The irreversible destruction of the cartilage, tendon, and bone that comprise synovial joints is the hallmark of both rheumatoid arthritis (RA) and osteoarthritis (OA). While cartilage is made up of proteoglycans and type II collagen, tendon and bone are composed primarily of type I collagen. RA is an autoimmune disease afflicting numerous joints throughout the body; in contrast, OA develops in a small number of joints, usually resulting from chronic overuse or injury. In both diseases, inflammatory cytokines such as interleukin-1 beta (IL-1 beta) and tumor necrosis factor-alpha (TNF-alpha) stimulate the production of matrix metalloproteinases (MMPs), enzymes that can degrade all components of the extracellular matrix. The collagenases, MMP-1 and MMP-13, have predominant roles in RA and OA because they are rate limiting in the process of collagen degradation. MMP-1 is produced primarily by the synovial cells that line the joints, and MMP-13 is a product of the chondrocytes that reside in the cartilage. In addition to collagen, MMP-13 also degrades the proteoglycan molecule, aggrecan, giving it a dual role in matrix destruction. Expression of other MMPs such as MMP-2, MMP-3 and MMP-9, is also elevated in arthritis and these enzymes degrade non-collagen matrix components of the joints. Significant effort has been expended in attempts to design effective inhibitors of MMP activity and/or synthesis with the goal of curbing connective tissues destruction within the joints. To date, however, no effective clinical inhibitors exist. Increasing our knowledge of the crystal structures of these enzymes and of the signal transduction pathways and molecular mechanisms that control MMP gene expression may provide new opportunities for the development of therapeutics to prevent the joint destruction seen in arthritis.

Matrix metalloproteinases: role in arthritis.

The role of synovitis in osteoarthritis pathogenesis

Angiogenesis is the propelling force for tumor growth and metastasis, and antiangiogenic therapy represents one of the most promising modalities for cancer treatment. CD105 (endoglin) is a proliferation-associated and hypoxia-inducible protein abundantly expressed in angiogenic endothelial cells (EC). It is a receptor for transforming growth factor (TGF) -beta1 and -beta3 and modulates TGF-beta signaling by interacting with TGF-beta receptors I and/or II. Immunohistochemistry studies have revealed that CD105 is strongly expressed in blood vessels of tumor tissues. Intratumoral microvessel density (MVD) determined using antibodies to CD105 has been found to be an independent prognostic indicator, wherein increased MVD correlates with shorter survival. CD105 is able to be shed into the circulation, with elevated levels detected in patients with various types of cancer and positively correlated with tumor metastasis. Tangible evidence of its proangiogenic role comes from knockout studies in which CD105 null mice die in utero as a result of impaired angiogenesis in the yolk sac and heart defects. The potential usefulness of CD105 for tumor imaging has been evaluated in tumor-bearing mice and dogs that have shown the rapid accumulation of radiolabeled anti-CD105 monoclonal antibody in the tumors with a high tumor-to-background ratio. The anti-CD105 antibody conjugated with immunotoxins and immunoradioisotopes efficiently suppressed/abrogated tumor growth in murine models bearing breast and colon carcinoma without any significant systemic side effects. Immunoscintigraphy in patients with renal cell carcinomas has shown specific localization of 99Tcm-labeled CD105 mab in tumor endothelial cells. Thus, CD105 is a promising vascular target that can be used for tumor imaging, prognosis, and bears therapeutic potential in patients with solid tumors and other angiogenic diseases.

CD105 is important for angiogenesis: evidence and potential applications.

This article focuses on the (functional) anatomy and biomechanics of the pelvic girdle and specifically the sacroiliac joints (SIJs). The SIJs are essential for effective load transfer between the spine and legs. The sacrum, pelvis and spine, and the connections to the arms, legs and head, are functionally interrelated through muscular, fascial and ligamentous interconnections. A historical overview is presented on pelvic and especially SIJ research, followed by a general functional anatomical overview of the pelvis. In specific sections, the development and maturation of the SIJ is discussed, and a description of the bony anatomy and sexual morphism of the pelvis and SIJ is debated. The literature on the SIJ ligaments and innervation is discussed, followed by a section on the pathology of the SIJ. Pelvic movement studies are investigated and biomechanical models for SIJ stability analyzed, including examples of insufficient versus excessive sacroiliac force closure.

/pdf/the-sacroiliac-joint-an-overview-of-its-anatomy-function-and-1mdjys7cqc.pdf

The sacroiliac joint: an overview of its anatomy, function and potential clinical implications

Osteoarthritis (OA) is a complex disease whose pathogenesis includes the contribution of biomechanical and metabolic factors which, altering the tissue homeostasis of articular cartilage and subchondral bone, determine the predominance of destructive over productive processes. A key role in the pathophysiology of articular cartilage is played by cell/extra-cellular matrix (ECM) interactions, which are mediated by cell surface integrins. In a physiologic setting, integrins modulate cell/ECM signaling, essential for regulating growth and differentiation and maintaining cartilage homeostasis. During OA, abnormal integrin expression alters cell/ECM signaling and modifies chondrocyte synthesis, with the following imbalance of destructive cytokines over regulatory factors. IL-1, TNF-alpha and other pro-catabolic cytokines activate the enzymatic degradation of cartilage matrix and are not counterbalanced by adequate synthesis of inhibitors. The main enzymes involved in ECM breakdown are metalloproteinases (MMPs), which are sequentially activated by an amplifying cascade. MMP activity is partially inhibited by the tissue inhibitors of MMPs (TIMPs), whose synthesis is low compared with MMP production in OA cartilage. Intriguing is the role of growth factors such as TGF-beta, IFG, BMP, NGF, and others, which do not simply repair the tissue damage induced by catabolic factors, but play an important role in OA pathogenesis.

The pathophysiology of osteoarthritis.

Objective Rheumatic diseases are a group of systemic disorders that may be concurrent with Raynaud's phenomenon and involvement of the internal organs, in particular the esophagus. Esophageal motor abnormalities have been widely described in systemic sclerosis, but have not frequently been reported in other diseases. In the present study we have examined the prevalence and pattern of esophageal motility disorders in different rheumatic diseases. Methods Esophageal manometry was performed on 150 patients, 21 males and 129 females, suffering from different rheumatic diseases (SSc, RA, SLE, MCTD, undifferentiated CTD, or DM/PM) and on 30 healthy controls. Results Functional involvement of the esophagus was demonstrated in all the rheumatic diseases considered, although at varying percentages. The frequencies of the functional abnormalities differed when each disease was considered separately. In SSc patients abnormalities were found more frequently in the lower esophageal sphincter (81.8%) and in the esophageal body (84.8%); data for the DM/PM and MCTD patients broadly overlapped. On the contrary, in SLE the lower sphincter appeared to be less (or even not at all) impaired, while the most specific disorder was an isolated abnormal peristalsis. RP did not always correlate with manometric changes in all of the groups studied. Conclusions Three conclusions derive from our study: i) motor disorders affecting the esophagus were not only found in SSc, but also in all forms of non-lupus CTD; ii) the simultaneous involvement of the esophageal body and the lower esophageal sphincter is discriminant between non-lupus CTD and SLE; and iii) RP may be regarded as a condition pathogenetically unrelated to manometrically detected esophageal motor abnormalities.

Esophageal motility disorders in the rheumatic diseases : a review of 150 patients

Cell-ECM (extracellular matrix) interactions are believed to play a key role in maintaining the normal structure of tissues such as cartilage. Cell surface adhesion molecules have been reported to mediate chondrocyte binding to ECM proteins in human normal cartilage but the behaviour of these molecules in human osteoarthritic cartilage is unknown. We studied receptor matrix proteins on freshly isolated chondrocytes obtained from 10 patients with osteoarthritis (OA). Chondrocytes were isolated by enzymatic digestion from three zones of the articular cartilage with a different degree of macroscopic and microscopic damage and chondrocyte phenotype was defined by flow cytometry. Chondrocytes strongly expressedβ1 integrin but notβ3 integrin. LFA-1 (CD18/CD11a) and ICAM-1 (CD54) antigens were almost undetectable. Interestingly,β1 expression was significantly higher in the minimally damaged zone than in the zones with medium and maximum damage. These data show thatβ1-integrin-mediated chondrocyte-ECM interactions decrease in osteoarthritic cartilage suggesting that perturbations of chondrocyte-matrix signalling occurs during OA.

Chondrocyte phenotyping in human osteoarthritis

OBJECTIVE To evaluate the cell surface expression of cell membrane-bound peptidases CD10 and CD26 on osteoarthritic (OA) chondrocytes, correlating it with the cell cycle phase and with the severity of OA lesions found in different load zones of the cartilage from human knees. METHODS Chondrocytes freshly isolated from three different load zones of cartilage, obtained from 10 OA patients undergoing surgical knee replacement, were analyzed for the expression of CD10 and CD26 and for their cell cycle phase by flow cytometry. Statistical analysis was carried out using the multifactorial analysis of the variance with the LSD (least square difference) range test. The Chi square test was used to compare the cell cycle phases. RESULTS Analysis of the chondrocyte cell cycle showed a significantly high proportion of cells in the S-phase in the maximum load zone in comparison with the minimum load zone (p < 0.001); the percentage of resting cells (G0/G1 phase) was significantly higher in the minimum load zone than in the maximum load zone (p < 0.001). The expression of CD10 and CD26 on chondrocytes was significantly reduced in the maximum load zone of the cartilage and was directly related to the progressive worsening of osteoarthritic lesions. CONCLUSIONS These data demonstrate, for the first time, that articular chondrocytes express on their surface CD10 and CD26 peptidases. Neprilysin 3.4.24.11 (CD10) and dipeptidyl peptidase IV 3.4.14.15 (CD26) have been shown to play a specific role in the control of growth and differentiation of many cell types by cleaving growth factors able to promote cellular proliferation. Our results indicate that CD10 and CD26 are down-regulated in the maximum load zone of the knee OA cartilage: this condition may allow the increase of local levels of growth factors causing chondrocyte activation. Furthermore, as CD26 mediates cell binding to fibronectin and collagen, its reduction in osteoarthritic cartilage may reflect a perturbation of chondrocyte interactions with the extracellular matrix.

Expression of membrane-bound peptidases (CD10 and CD26) on human articular chondrocytes. Possible role of neuropeptidases in the pathogenesis of osteoarthritis.

We studied interleukin-10 (IL-10) levels in the blood and synovial fluid (SF) of 15 patients with RA and in the blood of 15 healthy donors (HD). RA IL-10 levels were significantly higher in SF than in blood (p = 0.001) and did not correlate with the disease activity nor with the therapy. RA patients showed significantly reduced blood IL-10 levels compared to the HD (p = 0.002), suggesting that IL-10 synthesis is depressed in RA. Since IL-10 has anti-inflammatory properties, reducing pro-inflammatory cytokine release by monocytes and down-modulating T cell function, its defect in RA may play a role in perpetuating RA synovitis.

Interleukin-10 in rheumatoid arthritis

The authors describe three patients in whom septic arthritis of the sternoclavicular joint (SCJ) occurred, drug addiction and human immunodeficiency virus (HIV) infection representing the predisposing conditions. Infectious arthritis is well known in intravenous drug users, but it is rare in HIV positive patients, who are prone to bacterial infections from usual or unusual microorganisms. In one case, staphylococcus aureus methicillin sensitive was responsible for septic arthritis. In another case, SCJ infection was associated with pneumonitis.

Isolated sternoclavicular joint arthritis in heroin addicts and/or HIV positive patients: three cases.

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