Effects of products from macrophages, blood mononuclear cells and or retinol on collagenase secretion and collagen synthesis in chondrocyte culture.

Collagenase secretion was studied on cultures of rabbit articular chondrocytes. Differentiation of the cells was assessed by characterizing the type of 3H-labelled collagen produced during treatment with (1) conditioned media from rabbit peritoneal macrophages and human blood mononuclear cells, and (2) with retinol, a potent cartilage resorbing agent in tissue culture. Conditioned media stimulated collagenase secretion. Total collagen synthesis was reduced due to a decrease of synthesis of alpha 1 chains; the amount of alpha 2 chains synthesized was unchanged. This is thought to be due to a reduction in type II synthesis. Retinol did not stimulate collagenase secretion. Total collagen synthesis was reduced by retinol. alpha 2 chain synthesis, however, was significantly increased, suggesting a switch of collagen synthesis in favor of type I collagen, and therefore, dedifferentiation. These results demonstrate that dedifferentiation of chondrocytes with respect to collagen synthesis is not necessarily associated with a stimulation of collagenase secretion.

HapMap-based study of the 17q21 ERBB2 amplicon in susceptibility to breast cancer.

ERBB2 is frequently amplified in breast tumours as part of a wide region of amplification on chromosome 17q21. This amplicon contains many candidate genes for breast cancer susceptibility. We used a genetic association study design to determine if common genetic variation (frequency>or=5%) in a 400-kb region surrounding ERBB2 and containing the PPARBP, CRK7, NEUROD2, PPP1R1B, STARD3, TCAP, PNMT, CAB2, ERBB2, C17ORF37, GRB7 and ZNFN1A3 genes, was associated with breast cancer risk. Sixteen tagging single-nucleotide polymorphisms (tSNPs) selected within blocks of linkage disequilibrium from the HapMap database, one HapMap singleton SNP, and six additional SNPs randomly selected from dbSNP were genotyped using Taqman in a large study set of British women (2275 cases, 2280 controls). We observed no association between any of the genotypes or associated haplotypes and disease risk. In order to simulate unidentified SNPs, we performed the leave-one-out cross-validation procedure on the HapMap data; over 90% of the common genetic variation was well represented by tagging polymorphisms. We are therefore likely to have tagged any common variants present in our population. In summary, we found no association between common genetic variation in the 17q21 ERBB2 amplicon and breast cancer risk in British women.

Comparison of the inhibition of avian and mammalian bone alkaline phosphatases by levamisole and compound R8231.

Alkaline phosphatases from mammalian bone are inhibited much more than chick bone alkaline phsophatase by levamisole and compound R8231. Doses of R8231 (10(-4) to 10(-5) M) that almost completely inhibit mammalian alkaline phosphatases do not inhibit the growth of embryonic rat femurs in vitro. R8231 should be an excellent biological probe for the function of alkaline phosphatase in bone metabolism.

The effects of antirheumatic drugs on the production of collagenase and tissue inhibitor of metalloproteinases (TIMP) by stimulated rabbit articular chrondrocytes.

Conditioned medium from human peripheral blood mononuclear cells stimulated with concanavalin A (50 micrograms/ml) was used to induce rabbit articular chondrocytes to produce collagenase. In passaged chondrocyte cultures sodium aurothiomalate (GSTM) (either 5 micrograms/ml or 100 micrograms/ml). D-penicillamine (100 micrograms/ml) and dexamethasone (either 100 nM or 200 nM) did not reduce collagenase levels. Chloroquine (0.5 micrograms/ml) had a variable effect. Dexamethasone increased tissue inhibitor of metalloproteinases levels and also reduced collagenase levels in primary chondrocyte and cartilage fragment cultures. When the drugs were added to the mononuclear cells in culture, dexamethasone (10 nM), D-penicillamine (100 micrograms/ml), D-penicillamine (100 micrograms/ml) and copper sulphate (2 micrograms/ml) and chloroquine (5 micrograms/ml) reduced the activity of the conditioned medium when tested onchondrocytes. GSTM (100 micrograms/ml) and chloroquine (0.5 micrograms/ml) had no effect.

The expression of matrix metalloproteinases and their inhibitors by pig synovial cells and their regulation by combinations of cytokines and growth factors.

1. Pig synovial fibroblasts in culture were studied to determine if they were an easily reproducible model system for studying the actions of cytokines and growth factors on human synovial cells. The biochemical analyses were conducted by activity assays, enzymography and Northern blot. 2. Human recombinant interleukin-1 alpha, basic fibroblast growth factor and transforming growth factor-beta 1 were studied in combinations because of their known involvement in controlling tissue remodelling. 3. The response of pig fibroblasts to these agents, in terms of the expression of matrix metalloproteinases (collagenase, gelatinase and stromelysin) and their inhibitors (TIMPs), show that they behave similarly enough to human cells for use when supplies of human primary cells are unavailable.

Acute responsiveness to calcitonin in chronic renal failure.

The acute effect of porcine calcitonin was tested in 17 patients undergoing chronic haemodialysis. In normal adults calcitonin has no effect on plasma calcium or phosphate levels, but in nine patients both concentrations were substantially reduced after calcitonin. This hypocalcaemic and hypophosphataemic effect was a function of the initial plasma phosphate level but was unrelated to the initial plasma calcium level. Plasma hydroxyproline levels were not significantly different in the two groups an were unaffected by calcitonin. In 11 patients fasting plasma calcitonin levels were undetectable with an assay sensitive to 0-1 mug/1. Calcitonin seems to have an acute effect in chronic renal failure which may not operate by arresting bone resorption but is dependent on the plasma phosphate concentration.

Localisation of matrix metalloproteinases and TIMP-2 in resorbing mouse bone.

There is strong evidence that matrix metalloproteinases (MMPs) play a crucial role during osteogenesis and bone remodelling. Their synthesis by osteoblasts has been demonstrated during osteoid degradation prior to resorption of mineralised matrix by osteoclasts and their activities are regulated by tissue inhibitors of metalloproteinases (TIMPs). For this study we developed and utilised specific polyclonal antibodies to assess the presence of collagenase (MMP13), stromelysin 1 (MMP3), gelatinase A (MMP2), gelatinase B (MMP9) and TIMP-2 in both freshly isolated neonatal mouse calvariae and tissues cultured with and without bone-resorbing agents. Monensin was added towards the end of the culture period in order to promote intracellular accumulation of proteins and facilitate antigen detection. In addition, bone sections were stained for the osteoclast marker, tartrate-resistant acid phosphatase (TRAP). In uncultured tissues the bone surfaces had isolated foci of collagenase staining, and cartilage matrix stained for gelatinase B (MMP9) and TIMP-2. Calvariae cultured for as little as 3 h with monensin revealed intracellular staining for MMPs and TIMP-2 in mesenchymal tissues, as well as in cells lining the bone plates. The addition of cytokines to stimulate bone resorption resulted in pronounced TRAP activity along bone surfaces, indicating active resorption. There was a marked upregulation of enzyme synthesis, with matrix staining for collagenase and gelatinase B observed in regions of eroded bone. Increased staining for TIMP-2 was also observed in association with increased synthesis of MMPs. The new antibodies to murine MMPs should prove valuable in future studies of matrix degradation.