Ultrastructural Changes in the Uterine Luminal and Glandular Epithelium during the Oestrous Cycle of the Marsupial <i>Monodelphis domestica</i> (Grey Short-Tailed Opossum)

Abstract

Ultrastructural changes in the endometrium associated with the oestrous cycle were studied in the South American marsupial Monodelphis domestica. The most conspicuous changes include the height and the differentiation of the uterine luminal and glandular epithelium, which consists of ciliated and non-ciliated cells. The glandular epithelium attains its maximum development during oestrus, the luminal epithelium at postoestrus. A distinct increase in the number of ciliated cells can be observed during pro-oestrus, reaching a maximum number at oestrus; this is followed by a process of deciliation. The presence of solitary cilia on the apices of non-ciliated cells is very conspicuous during all oestrous stages and can best be seen on the luminal epithelium. These findings differ from the observations in eutherian mammals, where solitary cilia are only found in the immature uterus or after ovariectomy. The secretory activity of non-ciliated cells of the luminal epithelium is hardly noticeable along the apical membrane and stains only very faintly with Alcian blue. The glandular epithelium cells are filled apically with exocytotic vesicles at oestrus and early postoestrus. However, in contrast to the cervical gland cells, they hardly stain with Alcian blue, indicating that mucins of a different type must be present. Mechanisms for the remodelling of the luminal and glandular epithelium are especially conspicuous at metoestrus and early pro-oestrus and include the presence of autolysosomes, residual bodies and apoptotic bodies. In the endometrial stroma, around the uterine glands, macrophages accumulate and attain a typical oestrous stage-dependent appearance during their phagocytotic activities.

Evolution of mammalian pregnancy and the origin of the decidual stromal cell

“…The dominant feature of the marsupial endometrium are the endometrial glands, that even further increase in amount and density during pregnancy (Cruz and Selwood, 1993, Cruz and Selwood, 1997, Fleming and Harder, 1981. The stromal compartment is cell poor, with large spaces filled with extracellular matrix Selwood, 1997, Wick andKress, 2002)(see also Fig. 5.7 in Tyndale-Biscoe and Renfree, 1987).…”

“…Cyclical changes in the structure of the luminal and glandular epithelia are also occurring during the non-pregnant sexual cycle (Wick and Kress, 2002). In proestrus the LE is a thin (15 mm) and tightly packed "palisade" epithelium with dome-shaped apical extensions.…”

“…Enders and Enders described, but did not document, in the four eyed opossum, Philander opossum, "slightly enlarged fibroblasts which may constitute a primitive decidual reaction" at the localized sites of LE penetration (Enders and Enders, 1969). In Monodelphis during pregnancy as well during the sexual cycle the stroma becomes edematic and cell poor (Wick and Kress, 2002) and the dense layer of sub-epithelial fibroblast cells essentially disappears (K. Kin and G.P. Wagner, in preparation).…”

Novel immunocontraceptive targets in mammals: uterine secretions and the conceptus; a marsupial approach

“…In an oestrous cycle-dependent manner, a layer of macrophages and lymphocytes, presumably capable of acting as APCs, is found beneath the luminal epithelium in didelphid and dasyurid marsupials (Padykula 1976, Cruz & Selwood 1993, 1997, Wick & Kress 2002 and EPF has been identified in some marsupials (Cruz et al 2006), including Trichosurus vulpecula (Cui et al 2001).…”

“…Non-reproductive somatic tissues (heart, kidney, lens, liver and lung), immune tissues (lymph node and spleen) and reproductive tissues (ovary, oviduct, uterus, epididymis and testis) were collected from animals immunized against GST-CP4, GST and PBS processed for histology and compared with samples from unimmunized animals collected from the wild. Uterine morphology and immune cell distribution was compared between immunized (nZ6), control immunized (nZ1), unimmunized (nZ17) and published standards (Shorey & Hughes 1973, Padykula 1976, Cruz & Selwood 1993, 1997, Wick & Kress 2002.…”