The effect of estradiol on collagen structure and organization in the immature rat uterus.

Abstract

An examination of collagen ultrastructure in the lamina propria of the immature ovariectomized rat uterus revealed that a single injection of estradiol (40 micrograms/kg) produced a biphasic effect on collagen structure and organization. In saline-treated animals (controls) dense populations of collagen bundles were seen throughout the extracellular matrix (EX). Cross-sections of these bundles suggested that the bundles run parallel to the long axis of the uterus and thin filaments seemed to form cross-links between collagen fibers. In contrast, large clear spaces, collagen fragments, and loosely packed bundles of collagen were observed in the EX of animals injected with estradiol 24 hr earlier. In a time course study (0, 1, 2, 4, 24, and 48 hr), estradiol treatment altered collagen structure and organization 1 hr following administration. Collagen bundles did not appear to be as densely packed as in control tissues and large clear spaces were evident in the EX. Two hours following estrogen administration, collagen fibers appeared to be fragmented and seemed to be separating from the plasma membrane of stromal cells. Four hours following estrogen administration, large clear spaces occupied most of the EX in the lamina propria. Collagen fragments were diffusely distributed throughout the EX and small cross-sectional patches of collagen bundles were present. In 48-hr-treated animals, collagen bundles reappeared and were often closely associated with the plasma membrane of stromal cells. The collagen was not as abundant as in control animals. An overview of the cellular organization of the lamina propria revealed that stromal cells in control tissues were more densely packed than in estradiol-treated tissues (4, 24, and 48 hr) and the stromal cell size appeared to increase in hormone-treated tissues. These responses provide a good model system to study the role of estradiol in the control of collagen structure and organization in the uterus.