Relationship between cell shape and type of collagen synthesised as chondrocytes lose their cartilage phenotype in culture

TLDR: It is found that there is no strict correlation between cell morphology and type of collagen synthesised in cartilage colonies kept in monolayer culture at low density.

Abstract: WHEN chondrocytes from sternal or articular cartilage are kept in monolayer culture at low density, they eventually lose their cartilage phenotype1–4. Within four passages or approximately 1 month in culture they change from a polygonal or round to a flattened, amoeboid-like shape5–7, and instead of cartilage collagen (type II collagen8) they synthesise the genetically different type I collagen. It is not known whether there is a strict correlation between the occurrence of cell flattening and the change in collagen synthesis within individual cells. We have reported that preferentially flattened, fibroblast-like cells at the edge of cartilage colonies synthesise type I collagen, whereas round or polygonal chondrocytes generally synthesise type II collagen1–3. The change is nearly complete in a culture at a time when excessive flattening is observed4. Using an immunofluorescence double staining technique9,10, we have now found that there is no strict correlation between cell morphology and type of collagen synthesised.