Abstract
In macroscopically-normal and early degenerate human articular cartilage, chondrocytes often exhibit increased volume and abnormal morphology with cytoplasmic processes. With further degeneration, chondrocyte clusters are a characteristic feature. These changes can influence matrix metabolism leading to matrix loss and predisposition to osteoarthritis (OA). Here, we report that articular chondrocytes cultured in a weak 3D agarose gel develop some of the morphological changes observed in degenerate cartilage. Cells were isolated from bovine metacarpal-phalangeal joints using collagenase. Gels were prepared with agarose (2% or 0.2% (v/v)) and cultured for 7 days (Dulbecco's modified Eagle's medium;37superscriptC;pH7.4;fetal calf serum (FCS; 1–10%)). Cells were fluorescently-labelled and volume/morphology examined by confocal microscopy. After one week of culture, chondrocytes in 2% gels (10% FCS) were mostly spheroidal; only 18.5±1% cells exhibited fine processes and 42.5±0.1% formed small clusters. However, in weak (0.2%) gels 66.9±1.3% (P=0.011) of chondrocytes had processes with lengths 7–63μm and 80.8±0.2% (P<.005) formed large clusters. In the weak gel after seven days, increasing FCS concentration markedly elevated the %age of chondrocytes in clusters from 31.1±0.2% in 1% FCS, to 87.3±0.27% in 10% FCS (P⊖.05). (Data from a minimum of three separate experiments at each condition with at least three replicates). These results suggest some similarities between the morphological changes to chondrocytes with OA development and those observed in weak agarose gels. The increased prevalence of abnormal chondrocytes with raised FCS concentration suggests that action of e.g. growth factors on chondrocytes is a more potent controller of cell shape than the strength of agarose.
