Contribution of Circulatory Disturbances in Subchondral Bone to the Pathophysiology of Osteoarthritis

Soybean Isoflavones Alleviate Osteoarthritis Through Modulation of the TSC1/mTORC1 Signaling Pathway to Reduce Intrachondral Angiogenesis

BACKGROUND

The incidence of osteoarthritis (OA) is increasing, yet its pathogenesis remains largely unknown. Recent studies suggest that abnormal subchondral bone remodeling plays a crucial role in OA development, highlighting a gap in clinical treatments targeting this aspect. Soybean Isoflavone (SI) has shown potential in treating OA, although its mechanisms are not fully understood.

METHODS

This research investigated the effects of SI on subchondral bone remodeling in an OA rat model, assessing joint damage, OARSI scores, and type H vessel formation (CD31hiEmcnhi expression). Additionally, the expression of ALP, OCN, BMP, and TSC1 was evaluated to determine involvement of the mTORC1 pathway. In vitro studies on IL-1β-induced osteoblasts further examined the impact of SI on TSC1/mTORC1 signaling and related markers.

RESULTS

SI treatment reduced joint damage and OARSI scores in the rat OA model, significantly decreasing CD31hiEmcnhi expression, indicating a reduction in type H vessel formation. SI also downregulated ALP, OCN, and BMP expression while upregulating TSC1, suggesting inhibition of the mTORC1 signaling pathway and VEGF release. In vitro, SI increased TSC1 expression and decreased mTORC1 signaling, VEGF, ALP, OCN, and BMP levels in IL-1β-induced osteoblasts.

CONCLUSION

SI targets the TSC1/mTORC1 signaling pathway to suppress osteoblast activation and VEGF release, inhibiting type H vessel formation and slowing abnormal subchondral bone remodeling. These findings provide a novel therapeutic approach for OA by focusing on subchondral bone remodeling mechanisms.

Similar Pathophysiological Mechanisms Between Osteoarthritis and Vascular Disease

Osteoarthritis (OA) is a prevalent, chronic joint disorder affecting millions of people worldwide, characterized by articular cartilage degradation, subchondral bone remodeling, synovial cytokine secretion, and osteophyte formation. OA primarily affects the hips, knees, hands, and spine. Patients with OA exhibit a higher prevalence of cardiovascular comorbidities and potentially important associations between OA and cardiovascular diseases have prompted investigations into potentially similar pathophysiological associations. This review explores the coexistence of atherosclerotic peripheral vascular disease (ASPVD) in OA patients, including evidence from a contemporary study suggesting associations between OA and arterial wall thickness and blood flow changes which are characteristic of early atherosclerosis, and which stimulate reactive pathology in endothelial cells. Observations from this study demonstrate elevated arterial flow volume and increased intima-media thickness in arteries ipsilateral to OA knees, suggesting a potential link between OA and arterial wall disease. We further explore the intricate relationship between the vascular system and skeletal health, highlighting bidirectional interactions among endothelial cells, inflammatory cells, and various bone cells. Mechanical endothelial cell dysfunction is discussed, emphasizing the impact of vessel wall material changes and endothelial cell responses to alterations in fluid shear stress. Inflammatory changes in OA and ASPVD are also explored, showcasing shared pathophysiological processes involving immune cell infiltration and pro-inflammatory cytokines. Additionally, the role of hypofibrinolysis in OA and ASPVD is discussed, highlighting similarities in elevations of the hypercoagulative and hypofibrinolytic factor, plasminogen activator inhibitor (PAI-1). The review suggests a provocative relationship among low-grade chronic inflammation, endothelial dysfunction, and hypofibrinolytic states in OA and ASPVD, warranting further investigation. In conclusion, this review provides an exploration of the possible associations between OA and ASPVD. While the ongoing study's findings and other reports are observational, they suggest shared pathophysiological processes and emphasize the need for further research to elucidate additional potentially correlative linkages between these conditions. Understanding common molecular pathways may pave a way for targeted interventions that address both OA and ASPVD.

Non-coding RNAs as regulators of autophagy in chondrocytes: Mechanisms and implications for osteoarthritis

Osteoarthritis (OA) is a chronic degenerative joint disease with multiple causative factors such as aging, mechanical injury, and obesity. Autophagy is a complex dynamic process that is involved in the degradation and modification of intracellular proteins and organelles under different pathophysiological conditions. Autophagy, as a cell survival mechanism under various stress conditions, plays a key role in regulating chondrocyte life cycle metabolism and cellular homeostasis. Non-coding RNAs (ncRNAs) are heterogeneous transcripts that do not possess protein-coding functions, but they can act as effective post-transcriptional and epigenetic regulators of gene and protein expression, thus participating in numerous fundamental biological processes. Increasing evidence suggests that ncRNAs, autophagy, and their crosstalk play crucial roles in OA pathogenesis. Therefore, we summarized the complex role of autophagy in OA chondrocytes and focused on the regulatory role of ncRNAs in OA-associated autophagy to elucidate the complex pathological mechanisms of the ncRNA-autophagy network in the development of OA, thus providing new research targets for the clinical diagnosis and treatment of OA.

Hypobaric hypoxia aggravates osteoarthritis via the alteration of the oxygen environment and bone remodeling in the subchondral zone

A high prevalence of osteoarthritis (OA) has been observed among individuals living at high altitudes, and hypobaric hypoxia (HH) can cause bone mass and strength deterioration. However, the effect of HH on OA remains unclear. In this study, we aimed to explore the impact of HH on OA and its potential mechanisms. A rat knee OA model was established by surgery, and the rats were bred in an HH chamber simulating a high-altitude environment. Micro-computed tomography (Micro-CT), histological analysis, and RNA sequencing were performed to evaluate the effects of HH on OA in vivo. A hypoxic co-culture model of osteoclasts and osteoblasts was also established to determine their effects on chondrogenesis in vitro. Cartilage degeneration significantly worsened in the HH-OA group compared to that in the normoxia-OA (N-OA) group, 4 weeks after surgery. Micro-CT analysis revealed more deteriorated bone mass in the HH-OA group than in the N-OA group. Decreased hypoxia levels in the cartilage and enhanced hypoxia levels in the subchondral bone were observed in the HH-OA group. Furthermore, chondrocytes cultured in a conditioned medium from the hypoxic co-culture model showed decreased anabolism and extracellular matrix compared to those in the normoxic model. RNA sequencing analysis of the subchondral bone indicated that the glycolytic signaling pathway was highly activated in the HH-OA group. HH-related OA progression was associated with alterations in the oxygen environment and bone remodeling in the subchondral zone, which provided new insights into the pathogenesis of OA.

Mendelian randomization to evaluate the causal relationship between liver enzymes and the risk of six specific bone and joint-related diseases

Background

Studies of liver dysfunction in relation to bone and joint-related diseases are scarce, and its causality remains unclear. Our objective was to investigate whether serum liver enzymes are causally associated with bone and joint-related diseases using Mendelian randomization (MR) designs.

Methods

Genetic data on serum liver enzymes (alkaline phosphatase (ALP); alanine transaminase (ALT); gamma-glutamyl transferase (GGT)) and six common bone and joint-related diseases (rheumatoid arthritis (RA), osteoporosis, osteoarthritis (OA), ankylosing spondylitis, psoriatic arthritis, and gout) were derived from independent genome-wide association studies of European ancestry. The inverse variance-weighted (IVW) method was applied for the main causal estimate. Complementary sensitivity analyses and reverse causal analyses were utilized to confirm the robustness of the results.

Results

Using the IVW method, the positive causality between ALP and the risk of osteoporosis diagnosed by bone mineral density (BMD) at different sites was indicated (femoral neck, lumbar spine, and total body BMD, odds ratio (OR) [95% CI], 0.40 [0.23-0.69], 0.35 [0.19-0.67], and 0.33 [0.22-0.51], respectively). ALP was also linked to a higher risk of RA (OR [95% CI], 6.26 [1.69-23.51]). Evidence of potential harmful effects of higher levels of ALT on the risk of hip and knee OA was acquired (OR [95% CI], 2.48 [1.39-4.41] and 3.07 [1.49-6.30], respectively). No causal relationship was observed between GGT and these bone and joint-related diseases. The study also found that BMD were all negatively linked to ALP levels (OR [95% CI] for TBMD, FN-BMD, and LS-BMD: 0.993 [0.991-0.995], 0.993 [0.988-0.998], and 0.993 [0.989, 0.998], respectively) in the reverse causal analysis. The results were replicated via sensitivity analysis in the validation process.

Conclusions

Our study revealed a significant association between liver function and bone and joint-related diseases.

Knee Osteoarthritis: Epidemiology, Pathogenesis, and Mesenchymal Stem Cells: What Else Is New? An Update

Osteoarthritis (OA) is a chronic disease and the most common orthopedic disorder. A vast majority of the social OA burden is related to hips and knees. The prevalence of knee OA varied across studies and such differences are reflected by the heterogeneity of data reported by studies conducted worldwide. A complete understanding of the pathogenetic mechanisms underlying this pathology is essential. The OA inflammatory process starts in the synovial membrane with the activation of the immune system, involving both humoral and cellular mediators. A crucial role in this process is played by the so-called “damage-associated molecular patterns” (DAMPs). Mesenchymal stem cells (MSCs) may be a promising option among all possible therapeutic options. However, many issues are still debated, such as the best cell source, their nature, and the right amount. Further studies are needed to clarify the remaining doubts. This review provides an overview of the most recent and relevant data on the molecular mechanism of cartilage damage in knee OA, including current therapeutic approaches in regenerative medicine.

Chronic vein insufficiency correction in patients with lower extremities varicosity and knee osteoarthritis

Introduction. Chronic vein diseases in general and varicose veins of the lower extremities in particular represent a serious medical and social problem.

The aim was to study the influence of the therapy of venous outflow disorders on the treatment results of osteoarthritis of the knee joints in patients with varicose veins in combination with osteoarthritis of the knee joints.

Materials and methods. The study included 105 patients with varicose veins combined with knee osteoarthritis who had previously received treatment for osteoarthritis of the knee joints but had not received or had received extremely irregular therapy for varicose veins. The follow-up period for the patients was 12 months. The patients underwent the first course of phlebotropic drugs for 2 months from the start of the study. Then this course was repeated twice at 3-month intervals. The standard phlebotropic drug was a micronized purified flavonoid fraction. Compression knitwear was recommended in all patients. Class 2 stockings or tights with an ankle pressure of 23–32 mmHg were used in the vast majority of cases. Treatment of osteoarthritis included the use of nonsteroidal anti-inflammatory drugs, disease-modifying agents (chondroitin sulfate, glucosamine sulfate), and physical therapy.

Results. The VCSS scale reduced the degree of chronic venous insufficiency in the clinical group. At inclusion in the study, the average score in the clinical group was 7.1 ± 1.9, after 6 months the result was 6.1 ± 1.5, and after 12 months – 6.0 ± 1.2 points. In the control group, where patients did not receive therapy for varicose veins, there were no dynamics. The results of joint syndrome against the background of correction of venous outflow disturbances – decrease of Leken and WOMAC index values, decrease of pain syndrome according to the visual analogue scale. All this led to a decrease in the patients' need for taking analgesics.

Conclusions. Out of 100 patients with joint pathology, 68 patients were diagnosed with varicose veins. These diseases aggravate each other, but we can assume that the venous pathology is primary. A vicious circle is set in motion – progression of osteoarthritis due to the disturbances of venous outflow, and varicosity due to the deterioration of muscular-venous pump functioning.

Effect of cell receptors in the pathogenesis of osteoarthritis: Current insights

Osteoarthritis (OA) is a chronic arthritic disease characterized by cartilage degradation, synovial inflammation, and subchondral bone lesions. The studies on the pathogenesis of OA are complex and diverse. The roles of receptors signaling in chondrocyte anabolism, inflammatory factors expression of synovial fibroblast, and angiogenesis in subchondral bone are particularly important for exploring the pathological mechanism of OA and clinical diagnosis and treatment. By reviewing the relevant literature, this article elaborates on the abnormal expression of receptors and the signaling transduction pathways from different pathological changes of OA anatomical components, aiming to provide new research ideas and clinical therapeutic value for OA pathogenesis.

Osteoblasts induce glucose-derived ATP perturbations in chondrocytes through noncontact communication

Cartilage and subchondral bone communicate with each other through material and signal exchanges. However, direct evidence provided by experimental studies on their interactions is insufficient. In the present study, we establish a noncontact co-culture model with a transwell chamber to explore the energetic perturbations in chondrocytes influenced by osteoblasts. Our results indicate that osteoblasts induce more ATP generation in chondrocytes through an energetic shift characterized by enhanced glycolysis and impaired mitochondrial tricarboxylic acid cycle. Enhanced glycolysis is shown by an increase of secreted lactate and the upregulation of glycolytic enzymes, including glucose-6-phosphate isomerase (Gpi), liver type ATP-dependent 6-phosphofructokinase (Pfkl), fructose-bisphosphate aldolase C (Aldoc), glyceraldehyde-3-phosphate dehydrogenase (Gapdh), triosephosphate isomerase (Tpi1), and phosphoglycerate kinase 1 (Pgk1). Impaired mitochondrial tricarboxylic acid cycle is characterized by the downregulation of cytoplasmic aspartate aminotransferase (Got1) and mitochondrial citrate synthase (Cs). Osteoblasts induce the activation of Akt and P38 signaling to mediate ATP perturbations in chondrocytes. This study may deepen our understanding of the maintenance of metabolic homeostasis in the bone-cartilage unit.

Cellular alterations and crosstalk in the osteochondral joint in osteoarthritis and promising therapeutic strategies

Osteoarthritis (OA) is a joint disorder involving cartilage degeneration and subchondral bone sclerosis. The bone-cartilage interface is implicated in OA pathogenesis due to its susceptibility to mechanical and biological factors. The crosstalk between cartilage and the underlying subchondral bone is elevated in OA due to multiple factors, such as increased vascularization, porosity, microcracks and fissures. Changes in the osteochondral joint are traceable to alterations in chondrocytes and bone cells (osteoblasts, osteocytes and osteoclasts). The phenotypes of these cells can change with the progression of OA. Aberrant intercellular communications among bone cell-bone cell and bone cell-chondrocyte are of great importance and might be the factors promoting OA development. An appreciation of cellular phenotypic changes in OA and the mechanisms by which these cells communicate would be expected to lead to the development of targeted drugs with fewer side effects.

Porous 3D Scaffolds Enhance MSC Vitality and Reduce Osteoclast Activity

In the context of an aging population, unhealthy Western lifestyle, and the lack of an optimal surgical treatment, deep osteochondral defects pose a great challenge for the public health system. Biodegradable, biomimetic scaffolds seem to be a promising solution. In this study we investigated the biocompatibility of porous poly-((D,L)-lactide-ε-caprolactone)dimethacrylate (LCM) scaffolds in contrast to compact LCM scaffolds and blank cell culture plastic. Thus, morphology, cytotoxicity and metabolic activity of human mesenchymal stromal cells (MSC) seeded directly on the materials were analyzed after three and six days of culturing. Further, osteoclastogenesis and osteoclastic activity were assessed using reverse-transcriptase real-time PCR of osteoclast-specific genes, EIA and morphologic aspects after four, eight, and twelve days. LCM scaffolds did not display cytotoxic effects on MSC. After three days, metabolic activity of MSC was enhanced on 3D porous scaffolds (PS) compared to 2D compact scaffolds (CS). Osteoclast activity seemed to be reduced at PS compared to cell culture plastic at all time points, while no differences in osteoclastogenesis were detectable between the materials. These results indicate a good cytocompatibility of LCM scaffolds. Interestingly, porous 3D structure induced higher metabolic activity of MSC as well as reduced osteoclast activity.

The Role of Chronic Inflammatory Bone and Joint Disorders in the Pathogenesis and Progression of Alzheimer's Disease

Late-onset Alzheimer's Disease (LOAD) is a devastating neurodegenerative disorder that causes significant cognitive debilitation in tens of millions of patients worldwide. Throughout disease progression, abnormal secretase activity results in the aberrant cleavage and subsequent aggregation of neurotoxic Aβ plaques in the cerebral extracellular space and hyperphosphorylation and destabilization of structural tau proteins surrounding neuronal microtubules. Both pathologies ultimately incite the propagation of a disease-associated subset of microglia-the principle immune cells of the brain-characterized by preferentially pro-inflammatory cytokine secretion and inhibited AD substrate uptake capacity, which further contribute to neuronal degeneration. For decades, chronic neuroinflammation has been identified as one of the cardinal pathophysiological driving features of AD; however, despite a number of works postulating the underlying mechanisms of inflammation-mediated neurodegeneration, its pathogenesis and relation to the inception of cognitive impairment remain obscure. Moreover, the limited clinical success of treatments targeting specific pathological features in the central nervous system (CNS) illustrates the need to investigate alternative, more holistic approaches for ameliorating AD outcomes. Accumulating evidence suggests significant interplay between peripheral immune activity and blood-brain barrier permeability, microglial activation and proliferation, and AD-related cognitive decline. In this work, we review a narrow but significant subset of chronic peripheral inflammatory conditions, describe how these pathologies are associated with the preponderance of neuroinflammation, and posit that we may exploit peripheral immune processes to design interventional, preventative therapies for LOAD. We then provide a comprehensive overview of notable treatment paradigms that have demonstrated considerable merit toward treating these disorders.

Efficacy and Safety of Ultrasound-Guided Radiofrequency Treatment for Chronic Pain in Patients with Knee Osteoarthritis: A Systematic Review and Meta-Analysis

Background

Knee osteoarthritis (KOA) is a common degenerative disease associated with joint dysfunction and pain. Ultrasound-guided radiofrequency (RF) may be a promising therapy in the treatment of chronic pain for KOA patients.

Objective

To evaluate the efficacy and safety of ultrasound-guided RF treatment for chronic pain in patients with KOA.

Design

A systematic review was conducted, and a meta-analysis was carried out when possible. Setting. We examined the studies evaluating the clinical efficiency of ultrasound-guided RF on chronic pain in KOA population.

Method

A systematic review for the efficacy and safety of ultrasound-guided RF treatment for pain management of KOA patients was carried out in PubMed, EMBASE, Cochrane Library, Web of Science, Wanfang Data, and China National Knowledge Infrastructure (CNKI) from the date of inception to February 2020, and a meta-analysis was conducted. The primary outcomes of pain intensity (visual analogue scale or numerical rating scale) and knee function [the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC)] were evaluated from baseline to various follow-up times by random-effects model. Heterogeneity was assessed by I ² statistic and the potential sources of heterogeneity by subgroup and metaregression analyses, respectively.

Results

Eight publications with 256 patients were included in the meta-analysis. RF could relieve pain with -4.196 of pooled mean difference and improve knee function by decreasing 23.155 points in WOMAC. Three patients had ecchymosis, two with hypoesthesia and one with numbness after the procedure, and improved within 6 months. Furthermore, study design and treatment target were the sources of heterogeneity by subgroup and metaregression analyses, accounting for 37% and 74% of variances, respectively. Target of genicular nerve achieved better pain relief than intra-articular or sciatic nerve. Sensitivity analysis showed that removal of any single study was unlikely to overturn the findings. Limitations. There were some limitations in the study. Firstly, the small number of relevant studies limited the confidence level of the meta-analysis. Also, the significant heterogeneity may not be explained due to the limited data. Secondly, the direct comparison of two different guidance methods (ultrasound vs. fluoroscopy) for RF therapy is lacking. In addition, the outcomes were blindly assessed in the meta-analysis from all studies according to evaluation of bias, which could affect the reality of the data. Finally, most of the studies only provided short follow-up times, so we could not analyze the long-term effectiveness of ultrasound-guided RF in the treatment of patients with KOA.

Conclusions

Ultrasonography is an effective, safe, nonradiative, and easily applicable guidance method for RF in pain relief and functional improvement in KOA patients.

Bone Marrow Microvasculature

The skeleton is highly vascularized due to the various roles blood vessels play in the homeostasis of bone and marrow. For example, blood vessels provide nutrients, remove metabolic by-products, deliver systemic hormones, and circulate precursor cells to bone and marrow. In addition to these roles, bone blood vessels participate in a variety of other functions. This article provides an overview of the afferent, exchange and efferent vessels in bone and marrow and presents the morphological layout of these blood vessels regarding blood flow dynamics. In addition, this article discusses how bone blood vessels participate in bone development, maintenance, and repair. Further, mechanical loading-induced bone adaptation is presented regarding interstitial fluid flow and pressure, as regulated by the vascular system. The role of the sympathetic nervous system is discussed in relation to blood vessels and bone. Finally, vascular participation in bone accrual with intermittent parathyroid hormone administration, a medication prescribed to combat age-related bone loss, is described and age- and disease-related impairments in blood vessels are discussed in relation to bone and marrow dysfunction. © 2020 American Physiological Society. Compr Physiol 10:1009-1046, 2020.

Tougu Xiaotong capsule exerts a therapeutic effect by improving knee meniscus in the early osteoarthritis rat model

The aim of the study was to observe the effects of Tougu Xiaotong capsule (TGXTC) on the microstructure and ultrastructure of meniscus in rats with early knee osteoarthritis (KOA). A total of 27 Sprague Dawley rats were randomly divided into three groups: The normal group (non-papain-induced KOA; received saline only), the model group (papain-induced KOA; received saline only) and the TGXTC group [papain-induced KOA; received TGXTC (0.31g·kg-1·d-1)]. After 4 weeks treatment, the animals were anesthetized and the sagittal plane of the intact knees (n=6 per group) was obtained and prepared in paraffin section. Following hematoxylin and eosin staining, the degeneration of cartilage structure was evaluated via Mankin score, the microstructure of meniscus was observed and the area of calcification in meniscus was analyzed. Following toluidine blue staining, the content of proteoglycan in meniscus was analyzed. Three samples in each group were obtained and the ultrathin sections of meniscus were observed through a transmission electron microscope. The results showed that compared with the normal group, in the model group the joint space became narrow and the cartilage layer was slightly damaged and the Mankin score was 4.17±0.76, suggesting that the early KOA model was successfully established. After TGXTC treatment, the joint space stenosis and cartilage damage were improved as the Mankin score significantly decreased. Compared with the normal group, in the model group the surface of meniscal cartilage was much more uneven, the area of calcification was significantly increased and the content of proteoglycan of cartilage matrix was significantly decreased. However, following TGXTC treatment, the surface of the meniscal cartilage was much more smooth and flat, and the damage of tissue structure and the calcified area were significantly reduced, and the proteoglycan of cartilage matrix content was significantly increased. Compared with the normal group, the number of cellular processes and organelles, including the rough endoplasmic reticulum, mitochondria and Golgi apparatus of meniscal cartilage were reduced and swollen in the model group. In addition, the nuclei were deformed and heterochromatin agglutinated. The extracellular collagen fibrils became slender, disordered and sparse. Compared with the model group, the TGXTC group had more cell processes and organelles, alleviated swelling and heterochromatin agglutinating. Additionally, the collagen fibrils around the cells were thicker, larger and arranged in an orderly manner. In conclusion, TGXTC exerted its therapeutic effects on the development of KOA via reducing the destruction of the cartilage structure of the meniscus and improving the composition and function of the meniscus cartilage matrix.

Exercise and Osteoarthritis

Osteoarthritis (OA) is a degenerative disease of the articular cartilage with subchondral bone lesions. Osteoarthritis etiologies are mainly related to age, obesity, strain, trauma, joint congenital anomalies, joint deformities, and other factors. Osteoarthritis seriously affects the quality of life; however, there is no effective way to cure osteoarthritis. Aerobic exercise refers to a dynamic rhythmic exercise involving the large muscle groups of the body with aerobic metabolism. More and more evidence shows that exercise has become a useful tool for the treatment of osteoarthritis. This chapter will discuss the role of exercise in the prevention and treatment of osteoarthritis.

Reduced PDGF-AA in subchondral bone leads to articular cartilage degeneration after strenuous running

To identify the effects of running on articular cartilage and subchondral bone remodeling, C57BL/6 mice were randomly divided into three groups: control, moderate-, and strenuous running. Magnetic resonance imaging showed bone marrow lesions in the knee subchondral bone in the strenuous-running group in contrast with the other two groups. The microcomputed tomography analysis showed promoted bone formation in the subchondral bone in mice subjected to strenuous running. Histological and immunohistochemistry results indicated that terminal differentiation of chondrocytes and degeneration of articular cartilage were enhanced but, synthesis of platelet-derived growth factor-AA (PDGF-AA) in the subchondral bone was suppressed after strenuous running. In vitro, excessive mechanical treatments suppressed the expression of PDGF-AA in osteoblasts, and the condition medium from mechanical-treated osteoblasts stimulated maturation and terminal differentiation of chondrocytes. These results indicate that strenuous running suppresses the synthesis of PDGF-AA in subchondral bone, leading to downregulated PDGF/Akt signal in articular cartilage and thus cartilage degeneration.

Prophylactic and Therapeutic Use of Strontium Ranelate Reduces the Progression of Experimental Osteoarthritis

Introduction: Strontium ranelate (SrRan) has the potential to interfere in the progression of osteoarthritis (OA), multifactorial disease associated with mechanical problems and articular inflammatory changes. Objectives: This study aimed to test the effects of prophylactic and therapeutic use of SrRan on clinical parameters of pain, the inflammatory process, and degradation of the articular cartilage. Methods: This was an experimental study, using a model of knee OA induced by intra-articular injection of monoiodoacetate. Thirty Wistar rats were divided into five groups and treated as indicated: control, without intervention; prophylactic, received SrRan at a daily oral dose of 250 mg/kg for 28 days before OA induction; SrRan treatments, administered 250 or 500 mg/kg/day for 28 days after the induction; and model control, received saline solution after the induction. Behavioral tests (joint incapacity, mechanical hyperalgesia, tactile sensitivity, and forced ambulation), histological evaluation of articular cartilage, and determination of inflammatory cytokines in the synovial fluid (interleukin [IL]-6, IL-10, tumor necrosis factor [TNF]-α, and interferon [INF]-γ) were performed. Results: Both prophylactic and therapeutic treatments improved the articular discomfort. A prophylactic dose of 500 mg/kg/day also improved mechanical hyperalgesia and the same dose was beneficial on tactile sensitivity. SrRan did not improve ambulation. Levels of IL-6, IL-10, TNF-α, and IFN-γ in SrRan-treated groups with OA were not significantly different compared with those in the normal control animals. The histopathological evaluation showed less articular damage in the SrRan-treated and control groups compared to the saline-treated group. Conclusion: The prophylactic and therapeutic administration of SrRan was associated with improved behavioral patterns of pain, especially joint discomfort. SrRan administration mitigated histological changes in the articular cartilage and reduced the inflammatory process, which beneficially reduced the progression of OA in the experimental model studied.

Assessment of the zonal variation of perfusion parameters in the femoral head: a 3-T dynamic contrast-enhanced MRI pilot study

OBJECTIVE

The objective was to describe MR perfusion characteristics of the femoral head, with a focus on the subchondral bone.

MATERIALS AND METHODS

This prospective monocentric study was approved by our local Ethics Committee. Written informed consent was obtained from all subjects. Dynamic contrast-enhanced MRI of the right hip was performed in 59 adults with suspected spondyloarthritis (32 women, 28 men). Mean age was 37.5 (±12.5) years. Regions of interest were drawn in the femoral head epiphysis, in the subchondral areas the most exposed to mechanical load (superolateral, anterosuperior, and posterior zones) and in areas less exposed to mechanical load (inferior subchondral zone and center of the femoral head). Semi-quantitative and pharmacokinetic parameters were calculated using the Tofts model. Statistical analysis was performed with a linear mixed model to compare the perfusion parameters in the different femoral head zones.

RESULTS

Extravascular extracellular volume and area under the curve were lower in the superolateral zone than in the inferior zone (p = 0.0135 and p < 0.0001 respectively) and the central zone (p = 0.007 and p = 0.0134 respectively). Extravascular extracellular volume and rate constant were lower in the anterosuperior zone than in the inferior zones (p = 0.011 and p = 0.029). In the anterosuperior zone, extravascular extracellular volume was lower, and time to peak was higher than in the central zones (p = 0.0056 and p = 0.0013 respectively). No significant differences were found for any values between other paired zones.

CONCLUSION

The perfusion of femoral head subchondral bone assessed with dynamic contrast-enhanced magnetic resonance imaging is not homogeneous: the areas exposed to more mechanical loading are less perfused.

Pyruvate Kinase M2 Modulates the Glycolysis of Chondrocyte and Extracellular Matrix in Osteoarthritis

Pyruvate kinase M2 (PKM2) has been wildly verified to modulate glycolysis in tumor cells. However, the role of PKM2 on the glycolysis of osteoarthritis (OA) chondrocytes is still unclear. In present study, we investigate the function of PKM2 on OA chondrocyte glycolysis and the collagen matrix generation in vitro. Results showed that PKM2 was upregulated in OA chondrocytes compared with healthy control chondrocytes. In OA chondrocytes, ATP expression was lower compared with healthy control chondrocytes. Loss-of-function experiment showed that PKM2 knockdown mediated by lentivirus transfection could significantly suppress the glucose consumption and lactate secretion levels and decrease glucose transporter-1 (Glut-1), lactate dehydrogenase A (LDHA), and hypoxia inducible factor 1-alpha (HIF-1α), indicating the inhibition of PKM2 knockdown on glycolysis. Moreover, Cell Counting Kit-8 (CCK-8), flow cytometry, and terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) assay showed that PKM2 knockdown inhibited OA chondrocyte proliferation and promoted the apoptosis. Western blot and immunocytochemical staining showed that PKM2 knockdown downregulated the expression levels of COL2A1 and SOX-9. In summary, our results conclude that PKM2 modulates the glycolysis and extracellular matrix generation, providing the vital role of PKM2 on OA pathogenesis and a novel therapeutic target for OA.