Fig. 1

Histological analysis of mammary glands undergoing gradual vs. abrupt involution. A. Schematic diagram showing the workflow of mice subjected to abrupt involution (AI) and gradual involution (GI) followed by different harvest times. B. Representative images of H&E-stained sections of mouse mammary glands subjected to AI or GI and harvested at different days postpartum (PPM) as indicated. Scale bar = 200 μm C. Higher magnification images of H&E-stained section of GI mammary gland on indicated postpartum days. Day 8.5, 11 and 12: black arrows indicate large acini, and clear arrows indicate epithelial cells. Day17: clear arrows indicate epithelial cells, curved black arrows indicate a small group of adipocytes; Day 22: clear arrows indicate flattened epithelial cells, black arrows indicate the nuclear debris and arrowheads indicate repopulating adipocytes. Day 25: arrow heads indicate repopulating adipocytes; black arrows indicate immune cells. D. H&E-stained section of AI mammary gland on day 8.5: Grey arrow indicate lactating acini, black arrowheads indicate flattened epithelial cells and black arrows indicate karyorrhectic debris. Day 11: Grey arrows indicate collapsed alveoli, black arrows indicate immune cells and arrowheads indicate adipocytes. Day 12: arrowheads indicate adipose tissues, and black arrows indicate immune cells. Day17: arrow heads indicate adipose tissues. (C&D: Scale bar = 100 μm). E. Adipocyte repopulation over time, from day 7 to day 35 PPM. n = 6 per group per time point. F. Comparison of total number of adipocytes in AI and GI glands harvested on day 28 PPM. G. Comparison of total number of adipocytes categorized by size in AI vs.GI glands