Oxygen Tension Is a Determinant of the Matrix-Forming Phenotype of Cultured Human Meniscal Fibrochondrocytes

BACKGROUND: Meniscal cartilage displays a poor repair capacity, especially when injury is located in the avascular region of the tissue. Cell-based tissue engineering strategies to generate functional meniscus substitutes is a promising approach to treat meniscus injuries. Meniscus fibrochondrocytes (MFC) can be used in this approach. However, MFC are unable to retain their phenotype when expanded in culture. In this study, we explored the effect of oxygen tension on MFC expansion and on their matrix-forming phenotype. METHODOLOGY/PRINCIPAL FINDINGS: MFC were isolated from human menisci followed by basic fibroblast growth factor (FGF-2) mediated cell expansion in monolayer culture under normoxia (21%O(2)) or hypoxia (3%O(2)). Normoxia and hypoxia expanded MFC were seeded on to a collagen scaffold. The MFC seeded scaffolds (constructs) were cultured in a serum free chondrogenic medium for 3 weeks under normoxia and hypoxia. Constructs containing normoxia-expanded MFC were subsequently cultured under normoxia while those formed from hypoxia-expanded MFC were subsequently cultured under hypoxia. After 3 weeks of in vitro culture, the constructs were assessed biochemically, histologically and for gene expression via real-time reverse transcription-PCR assays. The results showed that constructs under normoxia produced a matrix with enhanced mRNA ratio (3.5-fold higher; p<0.001) of collagen type II to I. This was confirmed by enhanced deposition of collagen II using immuno-histochemistry. Furthermore, the constructs under hypoxia produced a matrix with higher mRNA ratio of aggrecan to versican (3.5-fold, p<0.05). However, both constructs had the same capacity to produce a glycosaminoglycan (GAG) -specific extracellular matrix. CONCLUSIONS: Our data provide evidence that oxygen tension is a key player in determining the matrix phenotype of cultured MFC. These findings suggest that the use of normal and low oxygen tension during MFC expansion and subsequent neo-tissue formation cultures may be important in engineering different regions of the meniscus

CMS physics technical design report : Addendum on high density QCD with heavy ions

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How is desertification research addressed in Spain ? Land versus soil approaches

This study intends to understand how desertification research is organised in Spain. We assume that a strong communication between scientific knowledge and stakeholders is needed to slow down and reverse the impacts of land degradation on drylands. With this purpose, we conducted an in-depth study at a national level in Spain. The work focused on a sample of published references on desertification in scientific journals indexed in the Web of Science (WoS). The keywords were related to desertification', drylands', land', soil', development' and Spain'. Multivariate analysis, bibliometric techniques and network analysis were used in order to (i) identify research categories and their temporal evolution throughout the period under consideration (1989-2012), (ii) determine if there were different approaches amongst different regions affected by desertification in Spain, (iii) establish the relationships between research categories, (iv) characterise types of co-authorship and (v) map out the Spanish network on the science of desertification. Erosion-soil degradation and soil analysis are the most important research categories, whereas climatic issues are subsidiary and quite isolated from the rest of topics. Very few articles consider desertification' as the main theme. Socio-economic issues have scant links with the core of biophysical science. The Spanish network on the science of desertification shows a low density. Moreover, the relationships between universities/research centres with other stakeholders are marginal. This is not the best scenario for transforming scientific knowledge into practical tools for policy makers and land users. Knowledge transfer should be a priority for national desertification programmes