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Biomedical subjects

M Gowen

Publications and source records attributed to M Gowen.

101 records · Page 6Linked to original sources
PubMed1984

Stimulation by human interleukin 1 of cartilage breakdown and production of collagenase and proteoglycanase by human chondrocytes but not by human osteoblasts in vitro.

Human articular chondrocytes in culture synthesise collagenase and neutral proteoglycanase in response to addition of a 12-17 kDa protein produced by cultured human monocytes. This factor copurifies with interleukin 1, as assessed by lymphocyte activating factor activity, on gel filtration chromatography and isoelectric focusing. The interleukin 1 and chondrocyte-stimulating activities are destroyed by pretreatment of the material with phenylglyoxal. The same materials also promote the release of glycosaminoglycans from cultures of intact bovine nasal cartilage. The proteoglycanase activity release from chondrocytes appears to be a metalloproteinase because it is inhibited by EDTA and not by phenylmethylsulphonyl fluoride (PMSF), and because detection of its activity is dependent on the presence of 4-aminophenylmercuric acetate. Human osteoblast-like cells do not respond to this factor by increased proteinase production, but are stimulated to produce prostaglandins. These results suggest that interleukin 1 has activities upon non-immune cells which promote the degradation of connective tissue matrices. Human osteoblasts do not synthesise neutral collagen- and proteoglycan-degrading enzymes and thus are unlikely to be directly responsible for the matrix degradation which occurs during bone resorption.

Animals↗
PubMed1983

Effects of retinol and dexamethasone on cytokine-mediated control of metalloproteinases and their inhibitors by human articular chondrocytes and synovial cells in culture.

Human articular chondrocytes in culture produced large amounts of specific mammalian collagenase, gelatinase and proteoglycanase when exposed to dialysed supernatant medium derived from cultured human blood mononuclear cells (mononuclear cell factor) or to conditioned medium, partially purified by fractionation with ammonium sulphate (60-90% fraction), from cultures of human synovial tissue (synovial factor). Human chondrocytes and synovial cells also released into culture medium an inhibitor of collagenase of apparent molecular weight about 30 000, which appeared to be similar to the tissue inhibitor of metalloproteinases synthesised by tissues in culture. The amounts of free collagenase inhibitor were reduced in culture media from chondrocytes or synovial cells exposed to mononuclear cell factor or synovial factor. While retinol inhibited the production of collagenase brought about by mononuclear cell factor or synovial factor, it restored the levels of inhibitor, which were reduced in the presence of mononuclear cell factor or synovial factor. Dexamethasone markedly reduced the production of collagenase by synovial cells, while only partially inhibiting factor-stimulated collagenase production by chondrocytes. Addition of puromycin as an inhibitor of protein synthesis reduced the amounts of both collagenase and inhibitor to control or undetectable levels.

Cartilage, Articular↗
PubMed1983

Stimulation of bone resorption in vitro by a non-prostanoid factor released by human monocytes in culture.

Cultured human monocytes produce a non-prostanoid factor which stimulates bone resorption in vitro. Production of the factor is not dependent on prostaglandin synthesis, but stimulation of resorption by the factor does involve prostaglandin production by bone. Salmon calcitonin inhibits the stimulatory activity by up to 80%. Production of the factor is not increased by the presence of lymphocytes in the monocyte cultures. Partial purification of the bone-resorbing activity by Ultrogel ACA 54 chromatography shows that it has an apparent molecular weight between 12 000 and 20 000. We suggest that the resorptive activity is due to an interleukin 1-like factor rather than an osteoclast activating factor.

Animals↗
PubMed1982

Effect of streptococcal cell wall components on bone metabolism in vitro.

Cell was components from Streptococcus mutans NCTC 10449 and Streptococcus sanguis ATCC 10558 stimulated the release of 45Ca from prelabeled mouse calvariae in organ culture. Bone resorbing activity was not blocked by fetal calf serum. It was, however, blocked by calcitonin, an inhibitor of osteoclast-mediated bone resorption. Indomethacin, a prostaglandin synthetase inhibitor, partially blocked endogenous but not antigen-stimulated 45Ca, suggesting that antigen-stimulated bone resorption was not mediated by prostaglandins. The antigen preparations also had an inhibitory effect on the incorporation of 3H-proline and 3H-thymidine into explants of rabbit and rat calvariae, respectively. The inhibitory effect of antigen on 3H-proline incorporation was not altered by the presence of calcitonin, which suggests that it represented a real inhibition of protein synthesis and not a reflection that the bones were resorbing. These findings indicate that plaque bacterial antigens may contribute directly to the progressive loss of alveolar bone during periodontal disease. The assumption that only Gram-negative organisms play an important role In the etiology of periodontal disease appears incorrect.

Animals↗
PubMed1982

Interactions in connective tissues involving monocyte/macrophages and control of production of proteinases and proteinase inhibitors.

Using human articular chondrocytes in monolayer culture as an experimental system, we have been studying mechanisms of control of production and activity of neutral proteases which degrade connective tissue matrices. Soluble factors from cultured human blood mononuclear cells (MCF) or synovial fragment cultures (SF) stimulate the production of collagenase and proteoglycanase by chondrocytes. Chondrocytes also release a collagenase inhibitor (mol. wt. 26-31,000), which is similar to the tissue inhibitor of metalloproteinases (TIMP) synthesized by cultured mammalian tissues and this is reduced in cultures exposed to MCF or SF. Retinol and dexamethasone partially inhibit the factor-stimulated collagenase, but increase the amount of inhibitor, restoring it to control levels in the presence of MCF or SF. The effects of these agents in cellular interactions in vitro will be discussed in relation to their possible roles in the control of connective tissue turnover in vivo.

Blood Proteins↗
PubMedDate not supplied

Are MG-63 and HOS TE85 human osteosarcoma cell lines representative models of the osteoblastic phenotype?

The aim of this study was to perform a systematic comparison of two widely used osteosarcoma cell lines and ascertain their relevance as experimental models for investigating osteoblast function. We have therefore compared growth, differentiated cell function, integrin expression and adhesive profiles of MG-63, HOS TE85, and human bone derived cells. Both osteosarcoma cell lines proliferated more rapidly than osteoblast-like cells with HOS cells exhibiting the shortest doubling time. HOS cells expressed higher levels of alkaline phosphatase than MG-63 cells under basal conditions but only MG-63 cells showed the increased enzyme activity following 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) administration, which is characteristic of bone derived cells. Osteocalcin was not detected in supernatants from any cells under basal conditions but levels produced by MG-63 cells on addition of 1,25(OH)2D3 were comparable with those of osteoblast-like cells. alpha 1, alpha 2, alpha 3, alpha 5, alpha V, and beta 1 integrin subunits were detected on all cells and there was no staining for alpha L, alpha M, beta 2, and beta 3. alpha 3 and beta 1 were the major subunits detected on MG-63, HOS, and bone derived cells but relative concentrations of other alpha subunits were dependent on cell type; alpha 4 and alpha 6 subunits could only be detected on osteosarcoma cell lines. Short term, serum-free cell adhesion assays showed that the three cell types adhered in a saturable manner to collagen I, fibronectin, and laminin.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMedDate not supplied

Novel bone antiresorptive agents that selectively inhibit the osteoclast V-H+-ATPase.

The vacuolar proton pump (V-ATPase) located on the plasma membrane of the osteoclast is a potential molecular target for the discovery of novel bone antiresorptive agents useful for the treatment of osteoporosis. In order to design novel compounds able to selectively inhibit the osteoclast V-ATPase we firstly identified the minimal structural requirements of bafilomycin A1, a macrolide antibiotic which potently inhibits all V-ATPases. This information allowed the design of 2-(indole)pentadienamide derivatives whose optimization led to a novel class of potent inhibitors that demonstrated a high degree of selectivity for the osteoclast V-ATPase. The most interesting derivative, SB-242784, was able to inhibit bone resorption by human osteoclasts in vitro and to completely prevent ovariectomy-induced bone loss in rats when administered orally at 10 mg kg(-1) day(-1). Structure activity relationships of this class of compounds were investigated further by replacing the 2,4-pentadienoyl chain with suitable spacers able to maintain the correct orientation and distance between the indole ring and the amide moiety.

Animals↗
PubMedDate not supplied

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.

Animals↗