Form and function: how estrogen and progesterone regulate the mammary epithelial hierarchy

Area of Science:

• Reproductive biology
• Cell biology
• Endocrinology

Background:

• The mammary gland exhibits significant post-natal growth, development during pregnancy/lactation, and regression post-lactation.
• This cyclical process suggests a hierarchy of stem and progenitor cells responsible for mammary epithelial regeneration.
• Ovarian steroids, estrogen and progesterone, are known regulators of mammary epithelial cell expansion.

Purpose of the Study:

• To review the current understanding of estrogen and progesterone regulation of mammary stem and progenitor cells.
• To explore the combined and separate actions of these hormones in human and mouse mammary tissues.
• To highlight the potential of this research for understanding breast cancer subtypes.

Main Methods:

• Review of existing literature on mammary gland development and hormonal regulation.
• Analysis of studies identifying mammary stem and progenitor cells via cell surface markers and functional assays.
• Comparative examination of hormonal effects in human and mouse models.

Main Results:

• Estrogen, via estrogen receptor alpha (ERα), and progesterone, via progesterone receptor (PR), play critical roles in regulating mammary epithelial cell populations.
• Diverse stem and progenitor cell populations exist within the mammary gland, characterized by specific markers and functions.
• Hormonal milieu significantly impacts the hierarchical organization and regulation of these cell populations.

Conclusions:

• Estrogen and progesterone are central regulators of mammary stem and progenitor cell dynamics.
• Understanding the interplay between hormones and mammary stem cells offers insights into normal gland function.
• Further research into these mechanisms may elucidate the origins of various breast cancer subtypes.