Synovial cells. A study of the morphology and an examination of protein synthesis of synovial cells

Analyses of origin of synovial cells and repairing mechanisms of arthritis by allogeneic bone marrow transplantation

MRL/lpr mice spontaneously develop rheumatoid arthritis (RA)-like disease. Recently we have observed that bone marrow transplantation (BMT) with bone graft to recruit donor stromal cells can be used to treat autoimmune diseases (including RA-like lesions) in MRL/lpr mice. In this paper, we characterize the origin of synovial cells with the use of radiation chimeras and elucidate the repairing mechanism of RA by BMT. Type A synoviocytes have been thought to play an important role in the initiation of inflamed synovia, since a large number of Type A synoviocytes have been seen in inflamed synovia of both RA patients and MRL/lpr mice. Using [C57BL/6JJic-bg-->MRL/lpr] chimeric mice, we found Type A synoviocytes to be derived from donor bone marrow cells. They appeared in the inflamed synovia 4 weeks after BMT. However, at this time, the repairing process was not prominent. Serial biopsy studies revealed that newly developed T cells with normal functions play a more crucial role in the treatment of RA in MRL/lpr mice than do Type A synoviocytes.

Cell populations of tendon: a simplified method for isolation of synovial cells and internal fibroblasts: confirmation of origin and biologic properties

Tendons transmit the force of muscle contraction to bone to effect limb movement. Special structural and biological properties of tendon have developed to facilitate force transmission. The tendon has a complex organization of cells surrounding the collagen bundles inside tendon as well as at the tendon surface. Internal cells may act to maintain the bulk of the collagen in tendon. External cells in the epitenon may provide lubrication for tendon gliding. To develop better understanding of these processes and the roles the cell populations play, we isolated cells from the surface and interior of tendon and studied them in vitro. Flexor tendons from 8-week-old white Leghorn chickens were separated into two distinct cell populations: the outer synovial cells and the fibroblasts more internal in tendon. These cell populations were discernible by their locations in the intact tendon, determined by sequential enzymatic and physical release from their substrata. Initially, some cells eluted in Hanks' salt solution (HSS) (population 1); then synovial cells were released after a 2-min treatment with 0.5% collagenase (population 2). Next, a population of synovial cells was released in high yield by treatment with 0.25% trypsin (step III, population 3). Step III, population 3 cells were used as synovial cells (SCs). Next, a population of SCs and fibroblasts were released by scraping with a rubber policeman (population 4). Subsequently, fibroblasts were released after incubation with 0.5% collagenase (population 5). A more direct procedure (procedure 2) to isolate the synovial and internal tendon cells involved treatment in 0.5% collagenase followed by sedimentation at 900 g. Cells that sedimented were largely fibroblasts, whereas the cells that remained at the top of the tube were largely SCs. Cells designated as SCs, isolated by procedure 2, most likely contained surface cells from epitenon and internal interfascicular cells from endotenon and paratenon. Surface tendon cells separated by sequential enzymatic and physical release from their substrata (by procedure 1) had all the following characteristics: distinct subpopulations of cells based on morphology; presence of cytoplasmic, lipid-containing vesicles; decreased sensitivity to trypsin; and reduced generation time as compared with that of internal fibroblasts. Conversely, the internal fibroblasts (IFs) appeared to represent a more uniform population based on morphological characteristics.

Activation of human synovial cells by cholera enterotoxin: correlation of morphological responses with adenylate cyclase activities, and the reversing effects of hyaluronidase

Previously described morphological changes in human synovial cell cultures due to cholera enterotoxin (CT) were studied in relation to activation of adenylate cyclase. A single pulse of CT at nanomolar concentration or less induced at least two-fold activation of adenylate cyclase, which persisted for 7 days or more. The enzyme hyaluronidase was found to cause a rapid reversal of the morphological effects of CT. There was also a reduction in adenylate cyclase activity but only with hyaluronidase concentrations greater than those required to produce maximum reversal of the CT-induced morphological changes. Removal of hyaluronidase was followed by reappearance of the CT-associated morphological effects and a slower reactivation of adenylate cyclase. The mechanism by which hyaluronidase produces the observed changes in synovial cells is not known, but might be related to the dispersal of hyaluronic acid gels bound to the surface of these cells.

Demonstration of Ia antigens on certain dendritic cells and on a novel elongate cell found in human synovial tissue

Adherent cells from dissociated human synovial tissue obtained at surgery contain two types of distinctive cells with one or more elongated branching processes that strongly express Ia antigens. One type of cell with Ia antigens is non-phagocytic and resembles the murine dendritic cell. It is primarily found in patients with rheumatoid arthritis and accounts for a considerable proportion of the identifiable cells with a stellate or dendritic morphology. The expression of Ia antigens progressively diminished in culture. The second type of novel cell with Ia antigens was highly elongate and fibroblastoid. It was readily obtained from patients with osteoarthritis. The cell was frequently characterized by a blunt-ended filopodium-like process at one pole of the cell, one or two tapering processes, and zones of microvilli. Evidence was obtained suggesting that this cell, which might otherwise be considered fibroblast-like, is in the mononuclear phagocyte lineage.

Protein synthesis in rheumatoid synovial tissue

1. Function of synoviocytes and other cells in the synovium A. Histologic Considerations 1. Electron microscopic studies 2. In vivo and in vitro phagocytosis studies 3. Fluorescent antibody staining B. Culture techniques 1. Problems posed by study of isolated cells 2. Long-term explant cultures 3. Advantages of short-term incubations of synovial fragments 4. Isolation of immunoglobulins C. Non-Immunoglobulin Products of the Synovium 1. Products of normal synovium 2. Alterations induced by rheumatoid arthritis II. The Local Immune response in Rheumatoid Synovitis A. Evidence for Active Immune Stimulation 1. Meditators of cellular immunity in synovial fluid 2. Effect of synovectomy 3. Type and amount of immunoglobulin produced B. Local Commitment of Antibody Response 1. Effect of exogenous immunization 2. Rheumatoid factors. 3. Pepsin agglutinators C. 1. Relative enrichment for IgG-3 subclass 2. Increase in lambda-light chain composition III. Pathogenetic Considerations in Rheumatoid Arthritis A. Comparison of Rheumatoid versus Experimental Immune Synovitis 1. Chronic synovitis as a local immune response. 2. Role of cartilage complexes in substaining chronic synovitis B. Significance of the Restriction in the Immunoglobulin Response in Rheumatoid Arthritis 1. Analogy with other disease states in man 2. Common antigen in RA?

Evidence for the presence of receptors for C3 and IgG Fc on human synovial cells

The presence of receptors for IgG Fc and fragments of C3 on primary cultures and cryostat sections of normal and rheumatoid synovial tissues was assessed. Significant proportions of large rounded cells with asteroid projections found in such cultures had receptors for both IgG Fc and fragments of C3. Moreover, Gram negative bacteria that had fixed complement, but not EAC, bound in a linear fashion on the superficial layers of synovial cryostat sections. On the basis of morphologic and histochemical criteria, the cultured cells bearing these receptors were tentatively determined to represent a subset of synovial lining cells. The possible role of such receptors on synovial lining cells in the pathogenesis of rheumatoid arthritis is discussed.

Patterns of induced variation in the morphology, hyaluronic acid secretion, and lysosomal enzyme activity of cultured human synovial cells

In contrast with newly isolated cells or early primary cultures, synovial cell lines in standardised growth conditions assume a rather uniform fibroblast-like appearance. However, 2 distinct variations in the cytological pattern can be induced at this stage. The first is characterised primarily by increased numbers of small phase-dense organelles that show the distinctive fluorescence of lysosomes after supravital staining, and are interspersed with vacuoles. The associated functional changes include increased enzyme activity and decreased net synthesis of hyaluronic acid. This variation can be induced by exposure to indigestible neutral sugars, adenosine, or its 5' nucleotides. The second variation consists of a striking reorganisation of cytoplasm by condensation into dense ridges or a dendritic network of processes. It is accompanied by increased hyaluronic acid secretion and is induced by agents that enhance intracellular activity of cyclic adenosine monophosphate, such as dibutyryl cyclic adenosine monophosphate and cholera enterotoxin. It appears possible to direct differentiation in synovial cell lines to correspond at least in part with the presumed functions of the different cell types in the parent tissue. The 2 patterns may be useful markers to correlate with other aspects of synovial cell function in vitro.

Intra-articular methotrexate. Clinical and laboratory study in rheumatoid and psoriatic arthritis

The effects of intra-articular methotrexate (MTX) were compared with saline in 20 patients with persistent knee effusions due to rheumatoid arthritis (15) and psoriasis (5) in a double-blind pilot study. Clinical improvement was seen in most patients given either MTX or saline and was attributed to joint irrigation during arthroscopy and the placebo effects. MTX had a local anti-inflammatory effect in the psoriatic arthropathies; the percentages of polymorphonuclear cells and pyroninophilic mononuclear cells in synovial fluids fell sharply. Intraarticular hydrocortisone acetate was not anti-inflammatory in 2 psoriatic patients treated subsequently. The anti-inflammatory action of MTX in joints may resemble its effectiveness in controlling the rash of psoriasis.

Mononuclear cells in human synovial fluid. Identification of lymphoblasts in rheumatoid arthritis

A simple method was developed to identify large mononuclear (LMN) cells in human synovial fluid based on morphology and staining with Sudan black B. All cells were classified as monocyte-derived macrophages (MDM), lymphoblasts (LB), or synovial lining cells (SLC). Lymphoblasts were seen in 58 of 60 rheumatoid fluids (mean: 69 +/- 18% LB per LMN cells). However lymphoblasts were rarely seen in synovial fluids from patients with crystal-induced synovitis or bacterial infections.

Elution and characterization of lymphocytes from rheumatoid inflammatory tissue

Lymphocytes were eluted from the synovial tissue of 19 patients with classical rheumatoid arthritis. The tissue was minced and dissociated by treatment with crude collagenase and DNase. The cell suspension obtained was filtered and incubated in plastic culture flasks overnight at 37 degrees C. The cells that did not adhere to the plastic surface were harvested and the lymphocytes further purified by the Ficoll-Isopaque gradient centrifugation technique. The lymphocyte yield varied from 0.64 to 32 times 10(6) cells. Differential counts showed on the average 85% lymphocytes, 12% mocrophage-like cells, and variable proportions of polymorphonuclear granulocytes, unclassified cells, and dead cells. An average of 77% of the cells were viable as assessed by the trypan blue exclusion test. This cell suspension was investigated for lymphocyte populations. T lymphocytes were predominant in all experiments (mean, 73.6%). The mean percentage of B lymphocytes was 9.7%, whereas the proportion of Fc-receptor-bearing lymphocytes was on the average 6.0%.

Immunofluorescent demonstration of an IgG-B1C complex in synovial lining cells of rheumatoid synovial membrane

Synovial tissues obtained at arthrotomy or by needle biopsy were digested with trypsin, and suspensions of synovial cells isolated. Immunofluorescent staining of these cells has shown the simultaneous presence of immunoglobulin G (IgG) and the β_1C component of complement in the cytoplasm of most of the phagocytic lining cells of fifteen of seventeen synovia obtained from both seropositive and seronegative patients with rheumatoid arthritis. This staining pattern was not found in synovial cells obtained from patients with other inflammatory or non-inflammatory arthritides. Discrete cytoplasmic inclusions composed of: (1) IgG and α_1C, and (2) IgG and rheumatoid factor were also observed, but only in synovial cells from seropositive rheumatoid patients. The significance of the presence of an apparent IgG–β_1C complex in the synovial lining cells of most patients with rheumatoid arthritis is discussed.