3D printed cell-free bilayer porous scaffold based on alginate with biomimetic microenvironment for osteochondral defect repair.

Despite significant progress in repairing osteochondral injuries using 3D printing technology, most cartilage layer scaffolds are made of degradable materials, making it difficult to simultaneously provide extracellular matrix functionality while replicating the mechanical properties of natural cartilage layers. Additionally, their degradation rate is challenging to align with cartilage regeneration. Furthermore, double-layer scaffolds commonly used for repairing osteochondral often exhibit inadequate bonding between the cartilage layer scaffolds and bone layer scaffolds. To solve these problems, we presented a bilayer scaffold composed of a 3D printed non-degradable thermoplastic polyurethane (TPU) scaffold filled with hydrogel (Gel) made of gelatin and sodium alginate as the cartilage layer (noted as TPU/Gel), meanwhile, a 3D printed polylactic acid (PLA) scaffold containing 10 % hydroxyapatite (HA) as the bone layer (noted as PLA/HA). At the junction of the bone layer and cartilage layer, TPU tightly bonded with the bone layer scaffold under high temperatures. The hydrogel filling within the TPU layer of cartilage served not only to lubricate the joint surface but also aided in creating a 3D microenvironment. The non-degradable nature of TPU allowed the cartilage layer scaffold to seamlessly integrate with the surrounding regenerated cartilage, achieving permanent replacement and providing shock absorption and weight-bearing effects. This effectively addressed the mechanical challenges associated with cartilage regeneration and resolved the inconsistency between cartilage regeneration and material degradation rates.

Estimating elbow loading conditions through the motion behaviors of subchondral bone density during joint movements.

Evaluating complicated stress across the elbow under joint motion remains difficult. Here, we aimed to evaluate the distribution of the subchondral bone density in the normal elbow bones and further characterize their spatial relationships during elbow motion to estimate the loading stress across the articular surface using three-dimensional computed tomography bone models. The normal elbow joint exhibited a consistent distribution pattern of subchondral bone density. High-density regions were distributed in the capitellum and posterior humeral trochlea, sagittal ridge of the ulnar trochlear notch and ulnar-volar side of the radial head. Motion analyses revealed that the high-density regions proximate with elbow flexion with forearm pronation in the radiocapitellar joint and in the fully extended position in the ulnohumeral joint. This reasonably reflects the stress acting on the joint surface under actual loading conditions. These findings suggest that daily activities involving lifting or carrying objects in these positions are stress-prone activities.

Microarray analysis of signalling interactions between inflammation and angiogenesis in subchondral bone in temporomandibular joint osteoarthritis.

Inflammation and angiogenesis, the major pathological changes of osteoarthritis (OA), are closely associated with joint pain; however, pertinent signalling interactions within subchondral bone of osteoarthritic joints and potential contribution to the peripheral origin of OA pain remain to be elucidated. Herein we developed a unilateral anterior crossbite mouse model with osteoarthritic changes in the temporomandibular joint. Microarray-based transcriptome analysis, besides quantitative real-time polymerase chain reaction, was performed to identify differentially expressed genes (DEGs). Overall, 182 DEGs (fold change ≥ 2, P < 0.05) were identified between the control and unilateral anterior crossbite groups: 168 were upregulated and 14 were downregulated. On subjecting significant DEGs to enrichment analyses, inflammation and angiogenesis were identified as the most affected. Inflammation-related DEGs were mainly enriched in T cell activation and differentiation and in the mammalian target of rapamycin/nuclear factor-κB/tumour necrosis factor signalling. Furthermore, angiogenesis-related DEGs were mainly enriched in the Gene Ontology terms angiogenesis regulation and vasculature development and in the KEGG pathways of phosphoinositide 3-kinase-protein kinase B/vascular endothelial growth factor/hypoxia-inducible factor 1 signalling. Protein-protein interaction analysis revealed a close interaction between inflammation- and angiogenesis-related DEGs, suggesting that phosphatidylinositol-4,5-bisphosphate 3-kinase catalytic subunit delta (Pi3kcd), cathelicidin antimicrobial peptide (Camp), C-X-C motif chemokine receptor 4 (Cxcr4), and MYB proto-oncogene transcription factor (Myb) play a central role in their interaction. To summarize, our findings reveal that in subchondral bone of osteoarthritic joints, signal interaction is interrelated between inflammation and angiogenesis and associated with the peripheral origin of OA pain; moreover, our data highlight potential targets for the inhibition of OA pain.

Amentoflavone maintaining extracellular matrix homeostasis and inhibiting subchondral bone loss in osteoarthritis by inhibiting ERK, JNK and NF-κB signaling pathways.

Amentoflavone (AF), a plant biflavone isolated from Selaginella sinensis ethanol extract, is characterized by anti-inflammatory and anti-oxidant properties. According to previous studies, inflammation and oxidative stress are closely related to the pathophysiology of osteoarthritis (OA). However, the effects and mechanisms of AF on OA have not been elucidated.To investigate the inhibitory effects and its molecular mechanism of AF on extracellular matrix (ECM) degradation stimulated by IL-1ß as well as subchondral bone loss induced by RANKL in mice chondrocytes. Quantitative PCR was used to detect the mRNA expression of genes related to inflammation, ECM, and osteoclast differentiation. Protein expression level of iNOS, COX-2, MMP13, ADAMTS5, COL2A1, SOX9, NFATc1, c-fos, JNK, ERK, P65, IκBα was measured by western blotting. The levels of TNF-α and IL-6 in the supernatants were measured by ELISA. The amount of ECM in chondrocytes was measured using toluidine blue staining. The levels of Aggrecan and Col2a1 in chondrocytes were measured using immunofluorescence. Tartrate-resistant acid phosphatase (TRAP) staining, F-actin staining and immunofluorescence were used to detect the effect of AF on osteoclast differentiation and bone resorption. The effect of AF on destabilization of the medial meniscus (DMM)-induced OA mice can be detected in hematoxylin-eosin (H&E) staining, Safranin O green staining and immunohistochemistry.AF might drastically attenuated IL-1ß-stimulated inflammation and reduction of ECM formation by blocking ERK and NF-κB signaling pathways in chondrocytes. Meanwhile, AF suppressed the formation of osteoclasts and the resorption of bone function induced by RANKL. In vivo, AF played a protective role by stabilizing cartilage ECM and inhibiting subchondral bone loss in destabilization of the medial meniscus (DMM)-induced OA mice, further proving its protective effect in the development of OA. Our study show that AF alleviated OA by suppressing ERK, JNK and NF-κB signaling pathways in OA models in vitro and DMM-induced OA mice, suggesting that AF might be a potential therapeutic agent in the treatment of OA.

Molybdenum nanodots act as antioxidants for photothermal therapy osteoarthritis.

Osteoarthritis (OA) manifests as the degradation of cartilage and remodeling of subchondral bone. Restoring homeostasis within the joint is imperative for alleviating OA symptoms. Current interventions primarily target singular aspects, such as anti-aging, inflammation inhibition, free radical scavenging, and regeneration of cartilage and subchondral bone. Herein, we developed molybdenum nanodots (MNDs) as bionic photothermal nanomaterials to mimic the antioxidant synthase to concurrently protected cartilage and facilitate subchondral bone regeneration. With near-infrared (NIR) irradiation, MNDs effectively eliminate reactive oxygen and nitrogen species (ROS/RNS) from OA chondrocytes, thereby reversed mitochondrial dysfunction, mitigating chondrocyte senescence, and simultaneously suppresses inflammation, hence preserving the inherent homeostasis between cartilage matrix synthesis and degradation while circumventing safety concerns. RNA sequencing of OA chondrocytes treated with MNDs-NIR revealed the reinstatement of chondrocyte functionality, activation of antioxidant enzymes, anti-aging properties, and regulation of inflammation. NIR irradiation induces thermogenesis and synergistically promotes subchondral bone regeneration via MNDs, as validated through histological assessments and microcomputed tomography (Micro-CT) scans. MNDs-NIR effectively attenuate cellular senescence and inhibit inflammation in vivo, while also remodeling mitochondrial dynamics by upregulating fusion proteins and inhibiting fission proteins, thereby regulating the oxidative stress microenvironment. Additionally, MNDs-NIR exhibited remarkable therapeutic effects in alleviating articular cartilage degeneration in an OA mouse model, evidenced by a 1.67-fold reduction in subchondral bone plate thickness, an 88.57 % decrease in OARSI score, a 5.52-fold reduction in MMP13 expression, and a 6.80-fold increase in Col II expression. This novel disease-modifying approach for OA utilizing MNDs-NIR offers insight and a paradigm for improving mitochondrial dysfunction by regulating the accumulation of mitochondrial ROS and ultimately alleviating cellular senescence. Moreover, the dual-pronged therapeutic approach of MNDs-NIR, which addresses both cartilage erosion and subchondral bone lesions in OA, represents a highly promising strategy for managing OA.

Differential effects of alendronate on chondrocytes, cartilage matrix and subchondral bone structure in surgically induced osteoarthritis in mice.

Bisphosphonates (BP) are considered a treatment option for osteoarthritis (OA) due to reduction of OA-induced microtrauma in the bone marrow, stabilization of subchondral bone (SB) layer and pain reduction. The effects of high-dose alendronate (ALN) treatment on SB and articular cartilage after destabilization of the medial meniscus (DMM) or Sham surgery of male C57Bl/6J mice were analyzed. We performed serum analysis; histology and immunohistochemistry to assess the severity of OA and a possible pain symptomatology. Subsequently, the ratio of bone volume to total volume (BV/TV), epiphyseal trabecular morphology and the bone mineral density (BMD) was analyzed by nanoCT. Serum analysis revealed a reduction of ADAMTS5 level. The histological evaluation displayed no protective effect of ALN-treatment on cartilage erosion. NanoCT-analysis of the medial epiphysis revealed an increase of BV/TV in ALN-treated mice. Only the DMM group had significantly higher SB volume accompanied by decreased subchondral bone surface. Furthermore Nano-CT analysis revealed an increase in trabecular density and number, a decreased BMD and reduced osteophyte formation in the ALN mice. ALN treatment affected bone micro-architecture by reducing osteophytosis with simultaneous increasing subchondral bone plate thickness, trabecular thickness and BMD. Accordingly, ALN cannot be considered as a potential treatment strategy in general, however in a subgroup of patients with high bone turnover in an early-stage of OA, ALN might be an option when applied during a restricted time frame.

Isosakuranetin inhibits subchondral osteoclastogenesis for attenuating osteoarthritis via suppressing NF-κB/CXCL2 axis.

As the most predominant form of arthritis, osteoarthritis (OA) is featured with irreversible progress and involvement of the whole joint. Since OA onset, abnormal mechanical load initiates excessive osteoclastogenesis, evolving a rapid turnover of subchondral bone, cyst creation, synovitis, cartilage degradation, and ultimately resulting in joint failure. Additionally, aberrant vascularization and nociceptive pain are invoked by osteoclast-induced angiogenesis and sensory innervation in the subchondral bone. Rhizoma anemarrhenae (Zhimu) has been extensively demonstrated to show multiple pharmacological effects including anti-inflammation, anti-aging, and immunomodulation. Herein, Broussonin a (BRA), Markogein (MAN), and Isosakuranetin (ISN) derived from Rhizoma anemarrhenae, were initially discovered for their affinity with Bone marrow mononuclear cell (BMMC) membranes using the Cell membrane chromatography/Time of flight mass spectrometry (CMC/TOFMS) method, while only ISN exerted a significant inhibitory effect on RANKL-induced osteoclastogenesis in BMMC in vitro. Intriguingly, we disclosed that ISN blunted the overactivation of Tartrate-resistant acid phosphatase positive (TRAP+) osteoclasts in subchondral bone in OA mice, as indicated by enhanced bone volume/total volume (BV/TV), trabecular number (Tb.N), and trabeculae thickness (Tb.Th), as well as diminished trabecular pattern factor (Tb.pf). Treatment with ISN also impaired aberrant angiogenesis and nociceptive reaction in the subchondral bone marrow. Moreover, ISN hindered the loss of articular cartilage proteoglycan and lowered the Osteoarthritis Research Society International (OARSI) grade, boosting the expression amount of Aggrecan (ACAN) and Collagen II (COL II) positive cells while reducing Matrix metalloproteinase 13 (MMP-13) positive cells. For mechanisms, We verified that ISN hampered subchondral osteoclastogenesis by blocking nuclear factor kappa light chain enhancer of activated B cells (NF-κB) signaling and C-X-C Motif Chemokine Ligand 2 (CXCL2) stimulation. Taken together, we reveal that ISN impedes the progression of OA by preventing hyperactivated subchondral osteoclastogenesis via suppressing the NF-κB/CXCL2 axis.

Disuse atrophy of articular cartilage can be restored by mechanical reloading in mice.

BACKGROUND: Moderate mechanical stress generated by normal joint loading and movements helps maintain the health of articular cartilage. Despite growing interest in the pathogenesis of cartilage degeneration caused by reduced mechanical stress, its reversibility by mechanical reloading is less understood. This study aimed to investigate the response of articular cartilage exposed to mechanical reloading after unloading in vivo and in vitro. METHODS AND RESULTS: Disuse atrophy was induced in the knee joint cartilage of adult mice through hindlimb unloading by tail suspension. For in vivo experiments, mice were subjected to reloading with or without daily exercise intervention or surgical destabilization of the knee joint. Microcomputed tomography and histomorphometric analyses were performed on the harvested knee joints. Matrix loss and thinning of articular cartilage due to unloading were fully or partially restored by reloading, and exercise intervention enhanced the restoration. Subchondral bone density decreased by unloading and increased to above-normal levels by reloading. The severity of cartilage damage caused by joint instability was not different even with prior non-weight bearing. For in vitro experiments, articular chondrocytes isolated from the healthy or unloaded joints of the mice were embedded in agarose gel. After dynamic compression loading, the expression levels of anabolic (Sox9, Col2a1, and Acan) and catabolic (Mmp13 and Adamts5) factors of cartilage were analyzed. In chondrocytes isolated from the unloaded joints, similar to those from healthy joints, dynamic compression increased the expression of anabolic factors but suppressed the expression of catabolic factors. CONCLUSION: The results of this study indicate that the morphological changes in articular cartilage exposed to mechanical unloading may be restored in response to mechanical reloading by shifting extracellular matrix metabolism in chondrocytes to anabolism.

An Evidence-Based Update on Fixation Procedures for Acute and Chronic Osteochondral Lesions of the Talus.

Osteochondral lesions of the talus (OLT) involve the subchondral bone and the overlying articular cartilage. Various surgical treatments for these lesions are available, such as bone marrow stimulation (BMS), autologous osteochondral grafting, and fixation of an osteochondral fragment. Treatment choice depends on the condition of the lesion, which includes lesion size, morphology, location, and the presence of cysts. Among the surgical procedures available to date, in situ fixation of the osteochondral fragment has the advantage of restoring the articular surface while preserving the native hyaline cartilage and its subchondral bone. Fixation for OLT has been shown to be clinically successful for the treatment of both acute and chronic lesions. Moreover, the indication for osteochondral fragment fixation is expanding as recent studies have found good clinical outcomes in relatively small-sized lesions. The present article describes the current evidence on fixation for acute and chronic OLT.

Regenerative Variability of Human Juvenile Chondrocyte Sheets From Different Cell Donors in an Athymic Rat Knee Chondral Defect Model.

PURPOSE: This study aimed to establish a combined histological assessment system of neo-cartilage outcomes and to evaluate variations in an established rat defect model treated with human juvenile cartilage-derived chondrocyte (JCC) sheets fabricated from various donors. METHODS: JCCs were isolated from the polydactylous digits of eight patients. Passage 2 (P2) JCC sheets from all donors were transplanted into nude rat chondral defects for 4 weeks (27 nude rats in total). Defect-only group served as control. Histological samples were stained for safranin O, collagen 1 (COL1), and collagen 2 (COL2). (1) All samples were scored, and correlation coefficients for each score were calculated. (2) Donors were divided into "more effective" and "less effective" groups based on these scores. Then, differences between each group in each category of modified O'Driscoll scoring were evaluated. RESULTS: (1) Modified O'Driscoll scores were negatively correlated with %COL1 area, and positively correlated with %COL2 area and COL2/1 ratio. (2) Four of 8 donors exhibited significantly higher modified O'Driscoll scores and %COL2 areas. JCC donors were divided into two groups by average score values. Significant differences between the two groups were observed in modified O'Driscoll categories of "Nature of predominant tissue," "Reconstruction of subchondral bone," and "Safranin O staining." CONCLUSION: The combined histological evaluation method is useful for detailed in vivo efficacy assessments of cartilage defect regeneration models. Variations in histological scores among juvenile cartilage-derived chondrocyte donors were correlated to the quality of regenerated cartilage hyaline structure and subchondral bone remodeling observed in the nude rat defect model.

Evaluation of Tibiofemoral Contact Mechanics After a Novel Hybrid Procedure for Femoral Osteochondral Defect Repairs With a Subchondral Implant and Dermal Matrix.

Background: There is a lack of procedures that adequately address the subchondral bone structure and function for reconstructing osteochondral defects in the femoral condyles. Purpose: To biomechanically evaluate the tibiofemoral joint contact characteristics before and after reconstruction of femoral condylar osteochondral defects using a novel hybrid reconstructive procedure, which was hypothesized to restore the contact characteristics to the intact condition. Study Design: Controlled laboratory study. Methods: Tibiofemoral contact areas, contact forces, and mean contact pressures were measured in 8 cadaveric knees (mean age 52 ± 11 years; 6 women, 2 men) using a custom testing system and pressure mapping sensors. Five conditions were tested for each condyle: intact, 8-mm defect, 8-mm repair, 10-mm defect, and 10-mm repair. Medial femoral condylar defects were evaluated at 30° of knee flexion and lateral condylar defects were evaluated at 60° of knee flexion, with compressive loads of 50, 100, and 150 N. The defects were reconstructed with a titanium fenestrated threaded implant countersunk in the subchondral bone and an acellular dermal matrix allograft. Repeated-measures analysis of variance with Bonferroni correction for multiple comparisons was used to compare the results between the 5 testing conditions at each load. Results: Medial condylar defects significantly increased mean contact pressure on the lateral side (P < .042), which was restored to the intact levels with repair. The lateral condylar defect decreased the mean contact pressure laterally while increasing the mean pressure medially. The lateral and medial mean contact pressures were restored to intact levels with the 8-mm lateral condylar defect repair. The medial mean contact pressure was restored to intact levels with the 10-mm lateral condylar defect repair. The lateral mean contact pressure decreased compared with the intact state with the lateral condylar 10-mm defect repair. Conclusion: Tibiofemoral joint contact pressure was restored to the intact condition after reconstruction of osteochondral defects with dermal allograft matrix and subchondral implants for the repair of both 8- and 10-mm lateral condylar defects as well as 8-mm medial condylar defects but not completely for 10-mm medial condylar defects. Clinical Relevance: The novel hybrid procedure for osteochondral defect repair restored tibiofemoral joint contact characteristics to normal in a cadaveric model.

Pain in osteoarthritis: Driven by intrinsic rather than extrinsic joint afferents and why this should impact treatment.

Pain in osteoarthritis (OA) results from erosion of joint cartilage, resulting in bone contacting bone without an intervening cushion. The periosteum, including its nociceptive innervation, ends at the border of the cartilage. No other innervated tissue is present between the denuded articular bone ends that could serve as a neuronal pathway to carry a bone-on-bone pain signal to the brain. The pain signaling pathway must therefore originate in afferent axons with electrogenic nociceptive sensory endings that reside within the bone itself, specifically in the opposing surfaces of epiphyseal subchondral bone. Selective ablation of this intrinsic nerve pathway, using any of a variety of approaches, is expected to permanently eliminate OA pain.

Post-traumatic osteoarthritic-mediated changes in condylar shape do not covary with changes in the internal microstructure of the bone.

Post-traumatic osteoarthritis (PTOA) in the temporomandibular joint (TMJ) is associated with remodeling of the subchondral bone. This remodeling changes both the external appearance of the condylar bone and the internal bony microstructure. The external geometry can be quantified using shape, a multivariate mathematical measurement that contains all of the structure's geometric information with location, scale, and rotation effects removed. There is an important gap in knowledge related to how TMJ PTOA affects the shape of the mandible and if the external shape covaries with the internal bony microstructure. To evaluate these gaps, TMJ PTOA was induced in male and female skeletally mature mice using a surgical destabilization procedure. After four weeks, tissues were collected and characterized using a high-resolution µCT scanner. Shape was calculated from surface reconstructions of the mandibular condyle, and the internal bony microstructure was characterized by the region of interest including the subchondral trabeculae. The covariance of shape with and without corrections for allometric scaling and internal bony microstructure was calculated using a Procrustes ANOVA. The data illustrate that PTOA significantly alters the shape of the condyle in a sex-independent manner. PTOA does alter some aspects of the internal bony microstructure in a sex-dependent manner. Allometric scaling was a significant factor in the variance of shape. Shape including the effects of allometric scaling significantly covaries with some internal bony microstructure variables in both sexes. Shape scaled to remove the effects of allometric scaling does not covary with internal bony microstructure in either sex. These findings indicate that PTOA progression is associated with changes in the size and shape of the condyle but variance in trabecular bone remodeling is only associated with size related shape change. Thus, the allostatic response of subchondral bone is multimodal, coordinating two independent biological processes controlling size and shape. Since subchondral bone participates in and guides the progression of PTOA, these findings have implications for identifying select and specific mechanisms contributing to the progression and pathophysiology of the PTOA in the TMJ.

Senolytics cocktail dasatinib and quercetin alleviate chondrocyte senescence and facet joint osteoarthritis in mice.

BACKGROUND CONTEXT: Low back pain (LBP) is a pervasive issue, causing substantial economic burden and physical distress worldwide. Facet joint osteoarthritis (FJ OA) is believed to be a significant contributor to this problem. However, the precise role of chondrocyte senescence in FJ OA remains unclear, as does whether the clearance of chondrocyte senescence can alleviate the progression of FJ OA. PURPOSE: The goal of this study was to understand the potential of Dasatinib (D) and Quercetin (Q) as a treatment to clear chondrocyte senescence during the progression of FJ OA. STUDY DESIGN: We used a preclinical bipedal standing mice model with the administration of Dasatinib (D) (5 mg/kg) and Quercetin (Q) (50 mg/kg) after 10 weeks of bipedal standing. MATERIALS AND METHODS: Human degenerative lumbar facet joint (LFJ) samples were obtained to investigate the relationship between chondrocyte cellular senescence and LFJ osteoarthritis (OA). Subsequently, we established an in vitro model of excessive mechanical stress on chondrocytes and an in vivo bipedal standing mice model to induce LFJ OA. IHC (immunohistochemistry) staining in vivo and SA-ß-gal staining, qRT-PCR and Western blot analysis were applied to test the senolytic effect of the combination of Dasatinib (D) and Quercetin (Q). IHC staining and X-ray microscope were also performed to examine the contribution of D+Q to the anabolism in cartilage and subchondral bone recoupling. Immunofluorescence and Western blot analysis in vitro and IHC staining in vivo were conducted to assess the impact of D+Q on the regulation of the NF-κB pathway activation during chondrocyte senescence. RESULTS: We observed that facet joint cartilage degeneration is associated with chondrocyte cellular senescence in both human and mouse degenerative samples. Following treatment with D+Q in vitro, cellular senescence was significantly reduced. Upon oral gavage administration of D+Q in the bipedal standing mice model, decreased cellular senescence and reversed chondrocyte anabolism were observed. Furthermore, administration of D+Q maintained subchondral bone remodeling homeostasis and potentially reversed the activation of the NF-κB pathway in chondrocytes of the lumbar facet joint. CONCLUSIONS: In summary, our investigation unveiled a significant correlation between chondrocyte senescence and LFJOA. Treatment with the senolytic combination of D+Q in FJ OA yielded a notable reduction in chondrocyte senescence, along with a decrease in the release of SASP factors. Additionally, it facilitated the promotion of cartilage anabolism, maintenance of subchondral bone coupling, and amelioration of NF-κB pathway activation. CLINICAL SIGNIFICANCE: Our outcomes revealed that D+Q, the renowned combination used for senolytic treatment, alleviate the progression of LFJ OA. The utilization of D+Q as a senolytic demonstrates a novel and promising alternative for LFJ OA treatment.

Advancements in Subchondral Bone Biomechanics: Insights from Computed Tomography and Micro-Computed Tomography Imaging in Equine Models.

PURPOSE OF REVIEW: This review synthesizes recent advancements in understanding subchondral bone (SCB) biomechanics using computed tomography (CT) and micro-computed tomography (micro-CT) imaging in large animal models, particularly horses. RECENT FINDINGS: Recent studies highlight the complexity of SCB biomechanics, revealing variability in density, microstructure, and biomechanical properties across the depth of SCB from the joint surface, as well as at different joint locations. Early SCB abnormalities have been identified as predictive markers for both osteoarthritis (OA) and stress fractures. The development of standing CT systems has improved the practicality and accuracy of live animal imaging, aiding early diagnosis of SCB pathologies. While imaging advancements have enhanced our understanding of SCB, further research is required to elucidate the underlying mechanisms of joint disease and articular surface failure. Combining imaging with mechanical testing, computational modelling, and artificial intelligence (AI) promises earlier detection and better management of joint disease. Future research should refine these modalities and integrate them into clinical practice to enhance joint health outcomes in veterinary and human medicine.

PLCγ1 deficiency in chondrocytes accelerates the age-related changes in articular cartilage and subchondral bone.

Ageing is the most prominent risk for osteoarthritis (OA) development. This study aimed to investigate the role of phosphoinositide-specific phospholipase Cγ (PLCγ) 1, previously linked to OA progression, in regulating age-related changes in articular cartilage and subchondral bone. d-galactose (d-Gal) was employed to treat chondrocytes from rats and mice or injected intraperitoneally into C57BL/6 mice. RTCA, qPCR, Western blot and immunohistochemistry assays were used to evaluate cell proliferation, matrix synthesis, senescence genes and senescence-associated secretory phenotype, along with PLCγ1 expression. Subchondral bone morphology was assessed through micro-CT. In mice with chondrocyte-specific Plcg1 deficiency (Plcg1flox/flox; Col2a1-CreERT), articular cartilage and subchondral bone were examined over different survival periods. Our results showed that d-Gal induced chondrocyte senescence, expedited articular cartilage ageing and caused subchondral bone abnormalities. In d-Gal-induced chondrocytes, diminished PLCγ1 expression was observed, and its further inhibition by U73122 exacerbated chondrocyte senescence. Plcg1flox/flox; Col2a1-CreERT mice exhibited more pronounced age-related changes in articular cartilage and subchondral bone compared to Plcg1flox/flox mice. Therefore, not only does d-Gal induce senescence in chondrocytes and age-related changes in articular cartilage and subchondral bone, as well as diminished PLCγ1 expression, but PLCγ1 deficiency in chondrocytes may also accelerate age-related changes in articular cartilage and subchondral bone. PLCγ1 may be a promising therapeutic target for mitigating age-related changes in joint tissue.

Zoledronate alleviates subchondral bone collapse and articular cartilage degeneration in a rat model of rotator cuff tear arthropathy.

OBJECTIVE: To evaluate the humeral head bone volume of patients with cuff tear arthropathy (CTA) and examine the therapeutic effect of zoledronate in a rat modified model of CTA (mCTA). DESIGN: The bone mass in patients with CTA was measured using Hounsfield units from CT images. The mCTA was induced by transecting the rotator cuff, biceps brachii tendon, and superior half of the joint capsule in adult rat shoulders. A single subcutaneous injection of zoledronate was followed by bone histomorphometry and immunohistochemistry of the humeral head, as well as the Murine Shoulder Arthritis Score (MSAS) assessment. RESULTS: The humeral head bone volume was decreased in patients with CTA. In the mCTA model, M1 macrophages were increased in the synovium and were decreased by zoledronate treatment. The increased expressions of TNF-α, IL-1ß and IL-6 in mCTA synovium and articular cartilage were suppressed in the zoledronate-treated mCTA group. The expression of catabolic enzymes in the articular cartilage and MSAS showed similar results. The zoledronate-treated mCTA group showed a decreased subchondral bone collapse with a decreased RANKL/OPG expression ratio and a suppressed number of osteoclasts compared with the control mCTA group. The enhanced expressions of HMGB1 and S100A9 in the mCTA shoulders were eliminated in the zoledronate-treated mCTA group. CONCLUSIONS: The humeral head subchondral bone was decreased in patients with CTA. In the mCTA model, the collapse and osteoarthritic changes were prevented by zoledronate administration. Zoledronate seemed to suppress the number of M1 macrophages in the synovium and osteoclasts in the subchondral bone.

A Preliminary Study of Quantitative MRI Cartilage Loss Fraction and Its Association With Future Arthroplasty Using the Osteoarthritis Initiative Database.

Background and objective  Osteoarthritis (OA) is the most common arthritis in the world. Despite the high disease burden, there is no therapy to prevent, halt, or reverse OA, and many clinical trials relied on radiographic biomarkers for therapy response. It is important to identify patients with early OA who will eventually need arthroplasty, the end-stage treatment for osteoarthritis. This pilot study evaluates a novel MRI biomarker, cartilage loss fraction, for association with future arthroplasty and evaluates its feasibility of use and effect size estimates. Materials and methods Publicly available knee MRIs from the Osteoarthritis Initiative were used. A total of 38 participants with Kellgren-Lawrence (K-L) grade >1 and 38 participants with K-L grade ≤ 1 at enrollment were matched in age, sex, race, and BMI, and assessed for the degree of full-thickness cartilage loss, or cartilage loss fraction. Univariate conditional logistic regression analysis was performed for differences in cartilage loss fractions between groups. Receiver operating characteristic (ROC) curve analysis was performed to assess the association of MRI biomarkers and knee arthroplasty during the eight-year follow-up. Results The medial femoral condyle, medial tibial plateau, total, and two-year progression cartilage loss fractions were significantly higher in participants with K-L grade >1 (p < 0.01 for all) and showed high area under the curve (AUC) values on ROC analysis (812, 0.827, 0.917, and 0.933, respectively). These results were comparable or more strongly associated with other OA grading schemes. Conclusion MRI biomarker cartilage loss fractions are significantly higher in subjects with K-L grade >1 and show a strong association with arthroplasty. After further validation, cartilage loss fracture may be used to predict future arthroplasty.

Intra-articular and intraosseous approach to temporomandibular joint-targeted injections: a cadaveric investigation.

PURPOSE: Temporomandibular joint osteoarthritis (TMJ-OA) management is complex, and several conservative and minimally invasive protocols have been proposed. Intra-articular injections of medications directed at OA have been performed, but in some cases, these medications do not directly contact the tissue lesion sites. Here, we propose a new real-time ultrasound-guided technique to inject medications directly into the subchondral bone. METHODS: Ultrasound image screening was carried out with the point-of-care Clarius L15 device. Then, with the patient's mouth closed, a stainless-steel cannula with a concentric trocar was US-guided using an in-plane approach until the perforating tip of the internal trocar touched the lateral pole of the mandibular condyle. Then, the trocar was inserted through the medullary bone, where a posterior injection was made. RESULTS: The technique's precision was confirmed by capturing an iodine contrast solution that imaged the medullary condyle of fresh anatomical specimens processed by computed tomography. CONCLUSION: The proposed technique was effective in accessing the mandibular condyle subchondral bone in the inferior TMJ space for the simultaneously intra-articular (IA) and intra-osseous (IO) in-plane US-guided injections. Thus, its implementation may represent an important advance in early TMJ-OA treatment. This may be a promising approach, especially in OA cases in which the cortical bone is still preserved.

Histological and Histopathological Features of the Third Metacarpal/Tarsal Parasagittal Groove and Proximal Phalanx Sagittal Groove in Thoroughbred Horses with Racing History.

Information regarding the histopathology of the proximal phalanx (P1) sagittal groove in racehorses is limited. Twenty-nine cadaver limbs from nine Thoroughbred racehorses in racing/race-training underwent histological examination. Histological specimens of the third metacarpal/metatarsal (MC3/MT3) parasagittal grooves and P1 sagittal grooves were graded for histopathological findings in hyaline cartilage (HC), calcified cartilage (CC), and subchondral plate and trabecular bone (SCB/TB) regions. Histopathological grades were compared between (1) fissure and non-fissure locations observed in a previous study and (2) dorsal, middle, and palmar/plantar aspects. (1) HC, CC, and SCB/TB grades were more severe in fissure than non-fissure locations in the MC3/MT3 parasagittal groove (p < 0.001). SCB/TB grades were more severe in fissure than non-fissure locations in the P1 sagittal groove (p < 0.001). (2) HC, CC, and SCB/TB grades including SCB collapse were more severe in the palmar/plantar than the middle aspect of the MC3/MT3 parasagittal groove (p < 0.001). SCB/TB grades including SCB collapse were more severe in the dorsal and middle than the palmar/plantar aspect of the P1 sagittal groove (p < 0.001). Histopathology in the SCB/TB region including bone fatigue injury was related to fissure locations, the palmar/plantar MC3/MT3 parasagittal groove, and the dorsal P1 sagittal groove.