Mammary alveolar epithelial cells convert to brown adipocytes in post-lactating mice

J Cell Physiol. 2017 Nov;232(11):2923-2928. doi: 10.1002/jcp.25858. Epub 2017 Mar 24.


During pregnancy and lactation, subcutaneous white adipocytes in the mouse mammary gland transdifferentiate reversibly to milk-secreting epithelial cells. In this study, we demonstrate by transmission electron microscopy that in the post-lactating mammary gland interscapular multilocular adipocytes found close to the mammary alveoli contain milk protein granules. Use of the Cre-loxP recombination system allowed showing that the involuting mammary gland of whey acidic protein-Cre/R26R mice, whose secretory alveolar cells express the lacZ gene during pregnancy, contains some X-Gal-stained and uncoupling protein 1-positive interscapular multilocular adipocytes. These data suggest that during mammary gland involution some milk-secreting epithelial cells in the anterior subcutaneous depot may transdifferentiate to brown adipocytes, highlighting a hitherto unappreciated feature of mouse adipose organ plasticity.

Keywords: Cre-loxP recombination system; adipose organ; electron microscopy; mammary gland; pregnancy.

MeSH terms

  • Adipocytes, Brown / metabolism
  • Adipocytes, Brown / physiology*
  • Adipocytes, Brown / ultrastructure
  • Animals
  • Cell Lineage
  • Cell Plasticity
  • Cell Transdifferentiation*
  • Epithelial Cells / metabolism
  • Epithelial Cells / physiology*
  • Epithelial Cells / ultrastructure
  • Female
  • Genotype
  • Integrases / genetics
  • Lactation*
  • Mammary Glands, Animal / cytology*
  • Mammary Glands, Animal / metabolism
  • Mammary Glands, Animal / ultrastructure
  • Mice, Inbred C57BL
  • Mice, Transgenic
  • Microscopy, Electron, Transmission
  • Milk Proteins / genetics
  • Milk Proteins / metabolism
  • Phenotype
  • Pregnancy
  • RNA, Untranslated / genetics
  • Uncoupling Protein 1 / metabolism
  • Weaning*
  • beta-Galactosidase / genetics
  • beta-Galactosidase / metabolism


  • Gt(ROSA)26Sor non-coding RNA, mouse
  • Milk Proteins
  • RNA, Untranslated
  • Ucp1 protein, mouse
  • Uncoupling Protein 1
  • whey acidic proteins
  • Cre recombinase
  • Integrases
  • beta-Galactosidase