Osteoimmunology and osteonecrosis of the femoral head

M2 macrophages-derived exosomes for osteonecrosis of femoral head treatment: modulating neutrophil extracellular traps formation and endothelial phenotype transition

Exosomes have shown good potential in ischemic injury disease treatments. However, evidence about their effect and molecular mechanisms in osteonecrosis of femoral head (ONFH) treatment is still limited. Here, we revealed the cell biology characters of ONFH osteonecrosis area bone tissue in single cell scale and thus identified a novel ONFH treatment approach based on M2 macrophages-derived exosomes (M2-Exos). We further show that M2-Exos are highly effective in the treatment of ONFH by modulating the phenotypes communication between neutrophil and endothelium including neutrophil extracellular traps formation and endothelial phenotype transition. Additionally, we identified that M2-Exos' therapeutic effect is attributed to the high content of miR-93-5p and constructed miR-93-5p overexpression model in vitro and in vivo based on lentivirus and adeno-associated virus respectively. Then we found miR-93-5p can not only reduce neutrophil extracellular traps formation but also improve angiogenic ability of endothelial cells. These results provided a new theoretical basis for the clinical application of ONFH therapeutic exosomes.

Differential risk of autoimmune disorders in non-traumatic osteonecrosis: clue to pathogenesis

INTRODUCTION

Non-traumatic osteonecrosis is a frequent complication in patients with autoimmune disorders, though its prevalence varies markedly depending upon the type of disorder. Understanding the causes of this difference can help uncover the underlying pathophysiology of osteonecrosis and guide the development of effective preventive and therapeutic strategies.

AREAS COVERED

In this perspective study, we reviewed available databases, including PubMed, Cochrane Library, Scopus, and Web of Science, to explore why the risk of osteonecrosis varies among different autoimmune disorders. Is this variation primarily due to the disease's pathophysiology, the use of medications such as corticosteroids, or a combination of both? If both factors are involved, what is the extent of each contribution in this context?

EXPERT OPINION

Non-traumatic osteonecrosis is often induced by an interaction between disease pathophysiology and corticosteroid use. In patients with different autoimmune disorders but an identical history of corticosteroid use, the risk of osteonecrosis is influenced by how the underlying pathophysiology compromises bone health. In autoimmune disorders with multiple adverse effects on bone, such as SLE (systemic lupus erythematosus), there is a much higher risk of osteonecrosis compared to disorders with minimal impact on bone health, such as celiac disease and MS (multiple sclerosis).

Fibroblast IRF7-mediated chondrocyte apoptosis affects the progression of collapse in steroid-induced osteonecrosis of the femoral head

PURPOSE

The objective of this study was to identify potential genes implicated in the "peri-collapse" synovium of osteonecrosis of the femoral head through coding gene sequencing and to further clarify their specific mechanisms via in vitro experiments.

METHODS

Steroid-induced osteonecrosis of the femoral head (SIONFH) (n = 3), femoral neck fracture (FNF) (n = 3), and hip osteoarthritis (HOA) (n = 3) Synovial tissue of the hip joint was collected in total hip arthroplasty. A cellular model of SIONFH constructed from rat synovial fibroblasts by lipopolysaccharide intervention. Lentiviral technology was used to construct a model for fibroblast knockout of the Irf7 gene. HE was used to compare the characteristics of synovial tissue damage, and immunofluorescence and immunohistochemistry were used to compare the expression levels of VIM, IRF7, and IFNα. PCR, WB, and IF were used to examine Irf7 knockdown efficiency, chondrocyte proliferation (Col2a1, Aggrecan, Sox9), cartilage matrix degradation (Mmp13), and apoptosis (Bcl2, Bax, and Caspase3) expression under co-culture conditions. Crystalline violet staining was used to observe the migration rate of fibroblasts, and flow cytometry was used to detect the apoptosis level of chondrocytes under co-culture conditions.

RESULTS

Transcriptome sequencing of synovial tissue and fibroblasts ultimately screened for six differential genes, HOOK1, RNPC3, KCNA3, CD48, IRF7, SAMD9. Compared to FNF and HOA, synovial inflammatory cell recruitment and synovial hyperplasia were more pronounced in SIONFH. IF and IHC confirmed high expression of IRF7 and IFNα in the synovium of SIONFH. PCR and WB results suggested that fibroblasts highly expressed Irf7, Hook1, Rnpc3, Kcna3, Cd48, Samd9, Il-6, and Tnfα after lipopolysaccharide intervention, and the expression levels of Il-6 and Tnfα were significantly reduced after knockdown of Irf7 (P < 0.001). In the co-culture system, fibroblasts intervened with lipopolysaccharide significantly promoted chondrocyte apoptosis, the rate of cartilage matrix degradation, while inhibiting the level of chondrocyte proliferation, and this result was significantly reversed in Irf7 knockout fibroblasts. This was supported by flow cytometry results.

CONCLUSIONS

IRF7, HOOK1, RNPC3, KCNA3, CD48, and SAMD9 as potential genes affecting the progression of SIONFH collapse. Irf7 mediates the fibroblast inflammatory response and affects the collapse process of SIONFH by influencing chondrocyte apoptosis. Thus, intervention in IRF7 holds promise as one of the key targets for reversing the collapse process of SIONFH.

Automated detection of early-stage osteonecrosis of the femoral head in adult using YOLOv10: Multi-institutional validation

OBJECTIVES

To develop a deep learning model based on the You Only Look Once version 10 (YOLOv10) for detecting early-stage ONFH in adult using radiographs.

METHODS

A retrospective database study enrolled patients with ONFH classified as the stage I-II by the Association Research Circulation Osseous (ARCO) staging system based on MRI, and with Kellgren-Lawrence (KL) grade ≤ 1, as the positive group. In negative group, femoral head exhibited normal or KL grade 1 changes. The model was developed by using internal dataset from one institution between November 2008 and June 2024, with patients were divided into training and internal validation sets in an 8:2 ratio. External test sets were enrolled from two independent institutions between December 2021 and June 2024. Intersection over Union (IoU) was utilized to assess accuracy of bounding box placement and inter-observer consistency. Classification performance was evaluated using the area under the curve (AUC).

RESULTS

A total of 2321 patients (mean age, 51 years ± 14 [SD]; 961 female) with 3970 unilateral hip joint radiographs were evaluated. The model achieved accuracies of 0.91, and 0.89 with IoU scores of 0.95 and 0.96 in two external test sets. The model outperformed the radiologists: for the external test set 1, AUC was 0.93 (95 % CI 0.88-0.97) versus an average AUC of 0.83 among radiologists (range: 0.78-0.88); for the external test set 2, AUC was 0.94 (95 % CI 0.90-0.98) versus an average AUC of 0.79 (range: 0.74-0.85).

CONCLUSIONS

The YOLOv10 model excelled in detecting early-stage ONFH in adult using radiographs, and outperforming radiologists with varying experience.

Progress in understanding Legg-Calvé-Perthes disease etiology from a molecular and cellular biology perspective

Legg-Calvé-Perthes disease (LCPD) is a hip disease caused by ischemia of the femoral epiphysis in children, which occurs in children aged 4-8 years (mean 6.5 years), with a male-to-female ratio of about 4:1. The disease has been reported for more than 100 years, but its etiology has not been elucidated. In recent years, a considerable amount of research has been carried out on the etiology of the disease, and the development of the disease is believed to involve a variety of molecular biological alterations, such as the COL2A1 mutation, which may be one of the causes of necrotic collapses of the epiphyseal cartilage matrix in LCPD. Tissue factor V Leiden mutation and insulin-like growth factor (IGF-1) abnormalities have also been reported in LCPD, but most theories need further confirmation. The in-depth study of LCPD cell biology has facilitated the suggestion regarding structural and/or functional abnormalities of microvascular endothelial cells in LCPD. This conjecture is supported by epidemiological and clinical evidence. Abnormal activation of osteoclasts, ischemic damage to epiphyseal cartilage, and activation of the bone marrow immune system all play important roles in the onset and progression of the disease. In this paper, we review the previous basic studies on LCPD and give an overview from the molecular biology and cell biology perspectives.

Multifunctional Scaffold Comprising Metal-Organic Framework, Hydrogel, and Demineralized Bone Matrix for the Treatment of Steroid-Induced Femoral Head Necrosis

Overproduction of reactive oxygen species (ROS) results in oxidative stress, a critical factor in the pathogenesis of steroid-induced osteonecrosis of the femoral head (SONFH). Excess ROS not only hinders the osteogenic differentiation of bone marrow-derived mesenchymal stem cells (BMSCs) but also impairs mitochondrial structure and function, resulting in irreversible cellular damage. Herein, a biomimetic multifunctional scaffold comprising Zn-modified metal-organic framework 818 (Zn-MOF-818) loaded with deferoxamine (DFO), gelatin methacryloyl (GelMA) hydrogel, and demineralized bone matrix (DBM) is shown to scavenge excess ROS, promote angiogenesis, and regulate immunity. Introduced Zn significantly enhances the superoxide dismutase- and catalase-like activities of MOF-818, which increases ROS-scavenging efficiency. Zn-MOF-818 disrupts the vicious intracellular cycle of mitochondrial dysfunction and ROS accumulation by enhancing mitophagy, stabilizing mitochondrial function, and upregulating antioxidant genes. Additionally, Zn-MOF-818 facilitates the polarization of macrophages toward the M2 phenotype and alleviates inflammation, creating an advantageous immune microenvironment for osteogenic differentiation of BMSCs. The release of DFO, an activator of the HIF-1α pathway, and Zn2+ from Zn-MOF-818, along with the secretion of various cytokines from DBM (such as bone morphogenetic proteins and vascular endothelial growth factors), enhances angiogenesis and osteogenesis. This scaffold targets multiple factors concurrently, offering a promising new approach for treating SONFH.

Multidimensional characteristics are associated with pain severity in osteonecrosis of the femoral head

Aims

Pain is the most frequent complaint associated with osteonecrosis of the femoral head (ONFH), but the factors contributing to such pain are poorly understood. This study explored diverse demographic, clinical, radiological, psychological, and neurophysiological factors for their potential contribution to pain in patients with ONFH.

Methods

This cross-sectional study was carried out according to the "STrengthening the Reporting of OBservational studies in Epidemiology" statement. Data on 19 variables were collected at a single timepoint from 250 patients with ONFH who were treated at our medical centre between July and December 2023 using validated instruments or, in the case of hip pain, a numerical rating scale. Factors associated with pain severity were identified using hierarchical multifactor linear regression.

Results

Regression identified the following characteristics as independently associated with higher pain score, after adjustment for potential confounders: Association Research Circulation Osseous classification stage IIIa or IIIb, bone marrow oedema, grade 3 joint effusion, as well as higher scores on pain catastrophizing, anxiety, and central sensitization. The final model explained 69.7% of observed variance in pain scores, of which clinical and radiological factors explained 37%, while psychological and neurophysiological factors explained 24% and demographic factors explained 8.7%.

Conclusion

Multidimensional characteristics jointly contribute to the severity of pain associated with ONFH. These findings highlight the need to comprehensively identify potential contributors to pain, and to personalize management and treatment accordingly.

Potential molecular targets for the pharmacologic management of non-traumatic osteonecrosis

INTRODUCTION

Non-traumatic osteonecrosis is a debilitating condition marked by bone death, primarily due to reduced blood supply. Currently, no effective pharmacologic intervention is available to manage this condition effectively.

AREAS COVERED

Lipid metabolic disorders, chronic inflammation, vascular dysfunction, coagulopathy, and impaired bone homeostasis are suggested as the key pathogenic mechanisms involved in the development of non-traumatic osteonecrosis. Targeting any of these dysfunctions offers a potential avenue for pharmacologic intervention. However, the potential molecular targets for pharmacologic treatment of non-traumatic osteonecrosis remain underexplored. In this study, we reviewed available databases to compile a comprehensive set of pathogenic mechanisms and corresponding therapeutic targets for non-traumatic osteonecrosis.

EXPERT OPINION

Evidence suggests that a single pathogenic mechanism cannot fully explain the development of osteonecrosis, supporting the adoption of a multi-pathogenic theory. This theory implies that effective management of non-traumatic osteonecrosis requires targeting multiple pathogenic mechanisms simultaneously. Moreover, the same pathogenic mechanisms are unlikely to explain osteonecrosis development in patients with different etiologies. Consequently, a one-size-fits-all approach to medication is unlikely to be effective across all types of non-traumatic osteonecrosis. Future research should, therefore, focus on developing multi-target pharmacologic treatments tailored to the specific etiology of non-traumatic osteonecrosis.

Advances in the Pathogenesis of Steroid-Associated Osteonecrosis of the Femoral Head

Osteonecrosis of the femoral head (ONFH) is a refractory orthopedic condition characterized by bone cell ischemia, necrosis, bone trabecular fracture, and clinical symptoms such as pain, femoral head collapse, and joint dysfunction that can lead to disability. The disability rate of ONFH is very high, which imposes a significant economic burden on both families and society. Steroid-associated osteonecrosis of the femoral head (SANFH) is the most common type of ONFH. However, the pathogenesis of SANFH remains unclear, and it is an urgent challenge for orthopedic surgeons to explore it. In this paper, the pathogenesis of SANFH and its related signaling pathways were briefly reviewed to enhance comprehension of the pathogenesis and prevention of SANFH.

m6A methylation modification and immune infiltration analysis in osteonecrosis of the femoral head

Osteonecrosis of the femoral head (ONFH) is a elaborate hip disease characterized by collapse of femoral head and osteoarthritis. RNA N6-methyladenosine (m6A) plays a crucial role in a lot of biological processes within eukaryotic cells. However, the role of m6A in the regulation of ONFH remains unclear. In this study, we identified the m6A regulators in ONFH and performed subtype classification. We identified 7 significantly differentially expressed m6A regulators through the analysis of differences between ONFH and normal samples in the Gene Expression Omnibus (GEO) database. A random forest algorithm was employed to monitor these regulators to assess the risk of developing ONFH. We constructed a nomogram based on these 7 regulators. The decision curve analysis suggested that patients can benefit from the nomogram model. We classified the ONFH samples into two m6A models according to these 7 regulators through consensus clustering algorithm. After that, we evaluated those two m6A patterns using principal component analysis. We assessed the scores of those two m6A patterns and their relationship with immune infiltration. We observed a higher m6A score of type A than that of type B. Finally, we performed a cross-validation of crucial m6A regulatory factors in ONFH using external datasets and femoral head bone samples. In conclusion, we believed that the m6A pattern could provide a novel diagnostic strategy and offer new insights for molecularly targeted therapy of ONFH.

X-ray, digital tomographic fusion, CT, and MRI in early ischemic necrosis of the femoral head

To investigate the imaging performance of radiography, digital tomographic fusion (DTS), computed tomography (CT), and magnetic resonance imaging (MRI) in the diagnosis of early avascular necrosis of the femoral head (ANFH). A total of 220 patients with ANFH who visited our hospital from January 2020 to January 2022 were included in the study. X-ray, DTS, CT, and MRI examinations of both hips were performed for all patients. The trabecular structure, bone density changes, femoral head morphology, and joint space changes were observed using the aforementioned imaging modalities. The staging was performed according to the Association Research Circulation Osseous (ARCO) criteria. The diagnostic detection rate of each imaging modality, and the sensitivity, specificity, positive predictive value, and negative predictive value of each examination for diagnosing early ANFH were calculated and compared. Patients were diagnosed with stage I (n = 65), stage II (n = 85), stage III (n = 32), and stage IV (n = 38) ANFH. For MRI, the detection rate (97.7%), sensitivity (94.7%), specificity (88.6%), positive predictive value (95.9%), and negative predictive value (92.5%), for diagnosing early ANFH, were significantly higher than those of other imaging methods (P < .05). MRI is the most accurate and sensitive imaging method for diagnosing early ANFH and has important clinical applications.

Differential Gene Expression and Immune Cell Infiltration in Patients with Steroid-induced Necrosis of the Femoral Head

OBJECTIVE

The study aimed to study the differential gene expression and immune cell infiltration in patients with steroid-induced necrosis of the femoral head (SANFH), identify the key genes and immune cells of SANFH, and explore the relationship between immune cells and SANFH.

METHODS

The high-throughput gene chip dataset GSE123568 was downloaded from the GEO database, and the differential gene expression was analyzed with the R language. The STRING database and Cytoscape software were used to analyze the protein interaction network and screen key genes, and enrichment analysis was carried out on key genes. The infiltration of immune cells in SANFH patients was analyzed and verified by immunohistochemistry.

RESULTS

EP300, TRAF6, STAT1, JAK1, CASP8, and JAK2 are key genes in the pathogenesis of SANFH, which mainly involve myeloid cell differentiation, cytokine-mediated signaling pathway, tumor necrosis factor-mediated signaling pathway, and cellular response to tumor necrosis factor through JAK-STAT, NOD-like receptor, toll-like receptor, and other signaling pathways, leading to the occurrence of diseases; immune infiltration and immunohistochemical results have shown the expression of memory B cells and activated dendritic cells as reduced in SANFH patients, while in the same SANFH samples, M1 macrophages have been positively correlated with monocytes, and neutrophils have been negatively correlated with monocytes expression.

CONCLUSION

EP300, TRAF6, STAT1, JAK1, CASP8, and JAK2 have exhibited significant differences in SANFH (spontaneous osteonecrosis of the femoral head). Memory B cells, activated dendritic cells, M1 macrophages, monocytes, and neutrophils have shown abnormal expression in SANFH.

Medication-Related Osteonecrosis of the Jaw: A Systematic Review and a Bioinformatic Analysis

The objective was to evaluate the current evidence regarding the etiology of medication-related osteonecrosis of the jaw (MRONJ). This study systematically reviewed the literature by searching PubMed, Web of Science, and ProQuest databases for genes, proteins, and microRNAs associated with MRONJ from the earliest records through April 2023. Conference abstracts, letters, review articles, non-human studies, and non-English publications were excluded. Twelve studies meeting the inclusion criteria involving exposure of human oral mucosa, blood, serum, saliva, or adjacent bone or periodontium to anti-resorptive or anti-angiogenic agents were analyzed. The Cochrane Collaboration risk assessment tool was used to assess the quality of the studies. A total of 824 differentially expressed genes/proteins (DEGs) and 22 microRNAs were extracted for further bioinformatic analysis using Cytoscape, STRING, BiNGO, cytoHubba, MCODE, and ReactomeFI software packages and web-based platforms: DIANA mirPath, OmicsNet, and miRNet tools. The analysis yielded an interactome consisting of 17 hub genes and hsa-mir-16-1, hsa-mir-21, hsa-mir-23a, hsa-mir-145, hsa-mir-186, hsa-mir-221, and hsa-mir-424. A dominance of cytokine pathways was observed in both the cluster of hub DEGs and the interactome of hub genes with dysregulated miRNAs. In conclusion, a panel of genes, miRNAs, and related pathways were found, which is a step toward understanding the complexity of the disease.

Deep Learning Approach for Diagnosing Early Osteonecrosis of the Femoral Head Based on Magnetic Resonance Imaging

BACKGROUND

The diagnosis of early osteonecrosis of the femoral head (ONFH) based on magnetic resonance imaging (MRI) is challenging due to variability in the surgeon's experience level. This study developed an MRI-based deep learning system to detect early ONFH and evaluated its feasibility in the clinic.

METHODS

We retrospectively evaluated clinical MRIs of the hips that were performed in our institution from January 2019 to June 2022 and collected all MRIs diagnosed with early ONFH. An advanced convolutional neural network (CNN) was trained and optimized; then, the diagnostic performance of the CNN was evaluated according to its accuracy, sensitivity, and specificity. We also further compared the CNN's performance with that of orthopaedic surgeons.

RESULTS

Overall, 11,061 images were retrospectively included in the present study and were divided into three datasets with ratio 7:2:1. The area under the receiver operating characteristic curve, accuracy, sensitivity, and specificity of the CNN model for identifying early ONFH were 0.98, 98.4, 97.6, and 98.6%, respectively. In our review panel, the averaged accuracy, sensitivity, and specificity for identifying ONFH were 91.7, 87.0, and 94.1% for attending orthopaedic surgeons; 87.1, 84.0, and 89.3% for resident orthopaedic surgeons; and 97.1, 96.0, and 97.9% for deputy chief orthopaedic surgeons, respectively.

CONCLUSION

The deep learning system showed a comparable performance to that of deputy chief orthopaedic surgeons in identifying early ONFH. The success of deep learning diagnosis of ONFH might be conducive to assisting less-experienced surgeons, especially in large-scale medical imaging screening and community scenarios lacking consulting experts.

Early depletion of M1 macrophages retards the progression of glucocorticoid-associated osteonecrosis of the femoral head

Inflammation stands as a pivotal factor in the pathogenesis of glucocorticoid-associated osteonecrosis of the femoral head (GA-ONFH). However, the vital role played by M1 macrophages, the principal constituents of the inflammatory process, remains largely underexplored. In this study, we employed reverse transcription-quantitative polymerase chain Reaction (RT-PCR), western blot, and flow cytometry to assess the impact of M1-conditioned medium on cultures of mouse bone marrow-derived mesenchymal stem cells (BMSCs) and Murine Long bone Osteocyte-Y4 (MLO-Y4) in vitro. Moreover, we quantified the levels of inflammatory cytokines in the M1-conditioned medium through the employment of an enzyme-linked immunosorbent assay (ELISA). For in vivo analysis, we examined M1 macrophages and investigated the NF-kB signaling pathway in specimens obtained from the femoral heads of animals and humans. We found that the number of M1 macrophages in the femoral head of GA-ONFH patients grew significantly, and in the mice remarkably increase, maintaining high levels in the intramedullary. In vitro, the M1 macrophage-conditioned medium elicited apoptosis in BMSCs and MLO-Y4 cells, shedding light on the intricate interplay between macrophages and these cell types. The presence of TNF-α within the M1-conditioned medium activated the NF-κB pathway, providing mechanistic insight into the apoptotic induction. Moreover, employing a robust rat macrophage clearance model and GA-ONFH model, we demonstrated a remarkable attenuation in TNF-α expression and NF-kB signaling subsequent to macrophage clearance. This pronounced reduction engenders diminished cellular apoptosis and engenders a decelerated trajectory of GA-ONFH progression. In conclusion, our study reveals the crucial involvement of M1 macrophages in the pathogenesis of GA-ONFH, highlighting their indispensable role in disease progression. Furthermore, early clearance emerges as a promising strategy for impeding the development of GA-ONFH.

Polarization Behavior of Bone Macrophage as Well as Associated Osteoimmunity in Glucocorticoid-Induced Osteonecrosis of the Femoral Head

Glucocorticoid-induced osteonecrosis of the femoral head (GIONFH) is a disabling disease with high mortality in China but the detailed molecular and cellular mechanisms remain to be investigated. Macrophages are considered the key cells in osteoimmunology, and the cross-talk between bone macrophages and other cells in the microenvironment is involved in maintaining bone homeostasis. M1 polarized macrophages launch a chronic inflammatory response and secrete a broad spectrum of cytokines (eg, TNF-α, IL-6 and IL-1β) and chemokines to initiate a chronic inflammatory state in GIONFH. M2 macrophage is the alternatively activated anti-inflammatory type distributed mainly in the perivascular area of the necrotic femoral head. In the development of GIONFH, injured bone vascular endothelial cells and necrotic bone activate the TLR4/NF-κB signal pathway, promote dimerization of PKM2 and subsequently enhance the production of HIF-1, inducing metabolic transformation of macrophage to the M1 phenotype. Considering these findings, putative interventions by local chemokine regulation to correct the imbalance between M1/M2 polarized macrophages by switching macrophages to an M2 phenotype, or inhibiting the adoption of an M1 phenotype appear to be plausible regimens for preventing or intervening GIONFH in the early stage. However, these results were mainly obtained by in vitro tissue or experimental animal model. Further studies to completely elucidate the alterations of the M1/M2 macrophage polarization and functions of macrophages in glucocorticoid-induced osteonecrosis of the femoral head are imperative.

Mesenchymal stem cell-derived extracellular vesicles, osteoimmunology and orthopedic diseases

Mesenchymal stem cells (MSCs) play an important role in tissue healing and regenerative medicine due to their self-renewal and multi-directional differentiation properties. MSCs exert their therapeutic effects mainly via the paracrine pathway, which involves the secretion of extracellular vesicles (EVs). EVs have a high drug loading capacity and can transport various molecules, such as proteins, nucleic acids, and lipids, that can modify the course of diverse diseases. Due to their ability to maintain the therapeutic effects of their parent cells, MSC-derived EVs have emerged as a promising, safe cell-free treatment approach for tissue regeneration. With advances in inflammation research and emergence of the field of osteoimmunology, evidence has accumulated pointing to the role of inflammatory and osteoimmunological processes in the occurrence and progression of orthopedic diseases. Several studies have shown that MSC-derived EVs participate in bone regeneration and the pathophysiology of orthopedic diseases by regulating the inflammatory environment, enhancing angiogenesis, and promoting the differentiation and proliferation of osteoblasts and osteoclasts. In this review, we summarize recent advances in the application and functions of MSC-derived EVs as potential therapies against orthopedic diseases, including osteoarthritis, intervertebral disc degeneration, osteoporosis and osteonecrosis.

[Research progress of immune cells regulating the occurrence and development of osteonecrosis of the femoral head]

OBJECTIVE

To summarize the characteristics of the occurrence and development of osteonecrosis of the femoral head (ONFH), and to review the important regulatory role of immune cells in the progression of ONFH.

METHODS

The domestic and foreign literature on the immune regulation of ONFH was reviewed, and the relationship between immune cells and the occurrence and development of ONFH was analyzed.

RESULTS

The ONFH region has a chronic inflammatory reaction and an imbalance between osteoblast and osteoclast, while innate immune cells such as macrophages, neutrophils, dendritic cells, and immune effector cells such as T cells and B cells are closely related to the maintenance of bone homeostasis.

CONCLUSION

Immunotherapy targeting the immune cells in the ONFH region and the key factors and proteins in their regulatory pathways may be a feasible method to delay the occurrence, development, and even reverse the pathology of ONFH.