Intercellular Messengers in Joint Tissues in Rheumatoid Arthritis

Tissue repair in rheumatoid arthritis: challenges and opportunities in the face of a systemic inflammatory disease

Rheumatoid arthritis (RA) is a systemic inflammatory disease that can elicit a variable disease course, can influence a variable number of joints, and can exhibit a variable response to treatment. All of these factors contribute to the degree and extent of damage to joint components, as well as the potential for repair of other injured joint tissues/components. Furthermore, some of the RA treatments/drugs themselves can influence repair and injury responses, as well as the outcome of surgical interventions for advanced disease. However, as treatments and interventions become more sophisticated and successful in patient populations, the opportunity to initiate the repair/replacement of the damaged joint tissues also becomes more of a reality. This review will address the current clinical findings in the literature, and then discuss the issues and opportunities to initiate repair of damaged or injured joint tissues in order to restore joint function. These include growth factors, gene therapy, and bioengineered tissues, alone or in combination to augment endogenous repair or replace tissue damaged beyond such repair capabilities.

IL-1 beta and TGF-beta 1 modulate the sulphation grade of chondro-disaccharides in porcine articular cartilage: a capillary electrophoresis study

This report describes the effect of interleukin-1 beta (IL-1 beta) and transforming growth factor-beta 1 (TGF-beta 1) on proteoglycan release from cartilage explants and modification at the sulphation level. Matrix proteoglycans purified by ion-exchange chromatography were composed of two distinct peaks (1 and 2) each showing a different Kav value when they were subjected to size-exclusion chromatography on a Sepharose CL-2B column. Glycosaminoglycans (GAGs) of conditioned medium and extracellular matrix proteoglycans were digested by chondroitin ABC and AC lyase, suggesting that chondroitin sulphate (CS) is the major GAG present (80-90%). Structural analysis of disaccharides, by capillary zone electrophoresis, revealed a different pattern of sulphated glycosaminoglycans when cartilage was treated with either IL-1 beta or TGF-beta 1. Analysis of GAGs released into the medium from TGF-beta 1 treated cartilage showed a reduction in the level of 4-S-disaccharide (delta Di4S) and an increase in non-sulphated disaccharides (delta Di0S), while no significant changes were found in IL-1 beta treated cartilage. In the extracellular matrix, IL-1 beta and TGF-beta 1 induced a more complex rearrangement of the GAGs. The level of non-sulphated disaccharides was increased whereas that of total sulphated disaccharides was reduced. Taken together, these results suggest that both cytokines modify the structure of GAGs, probably by interfering with the activity or the synthesis of sulphotransferases involved in GAG turnover.

Comparative and combined effects of transforming growth factors alpha and beta, interleukin-1 and interferon-gamma on rheumatoid synovial cell proliferation, glycolysis and prostaglandin E production

Enhanced cell proliferation, glycolysis and prostaglandin E production are all characteristic features of rheumatoid synovial tissue. The interrelationships of these three cellular parameters have been examined using rheumatoid synovial fibroblasts and their responses to specific cytokines in vitro. Transforming growth factor alpha (TGF alpha) caused a more than threefold increase in synovial cell proliferation whilst transforming growth factor beta (TGF beta), interleukin-1 alpha (IL-1 alpha) and interferon-gamma (IFN-gamma) produced only marginal changes. The combined addition of IL-1 alpha with TGF beta resulted in an enhanced proliferative response comparable with that produced by TGF alpha. Glycolysis, estimated by glucose utilisation and measurements of the glycolytic regulatory metabolite fructose 2,6-bisphosphate was significantly stimulated by TGF beta, IL-1 alpha and IFN-gamma, but less so by TGF alpha. Prostaglandin E production was significantly increased by IL-1 alpha to an extent much greater than that produced by TGF alpha or TGF beta, although the combined addition of IL-1 alpha with either TGF alpha or beta resulted in a synergistic increase in PGE production, a response partly diminished by the addition of IFN-gamma. These findings suggest that the extent to which a cytokine stimulates glycolysis is not consistently related to its mitogenicity, and that cytokine combinations which stimulate high levels of PGE production (a growth inhibitor) will not necessarily be associated with a reduced rate of cellular proliferation in cultured, adherent, rheumatoid synovial fibroblasts.

Dendritic cells in the pathogenesis of rheumatoid arthritis

The cause of rheumatoid arthritis is unknown. It appears that abnormal or overstimulated cell-mediated immune mechanisms are operating. Dendritic cells, with their potent antigen presenting and immunostimulatory properties, have been found in increased numbers of rheumatoid synovial fluids and membranes. It is postulated that these cells play a key role in inducing and perpetuating the immune response with subsequent synovial proliferation and joint destruction.

Histamine stimulates prostaglandin E production by rheumatoid synovial cells and human articular chondrocytes in culture

Histamine stimulates prostaglandin E (PGE) production by cultures of adherent rheumatoid synovial cells and human articular chondrocytes. When subcultured synovial fibroblasts or human articular chondrocytes were "primed" by preincubation with conditioned media from primary adherent rheumatoid synovial cell cultures (synovial factor), each produced even higher PGE levels upon histamine exposure. This histamine stimulation was prevented by histamine H1, but not H2, antagonists and was more marked if serum was absent from the culture media. Thus, histamine-induced PGE production by these cells is mediated via H1 receptor activation and subsequent arachidonic acid liberation.

Effects of 1-hydroxyethylidene-1,1 bisphosphonate and (chloro-4 phenyl) thiomethylene bisphosphonic acid (SR 41319) on the mononuclear cell factor-mediated release of neutral proteinases by articular chondrocytes and synovial cells

Articular chondrocytes and synovial cells were stimulated to produce collagenase, neutral casein and proteoglycan-degrading proteinases by conditioned medium from human peripheral blood mononuclear cells. Collagenase, neutral casein and proteoglycan-degrading proteinase secretion was inhibited by SR 41319, a new bisphosphonate, in a concentration-dependent manner. Complete inhibition was achieved at about 0.3 mM. EHDP exhibited the same general profile but was about 10-fold less active and never completely inhibited the enzyme secretion. When added before MCF, SR 41319 had a protective effect against subsequent activation of the cells by MCF. SR 41319 also inhibited the increase of enzyme secretion by cells previously stimulated with MCF. The results suggest that the ability of SR 41319 to inhibit the MCF-mediated secretion of neutral enzymes involved in cartilage destruction could be valuable in the management of connective tissue damage in rheumatoid arthritis.

Ascorbic acid stimulates the resorption of canine articular cartilage induced by a factor derived from activated rabbit macrophages

Articular cartilage explants from the knees of mongrel dogs release 5-10% of their proteoglycan content spontaneously when cultured for 4 days in serum-free modified Bigger's medium. A factor synthesized and secreted by lipopolysaccharide-stimulated rabbit macrophages can stimulate this release of proteoglycan by 2 to 3-fold. The release of proteoglycan in response to macrophage factor is maximal in the presence of 1.5-50 micrograms/ml L-ascorbic acid. In the absence of ascorbate, or with high levels of ascorbate (150 micrograms/ml), the effect of the factor is diminished by 50%. D-isoascorbate, reduced glutathione, or dithiothreitol cannot substitute for L-ascorbate in producing this effect, while dehydroascorbate can.

A catabolin-like factor from porcine kidney

Explants of pig kidney cortex and medulla release a catabolin-like factor (CLF). The CLF of both kidney cortex and medulla can be precipitated with ammonium sulphate, mainly in the 60-95 per cent fraction. By gel chromatography the kidney CLF showed a major active fraction at a molecular weight of around 22 500. Whole glomeruli and dissociated glomerular cells in culture also released into the medium a CLF that could be bioassayed in live cartilage but displayed no effect on dead cartilage. The possible role of such a local hormone is discussed.

Modulation of connective tissue metabolism by partially purified human interleukin 1

We have investigated the relationship between the monokine interleukin 1 (IL-1) and the connective tissue-stimulating activities produced by monocytes such as mononuclear cell factor (MCF). Using almost exclusively human tissue we have monitored a wide range of MCF-like activities through the partial purification of IL-1 by gel filtration and isoelectric focusing. Activities measured include stimulation of chondrocytes to produce prostaglandins, plasminogen activator and proteoglycanase, enhancement of synovial cell proliferation, and stimulation of cartilage resorption, in addition to IL-1 (lymphocyte activating factor) activity. The activities described show the same molecular heterogeneity; the active material has similar potencies in the different systems, and removal of IL-1 activity by pretreatment with phenylglyoxal also results in loss of the connective tissue-stimulating activities. These results show that the factors responsible for this wide range of activities are very closely related to IL-1 and give further evidence in support of the possible involvement of IL-1 in the processes of joint destruction occurring in chronic inflammatory conditions such as rheumatoid arthritis.

The effect of synovial catabolin on cartilage synthetic activity

The effect of porcine synovial catabolin on the incorporation of [3H]amino acids and [35S]sulfate into bovine nasal cartilage was investigated. The rapid breakdown of matrix caused by partially purified catabolin had little affect on the incorporation of [3H]amino acids but there was inhibition of [35S]sulfate uptake. While the 35S-labelled material released into the medium was largely incapable of aggregation with hyaluronate, this was only a small part (less than 10%) of the total incorporated. The principal inhibitory action was in the formation of large molecular size material (guanidinium chloride extractable). The amount of newly synthesized glycosaminoglycans (GAG) during the 8 day culture period was too low (less than 0.8%) to influence the very rapid breakdown of the matrix under catabolin stimulation. Cartilage organ cultures recovered from inhibition of [35S]sulfate incorporation and from the catabolic stimulation after removal of catabolin. It is suggested that the two properties of the catabolin preparation demonstrated in this study may work synergistically both in causing and prolonging cartilage damage in vivo.

An interleukin 1 like factor stimulates bone resorption in vitro

Many activities are now ascribed to the monokine interleukin 1 including enhancement of immune responses, stimulation of thymocyte proliferation, activation of B cells, stimulation of proteinase and prostaglandin production by connective tissue cells, stimulation of the production of acute phase proteins, induction of fever and the induction of neutrophilia. These activities were thought to be due to various different factors, but are now considered probably due to very similar, if not identical, molecules. The term interleukin 1 (IL-1) was coined to describe the factor released by monocyte/macrophages which acts on T and B lymphocytes. Only after this definition had been accepted was it shown that target cells other than lymphocytes were affected by IL-1. Products of human blood monocytes (mononuclear cell factor, MCF) have been implicated in the pathogenesis of inflammatory diseases such as rheumatoid arthritis and periodontal disease. Bone resorption is often a feature of such diseases, and monocytes are frequently found at sites of localized bone resorption. Preliminary experiments with monocyte-conditioned medium indicated that MCF could stimulate bone resorption. We therefore undertook this study to verify these observations and to determine whether purified IL-1 could stimulate connective tissue breakdown in vitro.