Sulfated proteoglycans produced by human lung fibroblasts during in vitro cellular aging

Vogel, K.G.; Pitcher, D.E.

European Journal of Cell Biology 29(1): 61-67


ISSN/ISBN: 0171-9335
PMID: 6818028
Accession: 006540578

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With progressive subcultivation, lung fibroblasts in culture cease proliferation and demonstrate senescent characteristics which include increased size, low culture density and loss of fibrillar fibronectin over the cell surfaces. Proteoglycans produced by senescent IMR-90 fibroblasts were characterized by gel-filtration chromatography under dissociating conditions after 48-h uptake of Na235SO4. The overall differences noted between proteoglycans of early and late-passage fibroblasts in culture were not great. In medium from late-passage cultures, larger components comprised an increased proportion of the total secreted proteoglycan, and a large chondroitin sulfate component had lower buoyant density in CsCl. Proteoglycans solubilized from early-passage cells by detergent eluted from Sepharose CL-4B with 2 peaks at Kav = 0.2 and 0.6. From late-passage cultures, proteoglycan migrating in the void volume was also frequently seen. This V0 component had low density in CsCl and was made smaller by trypsin treatment. These alterations are minor and were variably expressed, even in terminally senescent cultures. Proteoglycan turnover in early and late-passage cultures during a 48-h chase period showed similar movement of surface proteoglycan to the medium and degradation of intracellular components. Only 13% of cell-associated 35S-glycosaminoglycan was released from either culture by exogenous heparin. Senescent fibroblasts are not obviously differentiated toward production of specific matrix components, nor do they express unique proteoglycan metabolism which can be related to their lack of proliferation.