[Differential gene expression in the wear particle induced and infectious periprosthetic membrane of loosened knee-endoprostheses]

About 5 to 12 % of hip endoprostheses will loosen after ten years. The periprosthetic membran between bone and prosthesis plays a crucial role in prosthesis loosening. Different pathomechanisms lead to the growth of such a membran, which can be discriminated by different histomorphologies: wear particle induced type, infectious type, combined type, indifferent type. 8 hybridizations were performed on PIQOR cDNA arrays. Objects of the study were periprosthetic interface tissue samples from 3 patients with particle induced and 2 patients with infectious prosthesis loosening. Tissue parts directly adjacent to the site of RNA-isolation were analyzed immuno-/ histopathologically in order to overcome the problem of tissue heterogeneity. 34 genes were found constantly differentially expressed, among which were cd9, cd11b, cd18, cd68, osteopontin, ferritin heavy-chain upregulated in the particle induced membrane and collagen types 1alpha-1, 3alpha-1, integrin alpha-1, thrombospondin 2 and nidogen upregulated in the infectious membrane. The most striking finding was the strong upregulation (from 20 fold to 323 fold) of megakaryocyte stimulating factor (msf) in all wear particle cases and 1 out of 2 infectious cases, which was confirmed by real-time RT-PCR. The upregulation of msf suggests an important pathogenetic role: The msf splice product lubricin is responsible for the lubrification of healthy joints, but its excellent lubrification ability may disturb the tight interaction between bone and prosthesis and thereby contribute to prosthesis loosening.

Combination of reduced oxygen tension and intermittent hydrostatic pressure: a useful tool in articular cartilage tissue engineering

Cartilage cells are normally studied under atmospheric pressure conditions and without loading. However, since cartilage exists in a condition of reduced oxygen and intermittent hydrostatic pressure we hypothesized lower partial oxygen pressures (PO2) and different intermittent hydrostatic pressures (IHP) would increase articular chondrocyte proliferation and matrix production and to stabilize chondrocyte phenotype in vitro. Monolayers of adult bovine articular chondrocytes were cultured under 5% or 21% PO2 in combination with IHP (0.2 MPa amplitude, frequencies 5/5s = 0.1 Hz, 30/2 or 2/30 min on/off loading). We measured proliferation (3H-thymidine incorporation) and collagen secretion (protein-binding assay, collagen type II-ELISA and immunocytochemical staining of pericellular collagen types I, II and IX). Reduced PO2 stimulated proliferation and collagen type II and IX secretion of chondrocytes in comparison to 21% PO2. Additionally, collagen type I expression was delayed by low PO2, indicating a stabilization of the cell phenotype. IHP 5/5s and 30/2 min inhibited proliferation but increased collagen secretion (pericellular collagen type IX was decreased). IHP 30/2 min delayed first expression of collagen type I. In contrast, IHP 2/30 min increased proliferation, but lowered collagen expression. All stimulating or inhibiting effects of PO2 and IHP were additive and vice versa. Reduced PO2 and different settings of IHP increased proliferation, collagen secretion, and phenotype stability of chondrocytes. The oxygen- and IHP-induced effects were additive, suggesting that a combination of these parameters might be a useful tool in cartilage tissue engineering.

The EPS of Acidithiobacillus ferrooxidans--a model for structure-function relationships of attached bacteria and their physiology

To dissolve pyrite or sulphur, leaching bacteria like Acidithiobacillus ferrooxidans attach to these substrata by extracellular polymeric substances (specifically, lipopolysaccharides). The primary attachment to pyrite at pH 2 is mediated by exopolymer-complexed iron(III) ions in an electrostatic interaction with the negatively charged pyrite surface. Cells grown on sulphur exhibit a different composition of the extracellular lipopolysaccharides, namely with increased hydrophobic properties, and do not attach to pyrite. Thus, the cells adapt the chemical composition of their exopolymers to the substrate/substratum. It is concluded that the mechanism of bacterial pyrite oxidation is basically indirect. The actual corrosive agents are iron(III) ions. Preliminary data indicate that active strains complex more iron(III) ions in their EPS than less active ones. Obviously, the exopolymeric layer comprises a reaction space for the regeneration of these ions by the activity of the iron oxidising bacteria.

Evaluation of water content by spatially resolved transverse relaxation times of human articular cartilage

Non-invasive assessment of cartilage properties, specifically water content, could prove helpful in the diagnosis of early degenerative joint diseases. Transverse relaxation times T(2) of human articular cartilage (34 cartilage slices of three donors) were measured on a pixel-by-pixel basis in a clinical whole body MR system in vitro. In vivo feasibility to measure quantitative T(2) maps was shown for human patellar cartilage. The relaxation times of cartilage with collagen in the radial zone oriented perpendicular to the magnetic field increased from approximately 10 ms near the bone to approximately 60 ms near the articular surface. Cartilage water content of the tibial plateau and femoral condyles could be determined from the correlation with T(2) (R(2) = 0.71) with an error of approximately 2 wt.%. In vivo, directional variation would need to be considered. If confirmed in vivo, T(2) measurements could potentially serve as a non-invasive tool for the evaluation of the status and distribution of water content in articular cartilage.

Carbohydrates of the Organic Shell Matrix and the Shell-Forming Tissue of the Snail Biomphalaria glabrata (Say)

Sulfated carbohydrates may play a role in the biomineralization of the molluscan shell. The carbohydrates of the extracted water-insoluble organic shell matrix (IM) of the freshwater snail Biomphalaria glabrata were identified as glucose, mannose, galactose, and N-acetyl-glucosamine, whereas the water-soluble organic matrix (SM) additionally contained N-acetyl-galactosamine. A specific lectin binding pattern of the matrix was obtained. One prominent protein of the SM, with a size of 19.6 kDa and a pI of 7.4, was shown to be a glycoprotein with terminal glucosyl or mannosyl moieties. The acidic constitutents of the matrix showed a variety of possible terminal sugars, indicating a heterogenous mixture of proteoglycans or glycosaminoglycans (GAGs) and glycoproteins. At the shell-forming mantle edge, an alcian-blue-positive material was observed in the periostracum groove (PG), the belt, and apically in the cells of the outer mantle epithelium (OME). With the help of lectins, all sugars in question were detected in the PG and the belt, whereas the OME was bound by glucose/mannose- and GlcNac-specific lectins only. Although the complete set of GAGs will be produced in the PG and the belt, a very acidic fraction of GAGs and the 19.6-kDa protein can also be delivered by the OME.

Biliary atresia--bile acids and prostaglandin E2 in cell cultures of bile duct epithelia

In a cell culture model of bile duct epithelial cells, the effect of prostaglandin E2, lithocholic acid and deoxycholic acid was studied. Bile acids and prostaglandin are administered postoperatively in biliary atresia empirically as choleretics. Prostaglandin E2 and the bile acids all had inhibitory effects on bile duct epithelial cells in culture. There is no clinical study proving the efficacy of either bile acids or prostaglandin E2 in biliary atresia. The negative results with these substances in cell cultures warrants reserve in their routine clinical use in biliary atresia.