Relationship between chromosomal changes and alterations in the behaviour of a strain of human synovial cells during its life history in vitro

Interleukin-1 beta and interleukin-1 alpha stimulate the N-acetyl-beta-glucosaminidase activity of human synovial cells

The properties of synovial cells are altered in vitro by monocyte-macrophage polypeptides (monokines), and these changes could explain some of the properties of the inflamed synovium in rheumatoid disease. Purified monokines have become available only recently for testing on the target synovial cells. We report here that purified human interleukin (IL)-1 beta and recombinant human IL-1 alpha stimulate the extracellular activity of the lysosomal hydrolase, N-acetyl-beta-glucosaminidase (NAG), of human synovial fibroblast-like cells. In contrast, another monokine, synovial activator, does not increase the NAG activity. Thus NAG is another cellular activity which can be modulated by interleukin-1.

Diverse morphological responses of normal human synovial fibroblasts to mononuclear leukocyte products: relationship to prostaglandin production and plasminogen activator activities, and comparison with the effects of purified interleukin 1

Supernatant media from cultured human mononuclear blood leukocytes (MCCM) induced morphological changes in normal human synovial fibroblasts in culture, including the formation of cells with a dendritic or stellate morphology and, less frequently, cells with a striking fenestrated appearance. These changes were fully reversed within 1 h of removing the MCCM. They were inhibited by indomethacin, the glucocorticoids hydrocortisone, prednisolone and dexamethasone, and by colcemid, but not by actinomycin D and only weakly by cycloheximide. The morphological responses to MCCM could be reproduced by MCCM fractions containing interleukin 1-like activity and by purified forms of human interleukin 1 (IL-1), including monocyte-derived IL-1 beta and recombinant IL-1 alpha. These responses were also inhibited by indomethacin, indicating a link with prostanoid production. However, the morphological responses were not related to the stimulation of plasminogen activator activity due to MCCM, MCCM fractions, or IL-1.

Peripheral blood mononuclear cells stimulate N-acetyl-beta-glucosaminidase levels of human synovial fibroblast-like cells

Fibroblast-like synovial cells isolated from intact joints of non-arthritic human donors released up to nine-times higher activity of the lysosomal acid hydrolase N-acetyl-beta-glucosaminidase (NAG) than controls when incubated in conditioned medium from homologous peripheral blood mononuclear cells (MCCM). This increase occurred without decrease in cell numbers or other evidence of cytotoxicity. An increase in cell-associated NAG activity was also suggested, but this was not statistically significant. Indomethacin present during production of MCCM or added with MCCM to fibroblast cultures did not alter the response to MCCM, indicating that the effect of MCCM was not due to the presence of products from the cyclo-oxygenase pathway. At a concentration known to block protein synthesis in most cells (10(-5) M), cycloheximide markedly suppressed the NAG releasing response to MCCM. The secretion of NAG due to MCCM was not affected by all-trans retinoic acid (10(-6) M) but was suppressed by the corticosteroid, dexamethasone.

Stimulation of glycosaminoglycan production and lysosomal activity of human synovial cells in culture by low environmental pH

Glycosaminoglycan production, acid hydrolase activity, proliferation, and morphology were examined in human synovial cells subjected to low environmental pH. The amount and the molecular size of newly synthesised glycosaminoglycan (GAG) were increased without significant change in the rate of cell proliferation. Lowered pH produced an increase in the size of cytoplasmic organelles. Some of these possessed ultrastructural features of lysosomes, but others were clearly nonlysosomal and were of uncertain identity. Intracellular activity of the lysosomal acid hydrolase N-acetyl-beta-glucosaminidase (NAG) was not altered by low pH, but a marked increase occurred in extracellular NAG activity, indicating enhanced release.

Some in-vitro comparisons of synovial cells dispersed by trypsin from rheumatoid and nonrheumatoid synovium

Life spans, growth rate, glucose utilisation, response to hydrocortisone, and intracellular activity of lysosomal N-acetyl-beta-glucosaminidase of rheumatoid synovial cells in culture were compared with these properties in nonrheumatoid synovial cells. Except for a small group of RA cells derived from tissue explants, the cells were all isolated by trypsinisation of synovial tissue, either within intact joints or after synovectomy. Cell lines were established by passaging with trypsin. In a study of 56 nonrheumatoid and 24 rheumatoid synovial lines isolated during a 7-year period the latter were found to have a shortened mean life expectancy in culture, though there was wide variation between individual lines. This is in agreement with reported findings from untrypsinised explant-derived synovial lines. However, in the present study mean multiplication rates were identical for nonrheumatoid and rheumatoid synovial cells, and on clear differences could be demonstrated for the other properties studied. No correlation could be found between the life spans of synovial cell lines and the age of the cell donors, whether from rheumatoid or nonrheumatoid sources. Rheumatoid synovial cells isolated from intact joints were notable for especially high proportions of macrophage-like cells and suppression of fibroblasts. In most cases cell lines could not be established from these rheumatoid primary cultures, and in others the lines were short-lived. Early association with relatively high proportions of macrophage-like cells in rheumatoid cultures might thus be important in influencing the establishment and behaviour of synovial cell lines.

Cellular immunity to possible synovial antigens in rheumatoid arthritis

A reaction has been demonstrated between extracts of synovial cells removed from intact rheumatoid knee joints and autologous leucocytes. The cell mediated immunity test system used was leucocyte migration inhibition. Variable reactions were found with a spectrum of allogeneic extracts when donor leucocytes came from married or transfused females or transfused males. Leucocytes from healthy (nontransfused) males showed no reaction with any of the extracts. As a period of cell culture was used prior to preparation of this extract to remove nonspecific inhibitory substances, native immunoglobulins, and complexes, the data are best explained by the presence of a foreign pathogen or altered cell component in the synovial cells of these rheumatoid patients.

Effects of carrageenin on human synovial cells in vitro: morphology, hyaluronic acid production, growth, and the lysosomal system

Some in-vitro effects of the arthritogenic polysaccharide carrageenin were studied on cells from human synovium. Synovial cells were isolated from intact human knee joints, and cell lines were developed by passaging with trypsin. Carrageenin was ingested by the cells but did not significantly affect cell growth, numbers of lysosomes, intracellular lysosomal enzyme activity (N-acetyl-beta-D-glucosaminidase), or release of lysosomal enzyme from cells. Carrageenin produced a reduction in net hyaluronic acid synthesis. It also induced a striking morphological change in a high proportion of synovial cells, characterised by increased spreading over the culture surface and apparent condensation of the cytoplasm into a pattern of ridges. Nonrheumatoid and rheumatoid synovial cells behaved similarly to one another.

Lysosomal activation by neutral saccharides in cell cultures of synovium

On exposure to sucrose or neutral polysaccharides, cell cultures from human synovium showed cytoplasmic vacuolation, increased numbers of lysosomes, and ultrastructural changes simulating those described in rheumatoid synovial intima and similarly treated embryonic caritlage and bone. These changes were accompanied by raised intracellular lysosomal enzyme activity without corresponding increases in the extracellular level of these enzymes. Structural changes and enzymic responses were less intense during exposure to the neutral polysaccharides. The secretion of large polymers of hyaluronic acid was consistently decreased during sucrose treatment. Evidence of heightened hyaluronidase-like activity was found in cellular extracts of sucrose-treated cultures, but not in the culture medium.

On the reactions of human synovial cells exposed to homologous leucocytes in vitro

Human synovial cells were exposed in culture to leucocytes from unrelated donors and to hyaluronidase, separately and together. Polymorphonuclear leucocytes rapidly lowered pH and severely damaged the synovial cells. Lymphocytes carefully freed from PMN-stimulated synovial cell growth or, at the worst, depressed it slightly. Hyaluronidase alone tended to stimulate cell growth whereas lymphocytes and hyaluronidase together were often cytotoxic after latent periods of 48–72 hr. The stimulating and inhibitory effects of lymphocytes upon synovial cells depended on the ratios and on the particular pairings of the two cell types. Lymphocytes did not show blast transformation during the cytotoxic reactions. The inhibitory effects of lymphocytes combined with hyaluronidase were partially blocked by small amounts of heparin, and completely blocked by hydrocortisone. It is suggested that the potentiating action of hyaluronidase is attributable to removal of pericellular gels which thus allows the close contact necessary for cytotoxic effects of lymphocytes.

Cytotoxic reactions between lymphocytes and synovial cells were incidentally found to be associated with increased glucose consumption.