Figure 1. A Schematic Representation of Cyclical Adipocyte Dedifferentiation and Redifferentiation in the Mammary Gland during Reproduction.

Adipocytes account for the majority of the tissue volume in the virgin mammary gland. During pregnancy, mature adipocytes acquire morphological features and transcriptional signatures comparable to preadipocytes, as the mammary epithelium expands to produce milk. Upon weaning, the mammary tissue undergoes involution to a quiescent state similar to the pre-pregnancy mammary gland. During this process, the bulk of secretory epithelium is eliminated by apoptosis, and the preadipocyte-like precursors originally derived from mammary adipocytes repopulate the mammary gland by redifferentiating into mature adipocytes.