Functional Duality of Chondrocyte Hypertrophy and Biomedical Application Trends in Osteoarthritis

Bibliometric analysis of research trends and emerging insights of osteoarthritis and chondrocyte hypertrophy

Background

This study aims to systematically analyze the intersection of OA and chondrocyte hypertrophy using bibliometric methods, providing an quantitative and comprehensive overview of the current research status and emerging trends in this field.

Methods

Relevant publications were retrieved from the Web of Science Core Collection database using the search query TS = ("chondrocyte* hypertroph*" OR "hypertrophic chondrocyte*" OR "cartilage hypertroph*") AND ("osteoarthriti*" OR "OA" OR "degenerative arthritis"). Several bibliometric tools, including Vosviewer, CiteSpace, the R package (bibliometrix), and Excel 2021, were utilized to systematically analyze the publications on the intersection of chondrocyte hypertrophy and OA.

Results

A total of 639 publications, published between 1995 and 2025, were identified. The findings indicate a steady global increase in research on OA and chondrocyte hypertrophy, with an increasing number of studies being published in high-impact journals, suggesting a promising developmental trajectory. China and the United States are leading in this field. OSTEOARTHRITIS AND CARTILAGE is identified as the core journal in this area, while ANNALS OF THE RHEUMATIC DISEASES has the highest impact factor among the top publishing journals. Keyword analysis reveals that research hotspots primarily focus on stem cells, tissue engineering, cartilage repair, inflammation, oxidative stress, autophagy, apoptosis, senescence, and related bioactive factors.

Conclusion

This study elucidates the current research status and trends at the intersection of OA and chondrocyte hypertrophy, providing crucial references for future research. Future studies should continue to focus on these potential therapeutic approaches, key phenotypes, and regulatory mechanisms, enhance international cooperation to develop more effective strategies and treatments for OA.

Single monoiodoacetic acid injection reveals toll-like receptor, oestrogen, oxidative stress, and altered energy metabolism as key drivers of temporomandibular joint osteoarthritis in female rats

OBJECTIVES

This study aimed to establish a reproducible and minimally invasive rat model of temporomandibular joint osteoarthritis (TMJ-OA) using intra-articular monoiodoacetic acid (MIA) injection, and to investigate the pathological mechanisms underlying TMJ-OA development, aimed at providing insights for potential clinical treatments.

DESIGN

We compared the effects of single versus multiple MIA injections on body weight, pain behaviour, and condylar pathology in female Sprague-Dawley rats. We longitudinally assessed the progression of TMJ-OA over 5 weeks by evaluating condylar pathology and immunohistochemical staining. We investigated the potential mechanism of MIA-induced TMJ-OA through transcriptome sequencing and polymerase chain reaction validation.

RESULTS

A single MIA injection (0.5 mg) into the joint space effectively induced TMJ-OA in rats and sustained inflammatory reactions and pain without significantly affecting weight. MIA continuously promoted the development of TMJ-OA through the activation of the toll-like receptor pathway, oestrogen metabolism promotion, oxidative stress response enhancement, and energy metabolism alteration in condylar chondrocytes.

CONCLUSION

We have presented a simple and minimally invasive method for modelling TMJ-OA in rats, which can be utilised in animal trials focusing on TMJ-OA treatment strategies. The study also reveals toll-like receptor, oestrogen, oxidative stress, and altered energy metabolism as key drivers of TMJ-OA in female rats.

The potential molecular markers of inflammatory response in KOA with AD based on single-cell transcriptome sequencing analysis and identification of ligands by virtual screening

Alzheimer's disease (AD) and osteoarthritis (OA) are both senile degenerative diseases. Clinical studies have found that OA patients have a significantly increased risk of AD in their later life. This study hypothesized that chronic aseptic inflammation might lead to AD in KOA patients. However, current research has not yet clarified the potential mechanism between AD and KOA. Therefore, this study intends to use KOA transcriptional profiling and single-cell sequencing analysis technology to explore the molecular mechanism of KOA affecting AD development, and screen potential molecular biomarkers and drugs for the prediction, diagnosis, and prognosis of AD in KOA patients. It was found that the higher the expression of TXNIP, MMP3, and MMP13, the higher the risk coefficient of AD was. In addition, the AUC of TXNIP, MMP3, and MMP13 were all greater than 0.70, which had good diagnostic significance for AD. Finally, through the virtual screening of core proteins in FDA drugs and molecular dynamics simulation, it was found that compound Cobicistat could be targeted to TXNIP, Itc could be targeted to MMP3, and Isavuconazonium could be targeted to MMP13. To sum up, TXNIP, MMP3, and MMP13 are prospective molecular markers in KOA with AD, which could be used to predict, diagnose, and prognosis.

Morphology of the sternoclavicular joint and its microanatomical changes in response to osteoarthritic degeneration

Although the sternoclavicular joint shares structural similarities with the knee and hip joints as a diarthrodial joint, its biomechanics differ significantly due to its non-weight-bearing nature. Nevertheless, it is subject to considerable loading, leading to increased susceptibility to osteoarthritis, a prevalent condition characterized by the degeneration of the joint's articular surfaces and fibrocartilaginous intra-articular disc. The osteoarthritic degeneration of the fibrocartilaginous and cartilaginous surfaces of the sternoclavicular joint has been investigated, considering multiple factors. These include cell count, collagen alignment, surface fibrillation, cyst formation, and glycosaminoglycan content, with the findings deemed significant. However, current treatments for osteoarthritis of the sternoclavicular joint tend to focus on symptom management rather than active prevention of disease progression. Therefore, a detailed understanding of the anatomy, biomechanics, and morphological changes of the sternoclavicular joint during all stages of the osteoarthritic disease is essential for effective management to allow for maximum patient outcomes. This review explores the current literature on the anatomy of the sternoclavicular joint, starting with its structure and comparison to surrounding joints, biomechanics, and morphology, before considering the microanatomical changes that occur due to osteoarthritic degeneration. Early identification of osteoarthritic changes within this joint can enhance treatment and management outcomes before advancing joint degeneration, improving the quality of life for those affected.

Ferroptosis in Osteoarthritis: Current Understanding

Osteoarthritis (OA) is a prevalent degenerative disease in elderly people that is characterized by cartilage loss and abrasion, leading to joint pain and dysfunction. The aetiology of OA is complicated and includes abnormal mechanical stress, a mild inflammatory environment, chondrocyte senescence and apoptosis, and changes in chondrocyte metabolism. Ferroptosis is a regulated cell death modality characterized by the excessive accumulation of lipid peroxidation and mitochondrial dysfunction. The role of ferroptosis in OA pathogenesis has aroused researchers' attention in the past two years, and there is mounting evidence indicating that ferroptosis is destructive. However, the impact of ferroptosis on OA and how the regulators of ferroptosis affect OA development are unclear. Here, we reviewed the current understanding of ferroptosis in OA pathogenesis and summarized several drugs and compounds targeting ferroptosis in OA treatment. The accumulation of intracellular iron, the trigger of Fenton reaction, the excessive production of ROS, the peroxidation of PUFA-PLs, and mitochondrial and membrane damage are involved in chondrocyte ferroptosis. System Xc - and GPX4 are the most important regulators that control ferroptosis. Several compounds, such as DFO and Fer-1, have been proven effective in preventing ferroptosis and slowing OA progression on animal models. Collectively, targeting ferroptosis shows great potential in treating OA.

Knee osteoarthritis: disease burden, available treatments, and emerging options

Osteoarthritis (OA) is a prevalent condition that affects nearly 528 million people worldwide, including 23% of the global population aged ⩾40, and is characterized by progressive damage to articular cartilage, which often leads to substantial pain, stiffness, and reduced mobility for affected patients. Pain related to OA is a barrier to maintaining physical activity and a leading cause of disability, accounting for 2.4% of all years lived with disability globally, reducing the ability to work in 66% of US patients with OA and increasing absenteeism in 21% of US patients with OA. The joint most commonly involved in OA is the knee, which is affected in about 60%-85% of all OA cases. The aging population and longer life expectancy, coupled with earlier and younger diagnoses, translate into a growing cohort of symptomatic patients in need of alternatives to surgery. Despite the large number of patients with knee OA (OAK) worldwide, the high degree of variability in patient presentation can lead to challenges in diagnosis and treatment. Multiple society guidelines recommend therapies for OAK, but departures from guidelines by healthcare professionals in clinical settings reflect a discordance between evidence-based treatment algorithms and routine clinical practice. Furthermore, disease-modifying pharmacotherapies are limited, and treatment for OAK often focuses solely on symptom relief, rather than underlying causes. In this narrative review, we summarize the patient journey, analyze current disease burden and nonsurgical therapy recommendations for OAK, and highlight emerging and promising therapies-such as cryoneurolysis, long-acting corticosteroids, and gene therapies-for this debilitating condition.

Exploring Osteoarthritis Dynamics: Patient-Specific Cartilage Samples in an Organ-on-a-Chip Model

OBJECTIVE

This study aims to tackle the existing challenges associated with the prediction and optimization of pharmaceutical interventions for osteoarthritis (OA). The primary objective is to develop an innovative tool that provides objective and patient-specific information regarding the most affected tissue in OA, articular cartilage.

DESIGN

We employed an organ-on-a-chip (OoC) approach to replicate the 3D structure of cartilage in an in vitro setup. The study focused on assessing the individual drug responses of common medications using this innovative platform. Additionally, we conducted a biomarker analysis to gain insights into the variability of drug responses across patients.

RESULTS

Our findings reveal that OA articular cartilage demonstrates an individualized response to pharmaceutical interventions. Despite the diverse nature of patient responses, our study indicates that Triamcinolone, a standard-of-care medication, consistently exhibits a robust anti-inflammatory response across patient tests. However, as seen in clinical studies, Triamcinolone was concurrently associated with degeneration. The biomarker analysis further underscores the importance of considering individual drug responses in developing effective treatment plans.

CONCLUSION

In conclusion, this study introduces a valuable tool that not only mimics the 3D structure of cartilage but also provides crucial insights into the individualized responses of patients to various OA treatments. The application of an OoC approach may allow for a more accurate assessment of treatment efficacy. This objective biomarker analysis on patient-specific tissue offers clinicians a means to tailor treatment plans, thereby minimizing joint damage and advancing toward a more personalized approach in OA management.

Two Members of Vitamin-K-Dependent Proteins, Gla-Rich Protein (GRP) and Matrix Gla Protein (MGP), as Possible New Players in the Molecular Mechanism of Osteoarthritis

Objectives: The pathophysiology of osteoarthritis is mainly unknown. Matrix Gla protein (MGP) and Gla-rich protein (GRP) are both vitamin-K-dependent mineralization inhibitors. In this study, we aimed to compare the levels of MGP and GRP in the synovial fluid of osteoarthritic (OA) and non-osteoarthritic (non-OA) knee joints. Materials and Methods: Two groups were formed, with one consisting of patients with OA and the other non-OA, serving as a control group. The non-OA group included individuals who had arthroscopic surgery for non-cartilage-related issues. In the OA group, all participants had undergone total knee arthroplasty because of grade 4 primary degenerative osteoarthritis. During the operation, at least 1 mL of knee synovial fluid was collected. The GRP and MGP levels in the synovial fluid were measured using an ELISA kit. Results: The mean age in the OA group (62.03 ± 11.53 years) was significantly higher than that in the non-OA group (47.70 ± 14.49 years; p = 0.0001). GRP levels were significantly higher in the OA group (419.61 ± 70.14 ng/mL) compared to the non-OA group (382.18 ± 62.34 ng/mL; p = 0.037). MGP levels were significantly higher in the OA group (67.76 ± 11.36 ng/mL) compared to the non-OA group (53.49 ± 18.28 ng/mL; p = 0.001). Calcium levels (Ca++) were also significantly higher in the OA group (12.89 ± 3.43 mg/dL) compared to the non-OA group (9.51 ± 2.15 mg/dL; p = 0.0001). There was a significantly positive correlation between MGP levels and age (p = 0.011, R = +0.335). Linear regression analysis was performed to determine the effect of age on MGP levels (p = 0.011, R-Square = 0.112). The dependent variable in this analysis was MGP (ng/mL), and age was the predictor. Conclusions: In conclusion, both GRP and MGP are potentially usable biomarkers in osteoarthritis. However, GRP seems to be more valuable because it is not associated with age. In the future, both proteins could provide important contributions to the diagnosis and treatment of osteoarthritis.

The Increasing Diagnostic Role of Exosomes in Inflammatory Diseases to Leverage the Therapeutic Biomarkers

Inflammatory diseases provide substantial worldwide concerns, affecting millions of people and healthcare systems by causing ongoing discomfort, diminished quality of life, and increased expenses. In light of the progress made in treatments, the limited effectiveness and negative side effects of present pharmaceuticals need a more comprehensive comprehension of the underlying processes in order to develop more precise remedies. Exosomes, which are tiny vesicles that play a vital role in cell communication, have been identified as prospective vehicles for effective delivery of anti-inflammatory medicines, immunomodulators, and gene treatments. Vesicles, which are secreted by different cells, have a crucial function in communicating between cells. This makes them valuable in the fields of diagnostics and therapies, particularly for inflammatory conditions. Exosomes have a role in regulating the immune system, transporting cytokines, and influencing cell signaling pathways associated with inflammation. They consist of proteins, lipids, and genetic information that have an impact on immune responses and inflammation. Scientists are now investigating exosomes as biomarkers for inflammatory disease. This review article aims to develop non-invasive diagnostic techniques with improved sensitivity and specificity. Purpose of this review is a thorough examination of exosomes in pharmacology, specifically emphasizing their origin, contents, and functions, with the objective of enhancing diagnostic and therapeutic strategies for inflammatory conditions. Gaining a comprehensive understanding of the intricate mechanisms involved in exosome-mediated interactions and their impact on immune responses is of utmost importance in order to devise novel approaches for tackling inflammatory disease and enhancing patient care.

TMF suppresses chondrocyte hypertrophy in osteoarthritic cartilage by mediating the FOXO3a/BMPER pathway

Osteoarthritis (OA) is a disease of the joints, characterized by chronic inflammation, cartilage destruction and extracellular matrix (ECM) remodeling. Aberrant chondrocyte hypertrophy promotes cartilage destruction and OA development. Collagen X, the biomarker of chondrocyte hypertrophy, is upregulated by runt-related transcription factor 2 (Runx2), which is mediated by the bone morphogenetic protein 4 (BMP4)/Smad1 signaling pathway. BMP binding endothelial regulator (BMPER), a secreted glycoprotein, acts as an agonist of BMP4. 5,7,3',4'-tetramethoxyflavone (TMF) is a natural flavonoid derived from Murraya exotica L. Results of our previous study demonstrated that TMF exhibits chondroprotective effects against OA development through the activation of Forkhead box protein O3a (FOXO3a) expression. However, whether TMF suppresses chondrocyte hypertrophy through activation of FOXO3a expression and inhibition of BMPER/BMP4/Smad1 signaling remains unknown. Results of the present study revealed that TMF inhibited collagen X and Runx2 expression, inhibited BMPER/BMP4/Smad1 signaling, and activated FOXO3a expression; thus, protecting against chondrocyte hypertrophy and OA development. However, BMPER overexpression and FOXO3a knockdown impacted the protective effects of TMF. Thus, TMF inhibited chondrocyte hypertrophy in OA cartilage through mediating the FOXO3a/BMPER signaling pathway.

Modulation of Canine Adipose-Derived Mesenchymal Stem/Medicinal Signalling Cells with Ascorbic Acid: Effect on Proliferation and Chondrogenic Differentiation on Standard Plastic and Silk Fibroin Surfaces

Ascorbic acid (AA) plays a crucial role in both the proliferation and chondrogenic differentiation potential of mesenchymal stem/medicinal signalling cells (MSCs); these are both key aspects of their general therapeutic use and their increasing use in veterinary medicine. Current immunomodulatory therapies require efficient expansion of MSCs in the laboratory, while emerging tissue regeneration strategies, such as cartilage or bone repair, aim to use differentiated MSCs and modulate the expression of chondrogenic and hypertrophic markers. Our aim was to investigate whether the addition of AA to the growth medium enhances the proliferation of canine adipose-derived MSCs (cAMSCs) grown on standard plastic surfaces and whether it affects chondrogenic differentiation potential on silk fibroin (SF) films. We assessed cell viability with trypan blue and proliferation potential by calculating population doubling. Chondrogenic induction on SF films was assessed by Alcian blue staining and gene expression analysis of chondrogenic and hypertrophic genes. The results showed that growth medium with AA significantly enhanced the proliferation of cAMSCs without affecting cell viability and modulated the expression of chondrogenic and hypertrophic genes of cAMSCs grown on SF films. Our results suggest that AA may be used in growth medium for expansion of cAMSCs and, at the same time, provide the basis for future studies to investigate the role of AA and SF in chondrogenic differentiation of MSCs.

Spatiotemporal Modulated Scaffold for Endogenous Bone Regeneration via Harnessing Sequentially Released Guiding Signals

The design of a scaffold that can regulate the sequential differentiation of bone marrow mesenchymal stromal cells (BMSCs) according to the endochondral ossification (ECO) mechanism is highly desirable for effective bone regeneration. In this study, we successfully fabricated a dual-networked composite hydrogel composed of gelatin and hyaluronic acid (termed GCDH-M), which can sequentially release chondroitin sulfate (CS) and magnesium/silicon (Mg/Si) ions to provide spatiotemporal guidance for chondrogenesis, angiogenesis, and osteogenesis. The fast release of CS is from the GCDH hydrogel, and the sustained releases of Mg/Si ions are from poly(lactide-co-glycolide) microspheres embedded in the hydrogel. There is a difference in the release rates between CS and ions, resulting in the ability for the fast release of CS and sustained release of ions. The dual networks between the modified gelatin and hyaluronic acid via covalent bonding and host-guest interactions render the hydrogel with some dynamic feature to meet the differentiation development of BMSCs laden inside the hydrogel, i.e., transforming into a chondrogenic phenotype, further to a hypertrophic phenotype and eventually to an osteogenic phenotype. As evidenced by the results of in vitro and in vivo evaluations, this GCDH-M composite hydrogel was proved to be able to create an optimal microenvironment for embedded BMSCs responding to the sequential guiding signals, which aligns with the rhythm of the ECO process and ultimately boosts bone regeneration. The promising outcome achieved with this innovative hydrogel system sheds light on novel scaffold design targeting bone tissue engineering.

Hypertrophic chondrocytes at the junction of musculoskeletal structures

Hypertrophic chondrocytes are found at unique locations at the junction of skeletal tissues, cartilage growth plate, articular cartilage, enthesis and intervertebral discs. Their role in the skeleton is best understood in the process of endochondral ossification in development and bone fracture healing. Chondrocyte hypertrophy occurs in degenerative conditions such as osteoarthritis. Thus, the role of hypertrophic chondrocytes in skeletal biology and pathology is context dependent. This review will focus on hypertrophic chondrocytes in endochondral ossification, in which they exist in a transient state, but acting as a central regulator of differentiation, mineralization, vascularization and conversion to bone. The amazing journey of a chondrocyte from being entrapped in the extracellular matrix environment to becoming proliferative then hypertrophic will be discussed. Recent studies on the dynamic changes and plasticity of hypertrophic chondrocytes have provided new insights into how we view these cells, not as terminally differentiated but as cells that can dedifferentiate to more progenitor-like cells in a transition to osteoblasts and adipocytes, as well as a source of skeletal stem and progenitor cells residing in the bone marrow. This will provide a foundation for studies of hypertrophic chondrocytes at other skeletal sites in development, tissue maintenance, pathology and therapy.

Separating friend from foe: Inhibition of TGF-β-induced detrimental SMAD1/5/9 phosphorylation while maintaining protective SMAD2/3 signaling in OA chondrocytes

OBJECTIVE

Transforming growth factor-β (TGF-β) signaling via SMAD2/3 is crucial to control cartilage homeostasis. However, TGF-β can also have detrimental effects by signaling via SMAD1/5/9 and thereby contribute to diseases like osteoarthritis (OA). In this study, we aimed to block TGF-β-induced SMAD1/5/9 signaling in primary human OA chondrocytes, while maintaining functional SMAD2/3 signaling.

DESIGN

Human OA chondrocytes were pre-incubated with different concentrations of ALK4/5/7 kinase inhibitor SB-505124 before stimulation with TGF-β. Changes in SMAD C-terminal phosphorylation were analyzed using Western blot and response genes were measured with quantitative Polymerase Chain Reaction. To further explore the consequences of our ability to separate pathways, we investigated TGF-β-induced chondrocyte hypertrophy.

RESULTS

Pre-incubation with 0.5 µM SB-505124, maintained ±50% of C-terminal SMAD2/3 phosphorylation and induction of JUNB and SERPINE1, but blocked SMAD1/5/9-C phosphorylation and expression of ID1 and ID3. Furthermore, TGF-β, in levels comparable to those in the synovial fluid of OA patients, resulted in regulation of hypertrophic and dedifferentiation markers in OA chondrocytes; i.e. an increase in COL10, RUNX2, COL1A1, and VEGF and a decrease in ACAN expression. Interestingly, in a subgroup of OA chondrocyte donors, blocking only SMAD1/5/9 caused stronger inhibition on TGF-β-induced RUNX2 than blocking both SMAD pathways.

CONCLUSION

Our findings indicate that using low dose of SB-505124 we maintained functional SMAD2/3 signaling that blocks RUNX2 expression in a subgroup of OA patients. We are the first to show that SMAD2/3 and SMAD1/5/9 pathways can be separately modulated using low and high doses of SB-505124 and thereby split TGF-β's detrimental from protective function in chondrocytes.

Platelet-derived biomaterial with hyaluronic acid alleviates temporal-mandibular joint osteoarthritis: clinical trial from dish to human

BACKGROUND

Bioactive materials have now raised considerable attention for the treatment of osteoarthritis (OA), such as knee OA, rheumatoid OA, and temporomandibular joint (TMJ) OA. TMJ-OA is a common disease associated with an imbalance of cartilage regeneration, tissue inflammation, and disability in mouth movement. Recently, biological materials or molecules have been developed for TMJ-OA therapy; however, ideal treatment is still lacking. In this study, we used the combination of a human platelet rich plasma with hyaluronic acid (hPRP/HA) for TMJ-OA therapy to perform a clinical trial in dish to humans.

METHOD

Herein, hPRP was prepared, and the hPRP/HA combined concentration was optimized by MTT assay. For the clinical trial in dish, pro-inflammatory-induced in-vitro and in-vivo mimic 3D TMJ-OA models were created, and proliferation, gene expression, alcian blue staining, and IHC were used to evaluate chondrocyte regeneration. For the animal studies, complete Freund's adjuvant (CFA) was used to induce the TMJ-OA rat model, and condyle and disc regeneration were investigated through MRI. For the clinical trial in humans, 12 patients with TMJ-OA who had disc displacement and pain were enrolled. The disc displacement and pain at baseline and six months were measured by MRI, and clinical assessment, respectively.

RESULTS

Combined hPRP/HA treatment ameliorated the proinflammatory-induced TMJ-OA model and promoted chondrocyte proliferation by activating SOX9, collagen type I/II, and aggrecan. TMJ-OA pathology-related inflammatory factors were efficiently downregulated with hPRP/HA treatment. Moreover, condylar cartilage was regenerated by hPRP/HA treatment in a proinflammatory-induced 3D neocartilage TMJ-OA-like model. During the animal studies, hPRP/HA treatment strongly repaired the condyle and disc in a CFA-induced TMJ-OA rat model. Furthermore, we performed a clinical trial in humans, and the MRI data demonstrated that after 6 months of treatment, hPRP/HA regenerated the condylar cartilage, reduced disc displacement, alleviated pain, and increased the maximum mouth opening (MMO). Overall, clinical trials in dish to human results revealed that hPRP/HA promoted cartilage regeneration, inhibited inflammation, reduced pain, and increased joint function in TMJ-OA.

CONCLUSION

Conclusively, this study highlighted the therapeutic potential of the hPRP and HA combination for TMJ-OA therapy, with detailed evidence from bench to bedside. Trial registration Taipei Medical University Hospital (TMU-JIRB No. N201711041). Registered 24 November 2017. https://tmujcrc.tmu.edu.tw/inquiry_general.php .

Suppressing Chondrocyte Hypertrophy to Build Better Cartilage

Current clinical strategies for restoring cartilage defects do not adequately consider taking the necessary steps to prevent the formation of hypertrophic tissue at injury sites. Chondrocyte hypertrophy inevitably causes both macroscopic and microscopic level changes in cartilage, resulting in adverse long-term outcomes following attempted restoration. Repairing/restoring articular cartilage while minimizing the risk of hypertrophic neo tissue formation represents an unmet clinical challenge. Previous investigations have extensively identified and characterized the biological mechanisms that regulate cartilage hypertrophy with preclinical studies now beginning to leverage this knowledge to help build better cartilage. In this comprehensive article, we will provide a summary of these biological mechanisms and systematically review the most cutting-edge strategies for circumventing this pathological hallmark of osteoarthritis.

Spatial Lipidomic Profiling of Mouse Joint Tissue Demonstrates the Essential Role of PHOSPHO1 in Growth Plate Homeostasis

Lipids play a crucial role in signaling and metabolism, regulating the development and maintenance of the skeleton. Membrane lipids have been hypothesized to act as intermediates upstream of orphan phosphatase 1 (PHOSPHO1), a major contributor to phosphate generation required for bone mineralization. Here, we spatially resolve the lipid atlas of the healthy mouse knee and demonstrate the effects of PHOSPHO1 ablation on the growth plate lipidome. Lipids spanning 17 subclasses were mapped across the knee joints of healthy juvenile and adult mice using matrix-assisted laser desorption ionization imaging mass spectrometry (MALDI-IMS), with annotation supported by shotgun lipidomics. Multivariate analysis identified 96 and 80 lipid ions with differential abundances across joint tissues in juvenile and adult mice, respectively. In both ages, marrow was enriched in phospholipid platelet activating factors (PAFs) and related metabolites, cortical bone had a low lipid content, whereas lysophospholipids were strikingly enriched in the growth plate, an active site of mineralization and PHOSPHO1 activity. Spatially-resolved profiling of PHOSPHO1-knockout (KO) mice across the resting, proliferating, and hypertrophic growth plate zones revealed 272, 306, and 296 significantly upregulated, and 155, 220, and 190 significantly downregulated features, respectively, relative to wild-type (WT) controls. Of note, phosphatidylcholine, lysophosphatidylcholine, sphingomyelin, lysophosphatidylethanolamine, and phosphatidylethanolamine derived lipid ions were upregulated in PHOSPHO1-KO versus WT. Our imaging pipeline has established a spatially-resolved lipid signature of joint tissues and has demonstrated that PHOSPHO1 ablation significantly alters the growth plate lipidome, highlighting an essential role of the PHOSPHO1-mediated membrane phospholipid metabolism in lipid and bone homeostasis. © 2023 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).

Enhanced osteoarthritis therapy by nanoengineered mesenchymal stem cells using biomimetic CuS nanoparticles loaded with plasmid DNA encoding TGF-β1

Mesenchymal stem cells (MSCs) therapy shows the potential benefits to relieve clinical symptoms of osteoarthritis (OA), but it is uncertain if it can repair articular cartilage lesions — the main pathology of OA. Here, we prepared biomimetic cupper sulfide@phosphatidylcholine (CuS@PC) nanoparticles (NPs) loaded with plasmid DNA (pDNA) encoding transforming growth factor-beta 1 (TGF-β1) to engineer MSCs for enhanced OA therapy via cartilage regeneration. We found that the NPs not only promoted cell proliferation and migration, but also presented a higher pDNA transfection efficiency relative to commercial transfection reagent lipofectamine 3000. The resultant CuS/TGF-β1@PC NP-engineered MSCs (termed CTP-MSCs) were better than pure MSCs in terms of chondrogenic gene expression, glycosaminoglycan deposition and type II collagen formation, favoring cartilage repair. Further, CTP-MSCs inhibited extracellular matrix degradation in interleukin-1β-induced chondrocytes. Consequently, intraarticular administration of CTP-MSCs significantly enhanced the repair of damaged cartilage, whereas pure MSCs exhibited very limited effects on cartilage regeneration in destabilization of the medial meniscus (DMM) surgical instability mice. Hence, this work provides a new strategy to overcome the limitation of current stem cell therapy in OA treatment through developing more effective nanoengineered MSCs.

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Biomimetic CuS nanoparticles (NPs) loaded with TGF-β1 pDNA are prepared for nanoengineering of MSCs.

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CuS/TGF-β1@PC NPs are more efficient than commercial transfection agent in terms of pDNA transfection.

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The NP-engineered CTP-MSCs exhibit enhanced migration, chondrogenesis and inhibition of ECM degradation.

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CTP-MSCs effectively treat osteoarthritis (OA) mice models via cartilage regeneration.

Chondrocyte Hypertrophy in Osteoarthritis: Mechanistic Studies and Models for the Identification of New Therapeutic Strategies

Articular cartilage shows limited self-healing ability owing to its low cellularity and avascularity. Untreated cartilage defects display an increased propensity to degenerate, leading to osteoarthritis (OA). During OA progression, articular chondrocytes are subjected to significant alterations in gene expression and phenotype, including a shift towards a hypertrophic-like state (with the expression of collagen type X, matrix metalloproteinases-13, and alkaline phosphatase) analogous to what eventuates during endochondral ossification. Present OA management strategies focus, however, exclusively on cartilage inflammation and degradation. A better understanding of the hypertrophic chondrocyte phenotype in OA might give new insights into its pathogenesis, suggesting potential disease-modifying therapeutic approaches. Recent developments in the field of cellular/molecular biology and tissue engineering proceeded in the direction of contrasting the onset of this hypertrophic phenotype, but knowledge gaps in the cause-effect of these processes are still present. In this review we will highlight the possible advantages and drawbacks of using this approach as a therapeutic strategy while focusing on the experimental models necessary for a better understanding of the phenomenon. Specifically, we will discuss in brief the cellular signaling pathways associated with the onset of a hypertrophic phenotype in chondrocytes during the progression of OA and will analyze in depth the advantages and disadvantages of various models that have been used to mimic it. Afterwards, we will present the strategies developed and proposed to impede chondrocyte hypertrophy and cartilage matrix mineralization/calcification. Finally, we will examine the future perspectives of OA therapeutic strategies.

Potential of Using Infrapatellar–Fat–Pad–Derived Mesenchymal Stem Cells for Therapy in Degenerative Arthritis: Chondrogenesis, Exosomes, and Transcription Regulation

Infrapatellar fat pad–derived mesenchymal stem cells (IPFP-MSCs) are a type of adipose-derived stem cell (ADSC). They potentially contribute to cartilage regeneration and modulation of the immune microenvironment in patients with osteoarthritis (OA). The ability of IPFP-MSCs to increase chondrogenic capacity has been reported to be greater, less age dependent, and less affected by inflammatory changes than that of other MSCs. Transcription-regulatory factors strictly regulate the cartilage differentiation of MSCs. However, few studies have explored the effect of transcriptional factors on IPFP-MSC-based neocartilage formation, cartilage engineering, and tissue functionality during and after chondrogenesis. Instead of intact MSCs, MSC-derived extracellular vesicles could be used for the treatment of OA. Furthermore, exosomes are increasingly being considered the principal therapeutic agent in MSC secretions that is responsible for the regenerative and immunomodulatory functions of MSCs in cartilage repair. The present study provides an overview of advancements in enhancement strategies for IPFP-MSC chondrogenic differentiation, including the effects of transcriptional factors, the modulation of released exosomes, delivery mechanisms for MSCs, and ethical and regulatory points concerning the development of MSC products. This review will contribute to the understanding of the IPFP-MSC chondrogenic differentiation process and enable the improvement of IPFP-MSC-based cartilage tissue engineering.

Chloride Channel and Inflammation-Mediated Pathogenesis of Osteoarthritis

Articular cartilage allows the human body to buffer and absorb stress during normal exercise. It is mainly composed of cartilage cells and the extracellular matrix and is surrounded by the extracellular microenvironment formed by synovial fluid and various factors in it. Studies have shown that chondrocytes are the metabolic center of articular cartilage. Under physiological conditions, the extracellular matrix is in a dynamic balance of anabolism and catabolism, and various factors and physical and chemical conditions in the extracellular microenvironment are also in a steady state. This homeostasis depends on the normal function of proteins represented by various ion channels on chondrocytes. In mammalian chondrocyte species, ion channels are mainly divided into two categories: cation channels and anion channels. Anion channels such as chloride channels have become hot research topics in recent years. These channels play an extremely important role in various physiological processes. Recently, a growing body of evidence has shown that many pathological processes, abnormal concentration of mechanical stress and chloride channel dysfunction in articular cartilage lead to microenvironment disorders, matrix and bone metabolism imbalances, which cause partial aseptic inflammation. These pathological processes initiate extracellular matrix degradation, abnormal chondrocyte death, hyperplasia of inflammatory synovium and bony. Osteoarthritis (OA) is a common clinical disease in orthopedics. Its typical manifestations are joint inflammation and pain caused by articular cartilage degeneration, but its pathogenesis has not been fully elucidated. Focusing on the physiological functions and pathological changes of chloride channels and pathophysiology of aseptic inflammation furthers the understanding of OA pathogenesis and provides possible targets for subsequent medication development.

Therapeutic potential of epiphyseal growth plate cells for bone regeneration in an osteoporosis model

Bone growth occurs in the epiphyseal growth plate (EGP) and epiphyseal growth plate cells (EGPCs) exist in EGP. EGPCs, including skeletal stem cells (SSCs), are cells that induce bone growth and development through endochondral ossification. Recently, the superiority of bone regeneration through endochondral ossification has been reported. Our study compared EGPCs with bone marrow-derived mesenchymal stem cells (BM-MSCs) and suggested the therapeutic potential of new bone regeneration. In this study, we analyzed the characteristics between EGPCs and BM-MSCs based on morphological characteristics and molecular profiles. EGPCs expressed chondrogenic and osteogenic markers higher than BM-MSCs. Additionally, in co-culture with BM-MSCs, EGPCs induced an increase in chondrogenic, osteogenic, and hypertrophic markers of BM-MSCs. Finally, EGPCs induced higher bone regeneration than BM-MSCs in the osteoporosis model. Overall, we suggest the possibility of EGPCs as cell therapy for effective bone regeneration.

In Vitro Study of Licorice on IL-1β-Induced Chondrocytes and In Silico Approach for Osteoarthritis

Osteoarthritis (OA) is a common degenerative joint disorder that affects joint function, mobility, and pain. The release of proinflammatory cytokines stimulates matrix metalloproteinases (MMPs) and aggrecanase production which further induces articular cartilage degradation. Hypertrophy-like changes in chondrocytes are considered to be an important feature of OA pathogenesis. A Glycyrrhiza new variety, Wongam (WG), was developed by the Korea Rural Development Administration to enhance the cultivation and quality of Glycyrrhizae Radix et Rhizoma (licorice). This study examined the regulatory effect of WG against hypertrophy-like changes such as RUNX2, Collagen X, VEGFA, MMP-13 induction, and Collagen II reduction induced by IL-1β in SW1353 human chondrocytes. Additionally, in silico methods were performed to identify active compounds in licorice to target chondrocyte hypertrophy-related proteins. WG showed inhibitory effects against IL-1β-induced chondrocyte hypertrophy by regulating both HDAC4 activation via the PTH1R/PKA/PP2A pathway and the SOX9/β-catenin signaling pathway. In silico analysis demonstrated that 21 active compounds from licorice have binding potential with 11 targets related to chondrocyte hypertrophy. Further molecular docking analysis and in vivo studies elicited four compounds. Based on HPLC, isoliquiritigenin and its precursors were identified and quantified. Taken together, WG is a potential therapeutic agent for chondrocyte hypertrophy-like changes in OA.