Figure 5.

Effects of early and late deletion of mouse Cripto-1 on proliferation. Proliferation-positive cells were scored and labeling index expressed as a percentage of positive nuclei from at least 3000 counted cells in mammary glands. A: Representative immunohistochemical sections of mammary tissue collected from FVB/N, whey acidic protein-Cre⁺/Cripto^flox (WAP-CRKO), and MMTV-Cre⁺/Cripto^flox (MMTV-CRKO) mice at indicated times: 10-week-old nulliparous females (10 wk), 6 days pregnancy (Early preg.), 15 days pregnancy (Late preg.), one day lactation (1D lac.), and 3 days involution (Early Inv.). Mouse tissue was fixed and processed for proliferation marked by proliferating cell nuclear antigen expression, as described in Materials and Methods. Arrows indicate representative positive cells for proliferation. B: Positive cells were scored and labeling index was expressed as a percentage of positive nuclei from 3000 counted cells. Mammary epithelial proliferation is significantly lower in the WAP-CRKO and MMTV-CRKO mice mammary glands than the matching FVB/N mice for early and late pregnancy. Also, mammary epithelial proliferation of MMTV-CRKO is significantly lower than WAP-CRKO for early and late pregnancy. In contrast, cell proliferation is significantly higher in the 3 days involuting mammary glands of mCripto-1 KO mice than the matching control FVB/N involuting mammary glands. A total of at least five to six mice were used for each experiment. ^∗P < 0.05. Original magnification, ×100 (A).