Jill P. G. Urban

Degeneration of the intervertebral disc

The intervertebral disc is a cartilaginous structure that resembles articular cartilage in its biochemistry, but morphologically it is clearly different. It shows degenerative and ageing changes earlier than does any other connective tissue in the body. It is believed to be important clinically because there is an association of disc degeneration with back pain. Current treatments are predominantly conservative or, less commonly, surgical; in many cases there is no clear diagnosis and therapy is considered inadequate. New developments, such as genetic and biological approaches, may allow better diagnosis and treatments in the future.

Effect of nutrient deprivation on the viability of intervertebral disc cells

There is evidence that a fall in nutrient supply leads to disc degeneration but little understanding of the effects of nutrient deprivation on the physiology of disc cells which govern the composition of the disc. We examined the effects of changes in glucose and oxygen concentration and pH on the viability and metabolism of cells from bovine nucleus pulposus. Cells isolated from bovine discs and embedded in alginate beads were cultured under oxygen and glucose concentrations from zero to physiological levels and maintained at pH 7.4, pH 6.7, or pH 6.2 for up to 3 days. Interactions between nutrient concentrations were examined in relation to cell viability and lactic acid production. Cell viability was significantly reduced in the absence of glucose, with or without oxygen. Disc cells survived at 0% oxygen, provided that glucose was present, as seen previously. Cell viability decreased if the medium was acidic, more so when combined with low glucose concentrations. The rate of lactic acid production also fell as the pH became acidic and after 24 h or more at low glucose concentrations, but it did not appear to vary with oxygen concentration under the culture conditions used here. Glucose, rather than oxygen, appears to be the nutrient critical for maintaining disc cell viability. However, in an avascular tissue such as the disc, it is unlikely that glucose deprivation will occur alone; it will almost certainly correlate with a fall in oxygen concentration and pH. These results indicate that the combined nutrient and metabolite environment, rather than concentrations of any single nutrient, should be considered when studying cellular physiology in the disc.

Elastic fibre organization in the intervertebral discs of the bovine tail

Elastic fibres have been revealed by both elastin immunostaining and conventional histological orcein‐staining in the intervertebral discs of the bovine tail. These fibres are distributed in all regions of the disc but their organization varies from region to region. In the centre of the nucleus, long (> 150 µm) elastic fibres are orientated radially. In the transitional region between nucleus and annulus, the orientation of the elastic fibres changes, producing a criss‐cross pattern. In the annulus itself, elastic fibres appear densely distributed in the region between the lamellae and also in ‘bridges’ across the lamellae, particularly in the adult. Elastic fibres are apparent within the lamellae, orientated parallel to the collagen fibres of each lamella, particularly in the young (12‐day‐old) discs. In the region between the disc and the cartilaginous endplate, elastic fibres appear to anchor into the plate and terminate there. The results of this study suggest that elastic fibres contribute to the mechanical functioning of the intervertebral disc. The varying organization of the elastic fibres in the different regions of the disc is likely to relate to the different regional loading patterns.

Analysis of Nonlinear Coupled Diffusion of Oxygen and Lactic Acid in Intervertebral Discs

The transport of oxygen and lactate (i.e., lactic acid) in the human intervertebral disc was investigated accounting for the measured coupling between species via the pH level in the tissue. Uncoupled cases were also analyzed to identify the extent of the effect of such coupling on the solute gradients across the disc. Moreover, nonlinear lactic production rate versus lactic concentration and oxygen consumption rate versus oxygen concentration were considered. The nonlinear coupled diffusion equations were solved using an in-house finite element program and an axisymmetric model of the disc with distinct nucleus and anulus regions. A pseudotransient approach with a backward integration scheme was employed to improve convergence. Coupled simulations influenced the oxygen concentration and lactic acid concentration throughout the disc, in particular the gradient of concentrations along the disc mid-height to the nucleus-anulus boundary where the solutes reached their most critical values; minimum for the oxygen tension and maximum for the lactate. Results suggest that for realistic estimates of nutrient and metabolite gradients across the disc, it could be important to take into account the coupling between the rates of synthesis and overall local metabolite/nutrient concentration.

Histological and mechanical differences in the skin of patients with rectal prolapse

IntroductionIt is still an enigma that some patients develop rectal prolapse whilst others with similar risk factors do not. Biomechanical assessment of the skin may provide further insight into the aetiology of this complex condition. Elastin fibres are an abundant and integral part of many extracellular matrices and are especially critical for providing the property of elastic recoil to tissues. The significance of elastin fibres is clearly reflected by the numerous human conditions in which a skin phenotype occurs as a result of elastin fibre abnormalities.MethodBetween January and June 2013, skin specimens were obtained prospectively during surgery on 20 patients with rectal prolapse and 21 patients without prolapse undergoing surgery for other indications. Expression levels of elastin in the skin were measured by Orcein staining, and Image J. Tensile tests were performed using the Zwick Roell device, with custom ceramic clamps. For statistical analysis, Student’s t test was used.ResultsHistological analysis of prolapse vs control showed percentage dermal elastin fibres of 9 vs 5.8xa0% (pu2009=u20090.001) in males and 6.5 vs 5.3xa0% (pu2009=u20090.05) in females. Patients with more severe prolapse (external) had a significantly (pu2009=u20090.05) higher percentage dermal elastin fibres 6.9 vs 6.1xa0% than internal prolapse. Young’s modulus of patients with prolapse was lower in males (3.3 vs 2.8, pu2009=u20090.05) and females (3.1 vs 2.7, pu2009=u20090.05).ConclusionPatients with prolapse have a higher concentration of elastin fibres in the skin, and these differences are quantitatively demonstrated through mechanical testing. This suggests that the aetiology may be a result of a dysfunction of elastin fibre assembly.

Expression of fibulin-5 in the skin of patients with rectal prolapse

Components of connective tissue other than collagen have been found to be involved in patients with rectal prolapse. The organization of elastic fibres differs between controls and subsets of patients with rectal prolapse, and their importance for maintaining the structural and functional integrity of the pelvic floor has been demonstrated in transgenic mice, with animals which have a null mutation in fibulin‐5 (Fbln5¡/¡) developing prolapse. This study aimed to compare fibulin‐5 expression in the skin of patients with and without rectal prolapse.

PTU-170 Fibulin-5 expression in the skin of patients with rectal prolapse

Introduction Rectal prolapse is a prevalent disorder affecting up to 10% of patients in the United Kingdom. Components of the connective tissue other than collagen have been found to be involved in development of prolapse. Elastic fibre organisation differs between controls and subsets of patients with rectal prolapse. Transgenic mice have demonstrated the importance of elastic fibres for maintaining structural and functional integrity of the pelvic floor. Elastic fibres assembly is a complex process and fibulin-5 integral in this process. Mice with null mutation in fibulin-5 (Fbln5¡/¡) develop a prolapse that is remarkably similar to that of primates. Method Between January 2013 and February 2014, skin specimens were obtained prospectively during surgery from 20 patients with rectal prolapse and from 21 patients without prolapse undergoing surgery for other indications. Fibroblasts from the skin were cultured and levels of Fibulin -5 expression was determined on cultured fibroblasts, isolated from these specimens by Quantitative Real-Time PCR. Immunohistochemistry was performed on fixed tissue specimens to assess FIB-5 expression. Results FIB-5 mRNA expression and FIB-5 staining intensity was significantly lower in the young male patients with rectal prolapse when compared to age matched control groups. (FIB-5 mean +/- SD mRNA relative units) 1.1 +/- 0.41 vs. 0.53 +/- 0.22, p = 0.001] and Intensity score, median (range), 2 (0–3) vs. 1 (0–3), p = 0.05]. There was no significant differences in expression of FIB-5 in women with rectal prolapse compared with control. Conclusion FIB-5 maybe implicated in the aetiology of rectal prolapse in a subgroup of young male patients. Disclosure of interest None Declared.