Sinus‐like dilatations of the mammary milk ducts, Ki67 expression, and CD3‐positive T lymphocyte infiltration, in the mammary gland of wild European rabbits during pregnancy and lactation

Abstract

Sinus‐like dilatations of the mammary duct are recognisable in the mammary gland of pregnant and lactating wild European rabbits. These dilatations exhibit a bilaminar epithelial lining, with luminal epithelial cells expressing basal and lateral E‐cadherin. Occasional binucleated mammary epithelial cells are present in the luminal layer. Underlying the luminal epithelial cells is a basal layer of cytokeratin 14‐positive cells, supported by a thin layer of fibrous tissue. Multi‐segmental epithelial proliferation, as indicated by Ki67 expression, is apparent in the luminal epithelial cells, suggesting a capacity for division during pregnancy and lactation. CD3‐positive T lymphocytes are present both intraepithelially, suggesting exocytosis, and in foci subjacent to the ductular epithelium. We consider that sinus‐like dilatations of the mammary duct may have the potential to give rise to a subset of the mammary gland neoplasms classified as ductal in origin. Milk accumulation in these sinus‐like dilatations is likely to provide a niche for bacterial replication in cases of mastitis in rabbits. These structures are an important component of the innate immune system of the mammary gland, both as a physical barrier and as an interface between the milk and mammary immune cells.

Size of supernumerary teats in sheep correlates with complexity of the anatomy and microenvironment

“…Intraepithelial CD3-positive T lymphocytes, indicative of exocytosis, were also present in the bilaminar epithelial lining of the supernumerary teat cistern. This finding is consistent with other species: we have previously described intraepithelial CD3-positive T-lymphocytes in the epithelial lining of sinus-like dilations of the mammary ducts of rabbits and in foci adjacent to the mammary ducts (Hughes & Watson, 2018b) and infiltration of lymphocytes also occurs in the bovine teat cistern (Nickerson & Pankey, 1983). Iba-1-positive cells, with morphology and location consistent with macrophages, were also present adjacent to the supernumerary teat cistern (Fig.…”

Mammary mechanobiology: mechanically-activated ion channels in lactation and involution

“…Routine processing and paraffin embedding was performed; immersion in 70% ethanol (45 min), 90% ethanol (45 min slides were imaged on an Olympus VS120-L100-W Slide Scanner. Rabbit mammary tissue was collected and fixed in NBF (10%), processed and sectioned at 5 µm, as previously described (64).…”

Puberty is a critical window for the impact of diet on mammary gland development in the rabbit

“…Although histological analysis did not reveal any changes to the mammary epithelium, we investigated the integrity of MEC. One frequently studied molecular component of the adherent junctions is the adhesion receptor E‐cadherin (Cdh1), which is expressed in MEC during pregnancy . At 8 days of pregnancy, Cdh1 expression was below the detection threshold in LCM‐captured MEC.…”

“…One frequently studied molecular component of the adherent junctions is the adhesion receptor E-cadherin (Cdh1), which is expressed in MEC during pregnancy. 35,36 At 8 days of pregnancy, Cdh1 expression was below the detection threshold in LCM-captured MEC. However, E-cadherin was detected by immunolabelling, in basolateral position of MEC in both CD and OD mammary tissue ( Figure 8).…”