Type I collagen reduces the degradation of basal lamina proteoglycan by mammary epithelial cells.
When mouse mammary epithelial cells are cultured on a plastic substratum, no basal lamina forms. When cultured on a type I collagen gel, the rate of glycosaminoglycan (GAG) synthesis is unchanged, but the rate of GAG degradation is markedly reduced and a GAG-rich, basal lamina-like structure accumulates. This effect of collagen was investigated by comparing the culture distribution, nature, and metabolic stability of the 35S-GAG-containing molecules produced by cells on plastic and collagen. During 48 h of labeling with 35SO4, cultures on collagen accumulate 1.4-fold more 35S-GAG per microgram of DNA. In these cultures, most of the extracellular 35S-GAG is immobilized with the lamina and collagen gel, whereas in cultures on plastic all extracellular 35S-GAG is soluble. On both substrata, the cells produce several heparan sulfate-rich 35S-proteoglycan fractions that are distinct by Sepharose CL-4B chromatography. The culture types contain similar amounts of each fraction, except that collagen cultures contain nearly four times more of a fraction that is found largely bound to the lamina and collagen gel. During a chase this proteoglycan fraction is stable in cultures on collagen, but is extensively degraded in cultures on plastic. Thus, collagen-induced formation of a basal lamina correlates with reduced degradation and enhanced accumulation of a specific heparan sulfate-rich proteoglycan fraction. Immobilization and stabilization of basal laminar proteoglycan(s) by interstitial collagen may be a physiological mechanism of basal lamina maintenance and assembly.
D000818:Animals; D001485:Basement Membrane / Q000378:metabolism*; D002448:Cell Adhesion; D002478:Cells, Cultured; D003094:Collagen / Q000502:physiology*; D005260:Female; D006497:Heparan Sulfate / Q000378:metabolism; D008321:Mammary Glands, Animal / Q000166:cytology; D051379:Mice; D010969:Plastics; D011509:Proteoglycans / Q000378:metabolism*
D003094:Collagen; D006497:Heparan Sulfate; D010969:Plastics; D011509:Proteoglycans