Structure and function of aggrecan

Characterization of a chemically induced osteoarthritis model in zebrafish

Osteoarthritis (OA) is characterized by the progressive degeneration of the synovial joint, leading to irreversible damage to articular cartilage and subchondral bone. While animal models have advanced our understanding of OA, numerous unresolved issues still remain. The zebrafish, known for its transparent body, rapid developmental, and impressive regenerative capabilities, offers substantial potential for osteoarthritis research. This study seeks to establish a new OA model utilizing the zebrafish jaw joint, acting as a supplement to traditional animal models. In the future, this model could serve as a valuable platform for delving deeper into the mechanisms of this disease, as well as for advancing drug discovery and therapeutic interventions. Leveraging the skeletal structure of zebrafish, we targeted the largest jaw joint for our research. A custom fixation device was crafted, and a microinjection system was utilized to inject mono-iodoacetate (MIA) or collagenase type II (CTII) into the joint cavity of zebrafish. Subsequent analyses included histological staining, immunohistochemistry, OA research society international (OARSI) scoring, and real-time in vivo imaging were performed at 7, 14, and 28 days post injection. Our results effectively demonstrated the presence of synovial inflammation and cartilage damage within the zebrafish mandible, affirming the feasibility of inducing OA in zebrafish. In conclusion, the local injection of chemical agents into the joint cavity of zebrafish effectively induced the occurrence of OA. Establishing the zebrafish OA model enhances the array of animal models available for OA research. Moreover, zebrafish present distinct advantages, including robust regenerative abilities, genetic editing simplicity, and efficient drug screening. Consequently, this offers a fresh avenue for investigating the pathogenesis, prevention, and potential therapeutic approaches for human OA.

ROMP of Macromonomers Prepared by ROMP: Expanding Access to Complex, Functional Bottlebrush Polymers

Graft-through ring-opening metathesis polymerization (ROMP) of norbornene-terminated macromonomers (MMs) prepared using various polymerization methods has been extensively used for the synthesis of bottlebrush (co)polymers, yet the potential of ROMP for the synthesis of MMs that can subsequently be polymerized by graft-through ROMP to produce new bottlebrush compositions remains untapped. Here, we report an efficient "ROMP-of-ROMP" method that involves the synthesis of norbornene-terminated poly(norbornene imide) (PNI)-based MMs that, following ROMP, provide new families of bottlebrush (co)polymers and "brush-on-brush" hierarchical architectures. In the bulk state, the organization of the PNI pendants drives bottlebrush backbone extension to enable rapid assembly of asymmetric lamellar morphologies with large asymmetry factors. Overall, this work expands the scope of complex macromolecular architectures and provides insights into the interplay of backbone rigidity and self-assembly that will guide future nanolithography applications.

The myometrial transcriptome changes in mares with endometrosis

Mares with endometrosis exhibit histological changes not only in the endometrium but also in the myometrium that suggest possible functional impairment. The molecular background of these changes is not well understood. We hypothesize that the transcriptomic profile of the mare myometrium varies depending on the degree of endometrosis in mares. Myometria were collected from mares in the mid-luteal phase of the estrous cycle with endometrium categories I, IIA, IIB, and III (∑n = 23), according to Kenney and Doig´s histopathological classification. Myometrial RNA was isolated and subjected to RNA-seq analysis to identify differentially expressed transcriptionally active regions (deTARs) and their contribution to signaling pathways (KEGG database) and biological processes (GO terms). In results, 665, 491 and 499 deTARs were found in the myometrium of mares with endometrium IIA vs I, IIB vs I and III vs I, respectively. 200 common deTARs in the myometrium across all stages of endometrosis (IIA, IIB, and III) vs I were identified. Evaluated deTARs enriched several KEGG pathways including calcium signaling, cAMP signaling, oxytocin signaling, ECM-receptor interaction, and focal adhesion, and were classified into various GO terms including adaptive immune response, tissue homeostasis, muscle contractions, muscle development, and other. In conclusion, transcriptomic alterations in the myometrium of mares with endometrosis may indicate an impaired function of the contractile machinery, mechanisms regulating calcium influx and handling, as well as changes in ECM composition, leading to a decreased contractile activity and structural changes in the myometrium of affected mares.

Gene expression and immunohistochemistry analysis of ADAMTS-1 and its substrates in odontogenic keratocyst

BACKGROUND

Considering the significant participation of the microenvironment in the local aggressiveness of odontogenic keratocysts, this study aims to evaluate the expression of ADAMTS-1 and its substrates, versican, aggrecan and brevican in this locally invasive odontogenic cyst.

METHODS

Immunohistochemistry and polymerase chain reaction (PCR) were conducted on 30 cases of odontogenic keratocysts (OKCs) and 20 dental follicles (DFs).

RESULTS

The immunohistochemical expression of these proteins was predominantly cytoplasmic and granular across all samples. In epithelial tissue, the immunoexpression of aggrecan and versican was higher in OKC (p < 0.05) compared to DF. Comparing the expression of proteins between the OKC epithelium and the cystic capsule, it was observed that all molecules were more expressed in the epithelium (p < 0.001). RT-PCR confirmed the expression of ADAMTS-1 and proteoglycans in all samples.

CONCLUSION

ADAMTS-1, aggrecan, brevican, and versican were expressed in all samples with a granular and cytoplasmic pattern. RT-PCR confirmed their presence in both OKC and DF, but only aggrecan and versican exhibited significantly higher levels in OKC (p < 0.05). Protein expression was notably greater in the epithelial component of OKC. These findings underscore the potential role of these proteins in the biological behavior of OKC.

An "All-in-One" Strategy to Reconstruct Temporomandibular Joint Osteoarthritic Microenvironment Using γ-Fe2O3@TA@ALN Nanoparticles

Current clinical strategies for the treatment of temporomandibular joint osteoarthritis (TMJOA) primarily target cartilage biology, overlooking the synergetic effect of various cells and inorganic components in shaping the arthritic microenvironment, thereby impeding the effectiveness of existing therapeutic options for TMJOA. Here, γ-Fe2O3@TA@ALN magnetic nanoparticles (γ-Fe2O3@TA@ALN MNPs) composed of γ-Fe2O3, tannic acid (TA), and alendronate sodium (ALN) are engineered to reconstruct the osteoarthritic microenvironment and mitigate TMJOA progression. γ-Fe2O3@TA@ALN MNPs can promote chondrocytes' proliferation, facilitate chondrogenesis and anisotropic organization, enhance lubrication and reduce cartilage wear, and encourage cell movement. Magnetic-responsive γ-Fe2O3@TA@ALN MNPs also exhibit pH sensitivity, which undergoes decomposition within acidic environment to release ALN on demand. Under a 0.2 T static magnetic field, γ-Fe2O3@TA@ALN MNPs accelerate the synthesis of cartilage-specific proteins, and suppress catabolic-related genes expression and reactive oxygen species generation, affording additional protection to TMJ cartilage. In TMJOA mouse models, articular injection of γ-Fe2O3@TA@ALN MNPs effectively alleviates cartilage degeneration and subchondral bone loss in short and long terms, offering promising avenues for the development of therapeutic interventions for TMJOA.

Diacetoxy-6-gingerdiol protects the extracellular matrix of nucleus pulposus cells and ameliorates intervertebral disc degeneration by inhibiting the IL-1β-mediated NLRP3 pathway

Intervertebral disc degeneration (IDD) is a common cause of low back pain, causing a huge emotional and economic burden on patients and society. Reduction of nucleus pulposus cells (NPC) and extracellular matrix (ECM) is the main feature of IDD, and NPC is the main source of ECM. Thermal apoptosis is a newly discovered form of cell death in recent years that differs significantly from apoptosis in terms of molecular mechanisms and cellular morphological changes. Diacetoxy-6-gingerdiol(D-6-G), a type of gingerol, has anti-inflammatory and antioxidant effects, but whether it has an inhibitory effect on cellular pyroptosis is not clear. Therefore, in the present study, we investigated the effect of D-6-G on the ECM of the nucleus pulposus oblongata under IL-1β treatment, as well as the mechanism of its effect on NLRP3 inflammasome and cellular focal death. In vitro cellular experiments demonstrated that D-6-G could bind to and inhibit the activity of NLRP3 inflammasome, and interestingly, D-6-G could also inhibit cellular pyroptosis and protect the nucleus pulposusry cellular microenvironment by activating the Nrf2/HO-1 axis. In conclusion, we found that D-6-G could inhibit NLRP3 inflammatory vesicle activity as well as cellular pyroptosis in NPCs and protect the ECM, suggesting the potential of D-6-G to delay IDD.

Adamts1 and Cyst Expansion in Polycystic Kidney Disease

Key Points

Background

Autosomal dominant polycystic kidney disease is characterized by mutations in either the Pkd1 or Pkd2 genes, leading to progressive cyst growth and often kidney failure. We have previously demonstrated that tubules can enlarge after loss of Pkd1 without an increase in tubular cell numbers, suggesting that tubular basement membrane remodeling is important for cystic dilation. RNA sequencing of Pkd1 null kidneys revealed increased expression of 17 metalloproteinases, of which A Disintegrin and Metalloproteinase with Thrombospondin Motif 1 (Adamts1) is the most highly expressed and upregulated.

Methods

Mice were generated with inducible tubule-specific knock-out of Adamts1 alone (AtsTKO), Pkd1 alone (PkdTKO), or both (P/ATKO) after doxycycline induction from age 4 to 6 weeks. Uninduced mice were used as controls. AtsTKO mice had no detectable phenotype through age 12 weeks.

Results

Upregulation of Adamts1 in PkdTKO kidneys correlated with a significant increase in the 70 kDa cleavage product of the V1 isoform of versican, which localized to the tubular basement membrane and adjacent interstitial mononuclear cells. Simultaneous deletion of both Adamts1 and Pkd1 (P/ATKO) reduced Adamts1 expression levels by >90%, prevented V1 versican cleavage, and reduced interstitial macrophage accumulation and activation. P/ATKO mice demonstrated reduced cystic enlargement, improved BUN and creatinine, and better survival than did PkdTKO mice.

Conclusions

Preventing Adamts1 upregulation after loss of tubular Pkd1 effectively reduced cyst growth and preserved kidney function.

Distribution and Incorporation of Extracellular Vesicles into Chondrocytes and Synoviocytes

Osteoarthritis (OA) is a chronic disease affecting over 500 million people worldwide. As the population ages and obesity rates rise, the societal burden of OA is increasing. Pro-inflammatory cytokines, particularly interleukin-1β, are implicated in the pathogenesis of OA. Recent studies suggest that crosstalk between cartilage and synovium contributes to OA development, but the mechanisms remain unclear. Extracellular vesicles (EVs) were purified from cell culture-conditioned medium via ultracentrifugation and confirmed using transmission electron microscopy, nanoparticle tracking analysis, and western blotting. We demonstrated that EVs were taken up by human synoviocytes and chondrocytes in vitro, while in vivo experiments revealed that fluorescent-labelled EVs injected into mouse joints were incorporated into chondrocytes and synoviocytes. EV uptake was significantly inhibited by dynamin-mediated endocytosis inhibitors, indicating that endocytosis plays a major role in this process. Additionally, co-culture experiments with HEK-293 cells expressing red fluorescent protein (RFP)-tagged CD9 and the chondrocytic cell line OUMS-27 confirmed the transfer of RFP-positive EVs across a 600-nm but not a 30-nm filter. These findings suggest that EVs from chondrocytes are released into joint fluid and taken up by cells within the cartilage, potentially facilitating communication between cartilage and synovium. The results underscore the importance of EVs in OA pathophysiology.

Marine-Derived Bioactive Ingredients in Functional Foods for Aging: Nutritional and Therapeutic Perspectives

Aging is closely linked to various health challenges, including cardiovascular disease, metabolic disorders, and neurodegenerative conditions. This study emphasizes the critical role of bioactive compounds derived from marine sources, such as antioxidants, omega-3 fatty acids, vitamins, minerals, and polysaccharides, in addressing oxidative stress, inflammation, and metabolic disorders closely related to aging. Incorporating these materials into functional foods not only provides essential nutrients but also delivers therapeutic effects, thereby promoting healthy aging and mitigating age-related diseases. The growth of the global anti-aging market, particularly in North America, Europe, and Asia, underscores the significance of this study. This review systematically analyzes the current research, identifying key bioactive compounds, their mechanisms of action, and their potential health benefits, thus highlighting the broad applicability of marine-derived bioactive compounds to enhancing healthy aging and improving the quality of life of aging populations.

β-Hydroxybutyrate enhances chondrocyte mitophagy and reduces cartilage degeneration in osteoarthritis via the HCAR2/AMPK/PINK1/Parkin pathway

Osteoarthritis (OA) is widely recognized as the prevailing joint disease associated with aging. The ketogenic diet (KD) has been postulated to impede the advancement of various inflammatory ailments. β-Hydroxybutyrate (βOHB), a prominent constituent of ketone bodies, has recently been proposed to possess crucial signaling capabilities. In this study, we propose to explore the role and mechanism of βOHB in OA. Tissue staining and inflammatory factor assay were employed to evaluate the impacts of KD and βOHB on OA rats. The oxidative stress conditions in chondrocytes were induced using tert-butyl hydroperoxide (TBHP). The mechanisms were determined using the siRNA of hydroxycarboxylic acid receptor 2 (HCAR2), the antagonist of adenosine monophosphate-activated protein kinase (AMPK), and the inhibitor of mitophagy. The administration of KD demonstrated a reduction in pathological damage to cartilage, as well as a decrease in plasma levels of inflammatory factors. Furthermore, it resulted in an increase in the concentration of βOHB in the blood and synovial fluid. In vitro experiments showed that βOHB facilitated mitophagy and adenosine triphosphate production. Besides, βOHB mitigated chondrocyte senescence, inflammatory factors secretion, extracellular matrix degradation, and apoptosis induced by TBHP. Subsequent investigations indicated that the protective effects of βOHB were no longer observed following the knockdown of HCAR2, the antagonist of AMPK, or the inhibitor of mitophagy. Moreover, in vivo studies suggested that βOHB played a protective role by targeting the HCAR2-AMPK-PINK1 axis. In conclusion, βOHB enhanced chondrocyte mitophagy through the HCAR2/AMPK/PINK1/Parkin pathway, offering a potential therapeutic approach for the treatment of OA.

A multiphasic model for determination of mouse ascending thoracic aorta mass transport properties with and without aneurysm

Thoracic aortic aneurysms (TAAs) are associated with aortic wall remodeling that affects transmural transport or the movement of fluid and solute across the wall. In previous work, we used a Fbln4E57K/E57K (MU) mouse model to investigate transmural transport changes as a function of aneurysm severity. We compared wild-type (WT), MU with no aneurysm (MU-NA), MU with aneurysm (MU-A), and MU with an additional genetic mutation that led to increased aneurysm penetrance (MU-XA). We found that all aneurysmal aortas (MU-A and MU-XA) had lower fluid flux compared to WT. Non-aneurysmal aortas (MU-NA) had higher 4 kDa FITC-dextran solute flux than WT, but aneurysmal MU-A and MU-XA aortas had solute fluxes similar to WT. Our experimental results could not isolate competing factors, such as changes in aortic geometry and solid material properties among these mouse models, to determine how intrinsic transport properties change with aneurysm severity. The objective of this study is to use biphasic and multiphasic models to identify changes in transport material properties. Our biphasic model indicates that hydraulic permeability is significantly decreased in the severe aneurysm model (MU-XA) compared to non-aneurysmal aortas (MU-NA). Our multiphasic model shows that effective solute diffusivity is increased in MU-NA aortas compared to all others. Our findings reveal changes in intrinsic transport properties that depend on aneurysm severity and are important for understanding the movement of fluids and solutes that may play a role in the diagnosis, progression, or treatment of TAA.

Treatment of Short Stature in Aggrecan-deficient Patients With Recombinant Human GH: 3-year Response

Context

Patients with aggrecan (ACAN) deficiency present with dominantly inherited short stature, as well as early-onset joint disease.

Objective

The objective of this study was to evaluate the efficacy and safety of recombinant human GH (rhGH) on linear growth in ACAN-deficient children.

Methods

Open-label, single-arm, prospective study over 3 years recruiting 10 treatment-naïve patients with heterozygous mutations in ACAN, age ≥2 years, prepubertal, and normal IGF-I concentration. Patients were treated with rhGH (initially, 50 mcg/kg/day). Main outcomes were change in (Δ) height SD score (HtSDS) and height velocity (HV).

Results

Ten patients (6 females) enrolled with median chronological age (CA) of 5.6 years (range, 2.4-9.7). Baseline median HtSDS, HV, and bone age/CA were -2.5 (range, -4.3 to -1.1), 5.2 cm/year (range, 3.8 to 7.1), and 1.2 (range, 0.9 to 1.5), respectively. The cumulative median ΔHtSDS over 3 years was +1.21 (range, +0.82 to +1.94). Median HV increased to 8.3 cm/year (range, 7.3-11.2), 7.7 cm/year (range, 5.9-8.8), and 6.8 cm/year (range, 4.9-8.6) during years 1, 2, and 3, respectively. The median Δ predicated adult height was +6.8 cm over 3 years. Four female subjects entered puberty; nevertheless, median Δbone age/CA was -0.1. No adverse events related to rhGH were observed.

Conclusion

Linear growth improved in a cohort of ACAN-deficient patients treated with rhGH, albeit somewhat attenuated in older participants who entered puberty. Longitudinal follow-up is needed to assess the long-term efficacy of rhGH and adult height outcome.

Isolation and tracing of matrix-producing notochordal and chondrocyte cells using ACAN-2A-mScarlet reporter human iPSC lines

The development of human induced pluripotent stem cell (iPSC)-based regenerative therapies is challenged by the lack of specific cell markers to isolate differentiated cell types and improve differentiation protocols. This issue is particularly critical for notochordal-like cells and chondrocytes, which are crucial in treating back pain and osteoarthritis, respectively. Both cell types produce abundant proteoglycan aggrecan (ACAN), crucial for the extracellular matrix. We generated two human iPSC lines containing an ACAN-2A-mScarlet reporter. The reporter cell lines were validated using CRISPR-mediated transactivation and functionally validated during notochord and cartilage differentiation. The ability to isolate differentiated cell populations producing ACAN enables their enrichment even in the absence of specific cell markers and allows for comprehensive studies and protocol refinement. ACAN's prevalence in various tissues (e.g., cardiac and cerebral) underscores the reporter's versatility as a valuable tool for tracking matrix protein production in diverse cell types, benefiting developmental biology, matrix pathophysiology, and regenerative medicine.

Clinicopathological Features of Three Rare EWSR1::NFATC2 Sarcomas of Bone and Soft Tissues

Certain undifferentiated round cell sarcomas displaying EWSR1::NFATC2 fusion have recently been reported, mostly in the bones. This report presents clinicopathological features of 3 additional EWSR1::NFATC2 fusion sarcomas of bone and soft tissues. We present 2 soft tissue and 1 bone tumors: A 62-year-old man with pain and a slowly growing, 8-cm-sized soft tissue mass in the anterolateral compartment of his right calf, along with multiple pulmonary metastatic lesions; a 63-year-old man with a 5-cm sized axillary mass of 4 months duration and a cystic renal mass; and a 53-year-old man with a complaint of leg pain was found to have a 2-cm diameter, intramedullary, lytic mass in the diaphysis of his left femur. Microscopic examination of the tumors in all patients revealed round to epithelioid cells arranged in cords and trabeculae in a myxohyaline stroma. Immunohistochemically, the tumor cells were positive for MIC2/CD99 (3/3), EMA (3/3), NKX3.1 (3/3), NKX2.2 (2/2), CD10 (2/2), and aggrecan (1/1), while negative for S100P and GFAP. Various keratins were also negative except focal AE1/AE3 positivity in the third tumor. By fluorescence in-situ hybridization, 2 tumors (#1 and #3) revealed EWSR1 gene rearrangement and amplification. Furthermore, 2 tumors (#1 and #2) displayed EWSR1ex8::NFATC2ex3 fusion with next-generation sequencing (NGS). The first patient was offered chemotherapy. However, he died of pulmonary metastasis. This report highlights the value of combining histopathological features and immunostains such as NXK3.1, NKX2.2, CD10, and aggrecan, along with EWSR1 testing for triaging these tumors for rare gene fusions by NGS that has prognostic implications.

The Role of Biomarkers in Predicting Outcomes of Anterior Cruciate Ligament Reconstruction: A Systematic Review

Background

Anterior cruciate ligament (ACL) injury is frequently associated with injuries to other parts of the knee, including the menisci and articular cartilage. After ACL injury and reconstruction, there may be progressive chondral degradation. Biomarkers in blood, urine, and synovial fluid can be measured after ACL injury and reconstruction and have been proposed as a means of measuring the associated cellular changes occurring in the knee.

Purpose

To systematically review the literature regarding biomarkers in urine, serum, or synovial fluid that have been associated with an outcome measure after ACL reconstruction.

Study Design

Systematic review; Level of evidence, 3.

Methods

This review was performed according to the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines. The MEDLINE, Embase, CINAHL, and Web of Science databases were searched to identify studies published before September 2023 that reported on patients undergoing ACL reconstruction where a biomarker was measured and related to an outcome variable. Of 9360 results, 16 studies comprising 492 patients were included. Findings were reported as descriptive summaries synthesizing the available literature.

Results

A total of 45 unique biomarkers or biomarker ratios were investigated (12 serum, 3 urine, and 38 synovial fluid; 8 biomarkers were measured from >1 source). Nineteen different outcome measures were identified, including the International Knee Documentation Committee Subjective Knee Form, Knee injury and Osteoarthritis Outcome Score, numeric pain scores, radiological outcomes (magnetic resonance imaging and radiography), rates of arthrofibrosis and cyclops lesions, and gait biomechanics. Across the included studies, 17 biomarkers were found to have a statistically significant association (P < .05) with an outcome variable. Serum interleukin 6 (s-IL-6), serum and synovial fluid matrix metalloproteinase-3 (s-MMP-3 and sf-MMP-3), urinary and synovial fluid C-terminal telopeptide of type 2 collagen (u-CTX-II and sf-CTX-II), and serum collagen type 2 cleavage product (s-C2C) showed promise in predicting outcomes after ACL reconstruction, specifically regarding patient-reported outcome measures (s-IL-6 and u-CTX-II), gait biomechanical parameters (s-IL-6, sf-MMP-3, s-MMP-3, and s-C2C), pain (s-IL-6 and u-CTX-II), and radiological osteoarthritis (ratio of u-CTX-II to serum procollagen 2 C-propeptide).

Conclusion

The results highlight several biomarkers that have been associated with clinically important postoperative outcome measures and may warrant further research to understand if they can provide meaningful information in the clinical environment.

Lubricant Strategies in Osteoarthritis Treatment: Transitioning from Natural Lubricants to Drug Delivery Particles with Lubricant Properties

Osteoarthritis (OA) is a debilitating joint disease characterized by cartilage degradation, leading to pain and functional impairment. A key contributor to OA progression is the decline in cartilage lubrication. In physiological conditions, synovial fluid (SF) macromolecules like hyaluronic acid (HA), phospholipids, and lubricin play a crucial role in the boundary lubrication of articular cartilage. In early OA, cartilage damage triggers inflammation, altering SF composition and compromising the lubrication layer. This increases friction between mating interfaces, worsening cartilage degradation and local inflammation. Therefore, early-stage restoration of lubrication (by injecting in the joint different classes of compounds and formulations) could alleviate, and potentially reverse, OA progression. In the light of this, a broad variety of lubricants have been investigated for their ability to reduce friction in OA joints and promote cartilage repair in clinical and preclinical studies. This review examines recent advancements in lubricant-based therapy for OA, focusing on natural, bioinspired, and alternative products. Starting from the currently applied therapy, mainly based on natural lubricants as HA, we will present their modified versions, either in hydrogel form or with specific biomimetic moieties with the aim of reducing their clearance from the joint and of enhancing their lubricating properties. Finally, the most advanced and recent formulation, represented by alternative strategies, will be proposed. Particular emphasis will be placed on those ones involving new types of hydrogels, microparticles, nanoparticles, and liposomes, which are currently under investigation in preclinical studies. The potential application of particles and liposomes could foster the transition from natural lubricants to Drug Delivery Systems (DDSs) with lubricant features; transition which could provide more complete OA treatments, by simultaneously providing lubrication replacement and sustained release of different payloads and active agents directly at the joint level. Within each category, we will examine relevant preclinical studies, highlighting challenges and future prospects.

The joint protective function of live- and dead-Lactobacillus plantarum GKD7 on anterior cruciate ligament transection induces osteoarthritis

Osteoarthritis (OA) is a chronic inflammatory disease accompanied by joint pain, bone degradation, and synovial inflammation. Tumor necrosis factor (TNF)-α and interleukin (IL)-1β play key roles in chronic inflammation, and matrix metalloproteinase (MMP)3 is the first enzyme released by chondrocytes and synovial cells that promotes MMPs' degrading cartilage matrix (including collage II and aggrecan) function. Using an anterior cruciate ligament transection (ACLT) rat model, Lactobacillus plantarum GKD7 has shown anti-inflammatory and analgesic properties. The present investigation examined the chondroprotective effects of several dosages and formulas of GKD7 on rats in an ACLT-induced OA model. The findings indicate that oral treatment with both live-GKD7 (GKD7-L) and dead-GKD7 (GKD7-D), along with celecoxib (positive control), all reduce post-ACLT pain and inflammation in OA joints. Subsequently, the immunohistochemical staining results demonstrate that following GKD7-L and GKD7-D treatment, there was a reversal of the degradation of collagen II and aggrecan, as well as a decrease in the expression of IL-1β and TNF-α on the synovial tissue and MMP3 on the cartilage. Accordingly, our findings imply that the treatment of both GKD7-L and GKD7-D has chondroprotective and analgesic effects on the OA rat model, and that celecoxib and GKD7-L at dosages (100 mg/kg) have comparable therapeutic benefits. As a result, we propose that both GKD7-L and GKD7-D are helpful supplements for OA management.

Influence of feeding a soft diet on proteoglycan expression in rat temporomandibular joint discs

OBJECTIVES

Extracellular matrix components play a significant role in maintaining tissue integrity and pathological processes of the temporomandibular joint (TMJ). This study aimed to evaluate the influence of a soft diet on the mRNA expression of proteoglycans and glycosaminoglycans (GAGs) linked to proteoglycan core proteins in rat TMJ discs.

METHODS

Thirty 4-week-old male Wistar rats were assigned to one of two groups: a control group fed a regular pellet diet and a soft diet group fed a powdered diet for 4 weeks. The mRNA expression levels of 12 proteoglycans in TMJ discs were evaluated using real-time polymerase chain reaction (PCR). In addition, histomorphometric and biochemical analyses were performed to evaluate the thickness and deoxyribonucleic acid (DNA), GAG, and water content of the TMJ discs.

RESULTS

The TMJ disc thickness in the anterior, intermediate, and posterior bands decreased significantly in the soft diet group. The GAG content decreased significantly in the soft-diet group, whereas no significant differences in DNA content or water content ratio were observed between the groups. Real-time PCR indicated that the expression levels of aggrecan, versican, biglycan, decorin, fibromodulin, lumican, and chondroadherin decreased in the soft diet group. The expression levels of all versican isoforms decreased in the soft diet group.

CONCLUSIONS

These results indicate that the biomechanical environment of the TMJ caused by a soft diet is closely related to the expression of proteoglycans in TMJ discs, which may eventually increase the fragility of the TMJ discs.

Biomimetic strategies for the deputization of proteoglycan functions

Proteoglycans (PGs), which have glycosaminoglycan chains attached to their protein cores, are essential for maintaining the morphology and function of healthy body tissues. Extracellular PGs perform various functions, classified into the following four categories: i) the modulation of tissue mechanical properties; ii) the regulation and protection of the extracellular matrix; iii) protein sequestration; and iv) the regulation of cell signaling. The depletion of PGs may significantly impair tissue function, encompassing compromised mechanical characteristics and unregulated inflammatory responses. Since PGs play critical roles in the function of healthy tissues and their synthesis is complex, the development of PG mimetic molecules that recapitulate PG functions for tissue engineering and therapeutic applications has attracted the interest of researchers for more than 20 years. These approaches have ranged from semisynthetic graft copolymers to recombinant PG domains produced by cells that have undergone genetic modifications. This review discusses some essential extracellular PG functions and approaches to mimicking these functions.

Integrin signalling in joint development, homeostasis and osteoarthritis

Integrins are key regulators of cell-matrix interactions during joint development and joint tissue homeostasis, as well as in the development of osteoarthritis (OA). The signalling cascades initiated by the interactions of integrins with a complex network of extracellular matrix (ECM) components and intracellular adaptor proteins orchestrate cellular responses necessary for maintaining joint tissue integrity. Dysregulated integrin signalling, triggered by matrix degradation products such as matrikines, disrupts this delicate balance, tipping the scales towards an environment conducive to OA pathogenesis. The interplay between integrin signalling and growth factor pathways further underscores the multifaceted nature of OA. Moreover, emerging insights into the role of endocytic trafficking in regulating integrin signalling add a new layer of complexity to the understanding of OA development. To harness the therapeutic potential of targeting integrins for mitigation of OA, comprehensive understanding of their molecular mechanisms across joint tissues is imperative. Ultimately, deciphering the complexities of integrin signalling will advance the ability to treat OA and alleviate its global burden.

Nanoenabled Immunomodulatory Scaffolds for Cartilage Tissue Engineering

Articular cartilage regeneration is a challenge in tissue engineering. Although diverse materials have been developed for this purpose, cartilage regeneration remains suboptimal. The integration of nanomaterials into 3D network materials holds great potential in the improvement of key mechanical properties, particularly important for osteochondral replacement scaffolds and even to function as carriers for disease‐modifying drugs or other regulatory signals. In this study, a simple yet effective cell‐free nanoenabled Col‐PLA scaffold specially designed to enhance cartilage regeneration and modulate inflammatory response is proposed, by incorporating poly(lactic‐co‐glycolic acid) (PLGA) ibuprofen nanoparticles (NPs) into a collagen/polylactide (Col‐PLA) matrix. The developed nanoenabled scaffold successfully decreases IL‐1β release and leads to primary human chondrocytes survival, ultimately restoring extracellular matrix (ECM) production under inflammatory conditions. The nanoenabled Col‐PLA scaffolds secretome effectively decreases macrophage invasion in vitro, as well as neutrophil infiltration and inflammatory mediators’, namely the complement component C5/C5a, C‐reactive protein, IL‐1β, MMP9, CCL20, and CXCL1/KC production in vivo in a rodent air‐pouch model. Overall, the established nanoenabled scaffold has the potential to support chondrogenesis as well as modulate inflammatory response, overcoming the limitations of traditional tissue engineering strategies.

CNS/PNS proteoglycans functionalize neuronal and astrocyte niche microenvironments optimizing cellular activity by preserving membrane polarization dynamics, ionic microenvironments, ion fluxes, neuronal activation, and network neurotransductive capacity

Central and peripheral nervous system (CNS/PNS) proteoglycans (PGs) have diverse functional roles, this study examined how these control cellular behavior and tissue function. The CNS/PNS extracellular matrix (ECM) is a dynamic, responsive, highly interactive, space-filling, cell supportive, stabilizing structure maintaining tissue compartments, ionic microenvironments, and microgradients that regulate neuronal activity and maintain the neuron in an optimal ionic microenvironment. The CNS/PNS contains a high glycosaminoglycan content (60% hyaluronan, HA) and a diverse range of stabilizing PGs. Immobilization of HA in brain tissues by HA interactive hyalectan PGs preserves tissue hydration and neuronal activity, a paucity of HA in brain tissues results in a pro-convulsant epileptic phenotype. Diverse CS, KS, and HSPGs stabilize the blood-brain barrier and neurovascular unit, provide smart gel neurotransmitter neuron vesicle storage and delivery, organize the neuromuscular junction basement membrane, and provide motor neuron synaptic plasticity, and photoreceptor and neuron synaptic functions. PG-HA networks maintain ionic fluxes and microgradients and tissue compartments that contribute to membrane polarization dynamics essential to neuronal activation and neurotransduction. Hyalectans form neuroprotective perineuronal nets contributing to synaptic plasticity, memory, and cognitive learning. Sialoglycoprotein associated with cones and rods (SPACRCAN), an HA binding CSPG, stabilizes the inter-photoreceptor ECM. HSPGs pikachurin and eyes shut stabilize the photoreceptor synapse aiding in phototransduction and neurotransduction with retinal bipolar neurons crucial to visual acuity. This is achieved through Laminin G motifs in pikachurin, eyes shut, and neurexins that interact with the dystroglycan-cytoskeleton-ECM-stabilizing synaptic interconnections, neuronal interactive specificity, and co-ordination of regulatory action potentials in neural networks.

Miao medicine Gu Yan Xiao tincture inhibits mTOR to stimulate chondrocyte autophagy in a rabbit model of osteoarthritis

ETHNOPHARMACOLOGICAL RELEVANCE

The Gu Yan Xiao tincture, a blend of traditional Chinese herbs, is traditionally used for osteoarthritis and related pain. This study investigated its mechanism of action in order to rationalize and validate its therapeutic use.

AIM OF THE STUDY

This study analyzed, in a rabbit model of knee osteoarthritis, whether and how Gu Yan Xiao tincture exerts therapeutic benefits by modulating chondrocyte autophagy.

MATERIALS AND METHODS

The active constituents within the GYX tincture were identified using liquid chromatography-mass spectrometry. The rabbit model was established by injecting animals with type II collagenase intra-articularly, and the effects of topically applied tincture were examined on osteoarthritis lesions of the knee using histopathology, micro-computed tomography and x-ray imaging. Effects of the tincture were also evaluated on levels of inflammatory cytokines, matrix metalloproteases, and autophagy in chondrocytes. As a positive control, animals were treated with sodium diclofenac.

RESULTS

The tincture mitigated the reduction in joint space, hyperplasia of the synovium and matrix metalloproteases in serum that occurred after injection of type II collagenase in rabbits. These therapeutic effects were associated with inhibition of mTOR and activation of autophagy in articular chondrocytes. Inhibiting mTOR with rapamycin potentiated the therapeutic effects of the tincture, while inhibiting autophagy with 3-methyladenine antagonized them.

CONCLUSIONS

Gu Yan Xiao tincture mitigates tissue injury in a rabbit model of osteoarthritis, at least in part by inhibiting mTOR and thereby promoting autophagy in chondrocytes. These results rationalize the use of the tincture not only against osteoarthritis but also potentially other diseases involving inhibition of autophagy in bones and joints.

A comprehensive exploration of novel biomarkers for the early diagnosis of aortic dissection

Aortic dissection (AD) is a catastrophic life-threatening cardiovascular emergency with a 1-2% per hour mortality rate post-diagnosis, characterized physiologically by the separation of aortic wall layers. AD initially presents as intense pain that can then radiate to the back, arms, neck, or jaw along with neurological deficits like difficulty in speaking, and unilateral weakness in some patients. This spectrum of clinical features associated with AD is often confused with acute myocardial infarction, hence leading to a delay in AD diagnosis. Cardiac and vascular biomarkers are structural proteins and microRNAs circulating in the bloodstream that correlate to tissue damage and their levels become detectable even before symptom onset. Timely diagnosis of AD using biomarkers, in combination with advanced imaging diagnostics, will significantly improve prognosis by allowing earlier vascular interventions. This comprehensive review aims to investigate emerging biomarkers in the diagnosis of AD, as well as provide future directives for creating advanced diagnostic tools and imaging techniques.

3D Bioprinting of Biomimetic Alginate/Gelatin/Chondroitin Sulfate Hydrogel Nanocomposites for Intrinsically Chondrogenic Differentiation of Human Mesenchymal Stem Cells

3D-printed hydrogel scaffolds biomimicking the extracellular matrix (ECM) are key in cartilage tissue engineering as they can enhance the chondrogenic differentiation of mesenchymal stem cells (MSCs) through the presence of active nanoparticles such as graphene oxide (GO). Here, biomimetic hydrogels were developed by cross-linking alginate, gelatin, and chondroitin sulfate biopolymers in the presence of GO as a bioactive filler, with excellent processability for developing bioactive 3D printed scaffolds and for the bioprinting process. A novel bioink based on our hydrogel with embedded human MSCs presented a cell survival rate near 100% after the 3D bioprinting process. The effects of processing and filler concentration on cell differentiation were further quantitatively evaluated. The nanocomposited hydrogels render high MSC proliferation and viability, exhibiting intrinsic chondroinductive capacity without any exogenous factor when used to print scaffolds or bioprint constructs. The bioactivity depended on the GO concentration, with the best performance at 0.1 mg mL-1. These results were explained by the rational combination of the three biopolymers, with GO nanoparticles having carboxylate and sulfate groups in their structures, therefore, biomimicking the highly negatively charged ECM of cartilage. The bioactivity of this biomaterial and its good processability for 3D printing scaffolds and 3D bioprinting techniques open up a new approach to developing novel biomimetic materials for cartilage repair.

Unveiling interactions between intervertebral disc morphologies and mechanical behavior through personalized finite element modeling

Introduction: Intervertebral Disc (IVD) Degeneration (IDD) is a significant health concern, potentially influenced by mechanotransduction. However, the relationship between the IVD phenotypes and mechanical behavior has not been thoroughly explored in local morphologies where IDD originates. This work unveils the interplays among morphological and mechanical features potentially relevant to IDD through Abaqus UMAT simulations. Methods: A groundbreaking automated method is introduced to transform a calibrated, structured IVD finite element (FE) model into 169 patient-personalized (PP) models through a mesh morphing process. Our approach accurately replicates the real shapes of the patient's Annulus Fibrosus (AF) and Nucleus Pulposus (NP) while maintaining the same topology for all models. Using segmented magnetic resonance images from the former project MySpine, 169 models with structured hexahedral meshes were created employing the Bayesian Coherent Point Drift++ technique, generating a unique cohort of PP FE models under the Disc4All initiative. Machine learning methods, including Linear Regression, Support Vector Regression, and eXtreme Gradient Boosting Regression, were used to explore correlations between IVD morphology and mechanics. Results: We achieved PP models with AF and NP similarity scores of 92.06\% and 92.10\% compared to the segmented images. The models maintained good quality and integrity of the mesh. The cartilage endplate (CEP) shape was represented at the IVD-vertebra interfaces, ensuring personalized meshes. Validation of the constitutive model against literature data showed a minor relative error of 5.20%. Discussion: Analysis revealed the influential impact of local morphologies on indirect mechanotransduction responses, highlighting the roles of heights, sagittal areas, and volumes. While the maximum principal stress was influenced by morphologies such as heights, the disc's ellipticity influenced the minimum principal stress. Results suggest the CEPs are not influenced by their local morphologies but by those of the AF and NP. The generated free-access repository of individual disc characteristics is anticipated to be a valuable resource for the scientific community with a broad application spectrum.

Hyaluronic Acid Interacting Molecules Mediated Crosstalk between Cancer Cells and Microenvironment from Primary Tumour to Distant Metastasis

Hyaluronic acid (HA) is a prominent component of the extracellular matrix, and its interactions with HA-interacting molecules (HAIMs) play a critical role in cancer development and disease progression. This review explores the multifaceted role of HAIMs in the context of cancer, focusing on their influence on disease progression by dissecting relevant cellular and molecular mechanisms in tumour cells and the tumour microenvironment. Cancer progression can be profoundly affected by the interactions between HA and HAIMs. They modulate critical processes such as cell adhesion, migration, invasion, and proliferation. The TME serves as a dynamic platform in which HAIMs contribute to the formation of a unique niche. The resulting changes in HA composition profoundly influence the biophysical properties of the TME. These modifications in the TME, in conjunction with HAIMs, impact angiogenesis, immune cell recruitment, and immune evasion. Therefore, understanding the intricate interplay between HAIMs and HA within the cancer context is essential for developing novel therapeutic strategies. Targeting these interactions offers promising avenues for cancer treatment, as they hold the potential to disrupt critical aspects of disease progression and the TME. Further research in this field is imperative for advancing our knowledge and the treatment of cancer.

Molecular Changes in Immunological Characteristics of Bone Marrow Multipotent Mesenchymal Stromal Cells in Lymphoid Neoplasia

Immune system and bone marrow stromal cells play an important role in maintaining normal hematopoiesis. Lymphoid neoplasia disturbs not only development of immune cells, but other immune response mechanisms as well. Multipotent mesenchymal stromal cells (MSCs) of the bone marrow are involved in immune response regulation through both intercellular interactions and secretion of various cytokines. In hematological malignancies, the bone marrow stromal microenvironment, including MSCs, is altered. Aim of this study was to describe the differences of MSCs' immunological function in the patients with acute lymphoblastic leukemia (ALL) and diffuse large B-cell lymphoma (DLBCL). In ALL, malignant cells arise from the early precursor cells localized in bone marrow, while in DLBCL they arise from more differentiated B-cells. In this study, only the DLBCL patients without bone marrow involvement were included. Growth parameters, surface marker expression, genes of interest expression, and secretion pattern of bone marrow MSCs from the patients with ALL and DLBCL at the onset of the disease and in remission were studied. MSCs from the healthy donors of corresponding ages were used as controls. It has been shown that concentration of MSCs in the bone marrow of the patients with ALL is reduced at the onset of the disease and is restored upon reaching remission; in the patients with DLBCL this parameter does not change. Proliferative capacity of MSCs did not change in the patients with ALL; however, the cells of the DLBCL patients both at the onset and in remission proliferated significantly faster than those from the donors. Expression of the membrane surface markers and expression of the genes important for differentiation, immunological status maintenance, and cytokine secretion differed significantly in the MSCs of the patients from those of the healthy donors and depended on nosology of the disease. Secretomes of the MSCs varied greatly; a number of proteins associated with immune response regulation, differentiation, and maintenance of hematopoietic stem cells were depleted in the secretomes of the cells from the patients. Lymphoid neoplasia leads to dramatic changes in the functional immunological status of MSCs.

Impact of gadolinium-based MRI contrast agent and local anesthetics co-administration on chondrogenic gadolinium uptake and cytotoxicity

The gadolinium-based contrast agent DOTA-Gd is clinically used in combination with local anesthetics for direct magnetic resonance arthrography. It remains unclear whether gadolinium uptake into cartilage is influenced by co-administration of bupivacaine or ropivacaine and whether DOTA-Gd alters their chondrotoxicity. Gadolinium quantification of chondrogenic spheroids revealed enhanced gadolinium uptake after simultaneous exposure to local anesthetics. Analyses of the spatial gadolinium distribution using synchrotron X-ray-fluorescence scanning indicates gadolinium exposed chondrocytes. In vitro exposure to DOTA-Gd does not alter viability and proliferation of human chondrocytes and the chondrotoxic potential of the anesthetics. Reduced viability induced by ropivacaine was found to be reversible, while exposure to bupivacaine leads to irreversible cell death. Our data suggest that ropivacaine is more tolerable than bupivacaine and that DOTA-Gd exposure does not alter the cytotoxicity of both anesthetics. Enhanced gadolinium uptake into cartilage due to co-administration of anesthetics should find attention.

The Interplay Between Endoplasmic Reticulum Stress and Oxidative Stress in Chondrocyte Catabolism

OBJECTIVE

Oxidative stress and endoplasmic reticulum (ER) stress play pivotal roles in disrupting the homeostasis of chondrocytes by producing catalytic proteases and enhancing chondrocyte senescence, consequently contributing to the progression of osteoarthritis (OA). Despite their close interaction, the underlying molecular mechanisms remain poorly understood. Here, we show that ER stress and oxidative stress reciprocally modulate each other to promote cartilage degradation.

METHODS

Primary chondrocytes were obtained from the articular cartilage of 5-day-old C57BL/6J mice by excising distal femur and proximal tibia. Tunicamycin was applied to induce ER stress in primary chondrocytes. Surgical OA was induced in 12-week-old male C57BL/6J mice by destabilizing the medial meniscus (DMM).

RESULTS

Tunicamycin-induced ER stress led to an increase in the production of reactive oxygen species (ROS) and catalytic proteases, including MMP13 and Adamts5, in primary chondrocytes, and it was primarily dependent on the NADPH oxidase (NOX) system. ER stress directly increased the expression of NOX2, NOX3, NOX4, and p22phox. Specifically, the protein kinase RNA-like ER kinase (PERK) pathway is involved in the expression of NOX4 and p22phox, the inositol-requiring enzyme 1 alpha (IRE1α) pathway in NOX2 and NOX3 expression, and the activating transcription factor 6 (ATF6) pathway influences NOX3 expression in chondrocytes. Conversely, inhibiting NOX function significantly reduced both ER stress sensor-related signaling and chondrocyte catabolism, thereby decelerating the progression of surgically induced OA in vivo.

CONCLUSIONS

Our findings highlight the positive feedback loop between ER stress and oxidative stress in OA pathogenesis, suggesting that targeting NOX isoforms is a promising therapeutic strategy for OA.

Keratan sulfate, an electrosensory neurosentient bioresponsive cell instructive glycosaminoglycan

The roles of keratan sulfate (KS) as a proton detection glycosaminoglycan in neurosensory processes in the central and peripheral nervous systems is reviewed. The functional properties of the KS-proteoglycans aggrecan, phosphacan, podocalyxcin as components of perineuronal nets in neurosensory processes in neuronal plasticity, cognitive learning and memory are also discussed. KS-glycoconjugate neurosensory gels used in electrolocation in elasmobranch fish species and KS substituted mucin like conjugates in some tissue contexts in mammals need to be considered in sensory signalling. Parallels are drawn between KS's roles in elasmobranch fish neurosensory processes and its roles in mammalian electro mechanical transduction of acoustic liquid displacement signals in the cochlea by the tectorial membrane and stereocilia of sensory inner and outer hair cells into neural signals for sound interpretation. The sophisticated structural and functional proteins which maintain the unique high precision physical properties of stereocilia in the detection, transmittance and interpretation of acoustic signals in the hearing process are important. The maintenance of the material properties of stereocilia are essential in sound transmission processes. Specific, emerging roles for low sulfation KS in sensory bioregulation are contrasted with the properties of high charge density KS isoforms. Some speculations are made on how the molecular and electrical properties of KS may be of potential application in futuristic nanoelectronic, memristor technology in advanced ultrafast computing devices with low energy requirements in nanomachines, nanobots or molecular switches which could be potentially useful in artificial synapse development. Application of KS in such innovative areas in bioregulation are eagerly awaited.

Aggrecan-related bone disorders; a novel heterozygous ACAN variant associated with spondyloepimetaphyseal dysplasia expanding the phenotypic spectrum and review of literature

BACKGROUND

Spondyloepimetaphyseal dysplasias (SEMD) are a large group of skeletal disorders represented by abnormalities of vertebrae in addition to epiphyseal and metaphyseal areas of bones. Several genes have been identified underlying different forms. ACAN gene mutations were found to cause Aggrecan-related bone disorders (spondyloepimetaphyseal dysplasias,spondyloepiphyseal dysplasias, familial osteochondritis dissecans and short stature syndromes). This study aims to find the disease causing variant in Egyptian patient with SEMD using whole exome sequencing.

METHODS

Whole-exome sequencing was performed for an Egyptian male patient who presented with short stature, clinical and radiological features suggestive of unclassified SEMD.

RESULTS

The study identified a novel de novo heterozygous ACAN gene variant (c.7378G>A; p.Gly2460Arg) in G3 domain. Mutations in ACAN gene have been more commonly associated with short stature than SEMD. The phenotype of our patient was intermediate in severity between spondyloepiphyseal dysplasia presentation; Kimberley type(SEDK) and Spondyloepimetaphyseal dysplasias Aggrecan (SEMDAG) CONCLUSIONS: Whole exome sequencing revealed a novel de novo ACAN gene variant in patient with SEDK. The clinical and skeletal phenotype of our patient was much severe than those reported originally and showed more metaphyseal involvement. To the best of our knowledge, two previous studies reported a heterozygous variant in ACAN with spondyloepiphyseal dysplasia presentation; Kimberley type.

Proteoglycan Dysfunction: A Common Link Between Intervertebral Disc Degeneration and Skeletal Dysplasia

Proteoglycans through their sulfated glycosaminoglycans regulate cell-matrix signaling during tissue development, regeneration, and degeneration processes. Large extracellular proteoglycans such as aggrecan, versican, and perlecan are especially important for the structural integrity of the intervertebral disc and cartilage during development. In these tissues, proteoglycans are responsible for hydration, joint flexibility, and the absorption of mechanical loads. Loss or reduction of these molecules can lead to disc degeneration and skeletal dysplasia, evident from loss of disc height or defects in skeletal development respectively. In this review, we discuss the common proteoglycans found in the disc and cartilage and elaborate on various murine models and skeletal dysplasias in humans to highlight how their absence and/or aberrant expression causes accelerated disc degeneration and developmental defects.

Collagen type II solution extracted from supercritical carbon dioxide decellularized porcine cartilage: regenerative efficacy on post-traumatic osteoarthritis model

Osteoarthritis (OA) of the knee is a common degenerative articular disorder and is one of the main causes of pain and functional disability. Cartilage damage is frequently linked to elevated osteoarthritis incidence. Supercritical carbon dioxide (scCO2) decellularized cartilage graft produced from the porcine cartilage is an ideal candidate for cartilage tissue engineering. In the present study, we derived collagen type II (Col II) solution from the scCO2 decellularized porcine cartilage graft (dPCG) and compared its efficacy with hyaluronic acid (HA) in the surgical medial meniscectomy (MNX) induced post-traumatic osteoarthritis (PTOA) model. Dose-dependent attenuation of the OA (12.3 ± 0.8) progression was observed in the intra-articular administration of Col II solution (7.3 ± 1.2) which significantly decreased the MNX-induced OA symptoms similar to HA. The pain of the OA group (37.4 ± 2.7) was attenuated dose-dependently by Col II solution (45.9 ± 4.1) similar to HA (43.1 ± 3.5) as evaluated by a capacitance meter. Micro-CT depicted a dose-dependent attenuation of articular cartilage damage by the Col II solution similar to HA treatment. A significant (p < 0.001) dose-dependent elevation in the bone volume was also observed in Col II solution-treated OA animals. The protective competence of Col II solution on articular cartilage damage is due to its significant (p < 0.001) increase in the expression of type II collagen, aggrecan and SOX-9 similar to HA. To conclude, intra-articular administration of type II collagen solution and HA reestablished the injured cartilage and decreased osteoarthritis progression in the experimental PTOA model.

Inhibition of HOXD11 promotes cartilage degradation and induces osteoarthritis development

The 5'-HOXD genes are important for chondrogenesis in vertebrates, but their roles in osteoarthritis (OA) are still ambiguous. In our study, 5'-HOXD genes involvement contributing to cartilage degradation and OA was investigated. In bioinformatics analysis of 5'-HOXD genes, we obtained the GSE169077 data set related to OA in the GEO and analyzed DEGs using the GEO2R tool attached to the GEO. Then, we screened the mRNA levels of 5'-HOXD genes by quantitative reverse transcriptase-polymerase chain reaction (qRT-PCR). We discovered that OA chondrocyte proliferation was inhibited, and apoptosis was increased. Moreover, it was discovered that SOX9 and COL2A1 were downregulated at mRNA and protein levels, while matrix metalloproteinases (MMPs) and a disintegrin-like and metalloproteinase with thrombospondin motifs (ADAMTSs) were upregulated. According to the results of differentially expressed genes (DEGs) and qRT-PCR, we evaluated the protein level of HOXD11 and found that the expression of HOXD11 was downregulated, reversed to MMPs and ADAMTSs but consistent with the cartilage-specific factors, SOX9 and COL2A1. In the lentivirus transfection experiments, HOXD11 overexpression reversed the effects in OA chondrocytes. In human OA articular cartilage, aberrant subchondral bone was formed in hematoxylin-eosin (H&E) and Safranin O and fast green (SOFG) staining results. Furthermore, according to immunohistochemistry findings, SOX9 and HOXD11 expression was inhibited. The results of this study established that HOXD11 was downregulated in OA cartilage and that overexpression of HOXD11 could prevent cartilage degradation in OA.

Histological characterization of the human scapholunate ligament

The scapholunate interosseous ligament (SLIL) plays a fundamental role in stabilizing the wrist bones, and its disruption is a frequent cause of wrist arthrosis and disfunction. Traditionally, this structure is considered to be a variety of fibrocartilaginous tissue and consists of three regions: dorsal, membranous and palmar. Despite its functional relevance, the exact composition of the human SLIL is not well understood. In the present work, we have analyzed the human SLIL and control tissues from the human hand using an array of histological, histochemical and immunohistochemical methods to characterize each region of this structure. Results reveal that the SLIL is heterogeneous, and each region can be subdivided in two zones that are histologically different to the other zones. Analysis of collagen and elastic fibers, and several proteoglycans, glycoproteins and glycosaminoglycans confirmed that the different regions can be subdivided in two zones that have their own structure and composition. In general, all parts of the SLIL resemble the histological structure of the control articular cartilage, especially the first part of the membranous region (zone M1). Cells showing a chondrocyte-like phenotype as determined by S100 were more abundant in M1, whereas the zone containing more CD73-positive stem cells was D2. These results confirm the heterogeneity of the human SLIL and could contribute to explain why certain zones of this structure are more prone to structural damage and why other zones have specific regeneration potential. RESEARCH HIGHLIGHTS: Application of an array of histological analysis methods allowed us to demonstrate that the human scapholunate ligament is heterogeneous and consists of at least six different regions sharing similarities with the human cartilage, ligament and other anatomical structures.

A Tunable Glycosaminoglycan-Peptide Nanoparticle Platform for the Protection of Therapeutic Peptides

The popularity of Glycosaminoglycans (GAGs) in drug delivery systems has grown as their innate ability to sequester and release charged molecules makes them adept in the controlled release of therapeutics. However, peptide therapeutics have been relegated to synthetic, polymeric systems, despite their high specificity and efficacy as therapeutics because they are rapidly degraded in vivo when not encapsulated. We present a GAG-based nanoparticle system for the easy encapsulation of cationic peptides, which offers control over particle diameter, peptide release behavior, and swelling behavior, as well as protection from proteolytic degradation, using a singular, organic polymer and no covalent linkages. These nanoparticles can encapsulate cargo with a particle diameter range spanning 130-220 nm and can be tuned to release cargo over a pH range of 4.5 to neutral through the modulation of the degree of sulfation and the molecular weight of the GAG. This particle system also confers better in vitro performance than the unencapsulated peptide via protection from enzymatic degradation. This method provides a facile way to protect therapeutic peptides via the inclusion of the presented binding sequence and can likely be expanded to larger, more diverse cargo as well, abrogating the complexity of previously demonstrated systems while offering broader tunability.

Molecular Mechanisms in Pathophysiology of Mucopolysaccharidosis and Prospects for Innovative Therapy

Mucopolysaccharidoses (MPSs) are a group of inborn errors of the metabolism caused by a deficiency in the lysosomal enzymes required to break down molecules called glycosaminoglycans (GAGs). These GAGs accumulate over time in various tissues and disrupt multiple biological systems, including catabolism of other substances, autophagy, and mitochondrial function. These pathological changes ultimately increase oxidative stress and activate innate immunity and inflammation. We have described the pathophysiology of MPS and activated inflammation in this paper, starting with accumulating the primary storage materials, GAGs. At the initial stage of GAG accumulation, affected tissues/cells are reversibly affected but progress irreversibly to: (1) disruption of substrate degradation with pathogenic changes in lysosomal function, (2) cellular dysfunction, secondary/tertiary accumulation (toxins such as GM2 or GM3 ganglioside, etc.), and inflammatory process, and (3) progressive tissue/organ damage and cell death (e.g., skeletal dysplasia, CNS impairment, etc.). For current and future treatment, several potential treatments for MPS that can penetrate the blood-brain barrier and bone have been proposed and/or are in clinical trials, including targeting peptides and molecular Trojan horses such as monoclonal antibodies attached to enzymes via receptor-mediated transport. Gene therapy trials with AAV, ex vivo LV, and Sleeping Beauty transposon system for MPS are proposed and/or underway as innovative therapeutic options. In addition, possible immunomodulatory reagents that can suppress MPS symptoms have been summarized in this review.

Polyelectrolyte Brushes with Protein-Like Nanocolloids

Electrostatic interaction of ampholytic nanocolloidal particles (NPs), which mimic globular proteins, with polyelectrolyte brushes is analyzed within mean-field Poisson-Boltzmann approximation. In accordance with experimental findings, the theory predicts that an electrostatic driving force for the particle uptake by the brush may emerge when the net charge of the particle in the buffer and the charge of the brush are of the same sign. The origin of this driving force is change in the ionization state of weak cationic and anionic groups on the NP surface provoked by interaction with the brush. In experimental systems, the ionic interactions are complemented by excluded-volume, hydrophobic, and other types of interactions that all together control NP uptake by or expulsion from the brush. Here, we focus on the NP-brush ionic interactions. It is demonstrated that deviation between the buffer pH and the NP isoelectric point, considered usually as the key control parameter, does not uniquely determine the insertion free energy patterns. The latter depends also on the proportion of cationic and anionic groups in the NPs and their specific ionization constants as well as on salt concentration in the buffer. The analysis of the free energy landscape proves that a local minimum in the free energy inside the brush appears, provided the NP charge reversal occurs upon insertion into the brush. This minimum corresponds either to a thermodynamically stable or to a metastable state, depending on the pH offset from the IEP and salt concentration, and is separated from the bulk of the solution by a free energy barrier. The latter, being fairly independent of salt concentration in height, may strongly impede the NP absorption kinetically even when it is thermodynamically favorable. Hence, change reversal is a necessary but insufficient condition for the uptake of the NPs by similarly charged polyelectrolyte brushes.

Association of cartilage metabolism biomarkers and 25(OH)D levels with muscle biomechanical functions in professional rowers and canoeists

The purpose of the study was to assess the association of cartilage metabolism biomarkers and vitamin D metabolite levels with muscle biomechanical functions in professional rowers and canoeists. The serum levels of aggrecan, cartilage oligomeric matrix protein (COMP), and 25-hydroxyvitamin D (25(OH)D) were determined in elite male sweep-oar rowers (n = 24) and canoeists (n = 15). This was followed by a biomechanical study consisting in isometric measurement of peak torque (PT) of muscles involved in the rowing cycle in the athletes. There were found significant correlations of COMP with the ratio of trunk PT flexor to extensor (p < 0.05) and 25(OH)D with trunk PT-left rotators (p < 0.05), knee joints PT-left and right flexor (p ≤ 0.01), ratio of knee joint PT-right flexor to knee joint PT-right extensor (p < 0.05) in rowers and aggreccan with elbow joint PT of the right flexor (p ≤ 0.01) and extensor (p = 0.05) in canoeists. The correlations of COMP and aggrecan levels with PT of the muscle groups studied in rowers and canoeists indicate the importance of stabilizing the muscular system in cartilage metabolism. The relationship between 25(OH)D status and biomechanical parameters confirm that vitamin D plays an important role in maintaining skeletal muscle health.

Biological functions and applications of LncRNAs in the regulation of the extracellular matrix in osteoarthritis

Osteoarthritis (OA) is a major cause of disability, characterized by chronic pain, irreversible destruction, and loss of function of the articular cartilage. The integrity and arrangement of the composition and structure of the extracellular matrix (ECM) are essential for maintaining the elasticity, integrity, and mechanical support function of the cartilage tissue. Osteoarthritis causes substantial changes in the ECM, driving the progression of the disease. Recent studies have shown that the ECM plays a critical role in the development of cartilage tissue as well as the occurrence and development of osteoarthritis by directly or indirectly regulating chondrocyte proliferation, apoptosis, differentiation, and gene expression. Long non-coding RNAs (lncRNAs) are a class of non-coding RNAs derived from large transcripts. Mutations and disorders of lncRNAs are closely related to the development of osteoarthritis. Abnormal expression of lncRNAs in osteoarthritic cartilage regulates the synthesis and decomposition of the cartilaginous ECM. Therefore, the use of lncRNAs as nucleic acid drugs that regulate their targets may reduce ECM degradation, thereby delaying the pathological progression of osteoarthritis. In this review, the regulatory effects of lncRNAs on ECM in different cell behaviors related to OA are summarized. The roles of lncRNAs in the proliferation, apoptosis, differentiation, and ECM-related gene activity of chondrocytes, as well as the application of lncRNAs as potential gene therapy drugs for the repair and regeneration of osteoarthritic tissue, are also reviewed. A better understanding of the roles of lncRNAs in guiding chondrocyte behavior and ECM metabolism is critical for their future applications in osteoarthritis therapy and regenerative medicine.

Modulation of apoptosis and Inflammasome activation in chondrocytes: co-regulatory role of Chlorogenic acid

BACKGROUND

The B-cell lymphoma 2 (Bcl-2) protein regulates programmed cell death throughout the disease conditions by upholding apoptotic pathways. However, the mechanism by which it's expressed in chondrocytes still needs to be studied in chondrocyte-related disorders. Additionally, exploring the potential therapeutic role of Chlorogenic acid (CGA) in confluence with Bcl-2 modulation is of significant interest.

METHODS

In vivo and in vitro studies were performed according to our previous methodologies. The chondrocytes were cultured in specific growth media under standard conditions after expression verification of different microRNAs through high-throughput sequencing and verification of Bcl-2 involvement in tibial growth plates. The effect of Bcl-2 expression was investigated by transfecting chondrocytes with miR-460a, siRNA, and their negative controls alone or in combination with CGA. The RNA was extracted and subjected to a reverse transcription-quantitative polymerase chain reaction (RT-qPCR). Western blot analysis and immunofluorescence assays were performed to visualize the intracellular localization of Bcl-2 and associated proteins related to apoptotic and inflammasome pathways. Moreover, apoptosis through flow cytometry was also performed to understand the modulation of concerning pathways.

RESULTS

The suppression of Bcl-2 induced higher apoptosis and mitochondrial dysfunction, leading to IL-1β maturation and affecting the inflammasome during chondrocyte proliferation. Conversely, overexpression attenuated the activation, as evidenced by reduced caspase activity and IL-1β maturation. In parallel, CGA successfully reduced siRNA-induced apoptosis by decreasing Cytochrome C (Cyto C) release from the mitochondria to the cytoplasm, which in turn decreased Caspase-3 and Caspase-7 cleavage with Bcl-2-associated X protein (Bax). Furthermore, siBcl-2 transfection and CGA therapy increased chondrocyte proliferation and survival. The CGA also showed a promising approach to maintaining chondrocyte viability by inhibiting siRNA-induced apoptosis.

CONCLUSIONS

Targeting Bcl-2-mediated regulation might be a possible treatment for chondrocyte-related conditions. Moreover, these results add knowledge of the complicated processes underlying chondrocyte function and the pathophysiology of related diseases, highlighting the significance of target specific therapies. Video Abstract.

From biochemical markers to molecular endotypes of osteoarthritis: a review on validated biomarkers

INTRODUCTION

Osteoarthritis (OA) affects over 500 million people worldwide. OA patients are symptomatically treated, and current therapies exhibit marginal efficacy and frequently carry safety-risks associated with chronic use. No disease-modifying therapies have been approved to date leaving surgical joint replacement as a last resort. To enable effective patient care and successful drug development there is an urgent need to uncover the pathobiological drivers of OA and how these translate into disease endotypes. Endotypes provide a more precise and mechanistic definition of disease subgroups than observable phenotypes, and a panel of tissue- and pathology-specific biochemical markers may uncover treatable endotypes of OA.

AREAS COVERED

We have searched PubMed for full-text articles written in English to provide an in-depth narrative review of a panel of validated biochemical markers utilized for endotyping of OA and their association to key OA pathologies.

EXPERT OPINION

As utilized in IMI-APPROACH and validated in OAI-FNIH, a panel of biochemical markers may uncover disease subgroups and facilitate the enrichment of treatable molecular endotypes for recruitment in therapeutic clinical trials. Understanding the link between biochemical markers and patient-reported outcomes and treatable endotypes that may respond to given therapies will pave the way for new drug development in OA.

miR-92a-3p-inspired shRNA exhibits pro-chondrogenic and chondrocyte protective effects in osteoarthritis treatment through targeting SMAD6/7

INTRODUCTION

Osteoarthritis (OA) compromises patients' quality of life and requires further study. Although miR-92a-3p was reported to possess chondroprotective effects, the underlying mechanism requires further clarification. The objectives of this study were to elucidate the mechanism by which miR-92a-3p alleviates OA and to examine the efficacy of shRNA-92a-3p, which was designed based on mature miR-92a-3p.

MATERIALS AND METHODS

TargetScan and luciferase reporter assay were used to predict the target of miR-92a-3p. Adipose-derived stem cells (ADSCs) were transfected with miR-92a-3p/miR-NC mimic for the analysis of chondrogenic biomarkers and SMAD proteins. ADSCs and osteoarthritic chondrocytes were transduced with shRNA-92a-3p for the analysis of chondrogenic biomarkers and SMAD proteins. OA was surgically induced in C57BL/6JJcl mice, and ADSCs with/without shRNA-92a-3p transduction were intra-articularly injected for the assessment of cartilage damage.

RESULTS

SMAD6 and SMAD7 were predicted as direct targets of miR-92a-3p by TargetScan and luciferase reporter assay. Transfection of the miR-92a-3p mimic resulted in a decrease in SMAD6 and SMAD7 levels and an increase in phospho-SMAD2/3, phospho-SMAD1/5/9, SOX9, collagen type II, and aggrecan levels in ADSCs. Furthermore, shRNA-92a-3p decreased SMAD6 and SMAD7 levels, and increased phospho-SMAD2/3, phospho-SMAD1/5/9, SOX9, collagen type II, and aggrecan levels in ADSCs and osteoarthritic chondrocytes. Additionally, ADSC-shRNA-92a-3p-EVs reduced the rate of decrease of SOX9, collagen type II, and aggrecan in osteoarthritic chondrocytes. In mice with surgically induced OA, shRNA-92a-3p-treated ADSCs alleviated cartilage damage more effectively than nontreated ADSCs.

CONCLUSIONS

miR-92a-3p and shRNA-92a-3p exhibit therapeutic effects in treating OA by targeting SMAD6 and SMAD7, thereby enhancing TGF-β signaling.

Interaction of Polyanionic and Polycationic Brushes with Globular Proteins and Protein-like Nanocolloids

A large number of experimental studies have demonstrated that globular proteins can be absorbed from the solution by both polycationic and polyanionic brushes when the net charge of protein globules is of the same or of the opposite sign with respect to that of brush-forming polyelectrolyte chains. Here, we overview the results of experimental studies on interactions between globular proteins and polycationic or polyanionic brushes, and present a self-consistent field theoretical model that allows us to account for the asymmetry of interactions of protein-like nanocolloid particles comprising weak (pH-sensitive) cationic and anionic groups with a positively or negatively charged polyelectrolyte brush. The position-dependent insertion free energy and the net charge of the particle are calculated. The theoretical model predicts that if the numbers of cationic and anionic ionizable groups of the protein are approximately equal, then the interaction patterns for both cationic and anionic brushes at equal offset on the "wrong side" from the isoelectric point (IEP), i.e., when the particle and the brush charge are of the same sign, are similar. An essential asymmetry in interactions of particles with polycationic and polyanionic brushes is predicted when fractions of cationic and anionic groups differ significantly. That is, at a pH above IEP, the anionic brush better absorbs negatively charged particles with a larger fraction of ionizable cationic groups and vice versa.

Effect of Phytic Acid Addition on the Structure of Collagen-Hyaluronic Acid Composite Gel

Composite collagen gels with hyaluronic acid are developed tissue-engineered structures for filling and regeneration of defects in various organs and tissues. For the first time, phytic acid was used to increase the stability and improve the mechanical properties of collagen gels with hyaluronic acid. Phytic acid is a promising cross-linker for collagen hydrogels and is a plant-derived antioxidant found in rich sources of beans, grains, and oilseeds. Phytic acid has several benefits due to its antioxidant, anticancer, and antitumor properties. In this work, studies were carried out on the kinetics of the self-assembly of collagen molecules in the presence of phytic and hyaluronic acids. It was shown that both of these acids do not lead to collagen self-assembly. Scanning electron microscopy showed that in the presence of phytic and hyaluronic acids, the collagen fibrils had a native structure, and the FTIR method confirmed the chemical cross-links between the collagen fibrils. DSC and rheological studies demonstrated that adding the phytic acid improved the stability and modulus of elasticity of the collagen gel. The presence of hyaluronic acid in the collagen gel slightly reduced the effect of phytic acid. The presence of phytic acid in the collagen gel improved the stability of the scaffold, but, after 1 week of cultivation, slightly reduced the viability of mesenchymal stromal cells cultured in the gel. The collagen type I gel with hyaluronic and phytic acids can be used to replace tissue defects, especially after the removal of cancerous tumors.

Photo-Cross-Linkable, Injectable, and Highly Adhesive GelMA-Glycol Chitosan Hydrogels for Cartilage Repair

Hydrogels provide a promising platform for cartilage repair and regeneration. Although hydrogels have shown some efficacy, they still have shortcomings including poor mechanical properties and suboptimal integration with surrounding cartilage. Herein, hydrogels that are injectable, cytocompatible, mechanically robust, and highly adhesive to cartilage are developed. This approach uses GelMA-glycol chitosan (GelMA-GC) that is crosslinkable with visible light and photoinitiators (lithium acylphosphinate and tris (2,2'-bipyridyl) dichlororuthenium (II) hexahydrate ([RuII(bpy)3 ]2+ and sodium persulfate (Ru/SPS)). Ru/SPS-cross-linked hydrogels have higher compressive and tensile modulus, and most prominently higher adhesive strength with cartilage, which also depends on inclusion of GC. Tensile and push-out tests of the Ru/SPS-cross-linked GelMA-GC hydrogels demonstrate adhesive strength of ≈100 and 46 kPa, respectively. Hydrogel precursor solutions behave in a Newtonian manner and are injectable. After injection in focal bovine cartilage defects and in situ cross-linking, this hydrogel system remains intact and integrated with cartilage following joint manipulation ex vivo. Cells remain viable (>85%) in the hydrogel system and further show tissue regeneration potential after three weeks of in vitro culture. These preliminary results provide further motivation for future research on bioadhesive hydrogels for cartilage repair and regeneration.

Decreased expression of GEM in osteoarthritis cartilage regulates chondrogenic differentiation via Wnt/β-catenin signaling

BACKGROUND

GEM (GTP-binding protein overexpressed in skeletal muscle) is one of the atypical small GTPase subfamily members recently identified as a regulator of cell differentiation. Abnormal chondrogenesis coupled with an imbalance in the turnover of cartilaginous matrix formation is highly relevant to the onset and progression of osteoarthritis (OA). However, how GEM regulates chondrogenic differentiation remains unexplored.

METHODS

Cartilage tissues were obtained from OA patients and graded according to the ORASI and ICRS grading systems. The expression alteration of GEM was detected in the Grade 4 cartilage compared to Grade 0 and verified in OA mimic culture systems. Next, to investigate the specific function of GEM during these processes, we generated a Gem knockdown (Gem-Kd) system by transfecting siRNA targeting Gem into ATDC5 cells. Acan, Col2a1, Sox9, and Wnt target genes of Gem-Kd ATDC5 cells were detected during induction. The transcriptomic sequencing analysis was performed to investigate the mechanism of GEM regulation. Wnt signaling pathways were verified by real-time PCR and immunoblot analysis. Finally, a rescue model generated by treating Gem-KD ATDC5 cells with a Wnt signaling agonist was established to validate the mechanism identified by RNA sequencing analysis.

RESULTS

A decreased expression of GEM in OA patients' cartilage tissues and OA mimic chondrocytes was observed. While during chondrogenesis differentiation and cartilage matrix formation, the expression of GEM was increased. Gem silencing suppressed chondrogenic differentiation and the expressions of Acan, Col2a1, and Sox9. RNA sequencing analysis revealed that Wnt signaling was downregulated in Gem-Kd cells. Decreased expression of Wnt signaling associated genes and the total β-CATENIN in the nucleus and cytoplasm were observed. The exogenous Wnt activation exhibited reversed effect on Gem loss-of-function cells.

CONCLUSION

These findings collectively validated that GEM functions as a novel regulator mediating chondrogenic differentiation and cartilage matrix formation through Wnt/β-catenin signaling.

Cartilage-inspired terpolymer hydrogel with excellent mechanical properties and superior lubricating ability

Osteoarthritis (OA), the most common degenerative joint disorder, seriously affects patients' daily activities. Recently, hydrogels, due to their similar structure to articular cartilage, have shown great potential as cartilage-repairing materials. In the present work, we developed a simple process for fabricating terpolymer [P(acrylamide-co-acrylic acid-co-2-acrylamido-2-methyl-1-propanesulfonic acid)/Fe3+] hydrogel [P(AAm-co-AAc-co-AMPS)/Fe3+]. The content of AMPS was found to show a crucial effect on the mechanical and tribological performance of the terpolymer hydrogel. When the content of AMPS was 0.45 mol L-1, the compressive strength, modulus, and friction coefficient of the terpolymer hydrogel were 66.60 ± 1.79 MPa, 2.10 ± 0.16 MPa, and 0.032, respectively. In addition, the hydrogel showed high wear durability and the friction coefficient was as low as 0.038 after 3.6 × 105 sliding cycles.

Modeling of glycosaminoglycan biosynthesis in intervertebral disc cells

Loss of proteoglycan (PG) is a potential factor responsible for degeneration of the intervertebral disc (IVD). PG consists of a core protein with covalently attached glycosaminoglycan (GAG) chains. The objective of this study was to develop a mathematical model of GAG biosynthesis to investigate the effects of glycolytic enzymes on GAG biosynthesis of IVD cells. A new mathematical model of GAG biosynthesis was developed for IVD cells by incorporating biosynthesis of uridine diphosphate-sugars into the glycolytic pathway. This new model showed good agreement between the model predictions of intracellular ATP content and GAG biosynthesis and experimental data measured at different external glucose levels. The quantitative analyses demonstrated that GAG biosynthesis may be sensitive to the activities of hexokinase (HK) and phosphofructokinase (PFK), especially at low glucose supply, with GAG biosynthesis being significantly enhanced by a slight increase in activities of HK and PFK. This suggests that metabolic reprogramming could be a potential strategy for promoting PG biosynthesis in IVD cells. Furthermore, it was shown that GAG biosynthesis may be promoted by increasing intracellular glutamine concentration or activity of glutamine:fructose-6-phosphate amidotransferase in the hexamine pathway. This study provides a better understanding of the relationship between glycolysis and PG biosynthesis in IVD cells. The theoretical framework developed in this study is useful for studying the role of glycolysis in disc degeneration and developing new preventive and treatment strategies for degeneration of the IVD.