How should we define mammary stem cells?

Trends Cell Biol. 2021 Aug;31(8):621-627. doi: 10.1016/j.tcb.2021.03.012. Epub 2021 Apr 23.

Abstract

Mammary stem cells (MaSCs) have been defined by cell surface marker expression and their ability to repopulate a cleared fat pad, a capacity now known to result from reprogramming upon transplantation. Furthermore, lineage-tracing studies have provoked controversy as to whether MaSCs are unipotent or bi/multipotent. Various innovative experimental approaches, including single-cell RNA sequencing (scRNA-Seq), epigenetic analyses, deep tissue and live imaging, and advanced mouse models, have provided new and unexpected insights into stem and progenitor cells; thus, it is now timely to reappraise our concept of the MaSC hierarchy. Here, I highlight misconceptions, suggest definitions of stem and progenitor cells, and propose a way forward in our search for an understanding of MaSCs.

Keywords: hierarchy; mammary; progenitor; quiescent; stem.

Publication types

  • Research Support, Non-U.S. Gov't
  • Review

MeSH terms

  • Animals
  • Cell Differentiation
  • Cell Lineage
  • Mammary Glands, Animal*
  • Mice
  • Stem Cells*