[Uterine collagens. General review]

Abstract

Several collagen types (mainly types I, III, V and VI), elastin, fibronectin and some proteoglycans are active constituents of uterine myometer. They surround and associate smooth muscle cells. The type I collagen biosynthesis in the uterus is under the positive control of estrogens that in addition repress the collagenase secretion and in this way prevent collagen from degradation. The cervical softening and dilation are caused by a progressive degradation of collagen and by the synthesis of an additional proteoglycan that separates and disorganizes the collagen fibres. Prostaglandin E2 and relaxin participate in the activation of collagenases. After delivery, the drop in estrogens and progesterone permits collagenases to rapidly degrade uterine collagen in excess.