The effect of low dose intra-articular S(+) ketamine on osteoarthritis in rats: an experimental study.

BACKGROUND: This study aimed to investigate the analgesic impact of S(+)-ketamine on pain behavior and synovial inflammation in an osteoarthritis (OA) model. METHODS: Animals were grouped as follows: OA-Saline (n = 24) and OA-Ketamine (n = 24), OA induced via intra-articular sodium monoiodoacetate (MIA); a Non-OA group (n = 24) served as the control. On the 7th day post OA induction, animals received either saline or S(+)-ketamine (0.5 mg.kg-1). Behavioral and histopathological assessments were conducted up to day 28. RESULTS: S(+)-ketamine reduced allodynia from day 7 to 28 and hyperalgesia from day 10 to 28. It notably alleviated weight distribution deficits from day 10 until the end of the study. Significant walking improvement was observed on day 14 in S(+)-ketamine-treated rats. Starting on day 14, OA groups showed grip force decline, which was countered by S(+)-ketamine on day 21. However, S(+)-ketamine did not diminish synovial inflammation. CONCLUSION: Low Intra-articular (IA) doses of S(+)-ketamine reduced MIA-induced OA pain but did not reverse synovial histopathological changes. IRB APPROVAL NUMBER: 23115 012030/2009-05.

Treatment of Equine Tarsus Long Medial Collateral Ligament Desmitis with Allogenic Synovial Membrane Mesenchymal Stem/Stromal Cells Enhanced by Umbilical Cord Mesenchymal Stem/Stromal Cell-Derived Conditioned Medium: Proof of Concept.

Horses are high-performance athletes prone to sportive injuries such as tendonitis and desmitis. The formation of fibrous tissue in tendon repair remains a challenge to overcome. This impels regenerative medicine to develop innovative therapies that enhance regeneration, retrieving original tissue properties. Multipotent Mesenchymal Stem/Stromal Cells (MSCs) have been successfully used to develop therapeutic products, as they secrete a variety of bioactive molecules that play a pivotal role in tissue regeneration. These factors are released in culture media for producing a conditioned medium (CM). The aforementioned assumptions led to the formulation of equine synovial membrane MSCs (eSM-MSCs)-the cellular pool that naturally regenerates joint tissue-combined with a medium enriched in immunomodulatory factors (among other bioactive factors) produced by umbilical cord stroma-derived MSCs (eUC-MSCs) that naturally contribute to suppressing the immune rejection in the maternal-fetal barrier. A description of an equine sport horse diagnosed with acute tarsocrural desmitis and treated with this formulation is presented. Ultrasonographic ligament recovery occurred in a reduced time frame, reducing stoppage time and allowing for the horse's return to unrestricted competition after the completion of a physical rehabilitation program. This study focused on the description of the therapeutic formulation and potential in an equine desmitis treatment using the cells themselves and their secretomes.

Transmission electron microscopic study of the surface layer of surgical resected disc specimens in human temporomandibular joint.

In this study, we investigated specific and characteristic findings of the surface layer of surgical resected disc specimens in human temporomandibular joint osteoarthritis cases by transmission electron microscopy (TEM).Specimens were surgically removed from the TMJ of 5 cases (4 female patients: 5 cases) clinically osteoarthritis. Following findings were observed by TEM. Images were photographed on a JEM1400-Flash Electron microscope (JEOL, Japan) equipped with an EM-14661FLASH high-sensitivity digital complementary metal-oxide-semiconductor camera.Following findings were observed by TEM. 1) The surface is covered with plump fibroblastic and histiocytoid cells. 2) Collagen fiber bundles and collagenous matrix are exposed onto the eroded disc surface. 3) Fibrinous dense material is observed on the eroded disc surface. 4) Bundles of collagen fibers are densely observed. 5) Collagen bundles are rich around capillary vessels. 6) Synovial surface cells reveal features of activated macrophages with vacuole formation. Especially, plump fibroblastic and histiocytoid cells, and activated macrophages with vacuole, which were significant findings of the surface layer. These findings might have a significant effect on the regulation of synovial fluid.

General joint hypermobility in temporomandibular joint disease; clinical characteristics, biomarkers, and surgical aspects.

Objectives: This study aimed at identifying biomarkers in the temporomandibular joint (TMJ) synovial tissue analysing 28 extra cellular matrix proteins in TMJ diseased patients, classified with either general joint hypermobility (GJH) or normal joint mobility (NJM), and to compile clinical and protein characterisation to reveal potential surgical predictive factors. Study design: A prospective observational cohort study including 97 consecutive patients scheduled for TMJ surgery was performed. Joint mobility and several other predefined clinical variables were recorded. Synovial tissue was harvested during surgery followed by examination using multi-analytic profiling. A multivariate quantile regression model was used for analysis purposes. Results: The GJH/NJM ratio was 2:5. The GJH cohort were younger (P = 0.001) and more likely to be women (P = 0.026) compared to the NJM cohort. None of the protein concentrations could be correlated to joint mobility in the multivariate regression model, but often to the variable TMJ diagnosis. The surgical outcome after the six-month follow-up were equal between GJH and NJM patients. Conclusions: GJH was more common in the study cohort compared to general population frequencies, but GJH was not a negative factor for surgical outcome. Young age and female gender correlated to GJH. No TMJ biomarkers were GJH specific, and the results suggested that TMJ diagnosis more strongly correlated to the protein profile compared to GJH and the other investigated variables.

Increased n-6 Polyunsaturated Fatty Acids Indicate Pro- and Anti-Inflammatory Lipid Modifications in Synovial Membranes with Rheumatoid Arthritis.

Emerging evidence suggests that fatty acids (FAs) and their lipid mediator derivatives can induce both beneficial and detrimental effects on inflammatory processes and joint degradation in osteoarthritis (OA) and autoimmune-driven rheumatoid arthritis (RA). The present study characterized the detailed FA signatures of synovial membranes collected during knee replacement surgery of age- and gender-matched OA and RA patients (n = 8/diagnosis). The FA composition of total lipids was determined by gas chromatography and analyzed with univariate and multivariate methods supplemented with hierarchical clustering (HC), random forest (RF)-based classification of FA signatures, and FA metabolism pathway analysis. RA synovium lipids were characterized by reduced proportions of shorter-chain saturated FAs (SFAs) and elevated percentages of longer-chain SFAs and monounsaturated FAs, alkenyl chains, and C20 n-6 polyunsaturated FAs compared to OA synovium lipids. In HC, FAs and FA-derived variables clustered into distinct groups, which preserved the discriminatory power of the individual variables in predicting the RA and OA inflammatory states. In RF classification, SFAs and 20:3n-6 were among the most important FAs distinguishing RA and OA. Pathway analysis suggested that elongation reactions of particular long-chain FAs would have increased relevance in RA. The present study was able to determine the individual FAs, FA groups, and pathways that distinguished the more inflammatory RA from OA. The findings suggest modifications of FA elongation and metabolism of 20:4n-6, glycerophospholipids, sphingolipids, and plasmalogens in the chronically inflamed RA synovium. These FA alterations could have implications in lipid mediator synthesis and potential as novel diagnostic and therapeutic tools.

Proliferative tenosynovitis in Brazilian Mangalarga Marchador horses.

Proliferative tenosynovitis (PT) is an inflammatory and proliferative disorder of the synovial membrane of the tendon sheath that is rare in animals. The histological alterations are characterized by multinodular neovascularization, with infiltration of histiocytic and multinucleated giant cells and haemosiderin deposition. We reviewed necropsy and biopsy records of horses submitted to the Setor de Anatomia Patológica of the Universidade Federal Rural do Rio de Janeiro from January 2017 to December 2020 to select cases of PT. We identified PT in three adult Brazilian Mangalarga Marchador horses with nodular lesions on the metacarpophalangeal, metatarsophalangeal or carpal joints. The three horses were under 6 years of age and presented with lameness and pain on palpation. There were recurrences in two horses after surgical removal. Radiographic and ultrasound examinations detected masses in the flexor or extensor tendons and subtendinous bursa. Histological study of synovial membrane and tendon sheath revealed an increased number of vessels, fibroplasia, osseous metaplasia and infiltration of lymphocytes, plasma cells and siderophages. This is the first description of PT in horses, which should be included as an orthopaedic differential diagnosis, especially in Mangalarga Marchador horses with lameness.

Increased synovial immunohistochemistry reactivity of TGF-ß1 in erosive peripheral psoriatic arthritis.

BACKGROUND: Immune and non-immune cells contribute to the pathology of chronic arthritis, and they can contribute to tissue remodeling and repair as well as disease pathogenesis. The present research aimed to analyze inflammation and bone destruction/regeneration biomarkers in patients with psoriatic arthritis (PsA), rheumatoid arthritis (RA), osteoarthritis (OA), and ankylosing spondylitis (AS). METHODS: Samples were obtained from the inflamed knee of patients with knee arthritis who had been referred for undergoing arthroscopies. The synovial membrane was processed for pathological description, IHC analysis, and quantification of mRNA expression ratio by qRT-PCR. Serum levels of TGF-ß1, IL-23, IL-6, IL-17 A, IL-22, Dkk1, Sclerostin, BMP2, BMP4, Wnt1, and Wnt5a were measured by ELISA. All these data were analyzed and compared with the demographic, clinical, blood tests, and radiological characteristics of the patients. RESULTS: The synovial membrane samples were obtained from 42 patients for IHC, extraction, and purification of RNA for synovial mRNA expression analysis, and serum for measuring protein levels from 38 patients. IHC reactivity for TGF-ß1 in the synovial tissue was higher in patients with psoriatic arthritis (p 0.036) and was positively correlated with IL-17 A (r = 0.389, p = 0.012), and Dkk1 (r = 0.388, p = 0.012). Gene expression of the IL-17 A was higher in PsA patients (p = 0.018) and was positively correlated with Dkk1 (r = 0.424, p = 0.022) and negatively correlated with BMP2 (r = -0.396, p = 0.033) and BMP4 (r = -0.472, p = 0.010). It was observed that IHC reactivity for TGF-ß1 was higher in patients with erosive PsA (p = 0.024). CONCLUSIONS: The IHC reactivity of TGF-ß1 in synovial tissue was higher in patients with erosive psoriatic arthritis, and TGF-ß1 was in relation to higher levels of gene expression of IL-17 A and Dkk1.

Temporomandibular Joint: Review of Anatomy and Clinical Implications.

Temporomandibular joints (TMJ) are one of the most complex joints. Each one is located on one side of the face, and are composed of mandibular fossa, joint tubercle, and condylar process of mandible, separated by an articular disk. To these structures are attached ligaments and muscles, which will provide stability and movement. When TMJs work properly, jaw movements can be performed without pain or discomfort. It is important to mention that the complex formed by both TMJs will confront the maxillary with the mandibular bone and therefore will be related to the occlusion, linking these structures during growth and development.

[Particle disease and its effects on periarticular tissue]. / Abrieberkrankungen und deren Effekte auf das umliegende Gewebe.

Particle disease is the condition caused by wear debris on surrounding tissues and influences the well-being of arthroplasty patients. This condition is multifactorial due to the type of bearing couple, head size and implant position. Subsequent periprosthetic osteolysis and soft tissue reactions, can lead to revision THA surgery. The periprosthetic synovial membrane (synovial-like interface membrane, SLIM) is used in diagnostics when the cause of implant failure is uncertain. Detailed analysis of synovial fluid and bone marrow could improve the diagnostic procedure and strengthen the cases for revision surgery and the underlying biology. A large number of research approaches on this topic have evolved and continue to be utilized in the clinic.

Healthy and Osteoarthritis-Affected Joints Facing the Cellular Crosstalk.

Osteoarthritis (OA) is a chronic, progressive, severely debilitating, and multifactorial joint disease that is recognized as the most common type of arthritis. During the last decade, it shows an incremental global rise in prevalence and incidence. The interaction between etiologic factors that mediate joint degradation has been explored in numerous studies. However, the underlying processes that induce OA remain obscure, largely due to the variety and complexity of these mechanisms. During synovial joint dysfunction, the osteochondral unit undergoes cellular phenotypic and functional alterations. At the cellular level, the synovial membrane is influenced by cartilage and subchondral bone cleavage fragments and extracellular matrix (ECM) degradation products from apoptotic and necrotic cells. These "foreign bodies" serve as danger-associated molecular patterns (DAMPs) that trigger innate immunity, eliciting and sustaining low-grade inflammation in the synovium. In this review, we explore the cellular and molecular communication networks established between the major joint compartments-the synovial membrane, cartilage, and subchondral bone of normal and OA-affected joints.

Osteogenic Potential of Monosodium Urate Crystals in Synovial Mesenchymal Stem Cells.

Background and Objectives: Deposits of monosodium urate (MSU) crystals due to increased levels of uric acid (UA) have been associated with bone formation and erosion, mainly in patients with chronic gout. The synovial membrane (SM) comprises several types of cells, including mesenchymal stem cells (SM-MSCs); however, it is unknown whether UA and MSU induce osteogenesis through SM-MSCs. Materials and Methods: Cultures of SM were immunotyped with CD44, CD69, CD90, CD166, CD105, CD34, and CD45 to identify MSCs. CD90+ cells were isolated by immunomagnetic separation (MACS), colony-forming units (CFU) were identified, and the cells were exposed to UA (3, 6.8, and 9 mg/dL) and MSU crystals (1, 5, and 10 µg/mL) for 3 weeks, and cellular morphological changes were evaluated. IL-1ß and IL-6 were determined by ELISA, mineralization was assessed by alizarin red, and the expression of Runx2 was assessed by Western blot. Results: Cells derived from SM and after immunomagnetic separation were positive for CD90 (53 ± 8%) and CD105 (52 ± 18%) antigens, with 53 ± 5 CFU identified. Long-term exposure to SM-MSCs by UA and MSU crystals did not cause morphological damage or affect cell viability, nor were indicators of inflammation detected. Mineralization was observed at doses of 6.8 mg/dL UA and 5 µg/mL MSU crystals; however, the differences were not significant with respect to the control. The highest dose of MSU crystals (10 µg/mL) induced significant Runx2 expression with respect to the control (1.4 times greater) and SM-MSCs cultured in the osteogenic medium. Conclusions: MSU crystals may modulate osteogenic differentiation of SM-MSCs through an increase in Runx2.

Primary synovial chondromatosis of the hip joint (PrSC of the hip): A retrospective cohort analysis and review of the literature.

Introduction: Primary synovial osteochondromatosis (SOCM) or Synovial chondromatosis (SC) of the hip is a benign metaplastic condition of the synovium that is rare and may present with a spectrum of clinical features and radiological findings. Patients and methods: A retrospective search using the keyword 'Synovial chondromatosis' (SC) of the hip was performed at a tertiary care orthopaedic referral centre in the UK and a hospital in India. The radiology images were collected from our Picture Archiving and Communication System (PACS) and Radiology Information System (RIS), over 15 years. The patient's data was collated with Electronic Patient Records (EPR), RIS, and correlated with histo-pathology laboratory records where available. The demographic details of the patients, their clinical symptoms, imaging details, and management outcomes were collected. Results: We found 15 cases, with a mean age of 36.53 years (range: 14-50 years). There were 9 male and 6 female patients. The follow-up ranged from 1 year to 6 years. Predominantly unilateral presentation with insidious onset of symptoms was found. A spectrum of radiological Imaging was undertaken. Management strategies included supervised observation, arthroscopic or open synovectomy, and hip arthroplasty. No malignant transformation was found in the analysed cohort. Conclusion: Primary 'Synovial chondromatosis' of the hip had a male preponderance in our cohort, presenting with a range of clinical features. Radiologically, Magnetic Resonance Imaging (MRI) was the commonest modality of cross-sectional imaging utilised and crucial for the diagnosis, evaluating underlying articular involvement including guiding appropriate patient management presenting with Primary 'Synovial chondromatosis' of the hip.

Infiltration Profile of Regulatory T Cells in Osteoarthritis-Related Pain and Disability.

Emerging evidence indicates that regulatory T cells (Treg) intervene in the inflammatory processes that drive osteoarthritis (OA). However, whether polarized Tregs affect clinical features of the disease in the short- or long-term, and if so, what their role in OA-related pain and functional disability really is, remains elusive. Thus, the aim of the current study was to characterize the infiltration profile of Tregs in systemic (peripheral blood) and joint-derived (synovial fluid and synovial membrane) samples from patients with knee OA in relation to OA-induced symptoms. To this end, Treg infiltration (CD4+CD25+/high CD127low/-) was analyzed in matched samples of peripheral blood (PB), synovial fluid (SF) and synovial membrane (SM) from a total of 47 patients undergoing elective knee arthroplasty using flow cytometry. At the same time, knee pain and function were assessed and correlated with Treg proportions in different compartments (PB, SF, SM). Interestingly, matched-pair analysis revealed significantly higher Treg proportions in joint-derived samples than in PB, which was mainly attributed to the high Treg frequency in SF. Moreover, we found significant associations between infiltrating Tregs and OA-related symptoms which indicate that lower Treg proportions-especially in the SM-are related to increased pain and functional disability in knee OA. In conclusion, this study highlights the importance of local cellular inflammatory processes in OA pathology. Intra-articular Treg infiltration might play an important role not only in OA pathogenesis but also in the development of OA-related symptoms.

Synovial membrane-derived mesenchymal progenitor cells from osteoarthritic joints in dogs possess lower chondrogenic-, and higher osteogenic capacity compared to normal joints.

BACKGROUND: Synovial membrane-derived mesenchymal progenitor cells (SM-MPCs) are a promising candidate for the cell-based treatment of osteoarthritis (OA) considering their in vitro and in vivo capacity for cartilage repair. However, the OA environment may adversely impact their regenerative capacity. There are no studies for canine (c)SM-MPCs that compare normal to OA SM-MPCs, even though dogs are considered a relevant animal model for OA. Therefore, this study compared cSM-MPCs from normal and OA synovial membrane tissue to elucidate the effect of the OA environment on MPC numbers, indicated by CD marker profile and colony-forming unit (CFU) capacity, and the impact of the OA niche on tri-lineage differentiation. METHODS: Normal and OA synovial membrane were collected from the knee joints of healthy dogs and dogs with rupture of the cruciate ligaments. The synovium was assessed by histopathological OARSI scoring and by RT-qPCR for inflammation/synovitis-related markers. The presence of cSM-MPCs in the native tissue was further characterized with flow cytometry, RT-qPCR, and immunohistochemistry, using the MPC markers; CD90, CD73, CD44, CD271, and CD34. Furthermore, cells isolated upon enzymatic digestion were characterized by CFU capacity, and a population doublings assay. cSM-MPCs were selected based on plastic adherence, expanded to passage 2, and evaluated for the expression of MPC-related surface markers and tri-lineage differentiation capacity. RESULTS: Synovial tissue collected from the OA joints had a significantly higher OARSI score compared to normal joints, and significantly upregulated inflammation/synovitis markers S100A8/9, IL6, IL8, and CCL2. Both normal and OA synovial membrane contained cells displaying MPC properties, including a fibroblast-like morphology, CFU capacity, and maintained MPC marker expression over time during expansion. However, OA cSM-MPCs were unable to differentiate towards the chondrogenic lineage and had low adipogenic capacity in contrast to normal cSM-MPCs, whereas they possessed a higher osteogenic capacity. Furthermore, the OA synovial membrane contained significantly lower percentages of CD90+, CD44+, CD34+, and CD271+ cells. CONCLUSIONS: The OA environment had adverse effects on the regenerative potential of cSM-MPCs, corroborated by decreased CFU, population doubling, and chondrogenic capacity compared to normal cSM-MPCs. OA cSM-MPCs may be a less optimal candidate for the cell-based treatment of OA than normal cSM-MPCs.

Synovial Macrophages: Past Life, Current Situation, and Application in Inflammatory Arthritis.

Inflammatory arthritis is an inflammatory disease that involves the joints and surrounding tissues. Synovial hyperplasia often presents when joints become inflamed due to immune cell infiltration. Synovial membrane is an important as well as a highly specific component of the joint, and its lesions can lead to degeneration of the joint surface, causing pain and joint disability or affecting the patients' quality of life in severe cases. Synovial macrophages (SMs) are one of the cellular components of the synovial membrane, which not only retain the function of macrophages to engulf foreign bodies in the joint cavity, but also interact with synovial fibroblasts (SFs), T cells, B cells, and other inflammatory cells to promote the production of a variety of pro-inflammatory cytokines and chemokines, such as TNF-α, IL-1ß, IL-8, and IL-6, which are involved in the pathogenic process of inflammatory arthritis. SMs from different tissue sources have differently differentiated potentials and functional expressions. This article provides a summary on studies pertaining to SMs in inflammatory arthritis, and explores their role in its treatment, in order to highlight novel treatment modalities for the disease.

Synovial hemangioma: A rare cause of chronic knee pain.

Synovial hemangioma is a rare benign vascular tumor responsible for chronic knee pain and swelling. Given its non-specific symptoms, synovial hemangioma is often misdiagnosed. We report a case of synovial hemangioma of bilateral knee joints occurring in a young military man.

Histopathology of Psoriatic Arthritis Synovium-A Narrative Review.

Psoriatic arthritis (PsA) is a phenotypically heterogeneous chronic inflammatory disease associated to type I major histocompatibility complex alleles whose complex pathogenesis is still not completely understood. The psoriatic synovium shares general features of chronic inflammation with rheumatoid arthritis (RA) and other arthritis, such as hyperplasia of the intimal lining layer, sublining influx of inflammatory cells and neoangiogenesis, but recognizing disease-specific histopathologic findings may help in diagnosis and definition of therapeutic targets. Available literature reports conflicting data regarding the extension of lining hyperplasia, that does not allow depiction from RA. Sublining inflammatory cells consist of T and B cells and macrophages, plasma cells, mast cells and follicular dendritic cells, with a higher amount of overall T, mast cell and IL-17 producing CD8+ T lymphocytes and lower proportion of plasma cells when compared to the rheumatoid synovium. The amount of synovium IL17+ CD8+ T cells correlates positively to measures of disease activity. Lymphoid follicles with characteristics of germinal centers have been identified, similar to the ones described in RA. Neoangiogenesis is more prominent in PsA but can also be an outstanding feature in some RA samples, and different molecules involved in the process appear to have different influence in each disease. IL-17 and IL-22 expression in the synovium does not allow depiction between diseases. Among other cytokines and molecules likely implicated in disease physiopathology, only IL-35 is demonstrated to be reduced in PsA when compared to RA.

Infrapatellar Fat Pad-Synovial Membrane Anatomo-Fuctional Unit: Microscopic Basis for Piezo1/2 Mechanosensors Involvement in Osteoarthritis Pain.

The Infrapatellar Fat Pad (IFP) is a fibro-adipose tissue of the knee recently reconsidered as part of a single anatomo-functional unit (AFU) together with the synovial membrane (SM). Several evidence support the role of this unit in the mechanisms that trigger and perpetuate the onset and progression of osteoarthritis (OA) disease. Additionally, the contribution of IFP-SM AFU in OA-associated pain has also been supposed, but this assumption still needs to be fully elucidated. Within this context, the recent discovery of the mechanoceptive Piezo ion channels (i.e., Piezo1 and Piezo2) in mammals and consciousness on their role in mediating both mechanoceptive and inflammatory stimuli could shed some light on knee OA pain, as well as on the process leading from acute to chronic nociceptive responses. For this purpose, the IFP-SM AFUs of both healthy donors (non-OA IFP-SM AFUs, n = 10) and OA patients (OA IFP-SM AFUs, n = 10) were processed by histology and immunohistochemistry. After the attribution of a histopathological score to IFP-SM AFUs to confirm intrinsic differences between the two groups, the specimens were investigated for the expression and localization/distribution pattern of the mechanosensors Piezo1 and Piezo2. In addition, the presence of monocytes/macrophages (CD68), peripheral nerve endings (PGP9.5) and neoangiogenesis signs (YAP1) was evaluated for a broad tissue characterization. The study results lead to a better description of the IFP-SM AFU microscopic features in both healthy and pathological conditions, highlighting peculiar differences in the study cohort. Specifically, immunopositivity towards Piezo1/2, CD68 and YAP1 markers was detected at vessels level in the OA- IFP-SM AFUs compartments, differently from the non-OA-group. A correlation with pain was also inferred, paving the way for the identification of new and effective molecules in OA management.

[The effect of natural mineral bicarbonate sodium-calcium water «Tib-1¼ on the antioxidant status of rats with adjuvant rheumatoid arthritis]. / Vliyanie prirodnoi mineral'noi gidrokarbonatnoi natrievo-kal'tsievoi vody «Tib-1¼ na antioksidantnyi status krys s ad"yuvantnym revmatoidnym artritom.

The combination of traditional basic pharmacotherapy for rheumatoid arthritis (RA) and physiotherapeutic methods can reduce the activity of the disease and accelerate the onset of remission, and therefore the development of new non-drug methods for the treatment of RA is relevant. PURPOSE OF THE STUDY: Study of the effect of natural mineral water « Tib-1¼ on the lipid peroxidation system in an experiment with a model adjuvant-induced RA in rats. MATERIAL AND METHODS: The object of the study were Wistar rats, divided into three groups: negative control (solvents), positive control (model of adjuvant-induced RA by subcutaneous injection of complete Freund's adjuvant) and experimental (correction of RA with mineral water « Tib-1¼, diluted in a ratio of 1:3 during the first 2 weeks from the moment the model was formed in the ad libitum mode). On the 3rd and 7th weeks in the blood of the animals were determined: the total number of leukocytes, the content of hydroperoxides according to Gavrilov, the level of malondialdehyde (MDA), catalase activity. Pathological changes in the hip and knee joints were recorded using radiography. RESULTS: The inflammatory process in the positive control group by the 3rd week was characterized by an increase in the number of leukocytes by 66% (p<0.01) and was accompanied by an increase in MDA by 60% (p<0.001). By the 7th week, despite a relative increase in catalase activity (16%), the MDA level continued to be elevated compared to the negative control by 67% (p<0.001). Against the background of exposure to mineral water, inflammation decreased (the number of leukocytes in the "model/experiment" groups turned out to be reduced by 41%; p<0.01) and an increase in compensatory-adaptive reactions in the form of catalase activation was noted (by 8%; p<0.01), which was accompanied by a persistent (weeks 3 and 7) decrease in MDA output (by 20%; p<0.01). Using the method of radiation diagnostics, positive changes in the articular apparatus of experimental animals were revealed, consisting in the relief of signs of subchondral sclerosis of the bone heads, which were noted for animals of the model group. CONCLUSION: The use of natural mineral water «Tib-1¼ helps to reduce the acute inflammatory response during the formation of adjuvant-induced RA in Wistar rats, initiates the normalization of the balance of pro- and antioxidant processes in the body, and minimizes the intensity of degenerative-inflammatory joint lesions.