Articular chondrocytes and synoviocytes in culture: influence of antioxidants on lipid peroxidation and proliferation

Chondrocytes and synoviocytes are the main cell types in articular joints. Articular cartilage is fed by synoviocytes via synovial fluid and has a low partial oxygen pressure. Thus, chondrocytes show oxygen radical protective mechanisms in vivo and are unprotected against these factors under common culture conditions. We investigated the influence of ascorbic acid, Fe2+, glutathione and alpha-tocopherol on lipid peroxidation and proliferation of rat articular chondrocytes and rabbit synoviocytes (HIG-82) in vitro. A combination of ascorbic acid and Fe2+ induced the production of thiobarbituric acid-reactive material as a marker of radical-mediated lipid peroxidation in homogenates and/or supernatants of cultured chondrocytes and synoviocytes. The amount of lipid peroxidation of chondrocytes was about 3-fold higher than that of synoviocytes. Ascorbic acid or Fe2+ alone had no significant influence on the production of thiobarbituric acid-reactive material. Lipid peroxidation could be abolished by addition of the radical scavenger alpha-tocopherol, whereas glutathione had no effect. 25-50 microM alpha-tocopherol decreased the ascorbic acid-(100 micrograms/ml) and Fe(2+)-(3 microM) induced lipid peroxidation to a basal level. Moreover, ascorbic acid inhibited the proliferation of rat chondrocytes and rabbit synoviocytes measured by [3H]-thymidine incorporation. Alpha-tocopherol and glutathione had no influence on the proliferation of chondrocytes but alpha-tocopherol decreased the growth of synoviocytes and increased the anti-proliferative effect of ascorbic acid on these cells. The importance of these findings for the use of ascorbic acid, glutathione and alpha-tocopherol in chondrocyte and synoviocyte cultures, or the influence of these molecules on the etiology and treatment of articular diseases will be discussed.

Reconstruction culture system simulating human synovium: a three-dimensional collagen gel culture of synoviocytes

We developed a reconstruction culture system simulating human synovium to investigate the synoviocytes in a more physiological condition. This system with two types of dishes provided the two separated spaces corresponding to the joint cavity and nutrient vessels. The isolated normal synoviocytes were cultured in type-I collagen gel with a layer-seeded on top in a smaller inner dish with a porous bottom, which was placed in a larger outer dish. We added hyaluronic acid solution to the space on the gel to make an environment close to the physiological joint cavity. The space between the inner and outer dishes was filled with a complete medium to nourish the synoviocytes through the porous filter (Experiment 1). In addition, to examine cell-to-cell interaction, we created a co-culture model by mixing synoviocytes and peripheral blood mononuclear cells in the collagen gel matrix (Experiment 2). In this way we could reconstruct the synovium in vitro. The synoviocytes could survive and maintain their characteristics for four weeks of culture. In Experiment 1, almost all the cells were similar to type B synovial cells by histological, immunohistochemical and electron microscopic observations. In Experiment 2, the spherical cells in abundance of lysosomes like type A synovial cells appeared sporadically in the lining layer. Immunohistochemically, the majority of cultured cells expressed CD68 and matrix metalloproteinase 3. This culture system promises to be of use in investigating the pathogenesis of various joint diseases.

[Scanning electron microscopic investigations on the anatomy of the fetlock joint in horses]

Striking synovial structures were taken and their surface was investigated by scanning electron microscopy. Depending where the probes were taken from, the stratum synovial was arranged in a different way. The synovial intima seems to miss under the tendon of the long/commune extensor muscle, the collateral ligaments and the sesamoidean collateral ligaments. That is why the subsynovial tissue forms the superficial layer. The surface of the probes taken sidewards to the tendon of the extensor muscle and of the synovial fold, which is situated between the metacarpus/metatarsus and the proximal phalanx as well as from the palmar/plantar recess is dominated by synovial intima. Synovial cells are mainly arranged as monolayer. Synovial cells are variable in their appearance. Some resemble blackberrys, others show a quite undulating surface. The length of processes of synovial cells differs from 2-10 microns, the diameter of the synovial cells from 5-10 microns. The space between two cells amounts to 2-10 microns. The intercellular gap is put in relation to the length of the cells' processes. The synovial intima is supposed to form a barrier between the articular cavity and the surrounding structures.

dUTPase-minus caprine arthritis-encephalitis virus is attenuated for pathogenesis and accumulates G-to-A substitutions

The importance of the virally encoded dUTPase for CAEV replication, invasiveness, pathogenesis, and genetic stability was investigated in goats infected by viruses with single point (DU-G) and deletion (DU-1) mutations of the dUTPase gene (DU gene). The DU gene was found to be dispensable for CAEV replication in vivo as judged by times taken to seroconvert, frequencies of viral isolation, and tissue distribution of viral RNAs. DU- reversion at week 34 in one of three goats infected with the single point mutant DU-G, however, suggested that the viral dUTPase confers some advantages for replication in vivo. Moreover, we show that dUTPase is necessary for the timely development of bilateral arthritic lesions of the carpus. Finally, dUTPase was shown to efficiently prevent accumulation of G-to-A transitions in the viral genome.

Tachykinin regulation of basal synovial blood flow

1. Experiments were performed to investigate the role of endogenously released tachykinins in the regulation of blood flow to the rat knee joint. Synovial perfusion was assessed by laser Doppler perfusion imaging, which permitted spatial measurement of relative changes in perfusion from control (pre drug administration), expressed as the percentage change. Most experiments were performed on the exposed medial aspect of the knee joint capsule. 2. Neither the selective tachykinin NK1 receptor antagonist, FK888, nor the selective tachykinin NK2 receptor antagonist, SR48968, significantly influenced synovial blood flow at doses of 10(-12), 10(-10) and 10(-8) mol. However, topical co-administration of these agents produced significant dose-dependent reductions in basal synovial perfusion of 6.3 +/- 4.6 and 12.0 +/- 3.4 and 19.9 +/- 2.6%, respectively; n = 29. The non-selective tachykinin NK1/NK2 receptor antagonist, FK224, also produced significant (at 10(-10) and 10(-8) mol), but less potent, reductions in perfusion of 5.3 +/- 4.0, 8.4 +/- 2.2 and 5.9 +/- 2.8%, respectively; n = 25. 3. Topical administration of the alpha 1-, alpha 2-adrenoceptor antagonist phenoxybenzamine elicited a 31.3 +/- 6.2% increase in blood flow which was substantially reduced to 10.4 +/- 3.8% by co-administration of the FK888 and SR48968 (both at 10(-8) mol; n = 8-13), suggesting that normally there is sympathetic vasoconstrictor "tone' which is opposed by the vasodilator action of endogenous tachykinins. 4. One week after surgical interruption of the nerve supply to the knee joint, co-administration of FK888 and SR48968 (both at 10(-8) mol) now produced slight vasodilatation (6.7 +/- 4.6%; n = 9) which did not differ significantly from vehicle treatment. Depletion of tachykinins from sensory nerve fibres by systemic capsaicin administration also resulted in abolition of the vasoconstrictor effect of FK888 and SR48968 (both at 10(-8) mol), with these agents only producing a slight vasodilatation (2.5 +/- 5.3%; n = 6). 5. By use of a near infra-red laser source it was possible to image knee joint perfusion transcutaneously, the overlying skin being left intact. In this more physiological situation, close intra-arterial injection of the combination of FK888 and SR48968 (both at 10(-8) mol) again elicited vasoconstriction (48.8 +/- 16.2% reduction in blood flow; n = 4). 6. These results indicate that endogenous tachykinins may be continuously released from sensory fibers innervating the joint. Basal release of tachykinins could therefore be an important physiological influence opposing sympathetic vasoconstrictor tone.

Braided polypropylene augmentation device in reconstructive surgery of the anterior cruciate ligament: long-term clinical performance of 594 patients and short-term arthroscopic results, failure analysis by scanning electron microscopy, and synovial histomorphology

Long-term clinical results and short-term arthroscopic and microscopic findings from two augmented reconstruction procedures for the ruptured anterior cruciate ligament are reported. The braided polypropylene ligament augmentation device (Kennedy model) was used with temporary double-end fixation in 279 patients to augment the attachment of the anterior cruciate ligament after acute proximal rupture and in 315 patients to augment a bone-tendon-bone autograft, mainly after chronic instability. Check arthroscopy was performed and the metal fixation hardware was removed after a mean of 11 months. Of the 569 patients evaluated, 101 partial or total breakages of the ligament augmentation device were found. Together with nine breakages detected late in the follow-up period, 110 (19.3%) failures were found. Most of these failures were accompanied by effusion that was immediately alleviated when the failed device was removed. No generalized synovitis was visible. Scanning electron microscopic analysis of 24 retrieved failed ligament augmentation devices showed fatigue to be the principal failure mode, together with local abrasion at the fracture. Synovial biopsies were taken during arthroscopy in 84 patients with and without ligament augmentation device-failure who had given informed consent, and histological evaluation revealed that in 21 patients, chronic but no acute synovial inflammation was found, and wear particles could be identified in foreign body cells in 17. Statistically, the presence of chronic synovitis was predicted neither by wear particles and foreign body cells nor by abrasion or fatigue failure of the ligament augmentation device. Irrespective of the failures, for which ligament augmentation device removal is recommended, in the final Orthopaedische Arbeitsgemeinschaft Knie evaluation (after a mean of 6.2 years), excellent and good clinical results were found in 83.6% of all 594 patients.

[Ultramicrostructural changes of articular cartilage, subchondral bone and synovium in human osteoarthritis of patellofemoral joint]

Ten patients with patellofemoral joint osteoarthritis (OA) were studied by electron microscope (SEM&TEM) to identify ultramicrostructural changes in the destroyed articular cartilage, subchondral bone and synovium. According to the results obtained, the author suggested that (1) Articular cartilage, subchondral bone and synovium in patellofemoral joint OA were noted to be in various degree of ultramicrostructural changes; (2) The cartilage degeneration in lateral compartment of patellofemoral joint were much more severe than that in medial compartment; (3) The subchondral bone had a strong tendency to undergo selerosis in the form of thicking and confluence of the trabeculae to form massive block of bone, which were not parallel to alteration of cartilage, and the rules of alteration were related to the character of loading; (4) The repair tissues of I-II grade degenerative cartilage were similar to normal cartilage, but those of III-IV grade degenerative cartilage were similar to fibrocartilage in many ways, because the source of repair tissues were different between them; (5) Alteration of synovium revealed only mild non-specific inflammatory changes following the changes of articular cartilage; (6) I-II grade patellofemoral joint OA was treated by conservative methods and III-IV grade OA should be treated by patellofemoral joint resurfacing.

Surfactant protein A and lamellar bodies: a homologous secretory function of peritoneum, synovium, and lung

OBJECTIVE

To review recent discoveries on the existence of lamellar body secreting cells in extrapulmonary sites with respect to their constitution as a previously unrecognized coherent biological system and to evaluate the role of mesothelial research in peritoneal dialysis in initiating this new field of medical research.

DATA SOURCES

Studies in the literature on the production and metabolism of pulmonary surfactant with respect to lamellar bodies and surfactant protein A (SP-A). Published investigations on the identification of lamellar bodies and SP-A in extrapulmonary sites and their possible role in systemic expression of autoimmune disorders.

RESULTS

It is now established that lamellar bodies of identical periodicity and ultrastructural geometry are present in lung (type II pneumocytes), serosal mesothelium (peritoneum, pleura, and pericardium), and joints (type A and type B synoviocytes). Not only pulmonary lamellar bodies but those at extrapulmonary sites are found in association with SP-A, while SP-A or SP-A-like proteins are present in measurable quantities in normal serosal fluids. These findings have disclosed totally new avenues of research into multisystem disorders, where for the first time an organelle and associated protein provide a link between diverse tissues affected by rheumatoid disease. Evidence of shared epitopes between SP-A and mycobacterial 65-kD heat shock protein indicates a possible etiologic mechanism.

CONCLUSIONS

A hitherto ultrastructurally hidden system of lamellar body secretion is now being revealed as a major biological system which appears to subserve surfactant, lubricant, surface protection, and sealant functions in body surfaces and tissue interfaces. This new frontier was born out of investigations into the hitherto neglected biology of peritoneal mesothelium, research which was vital for advancing the therapy of peritoneal dialysis and for preservation of the dialyzing membrane.

Ultrastructural demonstration of spirochetal antigens in synovial fluid and synovial membrane in chronic Lyme disease: possible factors contributing to persistence of organisms

To perform the first systematic electronmicroscopic (EM) and immunoelectron microscopy (IEM) study of the pathological changes and the evidence of spirochete presence in synovial membranes and synovial fluid (SF) cells of patients with chronic Lyme arthritis. EM examination was performed on four synovial membrane and eight SF cell samples from eight patients with chronic Lyme disease. Spirochetal antigens in the samples were sought by IEM using monoclonal antibody to Borrelia burgdorferi outer surface protein A (OspA) as the immunoprobe. Prominent ultrastructural findings were surface fibrin-like material, thickened synovial lining cell layer and signs of vascular injury. Borrelia-like structures were identified in all four synovial membranes and in two of eight SF cell samples. The presence of spirochetal antigens was confirmed by IEM in all four samples studied (one synovial membrane and three SF cell samples). OspA labelling was in perivascular areas, deep synovial stroma among collagen bundles, and in vacuoles of fibroblasts in synovial membranes; and in cytophagosomes of mononuclear cells in SF cell samples. Electron microscopy adds further evidence for persistence of spirochetal antigens in the joint in chronic Lyme disease. Locations of spirochetes or spirochetal antigens both intracellulary and extracellulary in deep synovial connective tissue as reported here suggest sites at which spirochaetes may elude host immune response and antibiotic treatment.

Synovial surfactant: lamellar bodies in type B synoviocytes and proteolipid in synovial fluid and the articular lining

Previous studies have shown that synovial surfactant could have beneficial roles in the joint, especially as a very effective boundary lubricant capable of high load bearing. This study is aimed at further characterization and identification of the source. Known to be an important minor component of pulmonary surfactant, proteolipid has now been detected in appreciable quantities in bovine synovial fluid and bound to the articular surface. Using standard procedures to separate it from the major component [surface-active phospholipid (SAPL)] by column chromatography, proteolipid: phospholipid ratios were found to be comparable to those in the lung or in lamellar bodies (LBs). LBs are the unequivocal source of surfactant in the lung and we have confirmed an earlier study demonstrating their presence in Type B synoviocytes. Using a fixation procedure specifically designed to preserve the graphite-like structure of SAPL deposited as oligolamellar layers, or coiled as lamellar bodies, we were able to demonstrate these structures in equine joints adjacent to the Golgi apparatus associated with the secretory mechanism of the cell. These results indicate that proteolipid could be facilitating the deposition of the graphite-like surface lining of SAPL providing efficient boundary lubrication just as it promotes surfactant adsorption in the lung and in the formation of myelin. Any deficiency in synovial surfactant, compromising its roles in the joint, is discussed in relation to osteoarthritis and the possible administration of exogenous SAPL to the degenerating joint.

Postnatal development of substance P-, calcitonin gene-related peptide- and neuropeptide Y-like immunoreactive nerve fibres in the synovial membrane of the rat temporomandibular joint

The postnatal (0-24 days) development of substance P (SP)-, calcitonin gene-related peptide (CGRP)- and neuropeptide Y(NPY)-like immunoreactive (LI) nerves in the rat temporomandibular joint (TMJ) was investigated immunohistochemically. Immediately after birth, SP- or CGRP-LI nerves were observed in most disc attachments. A few NPY-LI nerves were observed around the large blood vessels in the joint capsule. From days 3 to 6, the SP- or CGRP-LI nerves were first found close to the anterior, lateral, medial (third day) or posterior (sixth day) peripheral portion of the disc. The synovial cells (type A and B) first appeared at the anterior peripheral portion of the disc (sixth day), and then at the posterior, lateral and medial portions (seventh day). NPY-LI nerves were found around the blood vessels at the disc attachment on the sixth day, and then entered into the peripheral portion of the disc from days 10 to 14. At 14 days a few NPY-LI nerves were first found close to the blood vessels in the sublining layer of the synovial membrane. From days 18 to 24, a few NPY-LI nerves were located in the superficial layer of the synovial membrane. The central portion of the disc did not contain any nerves from days 0 to 24. Thus SP- or CGRP-LI sensory nerves are shown to innervate the rat TMJ at an earlier age than NPY-LI sympathetic nerves, which may modulate the regulation of blood flow in the joint capsule, disc and synovial membrane. However, it is considered that the disc itself does not contribute to the transportation of the afferent sensory information. Furthermore, from the fact that SP- or CGRP-LI nerves were found earlier than the appearance of the synovial cells, it is suggested that these nerves may be associated with the growth and proliferation of synovial cells.

Ultrastructural demonstration of apoptosis, Fas and Bcl-2 expression of rheumatoid synovial fibroblasts

OBJECTIVE

There is evidence that proliferation of synovial fibroblasts and invasive growth in rheumatoid arthritis (RA) is due to impaired regulation of the cell cycle, i.e., the balance between proliferation and physiological cell death (apoptosis) We examined synovial tissues from patients with RA and osteoarthritis (OA) to determine the ultrastructural changes during apoptosis and the expression of the apoptosis regulating molecules Fas and Bcl-2 in synovial fibroblasts.

METHODS

We examined synovial tissues obtained from patients with RA and OA by electron microscopy and immunoelectron microscopy to evaluate the characteristics of apoptosis in RA synovial fibroblasts as well as Fas and Bcl-2 antigen expression.

RESULTS

Ultrastructurally, the majority of the RA synovial fibroblasts appeared transformed, and 3% of these were in different stages of apoptosis. In OA, no apoptotic cells could be observed. Apoptosis of synovial fibroblasts in RA showed a characteristic multistage pattern. In each of the distinguishable 4 stages, specific ultrastructural changes could be detected. The apoptotic synovial fibroblasts were mainly located in the deeper sublining layers of the synovium. Immunoelectron microscopy revealed that Fas antigen expression was limited to the first stage of apoptosis. Conversely, the synovial fibroblasts located in the synovial lining layer neither underwent apoptosis nor expressed Fas antigen. Several synovial lining cells expressed the cell death suppressor (anti-apoptosis) gene product Bcl-2.

CONCLUSION

Apoptosis of fibroblasts in the RA synovial sublining is characterized by a distinct multistep ultrastructural pattern with a detectable initial Fas antigen expression; conversely, reduced apoptosis in the synovial lining associated with the expression of Bcl-2 results in extended life of matrix degrading synovial fibroblasts at the site of synovial invasion into cartilage and bone.

Electron and immunoelectron microscopy on healing process of the rat anterior cruciate ligament after partial transection: the roles of multipotent fibroblasts in the synovial tissue

The healing process of the rat anterior cruciate ligament (ACL) after partial transection was examined. In sham operated samples, the synovial tissue near the infrapatellar fat pad includes an abundance of young fibroblasts which can be classified into two types: A type cells often exist along the surface of the synovial tissue and contain numerous lysosomes, while B type cells are often associated with small vessels and are actively involved in the production of fibronectin and laminin. At 1 week after transection of the ACL, B type cells frequently undergo mitotic proliferations and are eventually incorporated into the endothelium of the growing capillaries extending from the proximal remnants of the synovial tissue to the transected lesion. The transformation of B to A type cells is indicated by our electron micrographs. After 2 weeks, the replacement of the transected lesion by regenerated soft tissue becomes pronounced. After 4 weeks, B type cells in the deeper layer of the regenerated tissue are first involved in the production of type III and then in that of type I collagens as revealed by the immunocytochemistry. The present study indicates that B type cells are a kind of stem cell: they possess the ability to transform to vasoformative cells involved in a manner suggestive of vasculogenesis, to phagocytic A type cells and to the synthetic fibroblasts in the regeneration of the ACL.

An immunohistochemical and immunoelectron microscopic study of adhesion molecules in synovial pannus formation in rheumatoid arthritis

To investigate the mechanism of synovial pannus formation in rheumatoid arthritis, immunohistochemical and immunoelectron microscopic studies with monoclonal antibodies against the adhesion molecules, CD54 (ICAM-1), CD11a (LFA-1), CDw49a (VLA-1), CDw49b (VLA-2), CDw49c (VLA-3), Cdw49d (VLA-4) and CDw49e (VLA-5), were carried out to determine the pattern of distribution of these molecules at the rheumatoid synovial cartilage junction. Treatment with anti-ICAM-1 resulted in membrane staining of most of the macrophages and fibroblasts infiltrating the synovial tissue and bordering and pannus-cartilage junction, suggesting the possibility that ICAM-1 may function to facilitate the adhesion of synovial type A cells bearing ICAM-1 to type B cells of the pannus. ICAM-1 positive macrophages and fibroblasts were often found to be in contact with lymphoid cells, suggesting also that a cellular immune reaction occurs in the formation of the pannus. In addition, VLA-3, VLA-4 and, particularly, VLA-5 were the predominant beta 1 integrins expressed by rheumatoid synovial pannus. Sine these three integrins all function as fibronectin receptors, it is possible that the fibronectin-rich environment of the rheumatoid cartilage surface effectively traps pannus cells expressing high levels of these molecules. The VLA-5 molecule was found in a pericellular and interterritorial matrix distribution in the present study, strongly suggesting that a receptor-ligand interaction between VLA-5 and cartilage matrix may occur at the early stage of pannus formation. Furthermore, an increase in beta 1 integrin may be necessary for the growth of the pannus and also for the upregulation of the VLA molecules, leading secondarily to increased attachment.

Comparison and quantitation of wear debris of failed total hip and total knee arthroplasty

To compare the physical properties of debris particles associated with failed total hip and total knee arthroplasty, we applied a recently developed assay to electronically characterize the size, number, and composition of debris particles isolated from tissues adjacent to failed implants. We identified 21 samples (from 20 patients) of hip synovia and 35 samples (from 32 patients) of knee tissues that had been obtained at the time of revision arthroplasty. There were 12 females and 9 males in the hip group, and 16 females and 19 males in the knee group. Primary arthroplasty was performed for osteoarthritis (OA, 15 cases) or rheumatoid arthritis (RA, 6 cases) in the hip, and for OA (23) or RA (12) in the knee. Patients ranged in age from 23 to 85 (mean 59 years) for total hip, and from 27 to 84 (mean 61 years) for total knee arthroplasty. Implantation duration was from 5 to 123 months (mean 37.8) for total hip, and from 11 to 123 months (mean 63.1) for total knee arthroplasty. All of the implants were composed of cobalt-chromium alloy articulating with ultrahigh-molecular-weight polyethylene. The number of particles smaller than 10 microns ranged from 1.04 x 10(8)/g to 1.91 x 10(10)/g in the hip, and from 6.69 x 10(8)/g to 2.13 x 10(10)/g in the knee. Energy-dispersive X-ray spectroscopy and polarized light analysis showed both polyethylene and metal particles in most cases. The mean diameter of particles smaller than 10 microns was 0.72 +/- 0.2 microns in the hip, and 0.74 +/- 0.1 microns in the knee. Evaluation of particles larger than 10 microns showed a larger range of particle size in knee tissues (maximum 6.1 mm, mean 283 microns), than in the hip tissues (maximum 826 microns, mean 81 microns) (p < 0.001). Very small particles are common in both groups, but it appears that a larger range of particle sizes is present adjacent to failed knee than to failed hip prostheses. The higher frequency of large particles in failed knee prostheses probably reflects the perceived higher rate of delamination and fragmentation of tibial and patellar compared to that of acetabular polyethylene.

Structure of the normal synovial membrane of the temporomandibular joint: a review of the literature

PURPOSE

The structure of the normal synovial membrane of the temporomandibular joint (TMJ) is discussed, based on knowledge of synovial membrane in synovial joints in general.

Repair and function of synovium after arthroscopic synovectomy of the dorsal compartment of the equine antebrachiocarpal joint

The reparative ability of equine synovium was determined by gross, histological, and ultrastructural examination. The functional potential of the synovium was estimated by examination of synovial cell organelles with transmission electron microscopy. Results from rested and exercised horses were compared to determine the effect of exercise on synovial healing. The response of synovectomized joint to exercise was evaluated with a standardized lameness examination and by gross, histological, and histochemical observations of the articular cartilage. A 7-mm diameter motorized synovial resector was used to perform a subtotal synovectomy in 1 antebrachiocarpal joint of each of 8 horses; the contralateral joint served as a control. After 2 months rest, four randomly selected horses were rigorously exercised for the remainder of the study; the other four horses continued paddock rest. Lameness examinations and synovial fluid analyses were conducted at 0, 2, 30, 60, and 120 days. Synovium and articular cartilage from all horses were examined at necropsy at 120 days. None of the horses were lame during the study, and transient synovitis occurred in the synovectomized joints. The hyaluronan concentration of treated joints decreased at 2 days but returned to normal by 60 days. Synovial fluid composition, including hyaluronan concentration, was unchanged by exercise. Significant cartilage damage was not observed in any of the joints. At 120 days, the healing synovium was devoid of villi and its subintima was fibrotic, however transmission electron microscopy confirmed that an intimal layer was present within the repair tissue. The cells within the repair tissue appeared actively engaged in both synthesis and phagocytosis. Exercise did not modify any of these findings. The results of this study suggest that 120 days after subtotal synovectomy, the joint environment was maintained and and the resected synovium had evidence of restoration and increased metabolic potential. Synovectomized joints withstood exercise but synovial repair was not accelerated by exercise.

[Experimental bases for photodynamic laser therapy in chronic polyarthritis]

The principle of photodynamic laser therapy (PDT) for chronic polyarthritis consists in specifically concentrating a drug (photosensitizer) in the synovium. Subsequent activation of the photosensitizer by means of laser leads to a cytotoxic effect. The practicability of PDT was first shown in cell cultures of human synovial fibroblasts. For further tests an animal model consisting of IgG-induced arthritis in rabbits was used. In this model, concentration of the photosensitizer in the synovial lining cells, in the media of arteries and in the lymphoid infiltrate was seen. After laser irradiation there was total selective demarcation of the synovium. In contrast, bradytrophic tissues such as cartilage, meniscus and ligament structures were changed neither macroscopically nor microscopically. In the animal model PDT combines high selectivity with minimal invasiveness and can be used in small joints. PDT thus offers ideal preconditions for future minimal invasive treatment of chronic inflammatory joint diseases.

A one-day double-labelling technique for tissue specimens: immunogold-silver staining for in situ hybridization combined with alkaline phosphatase-anti-alkaline phosphatase (APAAP) immunohistochemistry for antigens

An improved technique is described that addresses the problems of sensitivity, specificity, the use of hazardous radioactive equipment and time consumption in immunohistochemical labelling and double labelling of in situ hybridization of tissue specimens. It consists of a two-step protocol in which digoxigenin-uridine triphosphate (UTP) labelled riboprobes in the in situ hybridization step are visualized by the immunogold-silver staining method, and double labelling of tissue antigens is achieved by the application of an alkaline phosphatase-anti-alkaline phosphatase staining step. We tested this protocol using snap-frozen tissue sections of synovial tissue from patients with rheumatoid arthritis. The target mRNA was detected by perforin or cathepsin D riboprobes, the double labelling was performed using anti-collagen type IV and alpha-smooth muscle actin antibodies. It is concluded that, in comparison with an established three- to four-day double-labelling protocol used in many laboratories, this one-day combination is currently the most rapid assay of reliable quality for double labelling of in situ hybridization products and tissue antigens.

Fine structure and distribution of lymphatics in the synovial membrane of monkey and human knee joints. A study using an enzyme-histochemical method

The fine structure and distribution of lymphatics in the synovial membrane of monkey knee joints, and human knees with osteoarthritis and rheumatoid arthritis, were studied by light and electron microscopy using an enzyme-histochemical method. Whole mount preparations and tissue sections were doubly stained for 5'-nucleotidase and alkaline phosphatase. The 5'-nucleotidase positive lymphatics could be distinguished from the alkaline phosphatase positive blood vessels. In monkey specimens the 5'-nucleotidase lymphatics were densely distributed in the medial and lateral parts of the suprapatellar pouch and infrapatellar fat pad, in both the superficial and deep of the sublining cell layers. Collecting lymphatics were well developed in the deep fibrous layer and in the merging epimysium. In the knees with both types of arthritis, the patterns of distribution were the same as in the monkey. No lymphatics were found in well developed villi in rheumatoid arthritis, but many blood vessels were present.

A syndrome of fibrosing pleuritis, pericarditis, and synovitis with infantile contractures of fingers and toes in 2 sisters: "familial fibrosing serositis"

We describe a family in which 2 sisters born to consanguineous parents developed childhood onset fibrosing pleuritis in association with constrictive pericarditis and bilateral deforming arthropathy of large and small joints of upper and lower extremities including flexion contractures of several fingers (camptodactyly) and toes. One patient also had mitral value prolapse. Histopathological examination of the synovium and pericardium revealed fibrosis, and ultrastructural study of synovium showed abundant inter and intracellular mesh of 9 nm microfibrils. We describe this distinct clinicopathological entity with pleiotropic manifestations, the common features of which appears to be the fibrosis of serous membranes. Therefore, the term "familial fibrosing serositis" is proposed for this entity.

A developmental study of the synovial membrane of the rat temporomandibular joint: changes in the three-dimensional configuration during postnatal development

The development of synovial membranes in the posterior synovial portion of the rat temporomandibular joint was studied and the three-dimensional structure of the posterior synovial portion reconstructed from sagittal semithin sections. Reconstructions showed that the synovial membrane expanded and that synovial folds increased in number and became complicated in shape with the growth of the joint. Using transmission-electron microscopy, it was observed that the synovial lining cells degenerated, that the synovial membrane split to make further synovial folds, and that the folded-end structures consisted of synovial lining cells that extended into the subsynovial connective tissue. It is suggested that in the development of the three-dimensional configuration of the synovial membrane, several processes proceed simultaneously to form the synovial folds: a splitting of the synovial membrane, infolding of the synovial membrane into the subsynovial connective tissue, and outgrowth of the synovial folds towards the synovial cavity.

Early ultrastructural changes of articular cartilage and synovial membrane in experimental vitamin A-induced osteoarthritis

OBJECTIVE

To evaluate the sequential ultrastructural changes of the articular cartilage and synovial membrane in the earliest phases of the vitamin A model of osteoarthritis (OA) in the rabbit.

METHODS

The superficial layer of the weight bearing zone of the articular cartilage and the synovial membrane from femorotibial joints of 12 osteoarthritic rabbits were evaluated 3, 6, and 9 days after the triggering intraarticular injection of 100,000 i.u. of retinol palmitate. Four uninjected rabbits were used as controls.

RESULTS

At 3 days, ultrastructural changes of chondrocytes could be seen (hypertrophic cells with increased lipid droplets, chondrocytes rich in microfilaments and glycogen, and some degenerating cells) with no evident lesions of the matrix. The synovium was similar to that of the control rabbits. At 6 days, chondrocyte changes seemed almost identical to those of 3 days, while the synovial membrane appeared markedly involved, substituted by a single layer of A-type cells lying on fibrous subsynovial tissue in which lymphocytes, mast cells, and blood vessels could be seen. Conspicuous alterations and necrobiosis of the cartilaginous cells characterized later stages (9 days). The intercellular matrix was mainly made up of amorphous material and bundles of collagen fibers. The synovial membrane was transformed into a thick fibrous tissue partially covered with scattered cells no longer distinguishable as A or B type.

CONCLUSION

Our data suggest that in the vitamin A model of OA the initial metabolic changes of the chondrocytes have a pivotal role in determining the relentless cascade of events leading to the full expression of this disease. Moreover, although several studies have been carried out on the early changes in experimental OA, no complete morphological evaluations on the developmental aspect of this model have been available.

Type VI collagen periodic fibrils in the synovium of the mouse temporomandibular joint

Immunohistochemical staining with anti-type VI collagen antibody was strongly positive in the intimal layer and moderately positive in the subsynovium. After treatment with 20 mM ATP, numerous structures with a periodicity of 100 +/- 10 nm (type VI collagen fibrils) appeared around the synovial cells. As the periodic dark bands were stained by ruthenium red, proteoglycan(s) or glycosaminoglycan(s) were probably associated with the type VI collagen fibrils. When the tissue was digested with testicular hyaluronidase before ATP treatment, the periodic fibrils were not found, and only a filamentous network of 100-nm interval was seen around the cells. Thus, type VI collagen is abundant in the synovium of the mouse mandibular joint and is associated with proteoglycans or glycosaminoglycans, which might have a role in its formation.

Radial organization of interstitial exchange pathway and influence of collagen in synovium

The synovial intercellular space is the path by which water, nutrients, cytokines, and macromolecules enter and leave the joint cavity. In this study two structural factors influencing synovial permeability were quantified by morphometry (Delesse's principle) of synovial electronmicrographs (rabbit knee), namely interstitial volume fraction Vv.1 and the fraction of the interstitium obstructed by collagen fibrils. Mean Vv.1 across the full thickness was 0.66 +/- 0.03 SEM (n = 11); but Vv.1 actually varied systematically with depth normal to the surface, increasing nonlinearly from 0.40 +/- 0.04 (n = 5 joints) near the free surface to 0.92 +/- 0.02 near the subsynovial interface. Tending to offset this increase in transport space, however, the space "blocked" by collagen fibrils also increased nonlinearly with depth. Bundles of collagen fibrils occupied 13.6 +/- 2.4% of interstitial volume close to the free surface but 49 +/- 4.8% near the subsynovial surface (full-thickness average, 40.5 +/- 3.5%), with fibrils accounting for 48.6-57.1% of the bundle space. Because of the two counteracting compositional gradients, the space available for fibril-excluded transport (hydraulic flow and macromolecular diffusion) was relatively constant > 4 microns below the surface but constricted at the synovium-cavity interface. The space available to extracellular polymers was only 51-53% of tissue volume, raising their effective concentration and hence the lining's resistance to flow and ability to confine the synovial fluid.

[Scanning electron microscopy of the synovial membrane of the distal phalangeal joint and the navicular bursa in horses]

20 extremities of horses were used to investigate the synovial membrane of the distal interphalangeal joint and the navicular bursa. From each extremity five specimens were taken from the distal interphalangeal joint capsule, two further from the navicular bursa. Synovial villi were found near the articular cartilage as well as everywhere where the joint capsule did not form a tight periostal cover or was not connected with ligaments or tendons. Some lay between the articular surfaces of the phalanx media and phalanx distalis. Besides synovial villi and synovial folds "trabecular-like" cords of synovial membrane were demonstrated in the dorsal recess of the distal interphalangeal joint. These extend from one side of synovial membrane to another but they do not have a free ending. The surface of the synovial membrane and the arrangement of several synovial structures are documented.

Structural and ultrastructural studies of the synovial membrane in temporomandibular joint disturbance syndrome

To gain further knowledge on temporomandibular joint disturbance syndrome (TMJDS), the synovial membranes of 7 patients and 3 cadavers were examined with light microscope and transmission electron microscope. The results showed that the synoviocytes degenerated or disappeared in TMJDS. The cytoplasm contained numerous fibrils, while the organelles diminished in number. The surface of the synovial membrane was covered with a fibrinoid material. The surface of the synovial membrane was covered with a fibrinoid material. The authors consider that these pathological changes reduce or eliminate the normal functions of the synovial membrane, which may lead to damage to the articular cartilage. The articular adhesion found sometimes in TMJDS may be related to the changes in the synovial membrane.

Quantitative analysis of chondroitin sulphate retention by tannic acid during preparation of specimens for electron microscopy

The ability of tannic acid to enhance binding of glycosaminoglycans to purified collagen was analysed in an in vitro system using amino sugar analysis on an amino acid analyser, transmission electron microscopy, and scanning electron microscopy. Collagen was purified by digestion with trypsin, papain, and hyaluronidase. Purified collagen was incubated with hyaluronic acid or with chondroitin sulphate glycosaminoglycan and then treated with tannic acid. Tannic acid was found to enhance retention during preparation for electron microscopy of either of the glycosaminoglycans onto collagen fibres. The ability of tannic acid to enhance binding of collagen and glycosaminoglycans might explain, at least in part, its structural reinforcement effect on resected synovial joint-apposing surfaces during preparation for scanning electron microscopy.

The angioarchitecture of the rat mandibular joint synovium

The synovium (or synovial membrane) lines all intra-articular surfaces of synovial joints except for the articulating surfaces. This study describes the angioarchitecture of the synovium of the adult rat temporomandibular joint using microvascular corrosion casts and scanning electron microscopy. To corroborate findings, India ink-injected, thick-sectioned specimens (200 microns) and haematoxylin and eosin-stained tissue sections (7 microns) were analysed. Rostrally, the synovial membrane was fed by several layers of vessels branching towards the superficial lining of highly convoluted capillary loops. Arterioles were rare, and venules organized in large plexuses. The membrane thinned out in the caudal direction. Villi were present on the surface. They were flat, with a core of two parallel linear feeder vessels, one arteriole and one venule, which were interconnected by capillary loops. At the periphery of the articulating surfaces, the vessels of the synovial layer were flatter. Caudally, the synovial membrane of the richly vascularized retrodiscal pad showed many synovial folds. Feeder vessels were directed rostrally and branched in all directions. The number of subdivisions depended on the size of the synovial fold. Again, venules were organized in plexuses and lining capillaries were convoluted. The densely capillarized synovial membrane with its folds and villi is considered well adapted to serve synovial fluid production and joint dynamics.

The distribution and abnormal morphology of plasma cells in rheumatoid synovium

This study assessed the distribution and structural features of plasma cells in rheumatoid synovial tissue. Plasma cells were found to be the predominant infiltrating mononuclear cells (mean 40%) in relation to lymphocytes and monocytes, and there was a direct relationship between their number in the infiltrates and the total number of mononuclear leucocytes (P = 0.007). Plasma cells were also seen in intimate contact with macrophages intermixed with synovial lining cells, and closely associated with small blood vessels. They often surrounded these blood vessels and sometimes were seen lying within the vessel walls themselves. Ultrastructural analysis revealed that many synovial plasma cells were considerably larger than plasma cells of a normal size and possessed a marked distension of the cisternae of rough endoplasmic reticulum. Furthermore, plasma cells in close proximity to blood vessels often appeared to be undergoing migration. These observations imply that in rheumatoid synovium, plasma cells are metabolically very active and occupy a pivotal position for the secretion of antibodies into both the vascular and the extravascular compartments.

Synovial and peritoneal macrophages in organoid culture

Cultivation of macrophages and their progenitors has been very useful for elucidation of function, behaviour and morphology of these cells. The purpose of this contribution is to describe a new in vitro system (organoid, high density or micromass culture) which proved to be convenient for cultivation of macrophages derived from human synovial fluid and tissue and mouse peritoneal fluid. Using this method, highly differentiated and functionally active macrophages of marked purity and long maintenance (up to 2 weeks) could be obtained even after previous cultivation and subcultivation in monolayer culture. The macrophages were identified by electron microscopy and immunomorphology using HLA-DR-DP, CD-68 (markers for human macrophages), anti-human-polymorphonuclear leukocyte-gelatinase and F4/80 (a mouse macrophage surface marker). The significance of this method as a research tool in the study of cartilage degradation by macrophages in co-cultures is stressed.

Cytochemical localization of hyaluronic acid in human synovium with special reference to its possible process of degradation

Fibroblast-like type B cells are known to produce hyaluronic acid (HA), but the process of its degradation remains unknown. In order to examine the possible route for the degradation of HA in normal human synovium, histochemical and immunohistochemical techniques were applied to the synovial tissue, using biotinylated HA binding region (HABR) and antibodies against CD44 and cathepsin B. Reaction products for HA and CD44 were detected on the cell surface of all synovial lining cells, while half of these lining cells contained intracellular stainings of HA and CD44. Electron microscopically, the lining cells containing intracellularly stained HA and CD44 extended cytoplasmic processes (type A cells), while the other lining cells possessed a smooth cell surface (type B cells). By light microscopic double staining, the intracellular stainings of HA and CD44 appeared co-localized in the cells immunopositive for cystatin beta, an endogenous cysteine proteinase inhibitor which has been shown to be localized in alveolar macrophages and osteoclasts. Moreover, these intracellular stainings of HA and CD44 were co-localized with immunodeposits for cathepsin B, a representative cysteine proteinase in lysosomes. In the extracellular staining of HA, dot-like reaction products appeared on fibrous structures with a periodicity of 41.7 nm. These results suggest that Type A cells in the normal human synovium participate in the degradation of HA by its CD44 mediated intake. Furthermore, HA may be closely associated with fibrous structures, probably type III collagen molecules.

True synovial metaplasia of breast implant capsules: a light and electron microscopic study

The formation of true synovial-lined membranes at tissue sites not intimately related to an articulation or a tendon sheath has been described in a variety of pathologic and postsurgical conditions, but until recently has not been well recognized to occur in association with tissue surrounding silicone breast implants. Of 15 cases with resected periprosthetic breast capsules, 7 (47%) demonstrated true synovial metaplasia with capsule-implant interfaces lined by typical synovial cells. Histochemical and immunohistochemical staining reactions were essentially identical to those observed in synovial control cases and featured positive reactions to Alcian blue-periodic acid-Schiff, reticulin, and vimentin. Focal positive immunoreactivity was observed with alpha 1-antitrypsin, alpha 1-antichromotrypsin, lysozyme, and CD68. No immunoreactivity was observed with cytokeratin AE1/AE3, S-100 protein, carcinoembryonic antigen, or basement membrane antigens. Transmission electron microscopy of the lining cells confirmed their true synovial nature with the type A (macrophage-like) cells, type B (fibroblast-like) cells, and intermediate forms or type AB cells identified. We conclude that the cellular lining surrounding silicone breast implants is a true synovial membrane, that synovial metaplasia may occur in nearly one half of all resected periprosthetic capsules, and that awareness of this entity will enable the surgical pathologist to render an accurate histopathologic diagnosis.

Lamellar body secretion: ultrastructural analysis of an unexplored function of synoviocytes

The intra- and extracellular distribution and relative density of lamellar bodies (LBs) were determined by electron microscopy in synovial biopsies from 20 non-rheumatoid arthritis (RA) patients. LBs were found on the synovial surface, in intimal cells, throughout intimal matrix, in blood vessel walls, in endothelial cytoplasm and within vascular lumena. Lamellar profiles were observed in type B synoviocytes within rough endoplasmic reticulum (RER), in association with the Golgi apparatus, and embedded in electron dense matrix (projection cores) in multivesicular bodies. Exocytotic release of mature LBs into intimal matrix was observed. In type A synoviocytes the outer lamellae of LBs were frequently found in contiguity with the limiting membrane of lysosomes. An in vitro investigation of the ultrastructural features of LB formation in cultured type B synoviocytes (from 3 non-RA patients) gave results similar to those obtained in biopsies. These studies provide ultrastructural evidence of synoviocyte activity in secreting and degrading phospholipid lubricant in a sophisticated system whose function and pathological derangements are largely unknown.

Effects of exercise on synovium and cartilage from normal and inflamed knees

The effect of running activity on normal and inflamed knees was determined by light microscopic (LM) and scanning electron microscopic (SEM) observations on hamster articular cartilage. Animals were split into two groups; one housed in standard cages and one given free access to running wheels. Twenty-one days prior to analysis, half of each group was given an intra-articular injection of lipopolysaccharide (LPS) to cause an inflammation, the other half were uninjected. No remarkable changes were observed by LM in either the control running or nonrunning groups. In contrast, cartilage proteoglycan depletion, and pannus and synovial hyperplasia were equally observed in both groups of LPS-injected animals. SEM observations on the patellae from control animals found them to be free from damage to the articular cartilage. The joints of both the LPS nonrunning and running animals contained synovial hypertrophy with villus projection from the synovial lining. However, only the LPS-injected running hamsters had cartilage fraying over large areas of the articular surface, as well as areas in which the villus projections had been flattened. These results demonstrated that mechanical stress applied to a proteoglycan-depleted cartilage enhances the breakdown of the collagen matrix as judged by fibrillation, and may aggravate the inflammation by crushing the swollen synovial lining where it encroaches on the joint space.

Stereological analysis of the synovial membrane in rheumatic disorders: diagnostic value of volume-weighted mean nuclear volume estimation

Quantitative evaluation of nuclear size of synoviocytes was performed on 48 synovial biopsies in various rheumatic disorders: osteoarthritis (n = 10), rheumatoid arthritis (11), and chronic non-specific synovitis (14). Thirteen tissue specimens from non-inflammatory synovial membrane were included as a control group. Using the point-sampled intercepts method, unbiased stereological estimates of volume-weighted mean nuclear volume (nuclear upsilon v) were obtained. A slight increase in nuclear volume was observed in osteoarthritis in comparison with the control group with an overlap in 90% of cases. However, in rheumatoid arthritis there was a significant increase of nuclear upsilon v. Significant differences were found between rheumatoid arthritis and the control and osteoarthritis groups (P < or = 0.001). In biopsies from patients diagnosed as chronic non-specific synovitis the averaged nuclear upsilon v values were between those in osteoarthritis and rheumatoid arthritis with a wide range of data. Similar, but less significant differences were demonstrated between rheumatic disorders when using mean nuclear area. Further analysis of chronic non-specific synovitis patients in combination with nuclear upsilon v estimates as a simple, unbiased, complementary tool are required to better establish the diagnostic value of nuclear stereology in the diagnosis of rheumatic disorders.

Ochronotic arthropathy: structural and ultrastructural features

Fragments of articular cartilage and synovial membrane in a case of ochronosis were studied by light microscopy (LM), polarized light, and transmission electron microscopy (TEM). Granular and/or shard-shaped pigments were observed in the synovia, cartilage, and subchondral tissue, and dispersed pigment was also seen in the synovial fluid. Zones of the articular cartilage surface showed small erosions near shards, and sometimes, when the degenerative process was in an advanced stage, a substitutive fibrosis of the cartilage edge was demonstrated. LM and TEM observations of the samples studied revealed an alteration of collagen fibrils that appeared wavy and sometimes fragmented with loss of periodicity. They were always mixed with the dispersed pigment. A peculiar finding that characterized this ochronotic case was the complete absence of inflammatory infiltrates or signs of monocyte-macrophage activation. These structural and ultrastructural observations suggest that the pigment deposition in the articular surfaces was due to the synovial fluid circulation and partially to subchondral blood flow, which transports and stores the ochronotic pigments in the synovia and cartilage. These etiopathologic elements associated with the mechanical pathogenesis naturally present in the joints can contribute to the explanation of the pathogenesis and origin of ochronotic arthropathy.

Histological appearance of the synovium in early rheumatoid arthritis

This report reviews and discusses studies on the synovial fluid and biopsy specimens of synovial membrane obtained during the first 6 weeks of synovitis that evolved into rheumatoid arthritis (RA). Five previously unreported cases are described. Early changes in the microvasculature and synovial lining seem to antedate the classical chronic inflammation of established RA. Further characterization in the joint tissues in very early RA offers opportunities for identification of exogenous triggers and may allow more appropriate targeting of early therapy to potentially reversible aspects of pathogenesis.

Lamellar bodies in synoviocytes, mesothelium and specific epithelia as possible site of auto-antigen in rheumatoid disease

Intracytoplasmic lamellar organelles identical in ultrastructure to surfactant-containing lamellar bodies found in type II pneumocytes, have been demonstrated in other tissues, in synoviocytes and mesothelial cells, in a distribution pattern which reflects the systemic expression of rheumatoid disease. Antibodies raised against surfactant protein A (SP-A), exhibit a ranking of tissue reactivity in area, intensity and density of cells which also parallels the frequency and degree of pathological involvement characteristic of rheumatoid disease, showing in ascending order of immunopositivity, lacrymal and salivary epithelia, pulmonary parenchyma, mesothelium and synoviocytes. Maximal tissue reactivity to anti-SP-A antibodies was found in the synovium of 55 rheumatoid patients exhibiting classical histopathological appearances of RA, in a pattern of immunostaining identical to that obtained with ML30, an antibody to mycobacterial heat shock protein 65kDa which, in turn, cross-reacted with SP-A in dot blot testing.

Alpha-mannosidosis. Report of a case with morphologic, cytologic and immunohistochemical considerations

We report the histopathologic features of the knee bone and synovium and the cytologic features of the synovial fluid from a patient with alpha-mannosidosis. The synovium showed marked papillary hyperplasia with infiltration of foamy histiocytes containing periodic acid-Schiff-positive, diastase-resistant material. Severe degenerative changes were seen in the knee bone. The synovial fluid showed increased numbers of macrophages containing periodic acid-Schiff-positive, diastase-resistant material. The differential diagnostic considerations in the synovial fluid are also discussed.

Histological assessment of fifty breast capsules from smooth and textured augmentation and reconstruction mammoplasty prostheses with emphasis on the role of synovial metaplasia

Fifty breast capsules surrounding smooth and textured breast prostheses were reviewed histologically, immunohistochemically, and ultrastructurally, and findings correlated with patient data. The histology of the capsules varied; although most consisted of a simple fibrocollagenous membrane, some were lined by organized, round to polyhedral cells similar to synovium. Histologically, the lining of the synovial type consisted of epithelioid cells overlying parallel bands of collagen, with basally located nuclei and cytoplasmic processes directed toward the surface and arranged within a well developed reticulin network. Immunohistochemically, the cells were vimentin positive, weakly positive focally for alpha-1-antitrypsin, alpha-antichymotrypsin, and lysozyme, and negative for EMA and AE1/AE3. Scanning electron photomicrographs showed a bosselated luminal lining overlying parallel bands of collagen. By transmission electron microscopy, both secretory and phagocytic cells could be distinguished. Some of the former were multinucleated. No basement membrane material could be identified, and cell junctions were rare. Histologically, immunohistochemically, and ultrastructurally the lining appeared identical to synovium and to the synovial metaplasia that has been described in sutured skin, after repeated subcutaneous injections of air, the bone-cement interface of loose hip prostheses and adjacent to gliding silastic tendon reconstruction rods. The physical and chemical composition of the prostheses, the mechanical forces, and the developmental response of the host mesenchymal tissue are thought to influence the formation and maintenance of the synovial metaplasia of the breast capsule.

Synovial metaplasia of a periprosthetic breast capsule

A 48-year-old woman presented for reconstruction mammoplasty 5 years after undergoing a mastectomy for breast carcinoma. She underwent tissue expansion, with subsequent placement of a permanent silicone implant, removal of the permanent implant because of asymmetry, and further tissue expansion for another attempt at permanent silicone implant placement. The periprosthetic breast capsule surrounding the initial permanent implant consisted of a lining intima, subintima, and fibrous capsule consistent with synovium on light microscopy, immunohistochemical studies, transmission electron microscopy, and scanning electron microscopy. Silicone was localized intracellularly within the lining cells and extracellularly within the fibrous capsule by electron probe microanalysis. We believe that this case represents synovial metaplasia of a periprosthetic breast capsule that was most likely induced by repeated manipulation and silicon exposure from silicone gel leakage and the prosthetic Silastic shell.

Hyaluronan reduces fluid escape rate from rabbit knee joints disparately from its effect on fluidity

The effect of hyaluronan, the major viscous component of synovial fluid, on trans-synovial flow was measured in rabbit knees. Hyaluronan reduced fluid escape rate by up to 45%. This was much less than the reduction in intra-articular fluidity (1/viscosity). Electron micrographs supported the view that hyaluronan might be partially reflected by synovium, creating a molecular filtercake at the surface.

Adenoviral-mediated gene transfer to rabbit synovium in vivo

Currently, treatment for rheumatoid arthritis and other inflammatory arthropathies is often ineffective in ameliorating the progression of the disease, particularly the invasive destruction of cartilage and bone by rheumatoid synovium. Multiple aspects of this inflammatory process are mediated by the synovial lining cells (synoviocytes). Genetic modification of these cells in vivo represents a potential method for the treatment of these conditions. In this report, we describe a novel technique for the genetic transduction of synovial lining cells in vivo using recombinant adenoviral vectors and intraarticular injection techniques. Purified high titer suspensions of a recombinant adenoviral vector containing the gene for Escherichia coli beta-galactosidase (AdCMVlacZ) were directly injected into the hind knees of New Zealand white rabbits. Synovial tissues were then examined for transgenic lacZ expression using a combination of in situ staining for beta-galactosidase activity, immunohistochemical staining, and transmission electron microscopy. High efficiency gene transfer and lacZ expression was observed in both type A and type B synoviocytes throughout the articular and periarticular synovium of the rabbit knee, with continued expression of transgenic lacZ detected for > or = 8 wk after infection.

Immuno-electron microscopic analysis of the distribution of ICAM-1 in human inflammatory tissue

An immuno-electron microscopic analysis was undertaken to determine ICAM-1 expression on vascular endothelium in human tonsils and in synovia from patients with rheumatoid arthritis. ICAM-1 was preferentially expressed on high endothelial venules (HEV) located in the parafollicular regions of the tonsils and HEV located in the villous processes of the synovia. On both tissues, these areas contained the greatest number of perivascular lymphocytes. In contrast, ICAM-1 was only weakly expressed on the low endothelium lining capillaries, venules and sinusoids. In both tonsils and synovia, ICAM-1 was confined to the luminal and lateral surfaces of the endothelial cells and absent from the abluminal surfaces adjacent to the basement membrane. We propose that in inflammatory tissues, ICAM-1 mediates the interaction of circulating lymphocytes with the high endothelial cells, but may not have a major role in promoting their migration through the whole thickness of the blood vessel wall.

Microfibrillar elements in the synovial joint: presence of type VI collagen and fibrillin-containing microfibrils

OBJECTIVES

The aims were to isolate and positively identify the microfibrillar elements which have been observed in the synovial lining. In addition, synovial fluid was examined for these elements to improve the understanding of the role of these structures in health and disease.

METHODS

Bacterial collagenase digestion of bovine synovial linings and human and bovine synovial fluids was used to release intact, non-denatured microfibrillar elements. The microfibrils were isolated by Sepharose CL-2B chromatography and viewed by rotary shadowing. They were characterised by immunogold labelling with specific antibodies.

RESULTS

Intact type VI collagen microfibrils and fibrillin-containing microfibrils were isolated and positively identified in the synovial lining from bovine ankle joints by immunogold labelling. Type VI collagen microfibrils were also present in the synovial fluid.

CONCLUSIONS

The role of the microfibrillar elements in vivo is not fully understood, but their distribution in the synovial lining suggests they have an important role in the mechanical and physical properties of this tissue. The presence of type VI collagen microfibrils in synovial fluid poses the intriguing possibility that it may represent a product of microfibril turnover and a potential early marker for rheumatoid arthritis. Alternatively, type VI collagen may be specifically secreted into the synovial fluid to interact with hyaluronan and form part of the structure of synovial fluid.

Calcium pyrophosphate dihydrate crystal deposition in synovium. Relationship to collagen fibers and chondrometaplasia

OBJECTIVE

Reasons for apparent primary deposition of calcium pyrophosphate dihydrate (CPPD) crystals in some synovial membranes have not been systematically examined. We undertook the present study to investigate for and compare possible cellular and matrix factors related to the presence of these crystals in synovium and cartilage.

METHODS

Ten synovial membrane specimens and 6 cartilage specimens were obtained at the time of joint surgery from 10 patients with CPPD crystal deposition disease, for light microscopic (LM) and electron microscopic (EM) studies.

RESULTS

In all synovial and cartilage specimens, we found many of the small CPPD crystals aligned on or in parallel to collagen fibers, as seen by EM. In 9 of the 10 crystal-containing synovia, we found foci of chondrometaplasia adjacent to CPPD, by LM. In 7 of the synovia, including the one without LM evidence of chondrometaplasia, we observed the presence of chondrocyte-like cells by EM. We did not note any predictable relationship between the crystals and matrix vesicles, either in synovium or in cartilage.

CONCLUSION

Our EM findings provide evidence of the relationship of small CPPD-like crystals, presumably early forms, to collagen fibers both in synovium and in cartilage. By LM and EM, we also demonstrate evidence of a close association between chondrometaplasia and CPPD deposits in synovium. We suggest that chondrometaplasia might be responsible for synovial CPPD formation in predisposed patients. Both the collagen fibers and chondrocyte-like cells seem to be involved in the primary formation of CPPD deposits in the synovium as well as in the cartilage.

The ultrastructure of articular cartilage of the chicken's knee joint

The articular cartilage and synovial membrane of immature and mature chicken knee joints were studied by light, scanning and transmission microscopy. The findings differed from human articular cartilage and we conclude that the chicken knee joint is not suitable as a model for human joint degeneration.

Chromosome aberrations in tenosynovial giant cell tumors and nontumorous synovial tissue

Five tenosynovial giant cell tumors--4 pigmented villonodular synovitis (PVNS) and 1 nodular tenosynovitis (NTS)--were investigated cytogenetically. Clonal chromosome aberrations were detected in 3 of them. One PVNS had t(7;16)(q22;q24) as the sole anomaly, whereas 1 PVNS and the NTS displayed aberrations suggesting clonal evolution: t(1;19)(p11;p12)/t(1;19), +12 and ins(5;1)(q31p34)/ins(5;1),t(2;4)(p23;q21), respectively. Including our 3 cases, a total of 6 tenosynovial giant cell tumors with karyotypic changes have been reported. Apart from 2 PVNS with trisomies 5 and 7, and 2 NTS with rearrangement of chromosome band 1p13, no recurrent chromosome change has been detected. Although the detection of clonal, acquired chromosome abnormalities has formerly generally been accepted as sufficient to conclude that a lesion is neoplastic, the interpretation of the pathogenetic significance of the karyotypic aberrations in synovial tumors is obscured by the fact that we have also detected comparable aberrations in obviously nonneoplastic synovial tissue. One of 2 lesions from patients with hemorrhagic synovitis carried a clonal del(13)(q12q21), and 2 of 4 synovectomy samples from patients with rheumatoid arthritis displayed -Y and -Y together with +7. The available cytogenetic data therefore cannot be used to resolve the controversy as to whether tenosynovial giant cell tumors are truly neoplastic or only reactive, inflammatory proliferations.