Fig. 5. X-Gal staining of primary cultures of mammary epithelial cells (A-H,L), mammary fibroblasts (I), and a whole mount (J) and its corresponding histological section (K) of an outgrowth from transplanted dissociated cells of parous (involuted) WAP-Cre/Rosa-lacZ mice into the cleared fat pad of nulliparous wild-type recipients. Note the high proliferative capacity of blue cells derived from parous WAP-Cre/Rosa-lacZ mice and cultured for 48 (A) and 72 hours (B). Grown as a monolayer, these blue parity-induced cells do not differ in their morphology from other epithelial subtypes (C), and they can actively migrate away from epithelial colonies (D). Epithelial cells derived from nulliparous double transgenic mice and cultured for 48 (E,F) and 72 hours (G) are mostly X-Gal negative. The few blue cells detected in these early cultures of nulliparous controls do not expand even after 96 hours in culture (H). Note also that mammary fibroblasts of parous double transgenic animals are X-Gal negative (I). (J) Reconstitution of the ductal tree after transplantation of a small number of epithelial cells from parous, non-pregnant WAP-Cre/Rosa-lacZ mice into the cleared fat pad of nulliparous wild-type recipients (limiting dilution experiment; X-Gal whole-mount staining). (K) Histological section of J counterstained with nuclear Fast Red.
