Histologic, morphometric, and immunocytochemical analysis of myometrial development in rats and mice: I. Normal development

Abstract

Myometrial development from the prenatal to adult period was examined in rats and mice 1) by histologic and immunocytochemical methods with anti-actin, -vimentin, and -laminin to assess cytodifferentiation of smooth muscle and fibroblastic cells; and 2) by morphometric procedures to assess quantitatively the expression of cellular orientation in the emerging inner circular myometrial layer. Uterine mesenchymal cells initially were uniformly vimentin-positive, undifferentiated, and randomly oriented during the late fetal period. By the early neonatal period, three mesenchymal layers became recognizable histologically, the middle one of which (prospective circular myometrium) developed distinct circular orientation and differentiated into a layer composed of actin-positive smooth muscle cells. The cells of the inner mesenchymal layer initially exhibited radial orientation. By 10 days postpartum, the outer longitudinal mesenchymal layer differentiated into bundles of smooth muscle cells representing the longitudinal myometrium. The inner mesenchymal layer remained vimentin-positive and differentiated into the randomly ordered endometrial stroma. The cells of the middle and outer mesenchymal layers that were destined to form myometrium initially expressed vimentin throughout and then coexpressed vimentin and actin, but with time vimentin staining disappeared in the maturing smooth muscle cells as they expressed actin.

Follistatin is essential for normal postnatal development and function of mouse oviduct and uterus

“…1m-p). However, segregation of the uterine mesenchymal cells into layers (inner, middle and outer) was apparent (Brody and Cunha 1989). Occasional leukocytes were observed in the uterine mesenchyme at PND0 for WT and transgenic mice (Fig.…”

Postnatal Deletion of Wnt7a Inhibits Uterine Gland Morphogenesis and Compromises Adult Fertility in Mice.

“…By PND 6, epithelial invaginations appear that represent formation of GE buds [10]. By PND 12, endometrial glands extend from the LE into the surrounding endometrial stroma, and the outer longitudinal layer of the myometrium is fully organized into bundles [3]. The basic adult configuration of the uterus in mice is established by PND 15 [11].…”

“…At birth, the neonatal mouse uterus lacks endometrial glands and consists of a simple LE supported by relatively undifferentiated mesenchyme [3]. Between birth (Postnatal Day [PND] 0) and PND 3, the three layers of mesenchyme are distinctly segregated into radially oriented endometrial stroma and inner circular and prospective outer longitudinal myometrial layers.…”

“…The histological organization of the adult uterine endometrium consists of a simple columnar luminal epithelium (LE) supported by stromal cells that contain coiled endometrial glands lined by simple columnar epithelial cells or glandular epithelium (GE) [1][2][3]. Circular and longitudinal layers of smooth muscle, termed the myometrium, surround the endometrium.…”

Interaction between genetic susceptibility and early-life environmental exposure determines tumor-suppressor-gene penetrance

“…To determine the effect of an environmental exposure during development on the myometrium of Eker rats, animals (Tsc-2 ϩ/ϩ and Tsc-2 Ek/ϩ ) were exposed to the xenoestrogen DES during neonatal days 3-5 of development, a critical period of myometrial differentiation (35). At postnatal day 21, before the onset of puberty (which in the rat is Ϸday 35), no differences were observed in the morphology of the immature uteri of animals exposed to VEH (neoVEH) or DES (neoDES) neonatally ( Fig.…”