Comparison of nociceptor properties using electrophysiology in preclinical models of osteoarthritis.

Osteoarthritis (OA) pain originates in the joint by sensitization of articular nociceptors. While behavioural assessments provide valuable information regarding pain symptoms, the techniques are subjective and open to interpretation by the experimenter. This study used in vivo electrophysiological approaches to measure objectively joint nociceptor properties in three rodent models of OA. Single unit extracellular recordings of joint mechanosensitive afferents were carried out in male and female rats following either (1) transection of the medial meniscus (MMT: post-traumatic OA), (2) intra-articular injection of sodium monoiodoacetate (MIA: chemically-induced OA), or (3) intra-articular injection of lysophosphatidic acid (LPA: neuropathic OA). In naïve male control rats, the mechanical threshold of joint mechanonociceptors (23.5 ± 1.8 mNm) was significantly reduced with MMT (9.4 ± 1.1 mNm) and MIA (15.1 ± 1.6 mNm). In females, the mechanical threshold of naïve rats (23.2 ± 3.1 mNm) was reduced following induction of MMT (8.3 ± 1.0 mNm) and LPA (10.6 ± 2.2 mNm). Afferent firing frequency increased in male MMT (∼275 %), LPA (∼175 %), MIA (225 %), and female MMT (∼146 %), LPA (∼200 %), and MIA (∼192 %). Mechanical threshold and evoked firing were negatively correlated in all models for both sexes except LPA rats (male + female) and female MMT. These data indicate that MMT, MIA, and LPA induce peripheral sensitization of joint afferents thereby validating their use in OA pain studies.

[Hematological toxicity of disinfection by-product iodoacetic acid].

OBJECTIVE: To clarify the effect of iodoacetic acid(IAA) on the blood system and electrolyte balance, hence further study the intrinsic relation of blood routine parameters and electrolyte levels, major hematological toxicity effects and their pattern after IAA treatment. METHODS: Forty-eight 21-day-old male SPF grade Sprague-Dawley(SD) rats were gavaged with 0, 6.25, 12.5 and 25 mg/kg IAA for 31 days. After detections of blood routine and plasma inorganic ion levels, Spearman correlation coefficients were performed to evaluate their relationship. Changes in ferritin, transferrin, hepcidin, C-reactive protein and glyceraldehyde-3-phosphate dehydrogenase(GAPDH) were assessed by enzyme-linked immunosorbent assays. The EDock bioinformatics tool was applied to docking model of IAA and GAPDH. RESULTS: Compared to the control, high-dose IAA exposure had obvious inhibition effect on rat leukocytes with the total number declined by 51.12%, and neutrophils were particularly sensitive to IAA with the number reduced by 73.66%(P<0.01), and rat erythrocytes exhibited a small cell low pigment effect with hemoglobin and hematocrit decreased by 8.60% and 8.70%, respectively(P<0.05). But IAA had little effects on the platelet. Plasma iron, phosphorus, zinc and potassium levels were repressed significantly, while chlorine, sodium and magnesium levels were elevated obviously through IAA exposure. However, plasma calcium levels were hardly affected by IAA. In comparison with the control, iron levels declined by 67.09%, whereas magnesium levels increased by 131.82% in the high-dose group(P<0.01). Overall, correlation analyses uncovered that plasma iron metabolism was most strongly and positively correlated with levels of leukocyte, erythrocyte and platelet system parameters after IAA exposure, and the correlation coefficients of leukocyte number, mean hemoglobin content and mean erythrocyte volume were 0.637, 0.410 and 0.365, respectively(P<0.05). Compared to the control, in the high-dose IAA group, the plasma content of C-reactive protein was significantly upregulated by 13.30%(P<0.05), and plasma levels of transferrin and ferromodulin were also respectively elevated by 12.73% and 11.02%(P<0.05). But plasma levels of ferritin and GAPDH did not differ between groups. The docking model exhibited that IAA could bind to the 150 Cys active site of rat GAPDH did. CONCLUSION: IAA not only had toxic effects on rat leukocytes and the plasma electrolyte balance, but also generated inflammation and iron deficiency, leading to smaller erythrocytes and lower pigment.

GRP78/IRE1 and cGAS/STING pathway crosstalk through CHOP facilitates iodoacetic acid-mediated testosterone decline.

Iodoacetic acid (IAA) is an emerging unregulated iodinated disinfection byproduct with high toxicity and widespread exposure. IAA has potential reproductive toxicity and could damage male reproduction. However, the underlying mechanisms and toxicological targets of IAA on male reproductive impairment are still unclear, and thus Sprague-Dawley rats and Leydig cells were used in this work to decode these pending concerns. Results showed that after IAA exposure, the histomorphology and ultrastructure of rat testes were abnormally changed, numbers of Leydig cells were reduced, the hypothalamic-pituitary-testis (HPT) axis was disordered, and testosterone biosynthesis was inhibited. Proteomics analyses displayed that oxidative stress, endoplasmic reticulum stress, and steroid hormone biosynthesis were involved in IAA-caused reproductive injury. Antioxidant enzymes were depleted, while levels of ROS, MDA, 8-OHdG, and γ-H2A.X were increased by IAA. IAA triggered oxidative stress and DNA damage, and then activated the GRP78/IRE1/XBP1s and cGAS/STING/NF-κB pathways in Leydig cells. The two signaling pathways constructed an interactive network by synergistically regulating the downstream transcription factor CHOP, which in turn directly bound to and negatively modulated steroidogenic StAR, finally refraining testosterone biosynthesis in Leydig cells. Collectively, IAA as a reproductive toxicant has anti-androgenic effects, and the GRP78/IRE1 and cGAS/STING pathway crosstalk through CHOP facilitates IAA-mediated testosterone decline.

Platelet-rich plasma alleviates neuropathic pain in osteoarthritis by downregulating microglial activation.

BACKGROUND: The development of neuropathic pain (NP) is one of the reasons why the pain is difficult to treat, and microglial activation plays an important role in NP. Recently, platelet-rich plasma (PRP) has emerged as a novel therapeutic method for knee osteoarthritis (KOA). However, it's unclarified whether PRP has analgesic effects on NP induced by KOA and the underlying mechanisms unknown. PURPOSE: To observe the analgesic effects of PRP on NP induced by KOA and explore the potential mechanisms of PRP in alleviating NP. METHODS: KOA was induced in male rats with intra-articular injections of monosodium iodoacetate (MIA) on day 0. The rats received PRP or NS (normal saline) treatment at days 15, 17, and 19 after modeling. The Von Frey and Hargreaves tests were applied to assess the pain-related behaviors at different time points. After euthanizing the rats with deep anesthesia at days 28 and 42, the corresponding tissues were taken for subsequent experiments. The expression of activating transcription factor 3 (ATF3) in dorsal root ganglia (DRG) and ionized-calcium-binding adapter molecule-1(Iba-1) in the spinal dorsal horn (SDH) was detected by immunohistochemical staining. In addition, the knee histological assessment was performed by hematoxylin-eosin (HE) staining. RESULTS: The results indicated that injection of MIA induced mechanical allodynia and thermal hyperalgesia, which could be reversed by PRP treatment. PRP downregulated the expression of ATF3 within the DRG and Iba-1 within the SDH. Furthermore, an inhibitory effect on cartilage degeneration was observed in the MIA + PRP group only on day 28. CONCLUSION: These results indicate that PRP intra-articular injection therapy may be a potential therapeutic agent for relieving NP induced by KOA. This effect could be attributed to downregulation of microglial activation and reduction in nerve injury.

Development of a novel animal model of lumbar vertebral endplate lesion by intervertebral disk injection of monosodium iodoacetate in rats.

PURPOSE: Vertebral endplate lesions (EPLs) caused by severe disk degeneration are associated with low back pain. However, its pathophysiology remains unclear. In this study, we aimed to develop a vertebral EPL rat model mimicking severe intervertebral disk (IVD) degeneration by injecting monosodium iodoacetate (MIA) into the IVDs and evaluating it by assessing pain-related behavior, micro-computed tomography (CT) findings, and histological changes. METHODS: MIA was injected into the L4-5 and L5-6 IVDs of Sprague-Dawley rats. Their behavior was examined by measuring the total distance traveled and the total number of rearing in an open square arena. Bone alterations and volume around the vertebral endplate were assessed using micro-CT. Safranin-O staining, immunohistochemistry, and tartrate-resistant acid phosphatase (TRAP) staining were performed for histological assessment. RESULTS: The total distance and number of rearing times in the open field were significantly reduced in a time-dependent manner. Micro-CT revealed intervertebral osteophytes and irregularities in the endplates at 12 weeks. The bone volume/tissue volume (BV/TV) around the endplates significantly increased from 6 weeks onward. Safranin-O staining revealed severe degeneration of IVDs and endplate disorders in a dose- and time-dependent manner. Calcitonin gene-related peptide-positive nerve fibers significantly increased from 6 weeks onward. However, the number of osteoclasts decreased over time. CONCLUSION: Our rat EPL model showed progressive morphological vertebral endplate changes in a time- and concentration-dependent manner, similar to the degenerative changes in human IVDs. This model can be used as an animal model of severe IVD degeneration to better understand the pathophysiology of EPL.

Anti-osteoarthritis, Bone Protective and Antiinflammatory Effect of Lusianthridin against Monosodium Iodoacetate Induced Osteoarthritis via Suppression of Inflammatory Pathway.

Osteoarthritis (OA) is characterized by the gradual deterioration and worsening of the knee joint, leading to both pain and deformity. The current research exhibited the anti-osteoarthritis effect of lusianthridin against monosodium iodoacetate (MIA) induced OA in rats. RAW cells were used for the cell viability. The inflammatory cytokines and mediators were estimated in the cell lines after the lipopolysaccharide (LPS) treatment. For the in vivo study, the rats were received the intraperitoneal administration of MIA (3 mg/kg) for the induction of OA. The rats were received the oral administration of lusianthridin (5, 10 and 20 mg/kg) and the body and organ weight estimated. Antioxidant, cytokines, inflammatory and matrix metalloproteinases (MMP) level were also estimated. The mRNA expression of MMP were also estimated. The lusianthridin treatment remarkably suppressed the cell viability. LPS induced RAW cell suppressed the level of nitrate, tumor necrosis factor-α (TNF-α), interleukin-1ß (IL-1ß), interleukin-6 (IL-6), cyclooxygenase-2 (COX-2), prostaglandin (PGE2), MMP-2 and MMP-9 level. Lusianthridin remarkably altered the level of body weight and organ weight (liver, spleen, renal and heart weight). lusianthridin suppressed the oxidative stress via altered the level of antioxidant parameters. Lusianthridin significantly (p < 0.001) decreased the level of cartilage oligometrix matrix protein (COMP) and c-reactive protein (CRP); cytokines such as TNF-α, IL-1ß, IL-6, IL-10; inflammatory parameters include 5- Lipoxygenase (5-LOX), COX-2, leukotriene B4 (LTB4), PGE2; transforming growth factor beta (TGF-ß); MMP level like MMP-1, 3, 9, 13, respectively. Lusianthridin significantly suppressed the mRNA expression of MMP. Collectively, the result of the study showed that antiosteoarthritis effect of lusianthridin via suppression of inflammatory parameters.

Novel evidence on iodoacetic acid-induced immune protein functional and conformational changes: Focusing on cellular and molecular aspects.

Elevated levels of iodide occur in raw water in certain regions, where iodination disinfection byproducts are formed during chloramine-assisted disinfection of naturally iodide-containing water. Iodoacetic acid (IAA) is one of the typical harmful products. The mechanisms underlying IAA-induced immunotoxicity and its direct effects on biomolecules remained unclear in the past. Cellular, biochemical, and molecular methods were used to investigate the mechanism of IAA-induced immunotoxicity and its binding to lysozyme. In the presence of IAA, the cell viability of coelomocytes was significantly reduced to 70.8 %, as was the intracellular lysozyme activity. Upon binding to IAA, lysozyme underwent structural and conformational changes, causing elongation and unfolding of the protein due to loosening of the backbone and polypeptide chains. IAA effectively quenched the fluorescence of lysozyme and induced a reduction in particle sizes. Molecular docking revealed that the catalytic residue, Glu 35, which is crucial for lysozyme activity, resided within the docking range, suggesting the preferential binding of IAA to the active site of lysozyme. Moreover, electrostatic interaction emerged as the primary driving force behind the interaction between IAA and lysozyme. In conclusion, the structural and conformational changes induced by IAA in lysozyme resulted in impaired immune protein function in coelomocytes, leading to cellular dysfunction.

Transcranial Direct Current Stimulation Attenuates the Chronic Pain of Osteoarthritis in Rats via Reducing NMDAR2B Expressions in the Spinal Cord.

OBJECTIVES: Osteoarthritis (OA) has been the common cause to lead to chronic pain. Transcranial direct current stimulation (tDCS) is effective in the treatment of chronic pain, but its analgesic mechanism is still unclear. This study observed the analgesic effects of tDCS in rats to explore the top-down analgesic modulation mechanism of tDCS. METHODS: Monosodium iodoacetate (MIA) was used to establish OA chronic pain model. After 21 days, the rats received tDCS for 14 consecutive days (20 min/day). We assessed the pain-related behaviors of rats at different time points. Western blot and Immunohistochemistry were performed to observe the expression level of NMDAR2B in the spinal cord after tDCS treatment. RESULTS: After MIA injection, rats developed apparent mechanical hyperalgesia and thermal hyperalgesia. However, the pain-related behaviors of rats were significantly improved after tDCS treatment. In addition, the expression of NMDAR2B and the proportion of positive stained cells of NMDAR2B were reversed by tDCS treatment. CONCLUSIONS: The results demonstrated that tDCS can attenuate OA-induced chronic pain in rats via reducing NMDAR2B expressions in the spinal cord. We believe that this may be the result of tDCS participating in the top-down modulation of pain pathway in the endogenous analgesic system.

Potentiating TRPA1 by Sea Anemone Peptide Ms 9a-1 Reduces Pain and Inflammation in a Model of Osteoarthritis.

Progressive articular surface degradation during arthritis causes ongoing pain and hyperalgesia that lead to the development of functional disability. TRPA1 channel significantly contributes to the activation of sensory neurons that initiate neurogenic inflammation and mediates pain signal transduction to the central nervous system. Peptide Ms 9a-1 from the sea anemone Metridium senile is a positive allosteric modulator of TRPA1 and shows significant anti-inflammatory and analgesic activity in different models of pain. We used a model of monosodium iodoacetate (MIA)-induced osteoarthritis to evaluate the anti-inflammatory properties of Ms 9a-1 in comparison with APHC3 (a polypeptide modulator of TRPV1 channel) and non-steroidal anti-inflammatory drugs (NSAIDs) such as meloxicam and ibuprofen. Administration of Ms 9a-1 (0.1 mg/kg, subcutaneously) significantly reversed joint swelling, disability, thermal and mechanical hypersensitivity, and grip strength impairment. The effect of Ms 9a-1 was equal to or better than that of reference drugs. Post-treatment histological analysis revealed that long-term administration of Ms9a-1 could reduce inflammatory changes in joints and prevent the progression of cartilage and bone destruction at the same level as meloxicam. Peptide Ms 9a-1 showed significant analgesic and anti-inflammatory effects in the model of MIA-induced OA, and therefore positive allosteric modulators could be considered for the alleviation of OA symptoms.

Bixa orellana ethyl acetate fraction and its isolated compound ellagic acid attenuate the progression of MIA-induced osteoarthritis in rat knees.

Osteoarthritis (OA) is a pathology that is characterized by progressive erosion of articular cartilage. In this context, medicinal plants have become relevant tools regarding their potential role in the prevention and treatment of OA, being safe and effective. The aim of this work was investigate the therapeutic efficacy of the ethyl acetate fraction of Bixa orellana leaves (BoEA) and ellagic acid (ElAc) for the therapeutic treatment of OA induced by monosodium iodoacetate (MIA) in rats. The plant material was extracted via maceration with 70 % hydroalcoholic solvent (BoHE). The ethyl acetate (BoEA) fraction was by solvents in increasing order of polarity. The ElAc was identified and isolated in BoEA using high performance liquid chromatography (HPLC-DAD) and analytical curve. The OA was induced using MIA in the right knee at the knee joint. Doses of BoEA and ElAc were administered daily (every 24 h, orally) at concentrations of 50, 100 and 50 mg/kg, respectively, for 28 days after induced OA. We evaluated the animals through clinical and radiological examinations every 7 days and, on the 29th day, the animals were euthanized, the joints being removed for histopathological analysis and the serum for cytokine analysis. BoEA and ElAc compounds reduced inflammation and nociception in OA and were as effective as indomethacin in clinical parameters of joint discomfort and allodynia in rats, in addition to showing improvements in radiological and histopathological images, acting on the progress of cartilage deterioration, proving properties related to anti-inflammatory and analgesic processes, being important allies for new therapeutic interventions for the treatment of OA.

Drinking water disinfection byproduct iodoacetic acid affects thyroid hormone synthesis in Nthy-ori 3-1 cells.

Iodoacetic acid (IAA) is an emerging and the most genotoxic iodinated disinfection byproduct to date. IAA can disrupt the thyroid endocrine function in vivo and in vitro, but the underlying mechanisms remain unclear. In this work, transcriptome sequencing was used to investigate the effect of IAA on the cellular pathways of human thyroid follicular epithelial cell line Nthy-ori 3-1 and determine the mechanism of IAA on the synthesis and secretion of thyroid hormone (TH) in Nthy-ori 3-1 cells. Results of transcriptome sequencing indicated that IAA affected the TH synthesis pathway in Nthy-ori 3-1 cells. IAA reduced the mRNA expression of thyroid stimulating hormone receptor, sodium iodide symporter, thyroid peroxidase, thyroglobulin, paired box 8 and thyroid transcription factor-2, inhibited the cAMP/PKA pathway and Na+-K+-ATPase, and decreased the iodine intake. The results were confirmed by our previous findings in vivo. Additionally, IAA downregulated glutathione and the mRNA expression of glutathione peroxidase 1, leading to increased reactive oxygen species production. This study is the first to elucidate the mechanisms of IAA on TH synthesis in vitro. The mechanisms are associated with down-regulating the expression of genes related to TH synthesis, inhibiting iodine uptake, and inducing oxidative stress. These findings may improve future health risk assessment of IAA on thyroid in human.

Protective effects of Pudilan Tablets against osteoarthritis in mice induced by monosodium iodoacetate.

Osteoarthritis (OA) is a complicated disorder that is the most prevalent chronic degenerative joint disease nowadays. Pudilan Tablets (PDL) is a prominent traditional Chinese medicine formula used in clinical settings to treat chronic inflammatory illnesses. However, there is currently minimal fundamental research on PDL in the therapy of joint diseases. As a result, this study looked at the anti-inflammatory and anti-OA properties of PDL in vitro and in vivo, as well as the mechanism of PDL in the treatment of OA. We investigated the anti-OA properties of PDL in OA mice that were generated by monosodium iodoacetate (MIA). All animals were administered PDL (2 g/kg or 4 g/kg) or the positive control drug, indomethacin (150 mg/kg), once daily for a total of 28 days starting on the day of MIA injection. The CCK-8 assay was used to test the vitality of PDL-treated RAW264.7 cells in vitro. RAW264.7 cells that had been activated with lipopolysaccharide (LPS) were used to assess the anti-inflammatory properties of PDL. In the MIA-induced OA model mice, PDL reduced pain, decreased OA-induced cartilage damages and degradation, decreased production of pro-inflammatory cytokines in serum, and suppressed IL-1ß, IL-6, and TNF-α mRNA expression levels in tibiofemoral joint. In RAW264.7 cells, PDL treatment prevented LPS-induced activation of the ERK/Akt signaling pathway and significantly decreased the levels of inflammatory cytokines, such as IL-1ß, IL-6, and TNF-α. In conclusion, these results suggest that PDL is involved in combating the development and progression of OA, exerts a powerful anti-inflammatory effect on the knee joint, and may be a promising candidate for the treatment of OA.

Establishment of an Animal Model of Disk Degeneration by Intradiskal Injection of Monosodium Iodoacetate.

BACKGROUND: Disk degeneration (DD) stands for the most common cause of low back pain. The establishment of an animal model plays an intrinsic role in the clarification of the physiopathology of DD. The purpose of this study is to select an optimal dose of monosodium iodoacetate (MIA) that may generate a reliable model of DD. METHODS: Thirty-four rats were used in this study. The disks (Co7/8, Co8/9, and Co 9/10) received 1 shot of intradiskal injection of 0.02 mg, 0.1 mg, and 0.5 mg of MIA solution, respectively. Half of the rats were euthanized 3 weeks after MIA injection, and the other half 6 weeks after injection. RESULTS: Magnetic resonance imaging evaluation showed that the mean T2-weighted signal intensity at 6 weeks decreased significantly in the 0.1 and 0.5 mg groups. The disk height of the control group was significantly higher than those of the 0.1 mg and 0.5 mg groups. Histologic and macroscopic results revealed time-and-dose-depending degeneration in the disks that received MIA. Additionally, MIA produced cell death in the nucleus pulposus cells with an elevated percentage. The injected disk with 0.1 mg MIA demonstrated a progressive degeneration, the disk injected with 0.5 mg MIA induced DD acutely 3 weeks post MIA injection, while the dose of 0.02 mg of MIA did not show much degeneration. CONCLUSIONS: We concluded that 0.1 mg MIA is the most suitable dose to establish a model of DD, which enabled us to replicate the onset, progression, and outcome of diverse histopathologies of DD in the clinic.

Pathological Characteristics of Monosodium Iodoacetate-Induced Osteoarthritis in Rats.

BACKGROUND: This study aimed to identify pain-related behavior and pathological characteristics of the knee joint in rats with monosodium iodoacetate (MIA)-induced osteoarthritis (OA). METHODS: Knee joint inflammation was induced by intra-articular injection of MIA (4 mg/50 µL, n = 14) in 6-week-old male rats. Knee joint diameter, weight-bearing percentage on the hind limb during walking, the knee bending score, and paw withdrawal to mechanical stimuli were measured to evaluate edema and pain-related behavior for 28 d after MIA injection. Histological changes in the knee joints were evaluated using safranin O fast green staining on days 1, 3, 5, 7, 14, and 28 after OA induction (n = 3, respectively). Changes in bone structure and bone mineral density (BMD) were examined 14 and 28 d after OA (n = 3, respectively) using micro-computed tomography (CT). RESULTS: The knee joint diameter and knee bending scores of the ipsilateral joint significantly increased 1 d after MIA injection, and the increased knee joint diameter and knee bending score persisted for 28 d. Weight-bearing during walking and paw withdrawal threshold (PWT) decreased from 1 and 5 d, respectively, and were maintained up to 28 d after MIA. Cartilage destruction started on day 1, and Mankin scores for bone destruction significantly increased for 14 d, as shown by micro-CT imaging. CONCLUSION: The present study demonstrated that histopathological structural changes in the knee joint due to inflammation started soon after MIA injection, which induced OA pain from inflammation-related acute pain to spontaneous and evoked associated chronic pain.

Comparison of chemical-induced temporomandibular osteoarthritis rat models (monosodium iodoacetate versus collagenase type II) for the study of prolonged drug delivery systems.

OBJECTIVE: To compare two agents that can induce a rat model of temporomandibular joint osteoarthritis (TMJOA) by chemical induction: monosodium iodoacetate (MIA) and collagenase type 2 (Col-2). We wished to ascertain the best agent for assessing drug-delivery systems (DDSs). METHOD: Male Wistar rats underwent intra-articular injection with MIA or Col-2. They were manipulated for 30 days. The head withdrawal threshold (HWT), immunohistological assessment, and positron emission tomography (PET) were used to evaluate the relevance of our models. RESULTS: For both the MIA and Col-2 groups, pain persisted for 30 days after injection. Change in the HWT showed that Col-2 elicited a strong action initially that decreased progressively. MIA had a constant action upon pain behavior. Histology of TMJ tissue from both groups showed progressive degradation of TMJ components. CONCLUSIONS: MIA and Col-2 induced orofacial pain by their local chemical action on TMJs. However, based on a prolonged and greater sustained effect on the pain threshold, persistent histological changes, and imaging results, MIA appeared to be more suitable for creation of a rat model of TMJOA for the study of DDSs.

Eplerenone modulates the inflammatory response in monosodium iodoacetate-induced knee osteoarthritis in rats: Involvement of RANKL/OPG axis.

AIMS: Osteoarthritis (OA) is a multifactorial degenerative disease marked by the progressive deterioration of articular cartilage with inflammation of the synovium. OA's main symptoms include pain and function loss. Monosodium Iodoacetate (MIA) experimental model is widely-used for OS induction since it produces symptoms comparable to those occurring in humans. MATERIALS AND METHODS: Thirty-two rats were divided into four groups (n = 8). The 1st group received saline and included the normal-control rats. Groups 2-4 received intra-articular injections of MIA (3 mg/50 µL) in the rats' knee joints to induce OA. Group 2 included the MIA-control rats. Groups 3 and 4 received intra-articular MIA followed by a 14-day oral eplerenone (50 and 100 mg/kg); respectively. KEY FINDINGS: Intra-articular injection of MIA in rats' knee joints caused significant inflammation and pain, elevation of Akt and ERK gene expression in knee joints along with significant alterations in the histological pictures of knee joints and OARSI scores. RANKL/OPG Axis was significantly disrupted. SIGNIFICANCE: Eplerenone treatment produced a significant improvement in motor coordination and spontaneous locomotor activity in rats and modulated the key inflammatory mediators in OA (TNF-α, NF-κß, and IL-6). Eplerenone also suppressed the qRT-PCR gene expression of Akt and ERK in knee joint tissues and improved the histological pictures and OARSI scores of knee joints of treated rats. Eplerenone caused a decline in RANKL concentration accompanied by a rise in OPG concentration thus modulating the RANKL/OPG Axis. Consequently, eplerenone is a candidate for OA therapy due to its potential anti-inflammatory effects.

Rotator cuff muscle degeneration in a mouse model of glenohumeral osteoarthritis induced by monoiodoacetic acid.

BACKGROUND: Osteoarthritis (OA) is a disease of joint degeneration and impaired function. Muscle atrophy, fatty infiltration, and fibrosis are degenerative features of muscle injury and predict poor outcomes in some degenerative and exercise-related injuries. Patients with glenohumeral joint OA usually have rotator cuff muscle degeneration, even though the rotator cuff is intact. However, the mechanism and correlation between OA and degeneration of muscles around joints are still unknown. METHODS: Forty-five 12-month-old C57BL/6J mice received a single injection of monoiodoacetic acid into the right glenohumeral joint. The sham group was injected with saline on the same day in the right glenohumeral joint. Three and 6 weeks after the operation, gait analysis was conducted to evaluate the function of the forelimb. Then, the shoulder joint and supraspinatus muscle were collected for histologic staining, reverse transcription quantitative polymerase chain reaction, and biomechanics test. Correlations between fat area fraction in muscle, percentage wet muscle weight change or Osteoarthritis Research Society International score, and gait analysis/muscle mechanics tests were assessed using Pearson's correlation coefficient or Spearman's correlation coefficient. RESULTS: Compared with the sham group, the monoiodoacetic acid group developed significant glenohumeral joint OA and the supraspinatus muscle developed significant fatty infiltration and muscle atrophy. Shoulder function correlated with glenohumeral joint OA/rotator cuff muscle severity, weight loss, and fatty infiltration. CONCLUSION: In mice, glenohumeral joint OA can lead to rotator cuff degeneration and inferior limb function. The small animal model could be a powerful tool to further study the potential mechanisms between glenohumeral OA and rotator cuff muscle degeneration.

Astragaloside IV as a novel CXCR4 antagonist alleviates osteoarthritis in the knee of monosodium iodoacetate-induced rats.

BACKGROUND AND PURPOSE: C-X-C chemokine receptor type 4 (CXCR4) inhibition protects cartilage in osteoarthritis (OA) animal models. Therefore, CXCR4 has becoming a novel target for OA drug development. Since dietary and herbal supplements have been widely used for joint health, we hypothesized that some supplements exhibit protective effects on OA cartilage through inhibiting CXCR4 signaling. METHODS: The single-cell RNA sequencing data of OA patients (GSE152805) was re-analyzed by Scanpy 1.9.0. The docking screening of CXCR4 antagonists was conducted by Autodock Vina 1.2.0. The CXCR4 antagonistic activity was evaluated by calcium response in THP-1 cells. Signaling pathway study was conducted by bulk RNA sequencing and western blot analysis in human C28/I2 chondrocytes. The anti-OA activity was evaluated in monosodium iodoacetate (MIA)-induced rats. RESULTS: Astragaloside IV (ASN IV), the predominate phytochemical in Astragalus membranaceus, has been identified as a novel CXCR4 antagonist. ASN IV reduced CXCL12-induced ADAMTS4,5 overexpression in chondrocytes through blocking Akt signaling pathway. Furthermore, ASN IV administration significantly repaired the damaged cartilage and subchondral bone in MIA-induced rats. CONCLUSION: The blockade of CXCR4 signaling by ASN IV could explain anti-OA activities of Astragalus membranaceus by protection of cartilage degradation in OA patients. Since ASN IV as an antiviral has been approved by China National Medical Products Administration for testing in people, repurposing of ASN IV as a joint protective agent might be a promising strategy for OA drug development.

Effectiveness of losartan on infrapatellar fat pad/synovial fibrosis and pain behavior in the monoiodoacetate-induced rat model of osteoarthritis pain.

Infrapatellar fat pad (IFP)/ synovial fibrosis is closely associated with the clinical symptoms of joint pain and stiffness, which contribute to locomotor restriction in osteoarthritis (OA) patients. Hence, this study was designed to gain insight on whether losartan, a selective angiotensin II type 1 receptor (AT1R) antagonist, has therapeutic benefit to reverse IFP/synovial fibrosis and secondarily to attenuate pain behavior. In male Wistar rats with monoiodoacetic acid (MIA)-induced IFP/synovial fibrosis, a possible role for increased AT1R expression in the pathogenesis of IFP/synovial fibrosis was assessed over an 8-week period. Pain behavior comprised static weight bearing and von Frey paw withdrawal thresholds (PWTs), which were assessed once or twice weekly, respectively. Groups of MIA-rats received oral losartan (30-mg/kg; n = 8 or 100-mg/kg; n = 9) or vehicle (n = 9) for 28-days according to a prevention protocol. Animals were euthanized on day 28 and various tissues (IFP/synovium, cartilage and lumbar dorsal root ganglia (DRGs)) were collected for histological, immunohistochemical and western blot analyses. Administration of once-daily losartan for 28-days dose-dependently attenuated the development of static weight bearing. This was accompanied by reduced IFP/synovial fibrosis and suppression of TGF-ß1 expression. Chronic treatment of MIA-rats with losartan had an anti-fibrotic effect and it attenuated pain behavior in this animal model.

Ameliorative Effect of Curcumin Nanoparticles against Monosodium Iodoacetate-Induced Knee Osteoarthritis in Rats.

Aim: This study is aimed at evaluating the use of curcumin-loaded polylactic-co-glycolic acid nanoparticles (CUR-loaded PLGA NPs) as a treatment against monosodium iodoacetate- (MIA-) induced knee OA. Materials and Methods: Eighteen rats were assigned to three groups (n = 6), namely, normal control group that received intra-articular injections (IAIs) of saline, an OA control group that received an IAIs of MIA (2 mg/50 µL), and a treatment group (MIA+CUR-loaded PLGA NPs) that received IAIs of CUR-loaded PLGA NPs (200 mg/kg b.wt). Results: The CUR NP treatment against knee OA alleviated radiographic alternations and histopathological changes and inhibited the upregulation in the serum levels of interleukin-1ß, tumor necrosis factor-α, interleukin-6, and transforming growth factor-beta and the downregulation in interleukin-10. CUR NP-treated joints also decreased the mRNA expression of nuclear factor-kappa B and inducible nitric oxide synthase and the protein expression of matrix metalloproteinase-13 and caspase-3. Finally, CUR-loaded PLGA NP treatment mitigated the loss of type II collagen, which resulted in a significant reduction in malondialdehyde level and increased the glutathione content and superoxide dismutase activity compared with that of the OA group. Conclusion: This study demonstrated that the administration of CUR NPs could provide effective protection against MIA-induced OA and knee joint histological deteriorated changes due to its anti-inflammatory, antioxidant, and antiapoptotic properties.