Differences in the collagen types synthesized by lapine articular chondrocytes in spinner and monolayer culture

In five different secondary monolayer cultures of rabbit articular chondrocytes, 72-89% of the the collagen synthesized was Type 1, as determined by alpha chain separation and CNBr-cleavage peptide analysis. When sister cells were transferred to spinner bottles after primary monolayer culture growth, 88% of the collagen formed in four separate experiments was Type II. A reversion to Type I collagen synthesis occurred when the spinner-cultured cells were returned to monolayer flasks. The change in the species of collagen depended on the suspension condition and not on the low Ca2+ content (0.33 mM) of the spinner medium. These findings parallel the switch to phenotypic glycosaminoglycan synthesis that also occurs when monolayer-cultured cells are transferred to spinner bottles. Whether this phenomenon arises through a genetic control mechanism rather than environmental selection for particular cohorts of cells has not yet been determined.