Proteoglycan-collagen associations in the non-lactating human breast connective tissue during the menstrual cycle

The human mammary gland undergoes a sequence of histological changes in both epithelial and stromal compartments during the menstrual cycle. Swelling and unswelling of the breast stromal tissue is a characteristic feature of the two phases of the cycle and is mediated by changes in the water content of sulfated proteoglycans in the matrix between the fibrils. In an ultrastructural study we investigated the distribution of sulfated proteoglycans identified as cupromeronic blue-positive needle-like structures and measured the distance between the dermatan sulfate-proteoglycan attachment sites at the d-bands of the collagen fibrils in the loose intralobular connective tissue and in the dense interlobular connective tissue. We characterized the dermatan sulfate proteoglycan by enzyme digestion and by immunogold-labeled antibody. In the follicular phase a relatively constant distance of 46 nm between neighboring proteoglycan attachment sites was found, while in the luteal phase the measured distances are strikingly variable and exceed the follicular value by up to 9 nm. This difference of the two cycle phases is more evident in the loose than in the dense connective tissue. Possibly the changes of the fibril-attached proteoglycans in the luteal phase reflect an influence of the higher water content of the matrix leading to a probably torsional swelling of the collagen fibril.