Application of Biomaterials in Treating Early Osteonecrosis of the Femoral Head: Research Progress and Future Perspectives

An injectable hydrogel loaded with miRNA nanocarriers promotes vessel-associated osteoclast (VAO)-mediated angiogenesis and bone regeneration in osteonecrosis of the rat femoral head

Osteonecrosis of the femoral head (ONFH) remains a significant clinical challenge. Despite various strategies aimed at promoting bone repair and halting disease progression, an effective cure remains elusive. Recent studies have identified a non-bone-resorbing osteoclast subtype, vessel-associated osteoclasts (VAOs), distinct from classical bone-associated osteoclasts (BAOs), offering new therapeutic opportunities for ONFH. Notably, we observed alterations in the populations and distributions of VAOs and BAOs in the femoral head of ONFH patients, suggesting that the imbalance between these two osteoclast subtypes contributes to ONFH pathology. Here, we developed an injectable alginate/hydroxyapatite hydrogel (AHH) loaded with graphene oxide-based miR-7b nanocarriers (GPC@miR) for ONFH treatment. The controlled release of GPC@miR from AHH/GPC@miR inhibited BAO formation by suppressing dendritic cell-specific transmembrane protein (DC-STAMP), thereby reducing bone resorption. Meanwhile, mono-/bi-nucleated VAOs were preserved and increased in number, promoting angiogenesis of type H vessels and osteogenesis via platelet-derived growth factor-BB (PDGF-BB) and vascular endothelial growth factor-A (VEGF-A) secretion. Intraosseous administration of AHH/GPC@miR rebalanced VAOs and BAOs, restored the femoral head microenvironment, and enhanced vascularization and bone regeneration in ONFH rat models. This study introduces a novel biomaterial-based strategy for ONFH repair by regulating osteoclast subtypes, providing insights into VAO-mediated angiogenesis and osteogenesis for bone regeneration.

Injectable Alginate/β-TCP Composite Hydrogel Incorporating P34HB/MgO+PEG Coaxial Electrospun Microfibers for Minimally Invasive Treatment of Osteonecrosis

Avascular necrosis of the femoral head (ANFH) is a debilitating musculoskeletal disorder that is typically caused by impaired blood supply to the hip joint. In treating irregular bone defects that resulted from ANFH, injectable hydrogels are particularly attractive as they can be administered in a minimally invasive manner and conform to the variable shape of a bone defect. However, they often lack the biochemical and mechanical properties for effective bone repair. To address these issues, an injectable composite hydrogel, SA/β-TCP@PMP, composed of sodium alginate (SA) and β-tricalcium phosphate (β-TCP) crosslinked with glucono-delta-lactone (GDL), and enforced with varying concentrations of poly(3-hydroxybutyrate-co-4-hydroxybutyrate)/magnesium oxide and polyethylene glycol (P34HB/MgO+PEG; PMP) coaxial electrospun microfibers are formulated. By varying the concentrations (0%, 1%, 2%, 4%) of PMP microfibers, the physical properties of the composite hydrogel, including its injectability, surface morphology, swelling, degradation, and mechanical properties, as well as magnesium ions (Mg2+) release can be finely tuned. Among all, SA/β-TCP@2%PMP composite hydrogel demonstrates superior angiogenic and osteogenic properties, and promotes robust new bone formation in a rabbit model of steroid-induced ANFH. Overall, this novel composite hydrogel offers significant application potential for minimally invasive treatment of irregular bone lesions in ANFH.

Enhanced osteogenic and angiogenic capabilities of adipose-derived stem cells in fish collagen scaffolds for treatment of femoral head osteonecrosis

Osteonecrosis of the femoral head (ONFH) is a debilitating condition that often leads to femoral head collapse due to insufficient blood supply and impaired bone regeneration. However, effective treatment options for this condition are limited. This study explored a novel fish collagen (FC) scaffold combined with adipose-derived stem cells (ADSCs) to enhance osteogenesis and angiogenesis in ONFH. ADSCs were isolated and cultured on FC scaffolds to evaluate their biocompatibility and differentiation capacity. Osteogenic and angiogenic differentiation potentials were assessed in vitro, and the FC/ADSC combination was further evaluated in vivo using a rat model of ONFH. The molecular mechanisms were investigated via gene expression profiling and Hippo signaling pathway analysis. The FC scaffolds promoted ADSCs adhesion, proliferation, and migration without cytotoxicity. In vitro, FC/ADSCs significantly enhanced mineralization and capillary-like structure formation compared to the controls. FC/ADSCs improved bone regeneration and neovascularization in the femoral head in vivo, as confirmed by histological and immunohistochemical analyses. Mechanistically, the Hippo pathway is activated, increasing HIF-1α expression, which enhances osteogenic and angiogenic differentiation. FC scaffolds combined with ADSCs provide a promising therapeutic strategy for ONFH by facilitating bone regeneration and vascularization through the p-YAP/HIF-1α/VEGF axis. This scaffold-cell approach represents a potential advancement in ONFH treatment.

Calcified Cartilage Zone Remodeling Induced by IL-1β Derived from Necrotic Subchondral Bone Initiates Cartilage Degeneration in Patients with Glucocorticoids-induced Osteonecrosis of the Femoral Head

Glucocorticoids-induced osteonecrosis of the femoral head (GONFH) is characterized by progressive cartilage degeneration, yet the role of calcified cartilage zone (CCZ) remodeling in this process remains poorly understood. This study investigated how the inflammatory microenvironment within necrotic subchondral bone drove CCZ remodeling and subsequent cartilage degeneration. Using osteochondral tissues from GONFH patients and interleukin-1β (IL-1β)-treated hypertrophic chondrocytes induced by ATDC5 cells, we combined histology, immunohistochemistry, scanning electron microscopy, energy dispersive spectrometer, transmission electron microscopy, nanoindentation testing, enzyme linked immunosorbent assay and fluorescent tracking to evaluate morphological, biomechanical, and molecular changes. Our findings revealed that CCZ of GONFH exhibited significant thinning, matrix decomposition, demineralization, diminished mechanical strength, and increased porosity. Spatial analysis demonstrated a strong correlation between CCZ remodeling and site-specific cartilage degeneration. Notably, IL-1β was overexpressed in necrotic subchondral bone and the site deep zones of cartilage. It potently enhanced catabolic activity in hypertrophic chondrocytes, promoting matrix metalloproteinase expression while impairing mineralization capacity. This study uncovers a novel pathological cascade in GONFH: necrotic subchondral bone-derived IL-1β drives CCZ remodeling via biomechanical and biological pathways, leading to cartilage degeneration independent of femoral head collapse. Our findings highlight IL-1β as a critical therapeutic target, providing a rationale for subchondral bone-targeted anti-inflammatory strategies to mitigate GONFH progression.

Injectable Hydrogel Technologies for Bone Disease Treatment

Injectable hydrogels represent a highly promising approach for localized drug delivery systems (DDSs) in the management of bone-related conditions such as osteoporosis, osteonecrosis, osteoarthritis, osteomyelitis, and osteosarcoma. Their appeal lies in their biocompatibility, adjustable mechanical properties, and capacity to respond to external stimuli, including pH, temperature, light, redox potential, ionic strength, and enzymatic activity. These features enable enhanced targeted delivery of bioactive agents. This mini-review evaluates the synthesis of injectable hydrogels as well as recent advancements for treating a range of bone disorders, focusing on their mechanisms as localized and sustained DDSs for delivering drugs, nanoparticles, growth factors, and cells (e.g., stem cells). Moreover, it highlights their clinical studies for bone disease treatment. Additionally, it emphasizes the potential synergy between injectable hydrogels and hydrogel-based point-of-care technologies, which are anticipated to play a pivotal role in the future of bone disease therapies. Injectable hydrogels have the potential to transform bone disease treatment by facilitating precise, sustained, and minimally invasive therapeutic delivery. Nevertheless, significant challenges, including long-term biocompatibility, scalability, reproducibility, and precise regulation of drug release kinetics, must be addressed to unlock their clinical potential fully. Addressing these challenges will not only advance bone disease therapy but also open new avenues in regenerative medicine and personalized healthcare.

Advancements in 3D printing technologies for personalized treatment of osteonecrosis of the femoral head

Three-dimensional (3D) printing technology has shown significant promise in the medical field, particularly in orthopedics, prosthetics, tissue engineering, and pharmaceutical preparations. This review focuses on the innovative application of 3D printing in addressing the challenges of osteonecrosis of the femoral head (ONFH). Unlike traditional hip replacement surgery, which is often suboptimal for younger patients, 3D printing offers precise localization of necrotic areas and the ability to create personalized implants. By integrating advanced biomaterials, this technology offers a promising strategy approach for early hip-preserving treatments. Additionally, 3D-printed bone tissue engineering scaffolds can mimic the natural bone environment, promoting bone regeneration and vascularization. In the future, the potential of 3D printing extends to combining with artificial intelligence for optimizing treatment plans, developing materials with enhanced bioactivity and compatibility, and translating these innovations from the laboratory to clinical practice. This review demonstrates how 3D printing technology uniquely addresses critical challenges in ONFH treatment, including insufficient vascularization, poor mechanical stability, and limited long-term success of conventional therapies. By introducing gradient porous scaffolds, bioactive material coatings, and AI-assisted design, this work outlines novel strategies to improve bone regeneration and personalized hip-preserving interventions. These advancements not only enhance treatment efficacy but also pave the way for translating laboratory findings into clinical applications.

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.

From death to birth: how osteocyte death promotes osteoclast formation

Bone remodeling is a dynamic and continuous process involving three components: bone formation mediated by osteoblasts, bone resorption mediated by osteoclasts, and bone formation-resorption balancing regulated by osteocytes. Excessive osteocyte death is found in various bone diseases, such as postmenopausal osteoporosis (PMOP), and osteoclasts are found increased and activated at osteocyte death sites. Currently, apart from apoptosis and necrosis as previously established, more forms of cell death are reported, including necroptosis, ferroptosis and pyroptosis. These forms of cell death play important role in the development of inflammatory diseases and bone diseases. Increasing studies have revealed that various forms of osteocyte death promote osteoclast formation via different mechanism, including actively secreting pro-inflammatory and pro-osteoclastogenic cytokines, such as tumor necrosis factor alpha (TNF-α) and receptor activator of nuclear factor-kappa B ligand (RANKL), or passively releasing pro-inflammatory damage associated molecule patterns (DAMPs), such as high mobility group box 1 (HMGB1). This review summarizes the established and potential mechanisms by which various forms of osteocyte death regulate osteoclast formation, aiming to provide better understanding of bone disease development and therapeutic target.

Core decompression, allogenic fibula fixation, and pedicled fibula grafting are effective for osteonecrosis of femoral head

OBJECTIVE

To explore the application effects of core decompression, allograft fibula fixation, and pedicled fibula grafting in osteonecrosis of the femoral head (ONFH).

METHODS

Forty patients with ONFH admitted to Ziyang Central Hospital from March 2017 to March 2022 were included in this study. According to the Association Research Circulation Osseous (ARCO) staging criteria, 20 patients at stage I underwent core decompression, 8 patients at stage II underwent core decompression combined with allogenic fibula fixation, and 12 patients at stage III underwent core decompression combined with pedicled fibula grafting.

RESULTS

After 1 year of follow-up, changes in hip joint function (Harris score) and pain level (visual analogue scale (VAS)) were compared before and after surgery. Imaging examination results were recorded, and efficacy and ARCO stage progression were compared with preoperative findings. All 40 patients received follow-up for 1 year. The results showed that the Harris score at 1 year post-operation was higher than pre-operation, while the VAS score was lower (P<0.05). Hip joint function evaluation in the 20 patients at stage I showed excellent, good, and fair results in 12 (60.00%), 5 (25.00%), and 3 (15.00%) cases, respectively, with X-ray examination indicating complete stability and no progression in ARCO staging. Among the 8 patients at stage II, hip joint function evaluation showed excellent, good, fair, and poor results in 4 (50.00%), 2 (25.00%), 1 (12.50%), and 1 (12.50%) cases, respectively. X-ray examination revealed stability in 7 cases, while 1 case progressed to ARCO stage IV and ultimately required artificial hip arthroplasty. Among the 12 patients at stage III, hip joint function evaluation revealed excellent, good, fair, and poor results in 5 (41.67%), 3 (25.00%), 2 (16.67%), and 2 (16.67%) cases, respectively. X-ray examination indicated stability in 10 cases, while 2 cases progressed to ARCO stage IV and ultimately required artificial hip arthroplasty.

CONCLUSION

Patients with stage I, II, and III ONFH achieved good short-term therapeutic outcomes using core decompression, core decompression with allogenic fibula fixation, and core decompression with pedicled fibula grafting. These methods effectively improved hip joint function and alleviated pain symptoms. Hence, it is crucial to select appropriate surgical methods based on the specific conditions of patients in clinical practice.

Thermoresponsive dual-network chitosan-based hydrogels with demineralized bone matrix for controlled release of rhBMP9 in the treatment of femoral head osteonecrosis

In an effort to mitigate or reverse the pathological progression of early-stage osteonecrosis of the femoral head (ONFH), this study employed a promising strategy that involves the sustained delivery of osteogenic factors to augment core decompression, facilitated by the use of composite hydrogels. Specifically, a hydrogel was synthesized by blending chitosan, Pluronic F-127, and tripolyphosphate, utilizing both ionic bonding and copolymer micelle cross-linking techniques. This hydrogel demonstrated exceptional biocompatibility, temperature responsiveness, pH-dependent biodegradation, and controlled release properties. The average pore diameter of the optimal hydrogel expanded to 45 μm, accompanied by zeta potentials of +34.72 ± 4.13 mV. The loading efficiency notably surpassed 90 %, while the sustained release of recombinant human bone morphogenetic proteins 9 (rhBMP9) was observed to last over 25 days at pH = 6.0 and over 36 days at pH = 7.4. This chitosan-based hydrogel, which sustained rhBMP9 release, significantly enhanced the proliferation and migration of bone marrow mesenchymal stem cells and human umbilical vein endothelial cells and promoted osteogenesis and angiogenesis both in vitro and in vivo. Collectively, our study presents an rhBMP9-loaded chitosan-based composite hydrogel system that offers innovative avenues for the research and clinical application of advanced biomaterials in the treatment of early ONFH.

The role of Piezo1 in bone marrow stem cells in response to elevated intraosseous pressure on regulating osteogenesis and angiogenesis of steroid-induced osteonecrosis of the femoral head

Objectives

Steroid-induced osteonecrosis of the femoral head (SONFH) remains a significant global health issue, with an unclear pathogenesis. Elevated intraosseous pressure is considered a key initiating factor in SONFH development. Impaired osteogenesis and angiogenesis are believed to be critical in SONFH progression. Piezo1, a mechanosensitive cation channel, may sense changes in intraosseous pressure. In this study, we set out to explore the role of Piezo1 in SONFH and how to target Piezo1 to treat SONFH.

Methods

Femoral head tissue specimens were collected from patients with ONFH and femoral neck fracture. Histological staining, Western blotting, and RT-PCR analysis were conducted to investigate the relationship between elevated intraosseous pressure and SONFH in rat models. Immunofluorescence staining of femoral head tissues was performed to study the spatiotemporal relationship between elevated intraosseous pressure and angiogenesis, osteogenesis, and development of SONFH.

Results

In the early stages of SONFH, elevated intraosseous pressure increased angiogenesis and osteogenesis. However, as the pressure continued to rise, both processes were inhibited. Furthermore, Elevated intraosseous pressure activated the Piezo1 signaling pathway in bone marrow stem cells. Piezo1 activation led to increased intracellular calcium influx, thus enhancing osteogenesis and angiogenesis through CAM-NFAT1 signaling pathway.

Conclusion

In the early stages of SONFH, Piezo1 in BMSCs senses increased intraosseous pressure, promoting angiogenesis and osteogenesis. Targeting Piezo1 to promote the osteogenic and angiogenic potential of stem cells, which could curb further increases in pressure, contribute to early treatment of SONFH.

The translational potential of this article

Currently, many mechanisms of the impact of elevated intraosseous pressure on osteonecrosis of the femoral head are still in the basic theoretical research stage, and we hope to translate them into clinical applications as soon as possible. We discovered that targeting Piezo1 curb further increases in intraosseous pressure, alleviating the damaging effects of glucocorticoids on stem cells and blood vessels, which exerting great significance in treatment of early stage SONFH.

Clinical Study on the Effects of Total Hip Arthroplasty Assisted by Virtual Planning Combined With Intraoperative Navigation Templates

OBJECTIVES

Although total hip arthroplasty (THA) effectively alleviates pain and restores joint function in the end-stage hip disease, challenges remain in achieving precise osteotomy and minimizing subjective dependency on prosthesis positioning. This study aims to evaluate the efficacy and safety of preoperative virtual planning and navigation templates compared to conventional techniques, providing new methods to enhance the precision and personalization of THA.

METHODS

During the period from 2022 to 2023, we conducted a retrospective case-control study on 74 patients who underwent THA surgery at our hospital, based on the inclusion and exclusion criteria. The study included 42 patients in the traditional method group, who underwent preoperative planning and surgical procedures according to traditional methods; and 32 patients in the digital assistance group, who used computer-assisted virtual preoperative planning and three-dimensional printed personalized navigation templates to assist in the surgery. The main parameters of the two groups were compared, including surgical time, blood loss, postoperative femoral anteversion, neck-shaft angle, anatomical-mechanical femoral axis angle (aMFA), leg length discrepancy (LLD), and the angle of hip prosthesis placement. The Harris hip score was recorded both preoperatively and at the final follow-up to assess the accuracy of the prosthesis placement and the prognosis of the patients.

RESULTS

There were no significant differences in femoral anteversion, neck-shaft angle, aMFA, or LLD between the two groups. However, the digital group showed smaller deviations between the planned and actual acetabular prosthesis angles compared to the conventional group, with shorter operative times and reduced blood loss. Follow-up Harris hip scores were significantly higher in the digital group (p < 0.05).

CONCLUSIONS

Digital technology enhances the accuracy and reproducibility of prosthesis placement in THA, reduces operative time and blood loss, and shows a promising potential for broader application.

A nomogram for predicting contralateral femoral head collapse after unilateral replacement of bilateral femoral head necrosis

This study aimed to develop and validate a nomogram, which can effectively predict the risk of contralateral asymptomatic femoral head collapse in patients with bilateral osteonecrosis of the femoral head (ONFH), undergoing unilateral total hip arthroplasty (THA). We retrospectively analyzed the clinical data of patients who underwent unilateral THA for bilateral non-traumatic ONFH in our center from 2015 to 2018. A total of 103 patients participated in at least 5 years of follow-up. The patients were randomly divided into a training set (70%) and a validation set (30%). Univariate and multivariate Cox analyses were used to determine the independent risk factors for contralateral femoral head collapse. Based on these factors, a predictive nomogram model for 3, 4, and 5 years after THA was developed, and the model was evaluated using receiver operating characteristic (ROC) curve analysis, area under the curve (AUC), decision curve analysis (DCA), and calibration curves. Among the103 patients, 64 patients (62.1%) experienced contralateral femoral head collapse after surgery. Independent risk factors included Japanese investigation committee (JIC) types C1 and C2, lower limb length difference, CE angle, and Harris hip score (HHS) one month after the primary THA. The AUC, calibration curves, and DCA for the predictive model at 3, 4, and 5 years demonstrated good performance of the nomogram. The predictive nomogram model shows good accuracy and clinical utility. Using this tool, clinicians can accurately judge the collapse of the contralateral asymptomatic femoral head after unilateral THA in patients with bilateral ONFH, and they can formulate individualized treatment plans.

Isovitexin targets SIRT3 to prevent steroid-induced osteonecrosis of the femoral head by modulating mitophagy-mediated ferroptosis

The death of osteoblasts induced by glucocorticoid (GC)-mediated oxidative stress plays a crucial role in the development of steroid-induced osteonecrosis of the femoral head (SIONFH). Improving bone formation driven by osteoblasts has shown promising outcomes in the prognosis of SIONFH. Isovitexin has demonstrated antioxidant properties, but its therapeutic effects on GC-induced oxidative stress and SIONFH remain unexplored. In this study, we analyzed clinical samples obtained from SIONFH patients using proteomic and bioinformatic approaches. We found an imbalance in mitochondrial homeostasis and ferroptosis-induced impairment of osteogenic capacity in SIONFH. Subsequently, we investigated the cause-and-effect relationship between mitochondria and ferroptosis, as well as the regulatory role of mitophagy in maintaining mitochondrial homeostasis and controlling ferroptosis. We then identified the critical involvement of SIRT3 in modulating mitochondrial homeostasis and ferroptosis. Furthermore, molecular docking and co-immunoprecipitation confirmed the strong interaction between SIRT3 and BNIP3. Strikingly, restoring SIRT3 expression significantly inhibited pathological mitophagy mediated by the BNIP3/NIX pathway. Additionally, we discovered that Isovitexin, by promoting SIRT3 expression, effectively regulated mitophagy, preserved mitochondrial homeostasis in osteoblasts, suppressed ferroptosis, and restored osteogenic capacity, leading to remarkable improvements in SIONFH. These findings reveal the effects and molecular mechanisms of Isovitexin on SIONFH and highlight the potential of targeting SIRT3 as a promising strategy to suppress mitophagy-mediated ferroptosis in osteoblasts and against SIONFH.

USP13 overexpression in BMSCs enhances anti-apoptotic ability and guards against methylprednisolone-induced osteonecrosis in rats

Methylprednisolone (MPS) use is linked to increased cases of osteonecrosis of the femoral head (ONFH). Bone marrow mesenchymal stem cells (BMSCs) have shown potential for treating MPS-induced ONFH, but their effectiveness is limited by high apoptosis rates post-transplantation. We developed a pretreatment strategy for BMSCs to improve their viability. In a rat model of MPS-induced ONFH, we evaluated the effects of USP13 overexpression in BMSCs through micro-CT, HE staining, and TUNEL staining. USP13-overexpressing BMSCs significantly reduced ONFH severity compared to plain BMSCs and direct lentivirus injection. USP13 also protected BMSCs from MPS-induced apoptosis by modulating PTEN and reducing AKT phosphorylation. This led to decreased expression of apoptotic genes and proteins in USP13-overexpressing BMSCs. Our findings highlight USP13 as a promising target for enhancing BMSC survival and efficacy in treating MPS-induced ONFH.

Osteogenic tailoring of oriented bone matrix organization using on/off micropatterning for osteoblast adhesion on titanium surfaces

Titanium (Ti) implants are well known for their mechanical reliability and chemical stability, crucial for successful bone regeneration. Various shape control and surface modification techniques to enhance biological activity have been developed. Despite the crucial importance of the collagen/apatite bone microstructure for mechanical function, antimicrobial properties, and biocompatibility, precise and versatile pattern control for regenerating the microstructure remains challenging. Here, we developed a novel osteogenic tailoring stripe-micropatterned MPC-Ti substrate that induces genetic-level control of oriented bone matrix organization. This biomaterial was created by micropatterning 2-methacryloyloxyethyl phosphorylcholine (MPC) polymer onto a titanium (Ti) surface through a selective photoreaction. The stripe-micropatterned MPC-Ti substrate establishes a distinct interface for cell adhesion, robustly inducing osteoblast cytoskeleton alignment through actin cytoskeletal alignment, and facilitating the formation of a bone-mimicking-oriented collagen/apatite tissue. Moreover, our study revealed that this bone alignment process is promoted through the activation of the Wnt/β-catenin signaling pathway, which is triggered by nuclear deformation induced by strong cellular alignment guidance. This innovative material is essential for personalized next-generation medical devices, offering high customizability and active restoration of the bone microstructure. STATEMENT OF SIGNIFICANCE: This study demonstrates a novel osteogenic tailoring stripe-micropatterned MPC-Ti substrate that induces osteoblast alignment and bone matrix orientation based on genetic mechanism. By employing a light-reactive MPC polymer, we successfully micropatterned the titanium surface, creating a biomaterial that stimulates unidirectional osteoblast alignment and enhances the formation of natural bone-mimetic anisotropic microstructures. The innovative approach of regulating cell adhesion and cytoskeletal alignment activates the Wnt/β-catenin signaling pathway, crucial for both bone differentiation and orientation. This study presents the first biomaterial that artificially induces the construction of mechanically superior anisotropic bone tissue, and it is expected to promote functional bone regeneration by enhancing bone differentiation and orientation-targeting both the quantity and quality of bone tissue.

Bone Regeneration: Mini-Review and Appealing Perspectives

Bone is a natural mineral-organic nanocomposite protecting internal organs and allowing mobility. Through the ages, numerous strategies have been developed for repairing bone defects and fixing fractures. Several generations of bone repair biomaterials have been proposed, either based on metals, ceramics, glasses, or polymers, depending on the clinical need, the maturity of technologies, and knowledge of the natural constitution of the bone tissue to be repaired. The global trend in bone implant research is shifting toward osteointegrative, bioactive and possibly stimuli-responsive biomaterials and, where possible, resorbable implants that actively promote the regeneration of natural bone tissue. In this mini-review, the fundamentals of bone healing materials and clinical challenges are summarized and commented on with regard to progressing scientific discoveries. The main types of bone-healing materials are then reviewed, and their specific relevance to the field is reminded, with the citation of reference works. In the final part, we highlight the promise of hybrid organic-inorganic bioactive materials and the ongoing research activities toward the development of multifunctional or stimuli-responsive implants. This contribution is expected to serve as a commented introduction to the ever-progressing field of bone regeneration and highlight trends of future-oriented research.

Advances in mechanism and management of bone homeostasis in osteonecrosis: a review article from basic to clinical applications

Osteonecrosis, characterized by bone cell death leading to impaired bone recovery, causes challenges in bone homeostasis maintenance. Bone homeostasis relies on the delicate balance between osteoclasts and osteoblasts, encompassing a series of complex and strictly regulated biological functions. Current treatments, including conservative therapies and surgeries, often fall short of expected outcomes, necessitating a reorientation towards more effective therapeutic strategies according to the pathogenesis. In this review, the authors hierarchically outlined risk factors, emerging mechanisms, and last-decade treatment approaches in osteonecrosis. By connecting mechanisms of bone homeostasis, the authors proposed future research directions should be focused on elucidating risk factors and key molecules, performing high-quality clinical trial, updating practice, and accelerating translational potential.

Inhibition of protein disulfide isomerase mitigates steroid-induced osteonecrosis of the femoral head by suppressing osteoclast activity through the reduction of cellular oxidative stress

Osteonecrosis of the femoral head (ONFH) is a devastating and irreversible hip disease usually associated with increased oxidative stress due to the clinical application of high-dose or long-term glucocorticoids (GCs). Previous publications have demonstrated protein disulfide isomerase (PDI) plays a critical role in regulating cellular production of reactive oxygen species (ROS). We therefore ask whether interfering PDI could affect GCs-stimulated osteoclastogenesis. To test the hypothesis, we conducted bioinformatics and network analysis based on potential gene targets of steroid-induced osteonecrosis of the femoral head (SIONFH) in light of multiple databases and concomitantly verified the associated biological effect via the in vitro model of dexamethasone (DEX)-stimulated osteoclastogenesis. The results revealed 70 potential gene targets for SIONFH intervention, including the P4HB gene that encodes PDI. Further analysis based on network topology-based analysis techniques (NTA), protein-protein interaction (PPI) networks, and mouse cell atlas database identified the importance of PDI in regulating the cellular redox state of osteoclast during ONFH. Western blotting (WB) validations also indicated that PDI may be a positive regulator in the process of DEX-stimulated osteoclastogenesis. Hence, various PDI inhibitors were subjected to molecular docking with PDI and their performances were analyzed, including 3-Methyltoxoflavin (3 M) which inhibits PDI expression, and ribostamycin sulfate (RS) which represses PDI chaperone activity. The binding energies of DEX, 3 M, and RS to PDI were -5.3547, -4.2324, and -5.9917 kcal/mol, respectively. The Protein-Ligand Interaction Profiler (PLIP) analysis demonstrated that both hydrogen bonds and hydrophobic interactions were the key contributions to the DEX-PDI and 3M-PDI complexes, while only hydrogen bonds were identified as the predominant driving forces in the RS-PDI complex. Subsequent experiments showed that both 3 M and RS reduced osteoclast differentiation and bone resorption activity by stifling the expression of osteoclastic markers. This reduction was primarily due to the PDI inhibitors boosting the antioxidant system, thereby reducing the production of intracellular ROS. In conclusion, our results supported PDI's involvement in SIONFH progression by regulating ROS in osteoclasts and highlighted PDI inhibitors may serve as potential options for SIONFH treatment.

Changes of bone and articular cartilage in broilers with femoral head necrosis

Femoral head necrosis (FHN) in broilers is a common leg disorder in intensive poultry farming, giving rise to poor animal health and welfare. Abnormal mechanical stress in the hip joint is a risk factor for FHN, and articular cartilage is attracting increasing attention as a cushion and lubrication structure for the joint. In the present study, broilers aged 3 to 4 wk with FHN were divided into femoral head separation (FHS) and femoral head separation with growth plate lacerations (FHSL) groups, with normal broilers as control. The features of the hip joint, bone, and cartilage were assessed in FHN progression using devices including computed tomography (CT), atomic force microscope (AFM), and transmission electron microscopy (TEM). Broilers with FHN demonstrated decreased bone mechanical properties, narrow joint space, and thickened femoral head stellate structures. Notably, abnormal cartilage morphology was observed in FHN-affected broilers, characterized by increased cartilage thickness and rough cartilage surfaces. In addition, as FHN developed, cartilage surface friction and friction coefficient dramatically increased, while cartilage modulus and stiffness decreased. The ultramicro-damage occurred in chondrocytes and the extracellular matrix (ECM) of cartilage. Cell disintegration, abnormal mitochondrial accumulation, and oxidative stress damage were observed in chondrocytes. A notable decline in cartilage collagen content was observed in ECM during the initial stages of FHN, accompanied by a pronounced reduction in collagen fiber diameter and proteoglycan content as FHN progressed. Furthermore, the noticeable loosening of the collagen fiber structure and the appearance of type I collagen were noted in cartilage. In conclusion, there was a progressive decrease in bone quality and multifaceted damage of cartilage in the femoral head, which was closely linked to the severity of FHN in broilers.

Hydrogel Use in Osteonecrosis of the Femoral Head

Osteonecrosis of the femoral head (ONFH) is a vascular disease of unknown etiology and can be categorized mainly into two types: non-traumatic and traumatic ONFH. Thus, understanding osteogenic-angiogenic coupling is of prime importance in finding a solution for the treatment of ONFH. Hydrogels are biomaterials that are similar to the extracellular matrix (ECM). As they are able to mimic real tissue, they meet one of the most important rules in tissue engineering. In ONFH studies, hydrogels have recently become popular because of their ability to retain water and their adjustable properties, injectability, and mimicry of natural ECM. Because bone regeneration and graft materials are very broad areas of research and ONFH is a complex situation including bone and vascular systems, and there is no settled treatment strategy for ONFH worldwide, in this review paper, we followed a top-down approach by reviewing (1) bone and bone grafting, (2) hydrogels, (3) vascular systems, and (4) ONFH and hydrogel use in ONFH with studies in the literature which show promising results in limited clinical studies. The aim of this review paper is to provide the reader with general information on every aspect of ONFH and to focus on the hydrogel used in ONFH.

Three-dimensional distribution of subchondral fracture lines in osteonecrosis of the femoral head

Objective

To investigate the characteristics of three-dimensional distribution of subchondral fracture lines on the surface of the osteonecrosis femoral head, and to discuss the underlying mechanisms that contribute to its collapse.

Methods

We retrospectively analyzed computed tomography (CT) images from 75 patients (comprising a total of 77 femoral heads) diagnosed with Association Research Circulation Osseous (ARCO) stage IIIA or IIIB femoral head necrosis. The three-dimensional structures of both the femoral head and the subchondral fracture line were reconstructed and subsequently fitted into normal femoral head model. A heat map of fracture line was generated to visualize its spatial distribution across the femoral heads surface.to observe its distribution. In addition to that, the femoral head was partitioned into four zones, and the frequency of each fracture line traversing different zones was calculated and analysed.

Results

Highest and lowest density of subchondral fracture lines was demonstrated in anterolateral and posterolateral zone respectively. and most sparse in posterolateral. Furthermore, the three-dimensional heat map of fracture lines highlighted their most frequent occurrence in the anterolateral area, particularly near the junction of the femoral head and neck. One fracture line may pass through multiple areas, passage frequencies for fracture lines was observed in zones I, II, III and IV for 66 times (85.7 %), 52 times (67.5 %), 25 times (32.5 %) and 46 times (59.7 %), respectively, with a significant difference between zone I and other zones (P < 0.001).

Conclusion

Subchondral fracture line of femoral head occurs most frequently in anterolateral femoral head, suggesting that the anterolateral part may be the initial location of collapse.

Translational potential of this article

We found that the subchondral fracture line was most frequently located anterolateral to the femoral head, suggesting that this may be the site of initiation of collapse. Furthermore, we propose an innovative method for analyzing and visualizing subchondral fracture distribution in femoral head necrosis in the form of fracture line heat maps. By doing so, we provide a valuable reference for physicians, enabling them to enhance their management strategies for femoral head necrosis. Ultimately, this approach holds the promise of significantly improving the prognosis and outcomes for patients afflicted with this condition.

Subchondral osteoclasts and osteoarthritis: new insights and potential therapeutic avenues

Osteoarthritis (OA) is the most common joint disease, and good therapeutic results are often difficult to obtain due to its complex pathogenesis and diverse causative factors. After decades of research and exploration of OA, it has been progressively found that subchondral bone is essential for its pathogenesis, and pathological changes in subchondral bone can be observed even before cartilage lesions develop. Osteoclasts, the main cells regulating bone resorption, play a crucial role in the pathogenesis of subchondral bone. Subchondral osteoclasts regulate the homeostasis of subchondral bone through the secretion of degradative enzymes, immunomodulation, and cell signaling pathways. In OA, osteoclasts are overactivated by autophagy, ncRNAs, and Rankl/Rank/OPG signaling pathways. Excessive bone resorption disrupts the balance of bone remodeling, leading to increased subchondral bone loss, decreased bone mineral density and consequent structural damage to articular cartilage and joint pain. With increased understanding of bone biology and targeted therapies, researchers have found that the activity and function of subchondral osteoclasts are affected by multiple pathways. In this review, we summarize the roles and mechanisms of subchondral osteoclasts in OA, enumerate the latest advances in subchondral osteoclast-targeted therapy for OA, and look forward to the future trends of subchondral osteoclast-targeted therapies in clinical applications to fill the gaps in the current knowledge of OA treatment and to develop new therapeutic strategies.

Insight into Steroid-Induced ONFH: The Molecular Mechanism and Function of Epigenetic Modification in Mesenchymal Stem Cells

Osteonecrosis of the femoral head (ONFH) is a common refractory orthopedic disease, which is one of the common causes of hip pain and dysfunction. ONFH has a very high disability rate, which is associated with a heavy burden to patients, families, and society. The pathogenesis of ONFH is not completely clear. At present, it is believed that it mainly includes coagulation dysfunction, abnormal lipid metabolism, an imbalance of osteogenic/adipogenic differentiation, and poor vascularization repair. The prevention and treatment of ONFH has always been a great challenge for clinical orthopedic surgeons. However, recent studies have emphasized that the use of mesenchymal stem cells (MSCs) to treat steroid-induced ONFH (SONFH) is a promising therapy. This review focuses on the role and molecular mechanism of epigenetic regulation in the progress of MSCs in the treatment of SONFH, and discusses the significance of the latest research in the treatment of SONFH from the perspective of epigenetics.

Icariin-loaded 3D-printed porous Ti6Al4V reconstruction rods for the treatment of necrotic femoral heads

Avascular necrosis of the femoral head is a prevalent hip joint disease. Due to the damage and destruction of the blood supply of the femoral head, the ischemic necrosis of bone cells and bone marrow leads to the structural changes and the collapse of the femoral head. In this study, an icariin-loaded 3D-printed porous Ti6Al4V reconstruction rod (referred to as reconstruction rod) was prepared by 3D printing technology. The mechanical validity of the reconstruction rod was verified by finite element analysis. Through infilling of mercapto hyaluronic acid hydrogel containing icariin into the porous structure, the loading of icariin was achieved. The biological efficacy of the reconstruction rod was confirmed through in vitro cell experiments, which demonstrated its ability to enhance MC3T3-E1 cell proliferation and facilitate cellular adhesion and spreading. The therapeutic efficacy of the reconstruction rod was validated in vivo through a femoral head necrosis model using animal experiments. The results demonstrated that the reconstruction rod facilitated osteogenesis and neovascularization, leading to effective osseointegration between bone and implant. This study provides innovative strategy for the treatment of early avascular necrosis of the femoral head. STATEMENT OF SIGNIFICANCE: The bioactivity of medical titanium alloy implants plays an important role in bone tissue engineering. This study proposed a medicine and device integrated designed porous Ti6Al4V reconstruction rod for avascular necrosis of the femoral head, whose macroscopic structure was customized by selective laser melting. The bionic porous structure of the reconstruction rod promoted the growth of bone tissue and formed an effective interface integration. Meanwhile, the loaded icariin promoted new bone and vascular regeneration, and increased the bone mass and bone density. Therefore, the implantation of reconstruction rod interfered with the further development of necrosis and provided a positive therapeutic effect. This study provides innovative strategies for the treatment of early avascular necrosis of femoral head.

Bone Regeneration Using Mesenchymal Stromal Cells and Biocompatible Scaffolds: A Concise Review of the Current Clinical Trials

Bone regenerative medicine is a clinical approach combining live osteoblast progenitors, such as mesenchymal stromal cells (MSCs), with a biocompatible scaffold that can integrate into host bone tissue and restore its structural integrity. Over the last few years, many tissue engineering strategies have been developed and thoroughly investigated; however, limited approaches have been translated to clinical application. Consequently, the development and clinical validation of regenerative approaches remain a centerpiece of investigational efforts towards the clinical translation of advanced bioengineered scaffolds. The aim of this review was to identify the latest clinical trials related to the use of scaffolds with or without MSCs to regenerate bone defects. A revision of the literature was performed in PubMed, Embase, and Clinicaltrials.gov from 2018 up to 2023. Nine clinical trials were analyzed according to the inclusion criteria: six presented in the literature and three reported in Clinicaltrials.gov. Data were extracted covering background trial information. Six of the clinical trials added cells to scaffolds, while three used scaffolds alone. The majority of scaffolds were composed of calcium phosphate ceramic alone, such as β-tricalcium phosphate (TCP) (two clinical trials), biphasic calcium phosphate bioceramic granules (three clinical trials), and anorganic bovine bone (two clinical trials), while bone marrow was the primary source of the MSCs (five clinical trials). The MSC expansion was performed in GMP facilities, using human platelet lysate (PL) as a supplement without osteogenic factors. Only one trial reported minor adverse events. Overall, these findings highlight the importance and efficacy of cell-scaffold constructs in regenerative medicine under different conditions. Despite the encouraging clinical results obtained, further studies are needed to assess their clinical efficacy in treating bone diseases to optimize their application.