Synovial membrane in traumatic effusion. Ultrastructure and autoradiography with tritiated leucine

Ultrastructural study of synovitis induced by trauma to the rat temporomandibular joint (TMJ)

BACKGROUND

Electron microscopy was used to examine the histologic effect of trauma on the rat temporomandibular joint synovial membrane.

METHODS

Trauma to the TMJ in male Wister rats (100-200 g) was introduced through repeated forced condylar hypermobility. Ultrastructural observations were made 5 days and 6 weeks after the trauma.

RESULTS

The early response of the synovial membrane was synovial hyperplasia, type A synovial cell loss, dilation of the r-ER in the type B synovial cells and fibrin deposition on the synovial surfaces. The late response included degeneration of synovial cells with swollen mitochondria and cell projections, and cell fragmentation. Large amount of fibrin deposition on opposing surface layers was also noticed.

CONCLUSION

The type A cell loss and fibrin deposition followed by the occurrence of fibrinous materials at opposing surface layers of the synovial membrane suggest that traumatic synovitis causes synovial adhesions.

In vitro loading of human synovial membrane with 5-hydroxydopamine: evidence for dense core secretory granules in type B cells

Ultrastructural studies of the synovial membrane were performed on tissue samples obtained from the human lumbar facet joint. Ultrastructural changes in synoviocytes were studied after loading synovial samples with 5-hydroxydopamine (5-OHDA) in an oxygenated Krebs' solution, prior to fixation. Synoviocytes were set loosely in the intimal matrix and classified into type A (phagocytic) and type B (secretory) cells. In general, type A cells populated the surface of the synovial lining, whereas type B cells were located deeper in the tissue, extending a process into the synovial fluid. Type B cells in control samples contained sparse secretory granules. Free nerve endings were not found in the synovial intima. In response to incubation in 5-OHDA, a precursor of biogenic monoamines, synoviocytes clustered and established contact. The ultrastructure of type B cells in the loaded group clearly differed from controls. They possessed typical membrane-bound vesicles, containing an electron dense interior surrounded by a lucent space. The size of these dense core vesicles ranged from 100 to 260 nm (on average 180 nm). They were in relation to microtubules and located preferentially in the marginal area of the cytoplasm, close to the Golgi complex. The ultrastructure of type A cells was not significantly altered. The present observations provide morphological evidence for the amine-handling properties of type B cells, indicating that they might be added to the list of 'APUD' cells of the diffuse neuroendocrine system. A recepto-secretory function for type B cells is discussed.

Inhibition of interleukin-1-induced effects in synoviocytes transduced with the human IL-1 receptor antagonist cDNA using an adenoviral vector

In this report, we present data showing that a recombinant adenoviral vector (Ad.RSVIL-1ra) containing the cDNA for human interleukin-1 receptor antagonist protein (IL-1ra) can genetically modify synoviocytes both in vitro and in vivo. Human synoviocytes infected with Ad.RSVIL-1ra in vitro expressed and secreted high levels of human IL-1ra that were detected by ELISA of tissue culture supernatants. New Zealand White rabbits that received intra-articular injections of Ad.RSVIL-1ra expressed transgenic IL-1ra in synoviocytes, and secretion was detected for at least 4 weeks post-infection. Further, biological activity of the transgenic IL-1ra was demonstrated by its ability to inhibit IL-1-induced prostaglandin E2 (PGE2) synthesis in vitro and IL-1-induced glycosaminoglycan (GAG) degradation in vivo. These data demonstrate that recombinant adenoviral vectors can mediate the intra-articular expression of anti-inflammatory proteins and may be a reasonable method to deliver therapeutically relevant proteins for the regional treatment of synovial inflammation.

Stimulation of glycosaminoglycan synthesis in cultured human dermal fibroblasts by interleukin 1. Induction of hyaluronic acid synthesis by natural and recombinant interleukin 1s and synthetic interleukin 1 beta peptide 163-171

Hyaluronic acid (HA) is believed to play a critical role in wound healing and in morphogenesis. Factors controlling the production of HA by fibroblasts in normal and pathological states are not completely understood. In this report we have observed that natural human interleukin (IL-1)1 beta and human recombinant (hrIL)-1 alpha and beta are potent stimulators of HA production by fibroblasts in vitro. Hyaluronic acid is the major species of glycosaminoglycan (GAG) stimulated by IL-1 in fibroblasts. PGE2 does not appear to be involved directly in this IL-1 effect on fibroblasts, but stimulation of HA production by IL-1 is dependent on protein synthesis. The synthetic human IL-1 beta peptide 163-171 (Val-Gln-Gly-Glu-Glu-Ser-Asn-Asp-Lys), which has been previously shown to stimulate thymocyte proliferation but not fibroblast PGE2 production, is also able to stimulate fibroblast HA production. The synthesis and secretion of IL-1 by mononuclear phagocytes at sites of inflammation and immune reactions in vivo could potentially serve as a signal for fibroblasts to synthesize HA, which in turn could serve to facilitate and modulate reparative and immune processes by virtue of its ability to alter cell-cell, cell matrix, and cell-membrane receptor interactions.

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.

Mononuclear phagocytes of normal and rheumatoid synovial membrane identified by monoclonal antibodies

The presence of cells bearing epitopes of the mononuclear phagocyte series was studied immunohistochemically in synovium removed from joints involved by trauma (T), osteoarthritis (OA) and rheumatoid arthritis (RA). Mononuclear phagocytes were the most consistent feature of the inflamed rheumatoid synovium. They shared at least five epitopes expressed by mononuclear phagocytes in other tissues. In OA/T samples, cells bearing markers of the less mature monocyte were present at the surface of the synovial membrane, namely the intimal layer, while those bearing macrophage epitopes were apparent throughout the intimal layer and subintimally. This suggested that maturation of the monocyte population takes place after the monocytes have entered the synovial tissues, settled at the surface, then moved downward into the subintimal layer. The synovial monocytes accounted for all the HLA-D region positive cells in the lining layer.

Effects of prostaglandins E1, E2, and F2 alpha on N-acetyl-beta-glucosaminidase activities of human synovial cells in culture

The acid hydrolase N-acetyl-beta-glucosaminidase (NAG) was used to examine the effects of prostaglandins E1 (PGE1), E2 (PGE2), and F2 alpha (PGF2 alpha) on the lysosomal system of human synovial cells in vitro. A spontaneous release of the enzyme occurred from control cultures, which was accelerated by each of the prostaglandins in a concentration-dependent manner, within the range of 10(-8)-10(-6) moles per litre (M). No clear order of potency could be established. The effects of the prostaglandins on release of NAG were less consistent and of smaller magnitude when human serum was replaced by bovine serum albumin in the medium. In the presence of serum small increases also occurred in intracellular NAG activity, but only the effect of PGE1 was statistically significant. The prostaglandins did not appreciably affect the previously established pattern of increased intracellular activity of NAG and reduced release produced by sucrose.

Overview article: the articular territory of the reticuloendothelial system

It has long been recognized that synovial intimal cells are phagocytic and that they are capable of picking up colloidal or particulate material injected into the circulation. Hence they have been described as the "articular territory of the reticuloendothelial system." Ultrastructural studies have added a wealth new knowledge and details about the remarkable endocytotic powers of synovial cells. It has been shown that they can endocytose not only small particulate substances like colloidal iron, colloidal gold, and thorotrast but also relatively large objects like masses of fibrin and entire erythrocytes. Controversy has arisen as to whether it is the Type A or Type B cell that is the main scavenger of the joint. Evidence will be presented to show that this is a somewhat fictitious controversy and that these are not distinct and different races of cells with different functions but merely cells whose differences in morphology reflects the function they are performing at a given moment.

Traumatic joint effusion and the synovium

The morphology and function of synovial membrane is considered for its roles in development of traumatic joint effusions. Careful diagnostic study, including analysis of synovial fluid, is needed to be certain that one is dealing with uncomplicated traumatic effusion. Conservative treatment with cold application, rest and aspiration, seems effective and in line with known, basic experimental work for this generally self-limiting problem.

Ultrastructural changes in the synovial membrane in lipohaemarthrosis

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Ultrastructure of synovial membrane in osteo-arthritis

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Ultrastructure of synovial membrane in rheumatoid arthritis

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Histochemistry of synovium in experimental haemarthrosis in the rabbit

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Ultrastructure of normal rat synovial membrane

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Pathology of experimental haemarthrosis

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Ultrastructure of rabbit synovial membrane

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