Bovine mammary gland development: new insights into the epithelial hierarchy

Abstract

Milk production is highly dependent on the extensive development of the mammary epithelium, which occurs during puberty. It is therefore essential to distinguish the epithelial cells committed to development during this key stage from the related epithelial hierarchy. Using cell phenotyping and sorting, we highlighted three sub-populations that we assume to be progenitors. The CD49fhighCD24neg cells expressing KRT14, vimentin and PROCR corresponded to basal progenitors whereas the CD49flowCD24neg cells expressing luminal KRT, progesterone and prolactin receptors, were of luminal lineage. The CD49flowCD24pos cells had features of a dual lineage, with luminal and basal characteristics (CD10, ALDH1 and KRT7 expression) and were considered to be early common (bipotent) progenitors. The mammary stem cell (MaSC) fraction was recovered in a fourth sub-population of CD49fhighCD24pos cells that expressed CD10/KRT14 and KRT7. The differential ALDH1 activities observed within the MaSC fraction allowed to discriminate between two states: quiescent MaSCs and lineage-restricted “activated” MaSCs. The in-depth characterization of these epithelial sub-populations provides new insights into the epithelial cell hierarchy in the bovine mammary gland and suggests a common developmental hierarchy in mammals.

Investigation of lncRNA in Bos taurus Mammary Tissue during Dry and Lactation Periods

“…Between birth and puberty, the mammary gland (which includes the nipple, areola, stroma, and parenchyma) is and remains primarily underdeveloped. The surging levels of hormones lead the mammary tissue to increase in size during puberty, but this growth does not proceed past the filling of the mammary fat pad at which time, and the duct network has begun to branch but is not fully developed [ 10 ]. Gestation leads to the final developmental push in the mammary gland where the parenchyma increases in size and its duct system finishes branching.…”

TGF-beta signalling in bovine mammary gland involution and a comparative assessment of MAC-T and BME-UV1 cells as in vitro models for its study

“…CD49f is responsible for cell-matrix adhesions and for transmitting signals between mammary epithelial cells and the ECM (Giancotti & Ruoslahti, 1999). CD49f is expressed in cells of both luminal and basal origin; however, it is more highly expressed in basal cells (Finot, Chanat & Dessauge, 2018; Rauner & Barash, 2012; Perruchot et al, 2016). CD10, on the other hand, is normally used as a marker of basal cells (Safayi et al, 2012), but it is also enriched in mammosphere-forming cell populations; hence CD10 is also used as a marker of stem cells (Maguer-Satta, Besançon & Bachelard-Cascales, 2011).…”

“…A further step would be to compare the effect of TGFβ1 on MAC-T cells to that on bi-potent progenitors derived from bovine mammary explants, in order to evaluate if cell line immortalization is a confounding variable. In recent years, several different models of epithelial cell hierarchy in the bovine mammary gland have been proposed (Rauner & Barash, 2012; Perruchot et al, 2016; Finot, Chanat & Dessauge, 2018). A better understanding of lineage commitment to basal or luminal phenotypes may shed light on the different origins of MAC-T and BME-UV1 cells, and thus guide their appropriate use in studies aimed to elucidate the role of TGFβ in bovine mammary epithelium apoptosis and bovine mammary gland biology in general.…”