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Differences in morphology of articular and nasal septum cartilage harvested for use in bioreactor-based tissue engineering

Cell-based therapies for the treatment of cartilage defects are currently based on the use of chondrocytes derived from articular cartilage biopsies, which are known to possess high donor-to-donor variability. As an alternative, more reproducible clinical outcomes could potentially be achieved by instead utilizing a more reproducible cell source, such as nasal chondrocytes. In fact, data from in vitro and ectopic in vivo models have shown that nasal chondroctyes proliferate faster and have a higher and more reproducible chondrogenic capacity than articular chondrocytes. The aim of this study was to analyse morphology of the articular and nasal septum cartilage. The nasal septum cartilage could be a promising alternative source of chondrocytes for cartilage tissue engineering in orthopedics. Cartilage samples from both knee femoral condyle and nasal septum were harvested from 3 healthy sheep under general anaesthesia and immediately immersed in 4% buffered paraformalydehyde (PFA) for light microscopy and in 2, 5% buffered glutaraldehyde (GA) for transmission electron microscopy (TEM) (samples from 1 sheep). Samples were then embedded in paraffin or Durcopan resin respectively, sectioned and stained or contrasted. For histology analysis, 5 µm thick sections were stained with hematoxylin-eosin (HE), Safranin O and Picrosirius Red. Immunofluorescence (IF) was performed against collagen type II. Semi-thin sections (1 µm) were stained with toluidine blue. HE, Safranin O and Picrosirius Red staining revealed similar morphology of the cartilage originating from the two locations. Although the nasal septum cartilage lacks mineralized zone and hypertrophic chondrocytes, in the area close to perichondrium chondrocytes are less rounded, more flattened, similar to chondrocytes of a superficial zone in the articular cartilage. Safranin O staining was more intensive in territrorium of the nasal cartilage compared to the articular cartilage indicating higher content of glycosaminoglycans (GAGs). Picrosirius Red and IF showed that matrix of both cartilages contains thin, collagen type II fibrils. Ultra-thin sections on TEM revealed the difference in extracellular matrix between these two cartilages. Volume density of collagen fibrils in the articular cartilage was 55% compared to 10% in nasal cartilage. Cell count was similar in both cartilages but cell number varies greatly in the articular cartilage (40.19±9.5 versus 36, 6±22, 6 cells/microscopic field).This study demonstrated hyaline nature of the nasal septum cartilage. There are some fine differences in the morphology between these two cartilages but high GAG content, collagen II and abundance of chondrocytes makes nasal septum cartilage a fine candidate for tissue engineering experiments in vitro and in vivo, as well as the potential use in clinical settings to treat articular cartilage defects. The research leading to these results has received funding from the European Union's Seventh Framework Programme (FP7/2007-2013) under grant agreement n°278807.

cartilage ; nasal septum chondrocytes ; tissue engineering

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