Articular cartilage repair remains a significant and growing clinical challenge with the aging population. The native extracellular matrix (ECM) of articular cartilage is a 3D structure composed of proteinaceous fibers and a hydrogel ground substance that together provide the physical and biological cues to instruct cell behavior. Here we present fibrous scaffolds composed of poly(vinyl alcohol) and the biological cue chondroitin sulfate with fiber dimensions on the nanoscale for application to articular cartilage repair. The unique, low-density nature of the described nanofiber scaffolds allows for immediate cell infiltration for optimal tissue repair. The capacity for the scaffolds to facilitate cartilage-like tissue formation was evaluated in vitro. Compared with pellet cultures, the nanofiber scaffolds enhance chondrogenic differentiation of mesenchymal stems cells as indicated by increased ECM production and cartilage specific gene expression while also permitting cell proliferation. When implanted into rat osteochondral defects, acellular nanofiber scaffolds supported enhanced chondrogenesis marked by proteoglycan production minimally apparent in defects left empty. Furthermore, inclusion of chondroitin sulfate into the fibers enhanced cartilage-specific type II collagen synthesis in vitro and in vivo. By mimicking physical and biological cues of native ECM, the nanofiber scaffolds enhanced cartilaginous tissue formation, suggesting their potential utility for articular cartilage repair.

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Despite the existing knowledge that urban rapid rail transit has many effects on surrounding areas, and despite some attempts to understand the links between transit and gentrification, there remain methodological gaps in the research. This study addresses the relationship between the implementation of urban rapid rail transit and gentrification, which is conceived of as an event. As such, an event analysis approach using 'survival analysis' is adopted as the statistical analytical tool. It tests whether proximity to rail transit is related to the onset of gentrification in census tracts in Canada's largest cities. It is found that proximity to rail transit, and to other gentrifying census tracts, have a statistically significant effect on gentrification in two of the three cities analysed. By providing a methodological framework for the empirical analysis of the impact of urban rail transit on gentrification, this paper is a reference for both researchers and transportation planners.