Stage-specific remodeling of the mammary gland basement membrane during lactogenic development.

Several in vitro studies have highlighted the importance of extracellular matrix proteoglycans as regulators of mammary epithelial cell differentiation. In this study monospecific antibodies to heparan (HS) and chondroitin/dermatan sulfate (CS/DS) proteoglycans were used to determine their possible significance in vivo. Immunohistochemical studies of proteoglycan distribution in virgin, pregnant, and lactating tissue demonstrated that heparan sulfate proteoglycan was found in the epithelial cell basement membrane at all stages of development. This was also true for CS/DS proteoglycans, but the relative proportions of CS and DS were strikingly modulated during lactogenesis. Notably DS glycosaminoglycans were the dominant components of the basement membrane in lactating tissue but CS glycosaminoglycans were the major proteoglycans of pregnant tissue. The possible significance of these results for gene expression in the gland is discussed.