Oxidative Stress Induced Osteocyte Apoptosis in Steroid-Induced Femoral Head Necrosis

Designing and synthesis of injectable hydrogel based on carboxymethyl cellulose/carboxymethyl chitosan containing QK peptide for femoral head osteonecrosis healing

Femoral head necrosis is a debilitating disorder that typically caused by impaired blood supply to the hip joint. In this study, a novel injectable hydrogel based on Oxidized Carboxymethyl Cellulose (OCMC)-Carboxymethyl Chitosan (CMCS) polymers containing an angiogenesis stimulator peptide (QK) with a non-toxic crosslinking interaction (Schiff based reaction) was synthesized to enhance angiogenesis following femoral head necrosis in an animal model. The physicochemical features of fabricated injectable hydrogel were analyzed by FTIR, swelling and degradation rate, rheometry, and peptide release. Also, the safety and efficacy were evaluated following an in vitro hydrogel injection study and an avascular necrosis (AVN) animal model. According to the results, the hydrogel exhibited an appropriate swelling ratio and water uptake (>90 %, 24 h) as well as a suitable degradation rate over 21 days accompanied by a continuous peptide release. Also, data showed that hydrogels containing QK peptide boosted the proliferation, differentiation, angiogenesis, and osteogenic potential of both Bone Marrow mesenchymal Stem Cells (BM-MSCs) and human umbilical vein endothelial cells (HUVECs) (****p < 0.0001 and ***p < 0.001, respectively). Furthermore, molecular and histological evaluations significantly demonstrated the overexpression of Runx2, Osteocalcin, Collagen I, VEGF and CD34 genes (**p < 0.01 and ***p < 0.001, respectively), and also femoral head necrosis was effectively prohibited, and more blood vessels were detected in defect area by OCMC-CMCS hydrogel containing QK peptide (bone trabeculae >9000, ***p < 0.001). In conclusion, the findings demonstrate that OCMC-CMCS-QK injectable hydrogel could be considered as an impressive therapeutic construct for femoral head AVN healing.

Defining the Most Potent Osteoinductive Culture Conditions for MC3T3-E1 Cells Reveals No Implication of Oxidative Stress or Energy Metabolism

The MC3T3-E1 preosteoblastic cell line is widely utilised as a reliable in vitro system to assess bone formation. However, the experimental growth conditions for these cells hugely diverge, and, particularly, the osteogenic medium (OSM)'s composition varies in research studies. Therefore, we aimed to define the ideal culture conditions for MC3T3-E1 subclone 4 cells with regard to their mineralization capacity and explore if oxidative stress or the cellular metabolism processes are implicated. Cells were treated with nine different combinations of long-lasting ascorbate (Asc) and β-glycerophosphate (βGP), and osteogenesis/calcification was evaluated at three different time-points by qPCR, Western blotting, and bone nodule staining. Key molecules of the oxidative and metabolic pathways were also assessed. It was found that sufficient mineral deposition was achieved only in the 150 μg.mL-1/2 mM Asc/βGP combination on day 21 in OSM, and this was supported by Runx2, Alpl, Bglap, and Col1a1 expression level increases. NOX2 and SOD2 as well as PGC1α and Tfam were also monitored as indicators of redox and metabolic processes, respectively, where no differences were observed. Elevation in OCN protein levels and ALP activity showed that mineralisation comes as a result of these differences. This work defines the most appropriate culture conditions for MC3T3-E1 cells and could be used by other research laboratories in this field.

Selenium nanoparticles/carboxymethyl chitosan/alginate antioxidant hydrogel for treating steroid-induced osteonecrosis of the femoral head

Oxidative stress plays a crucial role in steroid-induced osteonecrosis of the femoral head (SONFH). Although several antioxidant strategies have been investigated for treating SONFH, their antioxidant efficiencies and therapeutic effects remain unsatisfactory. Here, we developed a selenium nanoparticles/carboxymethyl chitosan/alginate (SeNPs/CMC/Alg) antioxidant hydrogel and evaluated its ability to treat SONFH. In vitro assays indicated that the SeNPs/CMC/Alg hydrogel exhibited excellent properties, such as low cytotoxicity, sustained SeNPs release, and favorable antioxidant activity. Under oxidative stress, the SeNPs/CMC/Alg hydrogel promoted reactive oxygen species (ROS) elimination and enhanced the osteogenic and proangiogenic abilities of bone marrow mesenchymal stem cells (BMSCs). After establishing a rabbit model of SONFH, the SeNPs/CMC/Alg hydrogel was transplanted into the femoral head after core decompression (CD) surgery. Radiographic and histological analyses revealed that the hydrogel treatment alleviated SONFH by eliminating ROS and promoting osteogenesis and angiogenesis compared to those in the CD and CMC/Alg groups. In vitro and in vivo studies indicated that the Wnt/β-catenin signaling pathway was activated by the SeNPs/CMC/Alg hydrogel in both hydrogen peroxide-conditioned BMSCs and necrotic femoral heads. These findings indicate that local transplantation of the SeNPs/CMC/Alg hydrogel is beneficial for treating SONFH, as it promotes ROS elimination and activation of the Wnt/β-catenin signaling pathway.

Glucocorticoids promote steroid-induced osteonecrosis of the femoral head by down-regulating serum alpha-2-macroglobulin to induce oxidative stress and facilitate SIRT2-mediated BMP2 deacetylation

Our study investigated the possible molecular mechanism of glucocorticoid in steroid-induced osteonecrosis of the femoral head (SINFH) through regulating serum alpha-2-macroglobulin and SIRT2-mediated BMP2 deacetylation. Essential genes involved in glucocorticoid-induced SINFH were screened by transcriptome sequencing and analyzed by bioinformatics, followed by identifying downstream regulatory targets. Rat bone marrow mesenchymal stem cells were isolated and treated with methylprednisolone (MP) for in vitro cell experiments. Besides, a glucocorticoid-induced rat ONFH was established using the treatment of MP and LPS. ChIP-PCR detected the enrichment of SIRT2 in the promoter region of BMP2, and the deacetylation modification of SIRT2 on BMP2 was determined. Bioinformatics analysis revealed that glucocorticoids may induce ONFH through the SIRT2/BMP2 axis. In vitro cell experiments showed that glucocorticoids up-regulated SIRT2 expression in BMSCs by inducing oxidative stress, thereby promoting cell apoptosis. The up-regulation of SIRT2 expression may be due to the decreased ability of α2 macroglobulin to inhibit oxidative stress, and the addition of NOX protein inhibitor DPI could significantly inhibit SIRT2 expression. SIRT2 could promote histone deacetylation of the BMP2 promoter and inhibit its expression. In vitro cell experiments further indicated that knocking down SIRT2 could protect BMSC from oxidative stress and cell apoptosis induced by glucocorticoids by promoting BMP2 expression. In addition, animal experiments conducted also demonstrated that the knockdown of SIRT2 could improve glucocorticoid-induced ONFH through up-regulating BMP2 expression. Glucocorticoids could induce oxidative stress by down-regulating serum α2M to promote SIRT2-mediated BMP2 deacetylation, leading to ONFH.

Morroniside-mediated mitigation of stem cell and endothelial cell dysfunction for the therapy of glucocorticoid-induced osteonecrosis of the femoral head

BACKGROUND

Prolonged use of glucocorticoids (GCs) potentially lead to a condition known as GCs-induced osteonecrosis of the femoral head (GIONFH). The primary mechanisms underlying this phenomenon lies in stem cells and endothelial cells dysfunctions. Morroniside, an iridoid glycoside sourced from Cornus officinalis, possesses numerous biological capabilities, including combating oxidative stress, preventing apoptosis, opposing ischemic effects, and promoting the regeneration of bone tissue.

PURPOSE

This study aimed to analyze the impact of Morroniside on Dexamethasone (DEX)-induced dysfunction in stem cells and endothelial cells, and its potential as a therapeutic agent for GIONFH in rat models.

METHODS

ROS assay, JC-1 assay, and TUNEL assay were used to detect oxidative stress and apoptosis levels in vitro. For the evaluation of the osteogenic capability of bone marrow-derived mesenchymal stem cells, we employed ALP and ARS staining. Additionally, the angiogenic ability of endothelial cells was assessed using tube formation assay and migration assay. Microcomputed tomography analysis, hematoxylin-eosin staining, and immunohistochemical staining were utilized to evaluate the in vivo therapeutic efficacy of Morroniside.

RESULTS

Morroniside mitigates DEX-induced excessive ROS expression and cell apoptosis, effectively reducing oxidative stress and alleviating cell death. In terms of osteogenesis, Morroniside reverses DEX-induced osteogenic impairment, as evidenced by enhanced ALP and ARS staining, as well as increased osteogenic protein expression. In angiogenesis, Morroniside counteracts DEX-induced vascular dysfunction, demonstrated by an increase in tube-like structures in tube formation assays, a rise in the number of migrating cells, and elevated levels of angiogenic proteins. In vivo, our results further indicate that Morroniside alleviates the progression of GIONFH.

CONCLUSION

The experimental findings suggest that Morroniside concurrently mitigates stem cell and endothelial cell dysfunction through the PI3K/AKT signaling pathway both in vitro and in vivo. These outcomes suggest that Morroniside serves as a potential therapeutic agent for GIONFH.

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.

Gss deficiency causes age-related fertility impairment via ROS-triggered ferroptosis in the testes of mice

Glutathione synthetase (GSS) catalyzes the final step in the synthesis of glutathione (GSH), a well-established antioxidant. Research on the specific roles of the Gss gene during spermatogenesis remains limited due to the intricate structure of testis. In this study, we identified pachytene spermatocytes as the primary site of GSS expression and generated a mouse model with postnatal deletion of Gss using Stra8-Cre (S8) to investigate the role of GSS in germ cells. The impact of Gss knockout on reducing male fertility is age-dependent and caused by ferroptosis in the testis. The 2-month-old S8/Gss-/- male mice exhibited normal fertility, due to a compensatory increase in GPX4, which prevented the accumulation of ROS. With aging, there was a decline in GPX4 and an increase in ALOX15 levels observed in 8-month-old S8/Gss-/- mice, resulting in the accumulation of ROS, lipid peroxidation, and ultimately testicular ferroptosis. We found that testicular ferroptosis did not affect spermatogonia, but caused meiosis disruption and acrosome heterotopia. Then the resulting aberrant sperm showed lower concentration and abnormal morphology, leading to reduced fertility. Furthermore, these injuries could be functionally rescued by inhibiting ferroptosis through intraperitoneal injection of GSH or Fer-1. In summary, Gss in germ cells play a crucial role in the resistance to oxidative stress injury in aged mice. Our findings deepen the understanding of ferroptosis during spermatogenesis and suggest that inhibiting ferroptosis may be a potential strategy for the treatment of male infertility.

Effects of external environment on promoter methylation of PIK3R5 and related pathway regulation in steroid-induced femoral head necrosis

BACKGROUND

Steroid-induced Avascular Necrosis of the Femoral Head (SANFH) is a condition characterized by the necrosis of the femoral head caused by long-term or high-dose hormone usage. Studies have shown that the PI3K/AKT pathway plays a crucial regulatory role in the development of SANFH. The aim of this study is to determine how external environmental factors induce changes in endogenous hormone levels, how these changes lead to steroid-induced femoral head necrosis, and the interrelationship between the changes in PIK3R5 promoter methylation levels and the regulation of the associated signaling pathways.

METHODS

Femoral head samples underwent molecular sequencing analysis. Candidate genes were screened by differential gene analysis and functional enrichment analysis.Methylation level of candidate gene PIK3R5 was verified by methylation-specific PCR(MS-PCR). SANFH model was constructed in New Zealand white rabbits, and the model results were verified by magnetic resonance imaging (MRI) and haematoxylin-eosin (HE) staining.The expression of PIK3R5, PI3K and AKT in rabbit models and human specimens was verified by real-time fluorescence quantitative PCR(RT-qPCR) and Western Blot(WB), respectively.

RESULTS

Human femoral head sequencing results indicate distinct differences in the methylation level and mRNA expression of PIK3R5 in SANFH. MS-PCR results showed the methylation level of SANFH patients was significantly higher than that of the control group (P < 0.01). The RT-qPCR results showed that PIK3R5 and PI3K expression levels in the SANFH group were lower than those in the control group (P < 0.05), and the WB experiment results were consistent with the RT-qPCR results. The MRI and HE staining results showed that the rabbit model of SANFH was successfully constructed, and the results of RT-qPCR and WB were consistent with the results of human tissues.

CONCLUSION

During the occurrence and development of SANFH, PIK3R5 gene regulates the PI3K/AKT pathway through methylation modification, promotes the oxidative stress response of cells, and accelerates the disease process.

SOX9 Inhibits the Progression of Osteonecrosis of the Femoral Head via the Activation of the Wnt/Beta-Catenin Pathway

Background: In this study, we aimed to explore whether the SRY-box transcription factor 9 (SOX9) can play protective roles against the occurrence and development of osteonecrosis of the femoral head (ONFH) by regulating the proliferation, apoptosis, and osteogenic differentiation of human bone marrow stromal cells (hBMSCs) via the Wnt/β-catenin pathway.Methods: We used 1600 mg of glucocorticoid (GC) to induce hBMSCs to establish an ONFH cell model and performed various experiments. Reverse transcription-quantitative polymerase chain reaction and western blotting assays were used to determine the expression levels of SOX9 and osteoblast markers, such as the RUNX family transcription factor 2 (RUNX2), alkaline phosphatase (ALP), osterix, Wnt3a, and β-catenin. An ALP detection kit was used to measure the ALP activity. Flow cytometry and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assays were performed to determine the cell viability.Results: GC treatment decreased the expression levels of RUNX2, ALP, and osterix, suppressed ALP activity, and inhibited SOX9 expression. SOX9 overexpression promoted GC-induced cell proliferation and decreased cell apoptosis. Additionally, hBMSCs were transfected with SOX9-small interfering RNA in GC treatment, and SOX9 knockdown was found to suppress the osteogenic differentiation of cells and decrease their viability.Conclusion: Our results revealed that SOX9 is related to the Wnt/β-catenin pathway in ONFH. Moreover, SOX9 participated in ONFH development by activating the Wnt/β-catenin pathway.

Plasma 8-OHdG act as a biomarker for steroid-induced osteonecrosis of the femoral head

BACKGROUND

Oxidative stress was closely related to the occurrence and development of Steroid-induced osteonecrosis of the femoral head (SIONFH). 8-hydroxy-2'-deoxyguanosine (8-OHdG) is a important index of oxidative stress. The aim of this study is to investigate the role of 8-OHdG in the development of SIONFH.

METHODS

From May 2021 and November 2021, 33 patients diagnosed with SIONFH and 26 healthy controls were recruited in this study. Assessment included the radiography and pathology evaluation of clinical bone tissue, expression position and level of 8-OHdG, level of plasma 8-OHdG, as well as the receiver operating characteristic (ROC) curve.

RESULTS

We observed that expression levels of 8-OHdG in bone samples decreased with Association Research Circulation Osseous (ARCO) stages. Plasma 8-OHdG levels were significantly increased in the SIONFH group compared to the healthy control group. Plasma 8-OHdG level of pre-collapse patients was higher than that of post-collapse patients, the decreased plasma 8-OHdG level was related to higher ARCO stages.

CONCLUSION

Plasma 8-OHdG may represent potential biomarkers during SIONFH at different stages. Higher plasma 8-OHdG levels indicated early stage of SIONFH. The current study provided new clues for early diagnosis and treatment for SIONFH.

Dragon blood resin ameliorates steroid-induced osteonecrosis of femoral head through osteoclastic pathways

Objective: Dragon's Blood resin (DBR) is a traditional medicinal substance renowned for its diverse pharmacological effects, which consists of potent anti-inflammatory, antioxidant and angiogenic properties. This study aimed to elucidate its therapeutic mechanism in alleviating steroid-induced osteonecrosis of the femoral head (SIONFH). Methods: Techniques such as SPR and LC-MS were employed to identify and analyze the target proteins of DBR in bone marrow macrophages (BMMs). In vitro, BMMs were treated with RANKL and DBR, and TRAcP staining and actin belt staining were utilized to assess osteoclast activity. The inhibitory effects and underlying mechanisms of DBR on osteoclastogenesis and reactive oxygen species (ROS) generation were determined using real-time PCR, western blotting and immunofluorescence staining. An in vivo SIONFH rat model was set up to assess the curative impacts of DBR using micro-CT scanning and pathological staining. Results: Bioinformatic tools revealed a pivotal role of osteoclast differentiation in SIONFH. Proteomic analysis identified 164 proteins binding in BMMs. In vitro assessments demonstrated that DBR hindered osteoclastogenesis by modulating the expression of specific genes and proteins, along with antioxidant proteins including TRX1 and Glutathione Reductase. Notably, the resin effectively inhibited the expression of crucial proteins, such as the phosphorylation of JNK and the nuclear localization of p65 within the TRAF6/JNK and NFκB signaling pathways. In vivo experiments further confirmed that DBR mitigated the onset of SIONFH in rats by curbing osteoclast and ROS activities. Conclusion: These findings underscore the potential of Dragon's Blood as an effective administration for early-stage SIONFH, shedding light on its therapeutic influence on ROS-mediated osteoclastic signaling pathways.

Sodium butyrate enhances titanium nail osseointegration in ovariectomized rats by inhibiting the PKCα/NOX4/ROS/NF-κB pathways

BACKGROUND

Elevated levels of oxidative stress as a consequence of estrogen deficiency serve as a key driver of the onset of osteoporosis (OP). In addition to increasing the risk of bone fractures, OP can reduce the bone volume proximal to titanium nails implanted to treat these osteoporotic fractures, thereby contributing to titanium nail loosening. Sodium butyrate (NaB) is a short-chain fatty acid produced by members of the gut microbiota that exhibits robust antioxidant and anti-inflammatory properties.

METHODS

OP fracture model rats parameters including bone mineral density (BMD), new bone formation, and the number of bonelets around the implanted nail were analyzed via micro-CT scans, H&E staining, and Masson's staining. The protective effects of NaB on such osseointegration and the underlying mechanisms were further studied in vitro using MC3T3-E1 cells treated with carbonyl cyanide m-chlorophenylhydrazone (CCCP) to induce oxidative stress. Techniques including Western immunoblotting, electron microscopy, flow cytometry, alkaline phosphatase (ALP) staining, and osteoblast mineralization assays were employed to probe behaviors such as reactive oxygen species production, mineralization activity, ALP activity, protein expression, and the ability of cells to attach to and survive on titanium plates.

RESULTS

NaB treatment was found to enhance ALP activity, mineralization capacity, and Coll-I, BMP2, and OCN expression levels in CCCP-treated MC3T3-E1 cells, while also suppressing PKC and NF-κB expression and enhancing Nrf2 and HO-1 expression in these cells. NaB further suppressed intracellular ROS production and malondialdehyde levels within the cytosol while enhancing superoxide dismutase activity and lowering the apoptotic death rate. In line with these results, in vivo work revealed an increase in BMD in NaB-treated rats that was associated with enhanced bone formation surrounding titanium nails.

CONCLUSION

These findings indicate that NaB may represent a valuable compound that can be postoperatively administered to aid in treating OP fractures through the enhancement of titanium nail osseointegration.

Astaxanthin as a Potent Antioxidant for Promoting Bone Health: An Up-to-Date Review

In recent years, bone loss and its associated diseases have become a significant public health concern due to increased disability, morbidity, and mortality. Oxidative stress and bone loss are correlated, where oxidative stress suppresses osteoblast activity, resulting in compromised homeostasis between bone formation and resorption. This event causes upregulation of bone remodeling turnover rate with an increased risk of fractures and bone loss. Therefore, supplementation of antioxidants can be proposed to reduce oxidative stress, facilitate the bone remodeling process, suppress the initiation of bone diseases, and improve bone health. Astaxanthin (3,3'-dihydroxy-4-4'-diketo-β-β carotene), a potent antioxidant belonging to the xanthophylls family, is a potential ROS scavenger and could be a promising therapeutic nutraceutical possessing various pharmacological properties. In bone, astaxanthin enhances osteoblast differentiation, osteocytes numbers, and/or differentiation, inhibits osteoclast differentiation, cartilage degradation markers, and increases bone mineral density, expression of osteogenic markers, while reducing bone loss. In this review, we presented the up-to-date findings of the potential anabolic effects of astaxanthin on bone health in vitro, animal, and human studies by providing comprehensive evidence for its future clinical application, especially in treating bone diseases.

Proanthocyanidins Inhibit Osteoblast Apoptosis via the PI3K/AKT/Bcl-xL Pathway in the Treatment of Steroid-Induced Osteonecrosis of the Femoral Head in Rats

BACKGROUND

Steroid-induced osteonecrosis of the femoral head (SONFH) is a common clinical disease caused by massive or prolonged use of steroids. Its pathogenesis is unclear, but its incidence is increasing annually. It is characterized by an insidious and rapid onset, and high disability rate, causing a great burden on patients' daily life. Therefore, clarifying its pathogenesis and providing early and effective treatment for steroid osteonecrosis is important.

METHODS

In vivo, we used methylprednisolone (MPS) to construct a SONFH rat model and employed Mirco-ct, Hematoxylin and eosin (H&E) staining, and TdT-mediated dUTP nick end labeling (TUNEL) staining analysis to evaluate the therapeutic effects of proanthocyanidins (PACs). Network pharmacology analysis was conducted to mine targets associated with femoral head necrosis, and PACs analyzed possible molecular mechanisms. In vitro, PACs were added at different doses after treatment of cells with dexamethasone (DEX), and human osteoblast-like sarcoma(MG-63) cell apoptosis was determined by Annexin V-FITC-PI. The mechanisms by which PACs regulate bone metabolism via the Phosphoinositide 3-kinase(PI3K)/protein kinase B(AKT)/Recombinant Human B-Cell Leukemia/Lymphoma 2 XL(Bcl-xL) axis were explored by Western blotting.

RESULT

In vivo studies showed that PACs prevented SONFH in rat model. The PI3K/AKT/Bcl-xL signaling pathway was selected by network pharmacology approach; in vitro studies showed that proanthocyanidin-activated AKT and Bcl-xL inhibited osteoblast apoptosis.

CONCLUSIONS

PACs can inhibit excessive osteoblast apoptosis in SONFH via the PI3K/AKT/Bcl-xL signaling axis and have potential therapeutic effects.

Steroid-induced avascular necrosis: A case report on a patient treated with steroid therapy for COVID-19

Introduction

COVID-19 must get a combined approach that involves epidemiology, surveillance, accurate diagnosis, and prophylaxis. Corticosteroids use in the treatment of COVID-19, for a long time at high doses, can cause steroid-induced avascular necrosis.

Case report

The patient is a 22-year-old female. She came with a complaint of bilateral groin pain for 4 months. The pain was abrupt in onset, continuous, non-radiating, aggravated by walking and relieved with rest. We did an X-ray of the bilateral hips, blood tests, and MRI. With the investigations, we established the diagnosis of avascular necrosis of the femoral head.

Discussion

Ischemia of the femoral head is caused by any interruption in the blood supply of the acetabulum. It is induced by high-dose and long-term steroid usage. Glucocorticoids affect the metabolism of lipids which results in the formation of fat emboli and lipoprotein globules. This blocks peripheral vessels and leads to necrosis of the bone due to ischemia.

Conclusion

Avascular necrosis of the femoral head has been reported in patients treated with corticosteroids while being treated for COVID-19. So, physicians should keep it as a possible diagnosis and enhance their knowledge on this topic.

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COVID-19 treatment also involves the use of corticosteroids. The use of corticosteroids, for a long time at high doses, can cause steroid-induced avascular necrosis.

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Glucocorticoids affect lipids' metabolism, which further blocks peripheral vessels causing necrosis.

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Regular screening is required for patients who have received corticosteroids.

Animal Models of Femur Head Necrosis for Tissue Engineering and Biomaterials Research

Femur head necrosis, also known as osteonecrosis of the femoral head (ONFH), is a widespread disabling pathology mostly affecting young and middle-aged population and one of the major causes of total hip arthroplasty in the elderly. Currently, there are limited number of different clinical or medication options for the treatment or the reversal of progressive ONFH, but their clinical outcomes are neither satisfactory nor consistent. In pursuit of more reliable therapeutic strategies for ONFH, including recently emerged tissue engineering and biomaterials approaches, in vivo animal models are extremely important for therapeutic efficacy evaluation and mechanistic exploration. Based on the better understanding of pathogenesis of ONFH, animal modeling method has evolved into three major routes, including steroid-, alcohol-, and injury/trauma-induced osteonecrosis, respectively. There is no consensus yet on a standardized ONFH animal model for tissue engineering and biomaterial research; therefore, appropriate animal modeling method should be carefully selected depending on research purposes and scientific hypotheses. In this work, mainstream types of ONFH animal model and their modeling techniques are summarized, showing both merits and demerits for each. In addition, current studies and experimental techniques of evaluating therapeutic efficacy on the treatment of ONFH using animal models are also summarized, along with discussions on future directions related to tissue engineering and biomaterial research. Impact statement Exploration of tissue engineering and biomaterial-based therapeutic strategy for the treatment of femur head necrosis is important since there are limited options available with satisfactory clinical outcomes. To promote the translation of these technologies from benchwork to bedside, animal model should be carefully selected to provide reliable results and clinical outcome prediction. Therefore, osteonecrosis of the femoral head animal modeling methods as well as associated tissue engineering and biomaterial research are overviewed and discussed in this work, as an attempt to provide guidance for model selection and optimization in tissue engineering and biomaterial translational studies.

Hyperoside exerts osteoprotective effect on dexamethasone-induced osteoblasts by targeting NADPH Oxidase 4 (NOX4) to inhibit the reactive oxygen species (ROS) accumulation and activate c-Jun N-terminal kinase (JNK) pathway

Hyperoside (Hyp) is a flavonoid active compound deriving from Chinese herbal medicines. Increasing studies have implicated that Hyp may serve as a predominant promoting factor in osteoblast differentiation. This paper investigates whether Hyp could relieve glucocorticoid-induced osteonecrosis of the femoral head (GONFH) via promoting osteoblast survival and differentiation as well as to uncover its potential mechanism. GONFH cell model was induced by treating MC3T3-E1 cells with dexamethasone (DEX). The viability, apoptosis, and osteogenic differentiation of DEX-induced cells with the presence or absence of Hyp were assessed by CCK-8, Tunel, ALP assay, and ARS staining, respectively. The NADPH Oxidase 4 (NOX4) overexpression was performed by transfection with overexpression vector. Besides, western blot was used to determine the levels of apoptosis-, osteogenic differentiation-, and c-Jun N-terminal kinase (JNK) signaling-related proteins. It was noticed that Hyp caused no significant effects on the viability of MC3T3-E1 cells without any treatment but significantly enhanced the viability of DEX-induced cells. Besides, Hyp inhibited the apoptosis in DEX-induced cells but enhanced ALP activity and calcium nodule formation. Additionally, Hyp declined NOX4 expression in DEX-induced cells. However, NOX4 overexpression partially reversed the impacts of Hyp on DEX-exposed MC3T3-E1 cells. Finally, Hyp suppressed the activation of ROS/JNK pathway in DEX-induced cells, which was then counteracted by NOX4 overexpression. In conclusion, Hyp could promote the survival and differentiation of DEX-induced osteoblasts by targeting NOX4 to inhibit the ROS/JNK pathway. These results provide evidence for the application of Hyp in treating GONFH.