Glycosaminoglycans in the basal lamina and extracellular matrix of the developing mouse mammary duct

Abstract

Mammary ductal elongation in the subadult virgin mouse takes place as the enlarged epithelial tip, or “end bud,” grows into the surrounding fatty stroma. By means of histochemical and autoradiographic techniques used in conjunction with enzyme susceptibility studies, we demonstrated that the basal lamina (BL) at the end bud tip is rich in hyaluronate, which is produced by a distinct outermost layer of epithelium, the “cap cells.” The posterior regions of the end bud are associated with ductal morphogenesis and tissue stabilization, and here both the epithelia and the stroma are sites of intense sulfated glycosaminoglycan (S-GAG) synthesis. Synthesis of S-GAGs was also found to extend beyond the region of collagen fibrillogenesis, and into the connective tissue between the advancing ducts, leading us to speculate that these S-GAGs play a role in the establishment of interductal spacing.