Critical Review on Physiological and Molecular Features during Bovine Mammary Gland Development: Recent Advances

Abstract

The mammary gland is a unique organ with the ability to undergo repeated cyclic changes throughout the life of mammals. Among domesticated livestock species, ruminants (cattle and buffalo) constitute a distinct class of livestock species that are known milk producers. Cattle and buffalo contribute to 51 and 13% of the total milk supply in the world, respectively. They also play an essential role in the development of the economy for farming communities by providing milk, meat, and draft power. The development of the ruminant mammary gland is highly dynamic and multiphase in nature. There are six developmental stages: embryonic, prepubertal, pubertal, pregnancy, lactation, and involution. There has been substantial advancement in our understanding of the development of the mammary gland in both mouse and human models. Until now, there has not been a thorough investigation into the molecular processes that underlie the various stages of cow udder development. The current review sheds light on the morphological and molecular changes that occur during various developmental phases in diverse species, with a particular focus on the cow udder. It aims to explain the physiological differences between cattle and non-ruminant mammalian species such as humans, mice, and monkeys. Understanding the developmental biology of the mammary gland in molecular detail, as well as species-specific variations, will facilitate the researchers working in this area in further studies on cellular proliferation, differentiation, apoptosis, organogenesis, and carcinogenesis. Additionally, in-depth knowledge of the mammary gland will promote its use as a model organ for research work and promote enhanced milk yield in livestock animals without affecting their health and welfare.

Bovine mammary epithelial cells can grow and express milk protein synthesis genes at reduced fetal bovine serum concentration

“…Although the exact composition of BPE is unknown, a variety of mitogens, including growth hormone (GH), basic fibroblast growth factor, epidermal growth factor‐like proteins, and platelet‐derived growth factor are present in this extract (Kent & Bomser, 2003). GH is known to regulate lactogenesis and galactopoiesis in the absence of prolactin hormone in ruminants, rats, and humans (Jaswal et al, 2022). However, the undefined composition of BPE can lead to varied cellular responses.…”

“…The milk protein profile at different periods of lactation, including early, peak, and late‐stage variations, is reported to be an indicative of mammary gland intracellular modifications. The protein profile of bovine MECs differs between these stages, influencing metabolic processes, binding, and catalytic activities in udder cells (Jaswal et al, 2022).…”

Cellular characteristics and milk component productivity of primary bovine mammary cells for cell-cultured milk component production

“…The parenchyma of alveoli is composed of inner milk secretory ECs that surround the lumen, outer MCs that attach to the base of the mammary epithelium, and the basement membrane that contacts the MCs. In addition, the stromal compartment comprises various stromal cells, such as FBs, adipocytes, endothelial cells, and the extracellular matrix [26]. Therefore, from the perspective of cellular structure, FBs and MCs are located on the outer side and ECs are positioned on the inner side of the mammary alveolus.…”

“…The cytoskeleton plays an important role in maintaining cellular integrity, structure, and function and has been reported to express different cytoskeletal proteins depending on cell type [26]. Therefore, cytoskeletal protein markers such as CK18, CK19, vimentin, and 𝛼-SMA were used to establish the primary bovine mammary cells [24,26].…”

Polyphenols and Lactation: Molecular Evidence to Support the Use of Botanical Galactagogues

“…The basement membrane separates the mammary epithelium from the stroma, which is made up of a variety of cells (fibroblasts, mesenchymal cells, adipocytes, leukocytes, and blood cells) as well as extracellular matrix (ECM) proteins (i.e., collagen, laminin, fibronectin, proteoglycans, etc.). [30] Successful lactation requires appropriate mammary gland development during embryogenesis, puberty and pregnancy, and the reader is referred to recent excellent reviews on ruminant, [30] rodent, [31] and human [1] mammary gland development, and discussion of differences between species for further insight. [32] In humans, successful lactation requires an exquisitely timed sequence of biological events organized into two stages, secretory differentiation (lactogenesis I) and secretory activation (lactogenesis II).…”