Malignant giant cell tumor of synovium and locally destructive pigmented villonodular synovitis: ultrastructural and immunohistochemical study and review of the literature

The first reported case of an intraarticular malignant giant cell tumor of synovium studied with electron microscopic and immunohistochemical examination is presented, together with a case of diffuse intraarticular pigmented villonodular synovitis with extensive bone destruction. The malignant case was dominated by uniform cells positive for histiocytic markers, the fine structure showing a gradual change from cells dominated by organelles serving a secretory function to cells with phagocytic activity. The reported cases of giant cell tumor of the tendon sheath indicate that the pertinent histologic changes regarding malignancy are an increase in cell polymorphism and in the number of mitoses, and a decrease in the number of multinucleated giant cells.

Macroscopic, microscopic and ultrastructural findings in experimental haemarthrosis of rhesus monkeys

The effects of a single episode of massive haemarthrosis in rhesus monkeys were studied morphologically. Autologous whole blood was injected into a femorotibial joint of 16 anaesthetized monkeys, equally divided into four groups and killed 7 days, 2, 3 and 6 months post injection (PI). Synovial membrane and articular cartilage were examined for macroscopic, microscopic and ultrastructural changes. Haemarthrosis was only evident in one monkey by 7 days PI. Slight yellow-brown discoloration of synovium and cartilage was evident in groups killed early after injection. Histologically, a hyperplastic and inflammatory reaction was present in the synovium at 7 days PI. Ultrastructural examination of synoviocytes in this group revealed numerous cytoplasmic vacuoles and prominent microplicae compatible with increased phagocytic activity. Erythrophagocytosis by synoviocytes was observed by light microscopy and confirmed by transmission EM. Results of scanning EM suggested that red cells might also pass through the synovial intima. Transmission EM also revealed mild degenerative changes in superficial chondrocytes. Rhesus monkeys reacted morphologically to haemarthrosis in the same way as dogs and rabbits, with mild morphological changes that resolved by 2 months PI.

Leukocyte migration in synovial tissue. Leukocyte distribution, orientation, and migratory pattern after immune complex deposition in rabbit knee joints

Complement-activating bovine serum albumin (BSA)-anti-BSA immune complexes (ICs) were injected into rabbit knee joint cavities; the contralateral control joint was injected with BSA together with normal rabbit serum. The migration of leukocytes from the synovial venules into the joint cavity was analyzed with light microscopy (LM), scanning (SEM) and transmission (TEM) electron microscopy. EM autoradiography was used to study the endocytosis of ICs by leukocytes. The shape, orientation, and distribution of migrating polymorphonuclear granulocytes (PMNGs) were analyzed by LM morphometry. PMNGs accumulated in the joints injected with ICs. The peak of the number of PMNGs in the synovial tissue was reached after 4 hours, in the joint cavity after 6 hours. PMNGs in the synovial tissue were concentrated in the intimal layer. Migrating PMNGs were polarized, as judged by the ratio between the long (D max) and short (D min) axes of the cells. There was a close association between the migrating PMNGs and the collagen fibers. The morphometric data showed that the nonflattened, cylindrically-shaped PMNGs were oriented along the collagen bundles, running parallel to the synovial surface, and did not migrate in the straight direction of a theoretic leukotactic gradient originating in the joint cavity after IC deposition. SEM and TEM showed that the PMNGs were aligned along the collagen fibers and interacted activity with the collagen by pseudopods and cytoplasmic projections. EM autoradiography showed that the PMNGs in the joint cavity had ingested 125I-labeled ICs and were degranulated. In contrast, the PMNGs within the synovial membrane did not show any signs of IC endocytosis or any apparent degranulation. Synovial type A cells were found to contain ICs. This study indicates that the response of PMNGs in IC-induced synovitis consists of two distinct phases: an initial, mainly migratory phase in the synovial membrane where the PMNGs appear to use the collagen fibres as a climbing framework, and a second phase, in the joint cavity, characterized by PMNG metabolic activation, endocytosis of ICs, and degranulation. The apparent inability of PMNGs in the synovial membrane to ingest ICs and become degranulated might be due to not only concentration differences of ICs and leukotactic factors between the joint cavity and the synovial tissue but also might be related to the apparently active interaction with collagen.

[Applied anatomic observation on the synovial membrane of the digital sheath]

The synovial membrane of various parts of flexor tendons and sheaths was examined with the aid of light and scanning electron microscopes. The results show that on the compressed sites such as the volar aspect of the tendon and the inner aspect of the pulley, no continuous synovial cell layer and blood vessel existed, indicating that these areas may not closely related to the secretion of synovial fluid. Alternatively, on the areas of lesser burden such as the reflexion of the synovial capsule, the short vincula and the small cul-de-sacs at either end of each pulley, the synovial membrane became thicker and the number of synovial cells greatly increased, and there were exuberant capillary networks underneath the synovial membrane. All these add up to a concept that these areas are closely associated with the secretion of synovial fluid, and should certainly be preserved during operation.

Ultrastructure of Borrelia burgdorferi in tissues of patients with Lyme disease

Spirochetal organisms were sought in 18 skin and 4 synovial membrane specimens obtained by biopsy from 22 Lyme disease patients. The presence of spirochetes in body tissues was histologically demonstrated in one patient with lymphadenosis benigna cutis, one patient with acrodermatitis chronica atrophicans and in one patient with active arthritis. The organisms were 5-30 microns long and 0.12-0.25 microns thick, had 8 or 11 flagella arising from both ends of the body, and their ultrastructure was analogous to that of cultured Borrelia burgdorferi strains. They were located intra- or perivascularly, or in the collagenous connective tissue of the skin and synovium. This implies that Lyme spirochetes may have a potential to survive in body tissues and cause injury to blood vessels.

Progressive ankylosis (ank/ank) in mice: an animal model of spondyloarthropathy. II. Light and electron microscopic findings

Murine progressive ankylosis was studied by light and electron microscopy (EM). By light microscopy, the earliest synovial lesion was inflammatory followed by synovial proliferation and cartilage erosions. Later changes included progressive joint ankylosis by fibrosis and ossification of articular and periarticular tissues and new bone proliferation. By EM, synovial cell proliferation and hypertrophy with collagen deposition was seen before the appearance of intracellular and extracellular hydroxyapatite crystals. These pathologic changes are the same as those found in the human spondyloarthropathies. Our EM findings demonstrate that hydroxyapatite crystals appear in the joints of ank/ank mice after the initial inflammatory phase.

Osteoarthrosis and apatite synovitis. Pathological study of a metacarpophalangeal joint

A case of metacarpophalangeal osteoarthrosis associated with synovial apatite deposits is reported. The size of the crystals indicates that they have been thickened by a recrystallization process; the latter could have been provoked by Ca and Po4 ions released by dissolution of some apatite crystals brought by calcified debris of bone or cartilage coming from the abraded osteoarthrotic surfaces. The role of such thickened crystals in synovial inflammation is discussed as well as their possible diagnostic value in determining origin and pathogenesis of a given synovial apatite deposit.

Oligolamellar lubrication of joints by surface active phospholipid

Six studies have been undertaken to test the hypothesis that oligolamellar phospholipid adsorbed to the articular surface contributes to joint lubrication. Synovial fluid (SF) proved highly surface active, rapidly depositing phosphatidylcholine (DPPC) on glass surfaces, rendering them hydrophobic--a property of well rinsed articular surface removable by the same fat solvents known to increase joint friction by 150%. Electron microscope studies demonstrated lamellar bodies (surface active DPPC) on the articular surface and in SF and lamellated phospholipid in light scrapings of joint surfaces. These were consistent with the quantity of phospholipid recovered by solvent rinsing. Friction measurements in vitro demonstrated excellent boundary lubrication imparted by multimolecular layers of DPPC under high load with coefficients of kinetic friction reaching physiological ranges (0.002-0.005).

Synovial chondromatosis of the temporomandibular joint: a light and electron microscopic study

The light and electron microscopic features of synovial chondromatosis of the temporomandibular joint of one patient are presented. The affected synovial membrane and the cartilaginous nodules, which were freely movable in the joint space as well as attached to or incorporated in the synovial membrane, were examined. Light microscopic observation revealed metaplastic formation of these nodules within the subintima of the synovial membrane. Different stages of development of the nodules were observable. Electron microscopic examination of the cartilaginous nodules revealed features of mature chondrocytes well endowed with rough-surfaced endoplasmic reticulum and Golgi apparatus. The synovial intimal cells had a differentiated ultrastructural appearance. Several cytoplasmic organelles of the chondrocytes and intimal cells are described. The results of this study support the benign nature of synovial chondromatosis.

In vivo and in vitro evidence of cell recovery from complement attack in rheumatoid synovium

In the previous article we have demonstrated, by quantifying terminal complement complexes in synovial fluid, that membrane attack complex activation occurs in the joint in rheumatoid arthritis. Here we describe evidence of synoviocyte resistance to complement attack in vivo and in vitro. Gel filtration of terminal complement complex positive synovial fluid on Sepharose 2B revealed two forms of terminal complement complex: one form, eluting coincident with the column void, did not react with antibody to the fluid-phase inhibitor of complement membrane attack, the S-protein, suggesting that it was composed of membrane attack complexes, the other form, eluting in the included volume, did react with the anti-S-protein antibody, suggesting that it was composed of functionally inactive SC5b-9 complexes. The high molecular weight membrane attack complex peak was demonstrated by electron microscopy to be composed of membrane vesicles bearing many lesions having the typical appearance of complement membrane attack complexes. No discernible structures were present in the lower molecular weight peak. The effects of non-lethal complement membrane attack on human synoviocytes in culture were also investigated. Synoviocytes were relatively resistant to killing by autologous complement, end-point lysis of optimally antibody-sensitized cells never exceeding 60% even at a serum dilution of 1:2. At serum dilutions of 1:20 or less, no significant cell killing occurred despite a high degree of membrane attack pathway activation, suggesting the existence of resistance and recovery mechanisms. Non-lethal complement membrane attack stimulated the release of toxic reactive oxygen metabolites from synoviocytes. These, and other reactive species released during non-lethal complement attack in vivo, may play a significant role in the pathogenesis of rheumatoid arthritis.

Characterization of human synovial mast cells

Human synovium obtained at arthroplasty from patients with rheumatoid arthritis (RA) and osteoarthritis (OA) were characterized by assessing mast cell morphology, content and function. Histological studies confirmed significant numbers of mast cells in both RA and OA synovium. Electron microscopic data support the morphologic similarity between human synovial mast cells and human mast cells in lung and intestine. Likewise, synovial mast cells do not appear to be functionally different from pulmonary or intestinal mucosal mast cells. Mast cell suspensions with a cellular histamine content of 4.3 +/- 0.5 pg/cell (mean +/- SEM) released histamine following provocation with anti-IgE and calcium ionophore but not compound 48/80, f-met peptide or bradykinin. Prostaglandin D2 (PGD2) and leukotriene C4 (LTC4) were also released in response to anti-IgE. Auranofin inhibited anti-IgE provoked histamine, PGD2 and LTC4 release while gold sodium thiomalate, cromolyn and indomethacin had no effect on histamine release. Theophylline inhibited anti-IgE induced histamine release only at concentrations greater than or equal to 10(-3) M. Our study argues against functional or morphologic mast cell heterogeneity of human intestinal, lung and synovial origin and suggests that mast cells may have a pathogenic role in both RA and OA.

Ultrastructural characterisation of macrophages (type A cells) in the synovial lining

The ultrastructural localisation of class II and macrophage antigens has been sought in the intimal layer of the human synovium. The cells described as type A in early morphological studies are shown to express both class II antigens and two markers of the macrophage/monocyte lineage of cells, OKM1 and MAB 24. The morphological type B cells were found to express none of these antigens. The findings are consistent with the idea that the synovial lining comprises two cell types, bone-marrow derived macrophages and mesenchymal fibroblasts.

Synovial lymphocyte response to chlamydial stimulation associated with intrasynovial chlamydial antigen in a patient with "rheumatoid arthritis"

A 48-year-old man with "rheumatoid arthritis" of 3 years duration was found to have synovial fluid lymphocytes that were maximally stimulated in vitro by chlamydial antigen, on 5 of 6 tests over 18 months. Immunocytochemical staining of a synovectomy specimen, using the peroxidase-antiperoxidase technique, subsequently revealed chlamydial antigen in the synovium. The possibility that Chlamydia in the synovium may produce features of rheumatoid arthritis is discussed.

Rapidly progressive osteoarthrosis of ochronotic origin. A pathologic study

A case of hip osteoarthrosis associated with ochronosis in a 65-year-old woman is reported. Characteristic features of both conditions were observed macroscopically and on light and electron microscopic examination. In the cartilage the pigment deposits were located on and between thick collagen fibrils. In the synovial membrane there were embedded packets of cartilage shards of which the collagen fibrils and pigment were phagocytosed, as well as calcified bone debris whose disaggregation might have explained the presence of some apatite deposits free of any underlying collagen structure. As also previously observed, the present case of ochronotic hip osteoarthrosis is remarkable for the minor osteophyte formation and for the inclusion of pigmented cartilage shards in the osteomedullar remodeled territory. It also demonstrates a collapse of the femoral head cortex presumably related to the rapid clinical and radiologic evolution. By the well-known origin of its chondropathy and by the pigment labeling of the cartilage, ochronotic arthropathy provides an almost experimental model for analyzing a broader problem, i.e., that of the various components of an osteoarthrotic remodeling.

Early alteration of synovial membrane in osteoarthrosis

Biopsy specimens of the synovial membrane were obtained during arthroscopy and surgical meniscectomy from the knees of 20 patients with meniscus lesions. The aim of this study was to identify the morphological and immunological changes which appear in the synovium during the earliest phase of osteoarthrosis. Interstitial deposits of IgG and, in some cases, C3 were found not only in patients with evident arthrotic degeneration (cartilaginous lesions and synovitis), but also in patients who showed no overt arthrotic changes. Furthermore, light and electron microscopy showed an increased number of mast-cells with peculiar semilunar or piecemeal aspects of their secretory granules. These ultrastructural modifications are characteristic of slow, chronic release of mediators in response to a constant, moderate degranulatory stimulus. Our findings suggest that synovial changes may occur before the advent of cartilage degeneration and that the latter may be directly influenced by early pathological changes in the synovial membrane.

Activation of rat synovium by iron

We observed a consistent sequence of activation changes in rat knee synovia following a single intravenous injection of sterile ferric citrate at a dosage sufficient to cause a transient saturation of transferrin. The initial alteration, appreciated 2 hours postinjection, consisted of an expansion in the lumen of synovial lining and subsynovial tissue due to the hypervascularity and increased cellularity was noted, along with peaks in the mitotic activity of synovial cells (fourfold over baseline) and pinocytosis by endothelial cells. During the period of 8-24 hours, mature collagen appeared in the space between pericyte layers and between pericytes and endothelial cells, and 2-9-fold increases in ferritin +, W3/13+, W3/25+, Ox8+, and Ox26+ mononuclear cells occurred. In contrast to the action on synovial fibroblasts, iron injection did not affect the mitotic activity of fibroblasts within the serosa of the small intestine. These findings demonstrate that, under experimental conditions, iron can readily induce changes in the synovium that are reminiscent of early events occurring in response to antigen.

Arthritis-associated changes in flow cytometric characteristics of cultured synovial fibroblasts

Synovial fibroblasts cultured from patients with rheumatoid or reactive arthritis and from controls were studied by flow cytometry, spectroscopy, and electron microscopy. Analysis of 29 cell lines revealed consistent differences between arthritic and normal fibroblasts. Cells cultured from inflamed synovial tissue exhibited higher autofluorescence than did control fibroblasts, and displayed exceptional light scatter properties in flow cytometry, indicating changes in cytoplasmic structures. Electron microscopic examination of the fibroblasts from arthritic synovial tissue revealed large numbers of round, swollen, laminated, mitochondrion-like bodies, which were not observed in the control fibroblasts. The changes observed by flow cytometry (light scatter and autofluorescence) coincided with the presence of the mitochondrion-like organelles. The strong autofluorescence observed in the arthritic fibroblasts resembled the fluorescence spectrum of mitochondrial flavoproteins. These data suggest that persistent metabolic and structural changes have occurred in the mitochondria of synovial fibroblasts and inflammatory synovial tissue. The usefulness of flow cytometry in identifying such cells is described.

Morphology of surface synoviocytes in situ at normal and raised joint pressure, studied by scanning electron microscopy

The synovial surface in rabbit knees was examined by scanning electron microscopy (SEM) to define normal surface contour, cell shape, and interstitial exposure. Comparison was made between specimens excised before immersion fixation (I), fixed in situ by vascular perfusion (V) before excision, or fixed in situ under an effusion pressure of 5-25 cmH2O (E). The deeply convoluted appearance of rabbit areolar-muscular synovium fixed after excision (I) was found to be an artefact; areolar-muscular synovium fixed in situ (V) was much smoother. The well documented cobblestone contour of immersion fixed adipose synovium was present after fixation in situ, but may be exaggerated by the SEM preparative process. At higher magnification the synoviocytes showed evidence of considerable surface activity (smooth granules, larger cauliflower-like excrescences, thin lamelliform filopodia). Cell shape was variable but many synoviocytes extended long cytoplasmic processes along the surface, producing fibroblastoid and even stellate outlines. At an intra-articular pressure of 25 cmH2O (E) the cytoplasmic processes were elongated and branched, creating a highly dendritic outline. Also, the exposure of interstitium increased markedly at the higher pressure. It is concluded that extension of lengthy cytoplasmic processes is a feature of normal healthy synoviocytes, and that an increase in interstitial area with joint pressure contributes to the increased hydraulic permeability of synovium at raised pressure.

Ultrastructural study of synovial membrane from the antebrachiocarpal joint of calves

The synovial intima from the antebrachiocarpal joint of 4-month-old calves was between 1 and 3 cells in thickness and did not have a basal lamina. Numerous areas of the intimal matrix were in direct contact with the joint lumen. The synovial membrane was comprised mainly of A-type synoviocytes usually located adjacent to the joint lumen. These cells were characterized by numerous filopodia (or lamellipodia), large, empty-appearing vacuoles, numerous lysosomes, large vacuoles containing granular material separated from the vacuolar membrane by a radiolucent band, and coated micropinocytotic vesicles. Smooth micropinocytotic vesicles were seen only rarely in these cells. In contrast, B-type cells had few filopodia, numerous smooth micropinocytotic vesicles, few coated micropinocytotic vesicles, a well-developed Golgi apparatus and rough endoplasmic reticulum, mitochondria that were longer and had a denser matrix than that of A cell mitochondria, and surprisingly, only few maturing or fully formed secretory granules. A distinct intermediate (C or AB) type synoviocyte could not be unequivocally identified. Desmosome-like structures were present between synoviocytes, although it was considered questionable if these were true intercellular junctions. No other junctions were present.

Etiopathogenesis of rheumatoid arthritis-like disease in MRL/1 mice: II. Ultrastructural basis of joint destruction

MRL/1 mice develop a spontaneous hindlimb arthropathy characterized by proliferation of synovial cells and by dissociation between early destruction of articular tissue and the presence of inflammatory cell infiltration. To characterize the ultrastructural details of the synovial cells of these mice, knee joints from MRL/1, MRL/n, and BALB/c mice were examined by light and electron microscopy. Since the proliferating synovial cells of MRL/1 mice resemble the previously described proliferative synovial cells seen in histopathologic specimens from early rheumatoid arthritis, further study of these cells may provide new insights into the pathogenesis of early joint tissue destruction in human rheumatic disease.

Cytochemical demonstration of constitutive H2O2 production by macrophages in synovial tissue from rats with adjuvant arthritis

Generation of toxic oxygen metabolites by inflammatory cells is considered to be one of the mechanisms by which inflammation produces tissue injury. This concept is based on in vitro studies of purified leukocyte populations because it has not been possible to assess production of these metabolites in tissues. In order to determine whether or not inflammatory cells in tissue generate H2O2, the authors modified an earlier cytochemical method for the localization of H2O2. The incubation medium consists of 0.5 mM CeCl3 in a Hepes-buffered balanced salt solution with Cl- as the only anion. Synovial tissue from the knees of normal and 16-day adjuvant arthritic rats was incubated in this medium for 30 minutes and then fixed and processed for electron microscopy. No H2O2 reaction product was visible in normal synovium. In contrast, patchy deposits of H2O2 reaction product were seen adjacent to a subpopulation of synovial lining macrophages in synovium from inflamed knee joints. These data show that rat synovial macrophages are capable of generating H2O2 when appropriately stimulated and that such a stimulus is present in adjuvant arthritis.

Synovisol as an irrigant for electrosurgery of joints

The appropriate irrigation fluid for use during arthroscopic procedures should be selected on the basis of fluid-tissue and fluid-instrumentation compatibility. This study describes a new irrigation fluid, Synovisol, that is isomolar, nonhemolytic, nonantigenic, has a low viscosity, and is nonconductive. The rabbit knee was used as a model to demonstrate the immediate and long-term (3 weeks) effects of irrigation with Synovisol compared with water, normal saline, mannitol, sorbitol, glycine, and with nonirrigated controls. Results were assessed by light- and electron-microscopic evaluation of synovium and cartilage dissected from rabbit knees. While the greatest amount of damage was seen in water-treated samples, significant effects were noted with other irrigants compared with Synovisol and controls. Long-term animals showed recovery of tissues in all cases. Systemic effects evaluated by measuring plasma glycerol levels showed a transient increase that peaked at 20 min. No hemolysis was detected and kidney morphology was normal. The physiological, electrocompatible, simplicity of formula, low cost, and long-shelf-life properties of this solution makes it a fluid uniquely suited to arthroscopy.

Synovial membrane and cartilage changes in experimental osteoarthrosis

The Hulth instability model was performed on 25 rabbit knee joints. Electron-microscopic, light-microscopic, and histomorphometric data demonstrated consistent chondrocyte alterations and cartilage destruction. The comparison between operated, sham, and control knees shows that surgical intervention without surgically induced instability is followed by changes in the synovial membrane and cartilage. The cartilage destruction is preceded by a synovial reaction, suggesting that the inflammatory response has an important role in the onset of cartilage damage in this model. The damage was more severe in the experimental knees, suggesting that mechanical instability is also a factor in cartilage destruction.

A histologic comparison of aseptic loosening of cemented, press-fit, and biologic ingrowth prostheses

The histology of interface membranes from aseptic loosened prostheses of various types including cemented, press-fit, and biologic ingrowth varieties was compared. Pseudosynovial implant-facing surfaces were present in specimens from all types. The remaining portions of these membranes showed distinct characteristics as well. Cemented implant membranes contained many macrophages and giant cells and evidenced frequent granuloma formation. Press-fit membranes consisted of poorly vascularized, dense fibrous tissue within the loosened press-fit membrane. Macrophages and giant cells were rare, except in one specimen containing ceramic debris particles. Biologic ingrowth membranes were the most vascular and contained loosely organized connective tissue and islands of woven bone. Macrophages were common. One out of six specimens from patients with rheumatoid arthritis contained massive numbers of lymphocytes and plasma cells but not mast cells. The greatest numbers of mast cells were present in membranes from patients with osteoarthritis and in all cases were associated with the presence of stainless steel and/or chrome cobalt particles.

An ultrastructural and light microscopic study of the synovium in ochronotic arthropathy

The synovium in two well-documented cases of alkaptonuric ochronosis was studied by transmission electron and light microscopy. A feature of alkaptonuria previously unreported in the English-language literature was the presence of phagocytosis of large collagen fibrils by synovial macrophages in both cases. The origin of these fibrils appeared to have been shards of ochronotic cartilage and areas of metaplastic cartilage. This finding suggests that active remodeling of the synovial tissues occurs in advanced ochronotic arthropathy. Numerous shards of ochronotic cartilage were embedded in the synovium. In addition, small aggregates of large collagen fibrils encrusted with apparent ochronotic pigment were occasionally noted in the interstitium. These aggregates of ochronotic collagen are best described as microshards, and they have not generally been recognized in the literature. What appeared by light microscopy to represent ochronotic pigment deposition in interstitial collagen actually represented embedded microshards of ochronotic cartilage in the interstitium. Slender and elongated microshards were most likely to be confused by light microscopy as ochronotic interstitial collagen.

[Oligo-arthritis associated with type IV hyperlipoproteinemia]

A case of chronic, corticosteroid-responsive arthritis affecting particularly one ankle in a patient with type IV hyperlipoproteinaemia is reported. After gout or inflammatory rheumatism of another nature had been excluded, and following synovial fluid examination and synovial membrane biopsy, a diagnosis of type IV hyperlipoproteinaemia rheumatism was made. At electron microscopy, the synovial membrane showed numerous large spumous cells and a peculiar appearance of the capillary vessels.

[Comparative anatomical study of the synovial membrane in representatives of 4 classes of terrestrial vertebrate]

The synovial membrane (SM) of some representatives of four terrestrial vertebrate classes was studied by means of scanning electron microscope (SEM). The figures of SM of the mammals (man, mini-pig), birds (fowl, Gallus domesticus L.), reptiles (lizard, Lacerta viridis Laur. and turtle, Testudo graeca L.) and amphibians (frog, Rana esculanta L.) are documented. The SM of all animal species investigated presents a great locally variable appearance in form and surface arrangement of the living cells. The surface of synoviocytes is mostly very rough, forked, the cells having a plenty of wart-like, spiny-like or leaf-like microvilli, with cytoplasmic projections protruding from cell bodies. The largest possible functional surface of SM in mammals is formed by multiple villi and folds, whereas in other animal classes--by a specific arrangement of the lining cells. Locally variable appearance of synoviocytes from human and rabbit joints was described by Date (1979); we have documented the same in birds, reptiles and amphibians, as well. Three characteristic types of locally variable appearance of the surface lining cells were picked out in representatives of the every animal class cited. These cells correspond to the histological types, classified by Key. Beside these basic types, a number of transitory cells appear, that increase the diversity of the appearance of the lining cells in different regions of the SM. We may conclude that all the synoviocytes present the largest possible functional surface, although their external form differs. Their cytoplasm contains all sorts of organelles necessary for synthesis and secretion of mucopolysaccharides of the synovial liquid, as well as for the resorption and phagocytosis.

The alterations of the synovial membrane in rheumatoid arthritis treated with corticosteroids

Sections of synovial tissue removed from patients with rheumatoid arthritis treated, for a long period of time or a brief period of time or not at all, with corticosteroids were examined for the incidence of histopathologic changes. Comparison of the quantification of these changes in the differently treated groups revealed that prolonged administration of corticosteroids had an inhibiting effect on the occurrence of lymphocytes and histiocytes in inflammatory infiltrates as well as on the hypertrophy of synoviocytes, on the proliferation both of fibroblasts and fibrocytes, and on the formation of villi and collagen fibers.

Long-term complications of trapeziometacarpal silicone arthroplasty

The trapeziometacarpal joint is often affected by arthritis and treated by surgical methods. The significant forces to which this joint is subjected challenge even the most sturdy prosthetic materials. Short-term complications of arthroplasty are caused by inadequate bony resection and instability. Serious long-term problems results from implant wear and the host tissues' response to the implant. Although silicone elastomer prostheses are generally well tolerated, wear-induced microparticles (15 micron or less) incite an intense inflammatory and destructive synovial response. This "silicone synovitis" typically presents more than two years after arthroplasty and is characterized by pain, swelling, and lytic lesions visible on roentgenogram. The silicone microparticles are generated by cyclic physiologic bearing, shear, and compression forces for which these implants have not been tested. The destructive synovitis is arrested by synovectomy, implant removal, and curettage of the lytic defects. Functional salvage requires conversion to resection arthroplasty or arthrodesis. Patients with silicone implant arthroplasty must be followed indefinitely, at frequent intervals, by clinical examination and roentgenograms. Overall, however, experience indicates that resection arthroplasty is the most predictable and functional procedure for the nonrheumatoid basal thumb joint.

Ochronotic arthropathy. A comparative scanning electron microscopic and light microscopic study of the synovium in ochronosis

The synovium in two cases of ochronosis was studied by scanning electron microscopy and light microscopy. Several features not yet described were seen by scanning electron microscopic examination and correlated with the light microscopic findings. This is the first report in the English language literature comparing scanning electron microscopic findings with the light microscopic findings in ochronosis.

[Fibroblastic rheumatism of the elderly. Histopathological, ultrastructural data and problems of differential diagnosis]

In order to contribute to the knowledge and the nosography of fibroblastic rheumatism, the authors report a case occurring in 68 years old patient. The differential diagnosis of the disease rests on histological and ultrastructural aspects of the dermal and articular tissues where numerous myofibroblasts are observed. On that score, among the acquired adult fibromatoses, fibroblastic rheumatism seems closer to Dupuytren's disease than to sclerodermis.

[Multicentric reticulohistiocytosis. A case with unusual clinical, radiologic and ultrastructural aspects]

We are reporting a case of multicentric reticulo-histiocytosis which is exceptional because of its gravity and the diversity of the clinical lesions: huge subcutaneous nodules, bone destruction in the spine responsible for spondylolisthesis, pulmonary fibrosis, acute pericarditis, laryngeal compression requiring a permanent tracheostomy. From ultrastructural observations, various hypotheses to explain the intra-macrophagic accumulation of membrane granules and lipids are discussed.

Ultrastructural localisation of muramidase in the human synovial membrane

The synovial intimal cell layer comprises two morphological types of cell, A and B, with an intermediate type also postulated. Type A cells show features in common with other cells of the mononuclear phagocyte system, while type B cells appear similar to fibroblasts and are assumed to have synthetic activity. Muramidase is a marker of mononuclear phagocytic cells, and we have investigated the synovial membrane for the presence of this enzyme in cells by an immunogold labelling technique. Muramidase was localised within intracytoplasmic vacuoles in subintimal macrophages and type A synoviocytes. This finding provides further evidence that type A cells are closely related to macrophages.

Histology and ultrastructure of the human flexor tendon sheath

Twenty human flexor tendons and their sheaths were studied to determine the gross, microscopic, and ultrastructural morphology of their surfaces. Specimens were obtained at the time of autopsy or at the time of reconstructive and reparative surgery. The flexor tendon sheath consists of a noninterrupted layer of parietal synovium reinforced externally at intervals by dense bands of collagen, the annular and cruciform pulleys, and the palmar plates of the respective finger joints. The sheath contents are independently covered by a second similar layer of visceral synovium. These two layers are continuous at the proximal cul-de-sac, the vincula origins, and the tendon insertions. While the synovial cells lining the pulleys and tendons differ quantitatively from those of the membranous portion of the sheath, they are morphologically identical. The presence of a visceral synovial layer covering each tendon may indicate a key role of the synovial cell in tendon healing.

Pathways to chronic inflammation in rheumatoid synovitis

Postcapillary venules resembling the high endothelial venules (HEVs) of lymphoid tissues have often been observed at sites of chronic inflammation. We have therefore postulated that such venules may be an important site of lymphocyte migration into rheumatoid synovial membrane and that inflammatory cell products may act on endothelial cells (ECs) to increase lymphocyte emigration. Electron microscopic examination of rheumatoid synovial membranes showed that a strong correlation existed between the proportion of lymphocytes in perivascular tissue and the height/base ratio of the ECs in those areas. In addition, binding experiments showed that peripheral blood mononuclear cells preferentially bound to ECs in sections of rheumatoid synovial membrane that had the morphological appearance of HEVs. In vitro binding experiments, in which lymphocyte adhesion to human umbilical vein EC monolayers was measured, showed that adhesion was enhanced by preincubation of the ECs with interferon-gamma or interleukin 1 (IL 1). The central role of IL 1 in increasing lymphocyte migration into the rheumatoid synovial membrane was also supported by the findings that IL 1 is chemotactic for lymphocytes, ECs can secrete IL 1, and IL 1 activity is readily detectable in synovial fluids of rheumatoid arthritis patients.

[Morphofunctional changes in the microcirculatory bed of the synovial membrane in antigen-induced arthritis]

Ultrastructural changes of synovial capillary and venule wall have been investigated in rabbits with antigen-induced arthritis, with the permeability of microcirculatory bed determined using 99mTc pertechnetate. The correlation between the incidence of ultrastructural microvascular damages in exudative phase of arthritis and the increased permeability has been established. Ultrastructural changes occurring in proliferative phase of arthritis are considered as adaptive to conditions of increased permeability.

Experimental haemarthrosis produces mild inflammation associated with intracellular Maltese crosses

Injection of autologous blood into rabbit joints induces an inflammatory reaction with Maltese cross-like birefringent spherulites. Similar microspherules seen in human joint fluids may be formed by lipids derived from breakdown of erythrocytes and other cells.

Functional role in self reactivity for Ia antigens on murine synovial cells

Cultures of synovial cells from normal CBA mice were established after collagenase treatment of synovial tissue collected from the knee joint. Morphological studies using light and electron microscopy have shown that confluent monolayers are composed of 90% triangular or stellate dendritic cells with numerous microvilli and 5% secreting cells containing many dense granules. Less than 5% contaminating cells, such as fibroblasts or macrophages, are present. The class I and class II antigens of the major histocompatibility complex, detected by indirect immunofluorescence or complement-dependent cytotoxicity, are expressed on the cell surface of normal CBA synovial monolayers. Functional Ia antigens borne by synoviocytes are evidenced by the proliferative responses they elicit from syngeneic (or allogeneic) spleen cells after a 3-day co-culture. Similarly, monolayers of Ia+ synovial cells were obtained from both MRL/lpr mice, which spontaneously develop an autoimmune syndrome, and the control MRL/n mice. Spleen cells from young MRL/lpr exhibited significantly higher levels of blastogenesis in syngeneic co-cultures than those from MRL/n mice. Conversely, with advancing age the syngeneic proliferative responses declined minimally for MRL/lpr mice and were unchanged for MRL/n mice. These findings suggest that Ia+ synovial cells can effectively interact with syngeneic lymphocytes and may initiate autoimmune reactivity.

Comparison of joint degeneration models. Surgical instability and repetitive impulsive loading

We used surgical instability and repetitive impulsive loading in rabbits to initiate degenerative changes in knee joints. Synovial membrane and cartilage samples were examined by light and electron microscopy. Early synovial inflammation at three days postoperatively preceded cartilage destruction in the instability model. Synovial inflammation was only apparent after eight weeks in the loading model and increased subsequently to cartilage destruction. Cartilage breakdown was focal and limited to the weight-bearing area. Comparison of the histological data of the two arthrosis models suggests that different inductive mechanisms may be involved in cartilage degeneration, but in both models the inflammatory changes appeared to be secondary to mechanical factors.

Characterization and functional studies of rheumatoid synovial mast cells. Activation by secretagogues, anti-IgE, and a histamine-releasing lymphokine

Microscopic analysis of synovial specimens from 35 patients with rheumatoid arthritis (RA) and 7 patients with osteoarthritis revealed mast cell hyperplasia in perivascular regions, in fibrous interstitial areas, and clustered around the periphery of lymphoid aggregates. Metachromatic staining, immunofluorescence studies, and ultrastructural analysis revealed a single population of connective tissue-type mast cells with surface IgE receptors. Total extractable histamine of synovial tissue was 4.15 +/- 2.30 micrograms/gm (n = 8) for RA synovium and 0.53 +/- 0.23 microgram/gm (n = 7) for OA synovium. Mast cell secretion was assessed and specific release of histamine from RA synovial mast cells was observed following stimulation with anti-IgE (32.3%), compound 48/80 (40.1%), calcium ionophore A23187 (25.2%), and a partially purified lymphokine with histamine-releasing activity (23.9%).

Liposome-induced synovitis in rabbits. Light and electron microscopic studies

A solution containing synthetic liposomes was injected into rabbit knee joints. This induced light and electron microscopic findings very similar to those seen in acute or chronic arthritis, not attributable to any mechanism other than to spherulites, in humans. Synovial fluid studies revealed leukocytosis and abundant extracellular, and/or intracellular positively birefringent spherulites, which appeared as Maltese crosses. Histologic studies of synovial membranes showed infiltration with polymorphonuclear neutrophils or mononuclear cells. Examination of the synovial fluids and synovial membranes by electron microscopy revealed intracellular multilayered membranous arrays of varying shapes. These observations suggest that further consideration should be given to a phlogistic role for similar spherulites found in some patients.

An ultrastructural study of age-associated changes in the rabbit synovial membrane

The synovial membranes of 5 young rabbits about 6 weeks old and 5 older rabbits about 3-4 years old were studied with the light and electron microscopes, with a view to discovering any age-associated changes that might occur. Several age-associated changes were noted. These included: (1) a reduction in the overall population of synovial intimal cells; (2) a statistically significant reduction in type B cells and a relative increase in type A cells; (3) the emergence of atrophic cells poorly endowed with organelles; (4) decreased vascularity; and (5) fibrosis.

Histologic findings in siblings with acute sarcoid arthritis: association with the B8,DR3 phenotype

Three siblings with acute sarcoid arthritis and hilar adenopathy on chest radiograph (Löfgren's syndrome) are presented. Synovianalysis from 2 of 3 showed a predominance of mononuclear cells, and synovial biopsies from 2 of the 3 showed a mild inflammatory synovitis. All 3 siblings exhibited the B8,DR3 phenotype, and HLA testing of 8 prior cases identified at this institution showed the B8,DR3 phenotype in 6 of 8 patients with the 2 other patients exhibiting either B8 or DR3 alone. We confirm an earlier report that the B8,DR3 phenotype identifies a group of patients who are more likely to have acute sarcoid arthritis and hilar adenopathy without developing chronic disease.

Electron microscopic study of HLA-DR and monocyte/macrophage staining cells in the rheumatoid synovial membrane

We examined synovial membrane samples from 6 rheumatoid arthritis (RA) and 3 osteoarthritis patients and from 1 normal subject, by an immunoelectron microscopic technique using anti-HLA-DR (anti-Ia) and anti-monocyte/macrophage (63D3) monoclonal antibodies. In the lining layer, the type A macrophage-like cells were strongly DR+ and 63D3+, whereas the type B fibroblast-like cells were almost completely negative. Lymphocyte-rich areas (containing more than 90% densely packed lymphocytes) showed weak and patchy DR staining of the lymphocytes. In these areas, 3-5% of the cells were macrophage-like cells which were 63D3-, a type of staining compatible with that of the interdigitating cell (IDC). In the plasma cell-containing (transitional) areas, many strongly DR+ macrophage-like cells were observed in close contact with lymphocytes and plasma cells. Ten to twenty percent of these cells were 63D3-, which suggests that they were IDC. Cells with the structural appearance of IDC were most frequently seen in those transitional areas which contained elevated concentrations (50-70%) of lymphocytes. In uninfiltrated interstitial areas, approximately 50% of the cells stained strongly with both anti-DR and 63D3 antibody, indicating that they were cells of monocyte/macrophage lineage, presumably histiocytes. This investigation has demonstrated the presence of the DR antigen in the RA synovial membrane on 1) phagocytic cells of the lining area, 2) lymphocytes and small numbers of IDC-like cells in dense, lymphocyte-rich areas, 3) large numbers of macrophage-like cells, of which some had the morphologic appearance of IDC, in transitional or plasma cell-containing areas, and 4) histiocytic cells in uninfiltrated interstitial areas. The observation of large numbers of DR+ macrophages and IDC-like cells in close contact with lymphocytes and plasma cells in the RA synovial membrane emphasizes their role in an active immune response. The observation of substantial numbers of potentially immunocompetent, DR+ histiocytic cells in uninfiltrated regions of the synovial membrane suggests that such cells may play a role in the progression of the synovial inflammatory reaction.

Scanning electron microscopy of antigen induced arthritic joints. I. Inflammatory cell interactions at synovial-meniscal surfaces during the Arthus response

Scanning electron microscopy has been used to study experimental antigen induced arthritis, providing a unique perspective of the early inflammatory events. An initial aggregation of acute inflammatory cells was noted at the synovial-meniscal junction with maximal numbers observed between 12 and 24 h post challenge. Variations in cell surface ruffling, which may represent different phases of activation, were observed throughout the Arthus response. By 48 h post challenge the meniscal and synovial surfaces were covered by a mat of fibrin and degraded cell remnants.

The promotion and inhibition of collagen-breakdown in organ cultures of pig synovium: the requirement for serum components and the involvement of cyclic adenosine 3':5'-monophosphate (cAMP)

In many pathological situations connective tissue cells acquire the ability to degrade the macromolecular components of their extracellular matrix. To study the destruction of collagen we used organ cultures of porcine synovial tissue. In the presence of 15% rabbit serum explants shrink considerably during 10-14 days, owing to early loss of interfibrillar material followed by retraction and local destruction of collagen fibres, partly by phagocytosis. These changes, and the release of latent collagenase into the medium, are largely inhibited by cortisol and partially by indomethacin. Collagen destruction can be greatly accelerated by the addition to the culture medium of one of the following: sodium fluoride, 3-isobutyl-1-methylxanthine, dibutyryl cyclic adenosine 3':5'-monophosphate or forskolin; these agents are known to affect cyclic adenosine monophosphate metabolism and our results suggest strongly that a change in the intracellular levels of cyclic adenosine monophosphate is a key-step in the process leading to the increased catabolism of collagen. With these compounds the destruction of collagen is largely extracellular; the histological changes and the increased levels of collagenase associated with the destruction can be prevented by cortisol and, except in the case of dibutyryl cyclic adenosine monophosphate, at least partially by indomethacin. Without serum only 3-isobutyl-1-methylxanthine sometimes causes drastic breakdown of collagen. This model system should be of great benefit in exploring the mechanisms involved in collagen destruction.