but also offer significant potential for developing new diagnostic methods and targeted treatments. Therefore, this review marks a crucial step in deciphering the elusive complexities of osteoporosis, leading towards improved patient care and enhanced quality of life.

Drug Loaded 3D-Printed Poly(ε-Caprolactone) Scaffolds for Local Antibacterial or Anti-Inflammatory Treatment in Bone Regeneration

Annual bone grafting surgeries due to bone fractures, resections of affected bones, skeletal anomalies, osteoporosis, etc. exceed two million worldwide. In this regard, the creation of new materials for bone tissue repair is one of the urgent tasks of modern medicine. Additive manufacturing, or 3D printing, offers great opportunities for the development of materials with diverse properties and designs. In this study, the one-pot technique for the production of 3D scaffolds based on poly(ε-caprolactone) (PCL) loaded with an antibiotic or anti-inflammatory drug was proposed. In contrast to previously described methods to prepare drug-containing scaffolds, drug-loaded PCL scaffolds were prepared by direct 3D printing from a polymer/drug blend. An investigation of the mechanical properties of 3D-printed scaffolds containing 0.5-5 wt% ciprofloxacin (CIP) or dexamethasone (DEX) showed almost no effect of the drug (compression modulus ~70-90 MPa) compared to unfilled PCL (74 MPa). At the same time, introducing the drug and increasing its content in the PCL matrix contributed to a 1.8-6.8-fold decrease in the specific surface area of the scaffold, depending on composition. The release of CIP and DEX in phosphate buffer solution and in the same buffer containing lipase revealed a faster release in enzyme-containing medium within 45 days. Furthermore, drug release was more intensive from scaffolds with a low drug load. Analysis of the release profiles using a number of mathematical dissolution models led to the conclusion that diffusion dominates over other probable factors. In vitro biological evaluation of the scaffolds containing DEX showed moderate toxicity against osteoblast-like and leukemia monocytic cells. Being 3D-printed together with PCL both drugs retain their biological activity. PCL/CIP and PCL/DEX scaffolds demonstrated antibacterial properties against Pseudomonas aeruginosa (a total inhibition after 48 h) and anti-inflammatory activity in experiments on TNFα-activated monocyte cells (a 4-time reduction in CD-54 expression relative to control), respectively.

Epimedin C protects dexamethasone-induced osteoblasts through NRF1/RhoA pathway

Osteoporosis (OP) is a metabolic bone disease that leads to decrease of bone strength and increase bone brittle and fracture. Dexamethasone (DXMS) usage is a common risk factor of OP. In present study, we found that the Epimedin C protect the DXMS-induced OP, Ras Homolog Family Member A transforming protein (RhoA) was increased in osteoblasts (OBs) and OP models. We further revealed that Nrf1 is a transcription factor that responds to Epimedin C and DXMS in modulating RhoA promoter. The results collectively demonstrate that Epimedin C functions as a positive modifier of RhoA via alteration of Nrf1 transcriptional activity on RhoA promoter, thereby, protecting OBs against OP. Our work is the first study identifying the Epimedin C function in balancing the OBs in OP model via Nrf1-RhoA.

Identification and Validation of Potential Ferroptosis-Related Genes in Glucocorticoid-Induced Osteonecrosis of the Femoral Head

Background and Objectives. Glucocorticoid-induced osteonecrosis of the femoral head (GIONFH) is a serve complication of long-term administration of glucocorticoids. Previous experimental studies have shown that ferroptosis might be involved in the pathological process of GIONFH. The purpose of this study is to identify the ferroptosis-related genes and pathways of GIONFH by bioinformatics to further illustrate the mechanism of ferroptosis in SONFH through bioinformatics analysis. Materials and Methods. The GSE123568 mRNA expression profile dataset, including 30 GIONFH samples and 10 non-GIONFH samples, was downloaded from the Gene Expression Omnibus (GEO) database. Ferroptosis-related genes were obtained from the FerrDb database. First, differentially expressed genes (DEGs) were identified between the serum samples from GIONFH cases and those from controls. Ferroptosis-related DEGs were obtained from the intersection of ferroptosis-related genes and DEGs. Only ferroptosis DEGs were used for all analyses. Then, we conducted a Kyoto encyclopedia of genome (KEGG) and gene ontology (GO) pathway enrichment analysis. We constructed a protein-protein interaction (PPI) network to screen out hub genes. Additionally, the expression levels of the hub genes were validated in an independent dataset GSE10311. Results. A total of 27 ferroptosis-related DEGs were obtained between the peripheral blood samples of GIONFH cases and non-GIONFH controls. Then, GO, and KEGG pathway enrichment analysis revealed that ferroptosis-related DEGs were mainly enriched in the regulation of the apoptotic process, oxidation-reduction process, and cell redox homeostasis, as well as HIF-1, TNF, FoxO signaling pathways, and osteoclast differentiation. Eight hub genes, including TLR4, PTGS2, SNCA, MAPK1, CYBB, SLC2A1, TXNIP, and MAP3K5, were identified by PPI network analysis. The expression levels of TLR4, TXNIP and MAP3K5 were further validated in the dataset GSE10311. Conclusion. A total of 27 ferroptosis-related DEGs involved in GIONFH were identified via bioinformatics analysis. TLR4, TXNIP, and MAP3K5 might serve as potential biomarkers and drug targets for GIONFH.

The Diagnostic and Therapeutic Role of Circular RNA HIPK3 in Human Diseases

Circular RNAs (circRNAs) are a class of noncoding RNAs with closed-loop of single-stranded RNA structure. Although most of the circRNAs do not directly encode proteins, emerging evidence suggests that circRNAs play a pivotal and complex role in multiple biological processes by regulating gene expression. As one of the most popular circRNAs, circular homeodomain-interacting protein kinase 3 (circHIPK3) has frequently gained the interest of researchers in recent years. Accumulating studies have demonstrated the significant impacts on the occurrence and development of multiple human diseases including cancers, cardiovascular diseases, diabetes mellitus, inflammatory diseases, and others. The present review aims to provide a detailed description of the functions of circHIPK3 and comprehensively overview the diagnostic and therapeutic value of circHIPK3 in these certain diseases.

Nrf2 signaling activation by a small molecule activator compound 16 inhibits hydrogen peroxide-induced oxidative injury and death in osteoblasts

We explored the potential activity of compound 16 (Cpd16), a novel small molecule Nrf2 activator, in hydrogen peroxide (H₂O₂)-stimulated osteoblasts. In the primary murine/human osteoblasts and MC3T3-E1 murine osteoblastic cells, Cpd16 treatment at micro-molar concentrations caused disassociation of Keap1-Nrf2 and Nrf2 cascade activation. Cpd16 induced stabilization of Nrf2 protein and its nuclear translocation, thereby increasing the antioxidant response elements (ARE) reporter activity and Nrf2 response genes transcription in murine and human osteoblasts. Significantly, Cpd16 mitigated oxidative injury in H₂O₂-stimulited osteoblasts. H₂O₂-provoked apoptosis as well as programmed necrosis in osteoblasts were significantly alleviated by the novel Nrf2 activator. Cpd16-induced Nrf2 activation and osteoblasts protection were stronger than other known Nrf2 activators. Dexamethasone- and nicotine-caused oxidative stress and death in osteoblasts were attenuated by Cpd16 as well. Cpd16-induced osteoblast cytoprotection was abolished by Nrf2 short hairpin RNA or knockout, but was mimicked by Keap1 knockout. Keap1 Cys151S mutation abolished Cpd16-induced Nrf2 cascade activation and osteoblasts protection against H₂O₂. Importantly, weekly Cpd16 administration largely ameliorated trabecular bone loss in ovariectomy mice. Together, Cpd16 alleviates H₂O₂-induced oxidative stress and death in osteoblasts by activating Nrf2 cascade.

Non-coding RNA delivery for bone tissue engineering: progress, challenges and potential solutions

More than 20 million individuals worldwide suffer from congenital or acquired bone defects annually. The development of bone scaffold materials that simulate natural bone for bone defect repair remains challenging. Recently, ncRNA-based therapies for bone defects have attracted increasing interest because of the great potential of ncRNAs in disease treatment. Various types of ncRNAs regulate gene expression in osteogenesis-related cells via multiple mechanisms. The delivery of ncRNAs to the site of bone loss through gene vectors or scaffolds is a potential therapeutic option for bone defect repair. Therefore, this study discusses and summarizes the regulatory mechanisms of miRNAs, siRNAs, and piRNAs in osteogenic signaling and reviews the widely used current RNA delivery vectors and scaffolds for bone defect repair. Additionally, current challenges and potential solutions of delivery scaffolds for bone defect repair are proposed, with the aim of providing a theoretical basis for their future clinical applications.

Synthesis of a novel monofilament bioabsorbable suture for biomedical applications

In this research, a novel bioabsorbable suture that is, monofilament and capable of localized drug delivery, was developed from a combination of natural biopolymers that where not previously applied for this purpose. The optimized suture formulation comprised of sodium alginate (6% wt/vol), pectin (0.1% wt/vol), and gelatin (3% wt/vol), in the presence of glycerol (4% vol/vol) which served as a plasticizer. The monofilament bioabsorbable sutures where synthesized via in situ ionic crosslinking in a barium chloride solution (2% wt/vol). The resulting suture was characterized in terms of mechanical properties, morphology, swelling, degradation, drug release, and biocompatibility, in addition to Fourier-transform infrared (FTIR) spectroscopy, Powder X-ray Diffraction (PXRD) and Differential Scanning Calorimetry (DSC) analysis. The drug loaded and non-drug loaded sutures had a maximum breaking strength of 4.18 and 4.08 N, in the straight configuration and 2.44 N and 2.59 N in the knot configuration, respectively. FTIR spectrum of crosslinked sutures depicted Δ9 cm^-1 downward shift for the carboxyl stretching band which was indicative of ionic interactions between barium ions and sodium alginate. In vitro analysis revealed continued drug release for 7 days and gradual degradation by means of surface erosion, which was completed by day 28. Biocompatibility studies revealed excellent hemocompatibility and no cytotoxicity. These results suggest that the newly developed bioabsorbable suture meets the basic requirements of a suture material and provides a viable alternative to the synthetic polymer sutures that are currently on the market.

High doses of dexamethasone induce endoplasmic reticulum stress-mediated apoptosis by promoting calcium ion influx-dependent CHOP expression in osteoblasts

Background

The long-term use of dexamethasone (Dex), a well-known immunosuppressant, leads to an imbalance in bone metabolism and rapid decline of bone mineral density due to apoptosis of osteoblasts. The molecular mechanisms by which Dex induces osteoblast apoptosis remain unclear.

Materials and methods

MC3T3-E1 cells were treated with 0, 10⁻⁸, 10⁻⁶, and 10⁻⁴ M Dex for 24 h. ATF6, phosphorylated PERK, PERK, phosphorylated IRE1, and IRE1 expression, cell apoptosis, and caspase-12 and caspase-3 activity were measured. CHOP expression and calcium ion influx rate were measured in cells treated with 0 and 10⁻⁴ M Dex for 24 h. The effect of 2-APB treatment was assessed in cells treated with 0 or 10⁻⁴ M Dex.

Results

Levels of ATF6 and phosphorylated PERK and IRE1 increased in a dose-dependent manner in MC3T3-E1 cells treated with 10⁻⁸, 10⁻⁶, and 10⁻⁴ M Dex, compared to the control group (P < 0.05). Cells treated with 10⁻⁶ and 10⁻⁴ M Dex had significantly increased apoptotic rates and caspase-12 and caspase-3 activities (P < 0.05). Cells treated with 10⁻⁴ M Dex had significantly increased CHOP levels and calcium ion influx rates (P < 0.05). Combined treatment with 10⁻⁴ M Dex and 2-APB abrogated the observed increases in cell apoptosis and caspase-12 and caspase-3 activities (P < 0.05).

Conclusions

High doses of Dex induce CHOP expression by promoting calcium ion influx-dependent induction of ATF6, phosphorylated PERK and phosphorylated IRE1, which induce endoplasmic reticulum stress-mediated apoptosis in osteoblasts. 2-APB protects the osteoblasts from the effects of Dex, preventing endoplasmic reticulum stress-mediated apoptosis.

Potential Adverse Effects of Dexamethasone Therapy on COVID-19 Patients: Review and Recommendations

In the context of the coronavirus disease 2019 (COVID-19) pandemic, the global healthcare community has raced to find effective therapeutic agents against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). To date, dexamethasone is the first and an important therapeutic to significantly reduce the risk of death in COVID-19 patients with severe disease. Due to powerful anti-inflammatory and immunosuppressive effects, dexamethasone could attenuate SARS-CoV-2-induced uncontrolled cytokine storm, severe acute respiratory distress syndrome and lung injury. Nevertheless, dexamethasone treatment is a double-edged sword, as numerous studies have revealed that it has significant adverse impacts later in life. In this article, we reviewed the literature regarding the adverse effects of dexamethasone administration on different organ systems as well as related disease pathogenesis in an attempt to clarify the potential harms that may arise in COVID-19 patients receiving dexamethasone treatment. Overall, taking the threat of COVID­19 pandemic into account, we think it is necessary to apply dexamethasone as a pharmaceutical therapy in critical patients. However, its adverse side effects cannot be ignored. Our review will help medical professionals in the prognosis and follow-up of patients treated with dexamethasone. In addition, given that a considerable amount of uncertainty, confusion and even controversy still exist, further studies and more clinical trials are urgently needed to improve our understanding of the parameters and the effects of dexamethasone on patients with SARS-CoV-2 infection.

Biogenesis, cellular effects, and biomarker value of circHIPK3

Competing endogenous RNAs (ceRNAs) can indirectly regulate gene expression by competitively binding to microRNA(miRNA) through miRNA response elements (MREs) to affect miRNA-induced gene regulation, which is of great biological significance. Among them, circular RNA (circRNA) has become a hotspot due to its highest binding capacity. A specific circRNA discussed in this review, circHIPK3, has been studied for its biological characteristics, function, cellular effects and its relationship with tumors and various diseases. Here, we review the recent researches about circHIPK3 in detail and aim to elucidate accurate conclusions from them. These circHIPK3-miRNAs-mRNA pathways will further advance the application of circHIPK3 in diseases development, early diagnosis and gene targeting therapy.

Atorvastatin Upregulates microRNA-186 and Inhibits the TLR4-Mediated MAPKs/NF-κB Pathway to Relieve Steroid-Induced Avascular Necrosis of the Femoral Head

Steroid-induced avascular necrosis of the femoral head (SANFH) is caused by the death of active components of the femoral head owing to hormone overdoses. The use of lipid-lowering drugs to prevent SANFH in animals inspired us to identify the mechanisms involving Atorvastatin (Ato) in SANFH. However, it is still not well understood how and to what extent Ato affects SANFH. This study aimed to figure out the efficacy of Ato in SANFH and the underlying molecular mechanisms. After establishment of the SANFH model, histological evaluation, lipid metabolism, inflammatory cytokines, oxidative stress, apoptosis, and autophagy of the femoral head were evaluated. The differentially expressed microRNAs (miRs) after Ato treatment were screened out using microarray analysis. The downstream gene and pathway of miR-186 were predicted and their involvement in SANFH rats was analyzed. OB-6 cells were selected to simulate SANFH in vitro. Cell viability, cell damage, inflammation responses, apoptosis, and autophagy were assessed. Ato alleviated SANFH, inhibited apoptosis, and promoted autophagy. miR-186 was significantly upregulated after Ato treatment. miR-186 targeted TLR4 and inactivated the MAPKs/NF-κB pathway. Inhibition of miR-186 reversed the protection of Ato on SANFH rats, while inhibition of TLR4 restored the protective effect of Ato. Ato reduced apoptosis and promoted autophagy of OB-6 cells by upregulating miR-186 and inhibiting the TLR4/MAPKs/NF-κB pathway. In conclusion, Ato reduced apoptosis and promoted autophagy, thus alleviating SANFH via miR-186 and the TLR4-mediated MAPKs/NF-κB pathway.

CircPVT1 up-regulation attenuates steroid-induced osteonecrosis of the femoral head through regulating miR-21-5p-mediated Smad7/TGFβ signalling pathway

Steroid‐induced osteonecrosis of the femoral head (SIONFH) has been a common disease following corticosteroid therapy. Presently, we aim to explore the functions of circular RNA (circ) PVT1 in SIONFH rats and the underlying mechanism. Glucocorticoid (GC) was used to treat SD rats and bone marrow‐derived mesenchymal stem cells (BMSCs) to construct SIONFH model in vitro and in vivo, respectively. The pathological injury of the femoral head in the SIONFH rats was detected via haematoxylin‐eosin (HE) staining and immunohistochemistry (IHC). The osteogenic differentiation, proliferation and apoptosis of BMSCs were detected. Western blot was used to detect Smad7, Bax, Bcl2 and Smad2/3. The potential targets of circPVT1 and miR‐21‐5p were validated through luciferase reporter gene assay and RNA pull‐down assay, respectively. We found that CircPVT1 was decreased in the femoral head of SIONFH rats and GC‐treated BMSCs, while miR‐21‐5p was markedly up‐regulated. Overexpressed circPVT1 attenuated the apoptosis and cell viability inhibition of BMSCs induced by GC, while miR‐21‐5p up‐regulation had the opposite effects. What's more, the in vivo experiments confirmed that up‐regulating circPVT1 repressed osteonecrosis in SIONFH rats through repressing apoptosis. Mechanistically, circPVT1 functioned as a ceRNA of miR‐21‐5p, which targeted at the 3'untranslated region of Smad7. CircPVT1 enhancing Smad7 and mitigating GC activated TGFβ/Smad2/3 pathway through inhibiting miR‐21‐5p. In conclusion, CircPVT1 exerts protective effects against SIONFH via modulating miR‐21‐5p‐mediated Smad7/TGFβ pathway.

MAFG-driven osteosarcoma cell progression is inhibited by a novel miRNA miR-4660

Osteosarcoma (OS) is the most common primary bone malignancy in the adolescent population. MAFG (v-maf avian musculoaponeurotic fibrosarcoma oncogene homolog G) forms a heterodimer with Nrf2 (NF-E2-related factor 2), binding to antioxidant response element (ARE), which is required for Nrf2 signaling activation. We found that MAFG mRNA and protein expression is significantly elevated in human OS tissues as well as in established and primary human OS cells. In human OS cells, MAGF silencing or knockout (KO) largely inhibited OS cell growth, proliferation, and migration, simultaneously inducing oxidative injury and apoptosis activation. Conversely, ectopic overexpression of MAFG augmented OS cell progression in vitro. MicroRNA-4660 (miR-4660) directly binds the 3′ untranslated region (UTR) of MAFG mRNA in the cytoplasm of OS cells. MAFG 3′ UTR luciferase activity and expression as well as OS cell growth were largely inhibited with forced miR-4660 overexpression but augmented with miR-4660 inhibition. In vivo, MAGF short hairpin RNA (shRNA) or forced overexpression of miR-4660 inhibited subcutaneous OS xenograft growth in severe combined immunodeficient mice. Furthermore, MAFG silencing or miR-4660 overexpression inhibited OS xenograft in situ growth in proximal tibia of the nude mice. In summary, MAFG overexpression-driven OS cell progression is inhibited by miR-4660. The miR-4660-MAFG axis could be novel therapeutic target for human OS.

The histone acetyltransferase HBO1 functions as a novel oncogenic gene in osteosarcoma

HBO1 (KAT7 or MYST2) is a histone acetyltransferase that acetylates H3 and H4 histones.

Methods: HBO1 expression was tested in human OS tissues and cells. Genetic strategies, including shRNA, CRISPR/Cas9 and overexpression constructs, were applied to exogenously alter HBO1 expression in OS cells. The HBO1 inhibitor WM-3835 was utilized to block HBO1 activation.

Results:HBO1 mRNA and protein expression is significantly elevated in OS tissues and cells. In established (MG63/U2OS lines) and primary human OS cells, shRNA-mediated HBO1 silencing and CRISPR/Cas9-induced HBO1 knockout were able to potently inhibit cell viability, growth, proliferation, as well as cell migration and invasion. Significant increase of apoptosis was detected in HBO1-silenced/knockout OS cells. Conversely, ectopic HBO1 overexpression promoted OS cell proliferation and migration. We identified ZNF384 (zinc finger protein 384) as a potential transcription factor of HBO1. Increased binding between ZNF384 and HBO1 promoter was detected in OS cell and tissues, whereas ZNF384 silencing via shRNA downregulated HBO1 and produced significant anti-OS cell activity. In vivo, intratumoral injection of HBO1 shRNA lentivirus silenced HBO1 and inhibited OS xenograft growth in mice. Furthermore, growth of HBO1-knockout OS xenografts was significantly slower than the control xenografts. WM-3835, a novel and high-specific small molecule HBO1 inhibitor, was able to potently suppressed OS cell proliferation and migration, and led to apoptosis activation. Furthermore, intraperitoneal injection of a single dose of WM-3835 potently inhibited OS xenograft growth in SCID mice.

Conclusion: HBO1 overexpression promotes OS cell growth in vitro and in vivo.

p38γ overexpression promotes osteosarcoma cell progression

Osteosarcoma (OS) is the most common primary bone malignancy in the adolescent population. Recent studies demonstrate that p38 gamma (p38γ) phosphorylates retinoblastoma (Rb) to promote cyclin expression, cell-cycle entry and tumorigenesis. Studying the potential function of p38γ in human OS, we show that p38γ mRNA and protein expression are significantly elevated in OS tissues and OS cells, whereas its expression is relatively low in normal bone tissue and in human osteoblasts/osteoblastic cells. Knockdown of p38γ in established (U2OS) and primary human OS cells potently inhibited cell growth, proliferation, migration and invasion, while promoting cell apoptosis. Furthermore, CRISPR/Cas9-induced p38γ knockout inhibited human OS cell progression in vitro. Conversely, ectopic overexpression of p38γ in primary human OS cells augmented cell growth, proliferation and migration. Signaling studies show that retinoblastoma (Rb) phosphorylation and cyclin E1/cyclin A expression were decreased following p38γ shRNA knockdown and knockout, but increased after ectopic p38γ overexpression. Collectively, these results show that p38γ overexpression promotes human OS cell progression.

The roles of miRNA, lncRNA and circRNA in the development of osteoporosis

Osteoporosis is a common metabolic bone disease, influenced by genetic and environmental factors, that increases bone fragility and fracture risk and, therefore, has a serious adverse effect on the quality of life of patients. However, epigenetic mechanisms involved in the development of osteoporosis remain unclear. There is accumulating evidence that epigenetic modifications may represent mechanisms underlying the links of genetic and environmental factors with increased risk of osteoporosis and bone fracture. Some RNAs, such as microRNAs (miRNAs), long non-coding RNAs (lncRNAs), and circular RNAs (circRNAs), have been shown to be epigenetic regulators with significant involvement in the control of gene expression, affecting multiple biological processes, including bone metabolism. This review summarizes the results of recent studies on the mechanisms of miRNA-, lncRNA-, and circRNA-mediated osteoporosis associated with osteoblasts and osteoclasts. Deeper insights into the roles of these three classes of RNA in osteoporosis could provide unique opportunities for developing novel diagnostic and therapeutic approaches to this disease.

miR-107 inhibition upregulates CAB39 and activates AMPK-Nrf2 signaling to protect osteoblasts from dexamethasone-induced oxidative injury and cytotoxicity

To human osteoblasts dexamethasone (DEX) treatment induces significant oxidative injury and cytotoxicity. Inhibition of CAB39 (calcium binding protein 39)-targeting microRNA can induce CAB39 upregulation, activating AMP-activated protein kinase (AMPK) signaling and offering osteoblast cytoprotection. Here we identified a novel CAB39-targeting miRNA: the microRNA-107 (miR-107). RNA-Pull down assay results demonstrated that the biotinylated-miR-107 directly binds to CAB39 mRNA in OB-6 human osteoblastic cells. Forced overexpression of miR-107, by infection of pre-miR-107 lentivirus or transfection of wild-type miR-107 mimic, largely inhibited CAB39 expression in OB-6 cells and primary human osteoblasts. Contrarily, miR-107 inhibition, by antagomiR-107, increased its expression, resulting in AMPK cascade activation. AntagomiR-107 largely attenuated DEX-induced cell death and apoptosis in OB-6 cells and human osteoblasts. Importantly, osteoblast cytoprotection by antagomiR-107 was abolished with AMPK in-activation by AMPKα1 dominant negative mutation, silencing or knockout. Further studies demonstrated that antagomiR-107 activated AMPK downstream Nrf2 cascade to inhibit DEX-induced oxidative injury. Conversely, Nrf2 knockout almost abolished antagomiR-107-induced osteoblast cytoprotection against DEX. Collectively, miR-107 inhibition induced CAB39 upregulation and activated AMPK-Nrf2 signaling to protect osteoblasts from DEX-induced oxidative injury and cytotoxicity.

Circular RNA HIPK3: A Key Circular RNA in a Variety of Human Cancers

Circular RNAs (circRNAs), which act as initiators and promoters of various diseases, were thought to be mostly noncoding RNAs (ncRNAs) in eukaryotes, until recent studies confirmed that some circRNAs have the function of encoding proteins. Accumulating research findings have proved that dysregulation of circRNAs is associated with the developmental process of multiple cancers. circHIPK3, an example of circRNA, is frequently expressed in many diseases, such as diabetes, age-related cataract, idiopathic pulmonary fibrosis, preeclampsia, osteoblasts, and retinal vascular dysfunction, leading to disease development and progression. In addition, circHIPK3 may also serve as a potential biomarker, to help us know more about the rules of occurrence and development of cancers. In recent studies, many circHIPK3-related cancers have been identified, including nasopharyngeal carcinoma, gallbladder cancer, lung cancer, hepatocellular carcinoma, osteosarcoma, glioma, colorectal cancer, ovarian cancer, bladder cancer, prostate cancer, gastric cancer, oral squamous cell carcinoma, and chronic myeloid leukemia. This review summarizes recent studies on the biological mechanisms of circHIPK3 and expounds the molecular mechanisms of circHIPK3 in these malignant tumors.

Dexmedetomidine alleviates postoperative cognitive dysfunction through circular RNA in aged rats

Circular RNA (circRNA) has been well studied in many diseases, whereas their role in patients with postoperative cognitive dysfunction (POCD) remains largely unclear. Here, we investigated the therapeutic effects of dexmedetomidine (Dex) on POCD and analyzed the role of circRNA as well as the pathways that may be involved. The Morris water maze test demonstrated that POCD rats have a longer incubation period than the normal group, but the latency of POCD rats was significantly lower after Dex treatment. Moreover, HE staining showed that Dex improved hippocampal pathological changes. RNA sequencing showed 164 differentially expressed circRNAs between POCD and Dex groups; 74 were upregulated and 90 were downregulated in the Dex group. A total of 20,790 target genes for differentially expressed circRNAs were observed in RNAhybrid and Miranda databases. Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses showed that the target genes of differentially expressed circRNAs are mainly focused on positive regulation of intrinsic apoptotic signaling pathway in response to DNA damage, negative regulation of cell adhesion mediated by integrin, and response to cytokines and other function of life activities and involved in the P53 signaling pathway and nuclear factor kappa B (NF-κB) signaling pathway. Furthermore, the expression of five candidate circRNAs (circ-Shank3, circ-Cdc42bpa, circ-chrx-24658, cir-chr17-3642 and circ-Sgsm1) and target genes were consistent with the RNA sequencing results, which was verified by quantitative real-time polymerase chain reaction (qRT-PCR). These results indicate that circ-Shank3 participate in the process of Dex improved POCD through regulating the P53 and NF-κB signaling pathways and may potentially facilitate POCD treatment through the development of clinical drugs.

Prolactin-Responsive Circular RNA circHIPK3 Promotes Proliferation of Mammary Epithelial Cells from Dairy Cow

The highly expressed circHIPK3 is a circular RNA that has been previously reported to regulate the growth of human cells. In this study, we found an increased expression of circHIPK3 in bovine mammary epithelial cells treated with prolactin (PRL) in high-throughput sequencing data. Thus, we further investigated the effect of circHIPK3 on the proliferation and differentiation of mammary epithelial cells. We used qRT-PCR/Cell Counting Kit-8 (CCK-8) and a Western blotting analysis to evaluate the effects on cell proliferation. We found that circHIPK3 promotes the proliferation of mammary epithelial cells. The STAT5 signaling pathway was previously associated with the prolactin response and when the STAT5 was suppressed, the expression of circHIPK3 decreased. The results suggest that the response to prolactin and the associated STAT5 signaling pathway affect the expression of circHIPK3, which subsequently affects the proliferation of mammary epithelial cells in dairy cows.

Noncoding RNAs in Steroid-Induced Osteonecrosis of the Femoral Head

Steroid-induced osteonecrosis of the femoral head (ONFH) is a severe orthopedic disease caused by the long-term administration of glucocorticoids. The main pathological feature of ONFH is the gradually progressive necrosis of bone cells and the bone marrow, ultimately resulting in structural changes or even complete collapse of the femoral head. However, the exact pathogenic mechanism of ONFH remains unknown. Noncoding RNAs (ncRNAs) have emerged as very powerful regulators of gene expression, functioning at both transcriptional and posttranscriptional levels in the pathogenesis of ONFH. Here, we review the current knowledge of the role of ncRNAs, including microRNAs, long noncoding RNAs, and circular RNAs, in the pathogenesis of steroid-induced ONFH. Further focus and validation of these associations can provide new insight into the pathogenic mechanisms at the molecular level to suggest targets for treatment and prevention.

PGK1 depletion activates Nrf2 signaling to protect human osteoblasts from dexamethasone

Activation of nuclear-factor-E2-related factor 2 (Nrf2) cascade can alleviate dexamethasone (DEX)-induced oxidative injury and death of human osteoblasts. A recent study has shown that phosphoglycerate kinase 1 (PGK1) inhibition/depletion will lead to Kelch-like ECH-associated protein 1 (Keap1) methylglyoxal modification, thereby activating Nrf2 signaling cascade. Here, in OB-6 osteoblastic cells and primary human osteoblasts, PGK1 silencing, by targeted shRNA, induced Nrf2 signaling cascade activation, causing Nrf2 protein stabilization and nuclear translocation, as well as increased expression of ARE-dependent genes (HO1, NQO1, and GCLC). Functional studies demonstrated that PGK1 shRNA largely attenuated DEX-induced oxidative injury and following death of OB-6 cells and primary osteoblasts. Furthermore, PGK1 knockout, by the CRISPR/Cas9 method, similarly induced Nrf2 signaling activation and protected osteoblasts from DEX. Importantly, PGK1 depletion-induced osteoblast cytoprotection against DEX was almost abolished by Nrf2 shRNA. In addition, Keap1 shRNA mimicked and nullified PGK1 shRNA-induced anti-DEX osteoblast cytoprotection. At last we show that PGK1 expression is downregulated in human necrotic femoral head tissues of DEX-taking patients, correlating with HO1 depletion. Collectively, these results show that PGK1 depletion protects human osteoblasts from DEX via activation of Keap1-Nrf2 signaling cascade.

Dysregulation of cPWWP2A-miR-579 axis mediates dexamethasone-induced cytotoxicity in human osteoblasts

Dexamethasone (DEX) induces significant cytotoxicity to human osteoblasts. cPWWP2A is recently-indentified novel circular RNA (circRNA), acting as an endogenous sponge of microRNA-579 (miR-579). The present study tested the expression and potential functions of the cPWWP2A-miR-579 axis in DEX-treated osteoblasts. We show that cPWWP2A is downregulated in the necrotic femoral head tissues of DEX-taking human patients as well as in DEX-treated human osteoblasts. In OB-6 osteoblastic cells and primary human osteoblasts ectopic overexpression of cPWWP2A potently inhibited DEX-induced miR-579 accumulation, cell death, apoptosis and programmed necrosis. Silencing miR-579, by targeted siRNAs, also attenuated DEX-induced cytotoxicity in human osteoblasts. Significantly, mimicking DEX-induced actions, cPWWP2A silencing or forced miR-579 overexpression induced significant cytotoxicity in human osteoblasts. Further analyses demonstrated that miR-579's targets, including SIRT1 and PDK1 (phosphoinositide-dependent protein kinase 1), were downregulated in DEX-treated osteoblasts. Their levels were decreased as well in the necrotic femoral head tissues of DEX-taking human patients. Taken together we show that dysregulation of the cPWWP2A-miR-579 axis is involved in DEX-induced cytotoxicity in human osteoblasts.