Bonding of articular cartilage using a combination of biochemical degradation and surface cross-linking

After trauma, articular cartilage often does not heal due to incomplete bonding of the fractured surfaces. In this study we investigated the ability of chemical cross-linkers to facilitate bonding of articular cartilage, either alone or in combination with a pre-treatment with surface-degrading agents. Articular cartilage blocks were harvested from the femoropatellar groove of bovine calves. Two cartilage blocks, either after pre-treatment or without, were assembled in a custom-designed chamber in partial apposition and subjected to cross-linking treatment. Subsequently, bonding of cartilage was measured as adhesive strength, that is, the maximum force at rupture of bonded cartilage blocks divided by the overlap area. In a first approach, bonding was investigated after treatment with cross-linking reagents only, employing glutaraldehyde, 1-ethyl-3-diaminopropyl-carbodiimide (EDC)/N-hydroxysuccinimide (NHS), genipin, or transglutaminase. Experiments were conducted with or without compression of the opposing surfaces. Compression during cross-linking strongly enhanced bonding, especially when applying EDC/NHS and glutaraldehyde. Therefore, all further experiments were performed under compressive conditions. Combinations of each of the four cross-linking agents with the degrading pre-treatments, pepsin, trypsin, and guanidine, led to distinct improvements in bonding compared to the use of cross-linkers alone. The highest values of adhesive strength were achieved employing combinations of pepsin or guanidine with EDC/NHS, and guanidine with glutaraldehyde. The release of extracellular matrix components, that is, glycosaminoglycans and total collagen, from cartilage blocks after pre-treatment was measured, but could not be directly correlated to the determined adhesive strength. Cytotoxicity was determined for all substances employed, that is, surface degrading agents and cross-linkers, using the resazurin assay. Taking the favourable cell vitality after treatment with pepsin and EDC/NHS and the cytotoxic effects of guanidine and glutaraldehyde into account, the combination of pepsin and EDC/NHS appeared to be the most advantageous treatment in this study. In conclusion, bonding of articular cartilage blocks was achieved by chemical fixation of their surface components using cross-linking reagents. Application of compressive forces and prior modulation of surface structures enhanced cartilage bonding significantly. Enzymatic treatment in combination with cross-linkers may represent a promising addition to current techniques for articular cartilage repair

The militarisation of English schools: Troops to Teaching and the implications for Initial Teacher Education and race equality

This article considers the implications of the Troops to Teaching (TtT) programme, to be introduced in England in autumn 2013, for Initial Teacher Education (ITE) and race equality. TtT will fast-track ex-armed service members to teach in schools, without necessarily the requirement of a university degree. Employing theories of white supremacy, and Althusser’s (1971) concept of Ideological and Repressive State Apparatus, I argue that this initiative both stems from, and contributes to, a system of social privilege and oppression in education. Despite appearing to be aimed at all young people, the planned TtT initiative is actually aimed at poor and racially subordinated youth. This is likely to further entrench polarisation in a system which already provides two tier educational provision: TtT will be a programme for the inner-city disadvantaged, whilst wealthier, whiter schools will mostly continue to get highly qualified teachers. Moreover, TtT contributes to a wider devaluing of current ITE; ITE itself is rendered virtually irrelevant, as it seems TtT teachers will not be subject specialists, rather will be expected to provide military-style discipline, the skills for which they will be expected to bring with them. More sinister, I argue that TtT is part of the wider militarisation of education. This military-industrial-education complex seeks to contain and police young people who are marginalised along lines of race and class, and contributes to a wider move to increase ideological support for foreign wars - both aims ultimately in the service of neoliberal objectives which will feed social inequalities

Glycosaminoglycan (GAG) release from cartilage blocks determined after treatment with surface-degrading agents

<p><b>Copyright information:</b></p><p>Taken from "Bonding of articular cartilage using a combination of biochemical degradation and surface cross-linking"</p><p>http://arthritis-research.com/content/9/3/R47</p><p>Arthritis Research & Therapy 2007;9(3):R47-R47.</p><p>Published online 15 May 2007</p><p>PMCID:PMC2206351.</p><p></p> Cartilage blocks were subjected to pre-treatment with trypsin, pepsin, or guanidine, as indicated for the bonding experiments; the samples in the control group were incubated in PBS buffer. Subsequently, the GAG content within the cartilage blocks was determined. Additionally, the amount of GAG released into the medium (per cartilage block) was measured. Nine samples were measured per group. Bars represent the mean with standard error of the mean. values are from Tukey test for pairwise comparisons. Additionally, histological cross-sections of cartilage blocks were stained for GAGs

Stress-relaxation curves for the two sample geometries and bonding dependence on compression

<p><b>Copyright information:</b></p><p>Taken from "Bonding of articular cartilage using a combination of biochemical degradation and surface cross-linking"</p><p>http://arthritis-research.com/content/9/3/R47</p><p>Arthritis Research & Therapy 2007;9(3):R47-R47.</p><p>Published online 15 May 2007</p><p>PMCID:PMC2206351.</p><p></p> Stress-relaxation curves for the sample geometries G1 and G2 (see Figure 1e) were determined in a standardised creep modulus set-up. Samples were compressed by a stamp and the resulting force relaxation behaviour was analysed by recording the load over time. G1 (almost no compression) or G2 (compression) cartilage blocks were subjected to different cross-linkers (without degrading pre-treatment). Adhesive strength as a measure of bonding was determined immediately after cross-linking. Bars represent the mean with standard error of the mean of at least 16 samples derived from 4 independent experiments, each with at least 4 replicates per group. values in the graph are from pairwise comparisons using the Mann Whitney-U test. EDC, 1-ethyl-3-diaminopropyl-carbodiimide; NHS, N-hydroxysuccinimide