Booth Brian W, Boulanger Corinne A, Smith Gilbert H
Mammary Biology and Tumorigenesis Laboratory, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA.
J Cell Physiol. 2007 Sep;212(3):729-36. doi: 10.1002/jcp.21071.
We have previously described pluripotent, parity-induced mammary epithelial cells (PI-MEC) marked by Rosa26-lacZ expression in the mammary glands of parous females. PI-MEC act as lobule-limited epithelial stem/progenitor cells. To determine whether parity is necessary to generate PI-MEC, we incubated mammary explant cultures from virgin mice in vitro with insulin alone (I), hydrocortisone alone (H), prolactin alone (Prl), or a combination of these lactogenic hormones (IHPrl). Insulin alone activated the WAP-Cre gene. Hydrocortisone and prolactin alone did not. Any combination of hormones that included insulin was effective. Only I, H and Prl together were able to induce secretory differentiation and milk protein synthesis. In addition, EGF, IGF-2 and IGF-1 added individually produced activated (lacZ(+)) PI-MEC in explant cultures. Neither estrogen nor progesterone induced WAP-Cre expression in the explants. None of these positive initiators of WAP-Cre expression in PI-MEC were effective in mammospheres or two-dimensional cultures of mammary epithelium, indicating the indispensability of epithelial-stromal interaction in PI-MEC activation. Like PI-MEC, lacZ(+) cells from virgin explants proliferated and contributed progeny to mammospheres in vitro and to epithelial outgrowths in vivo after transplantation. LacZ(+) cells induced in virgin mouse mammary explants were multipotent (like PI-MEC) in impregnated hosts producing lacZ(+) mammary alveolar structures comprised of both myoepithelial and luminal progeny. These data demonstrate PI-MEC, a mammary epithelial sub-population of lobule-limited progenitor cells, are present in nulliparous female mice before parity and, like the PI-MEC observed following parity, are capable of proliferation, self-renewal and the capacity to produce progeny of diverse epithelial cell fates.
我们之前描述过，在经产雌性小鼠乳腺中，以Rosa26 - lacZ表达为标记的多能、经产诱导乳腺上皮细胞（PI - MEC）。PI - MEC作为小叶局限性上皮干细胞/祖细胞。为了确定经产对于生成PI - MEC是否必要，我们将未孕小鼠的乳腺外植体培养物在体外分别与单独的胰岛素（I）、单独的氢化可的松（H）、单独的催乳素（Prl）或这些泌乳激素的组合（IHPrl）一起孵育。单独的胰岛素激活了WAP - Cre基因。单独的氢化可的松和催乳素则没有。任何包含胰岛素的激素组合都是有效的。只有I、H和Prl共同作用才能诱导分泌分化和乳蛋白合成。此外，单独添加表皮生长因子（EGF）、胰岛素样生长因子2（IGF - 2）和胰岛素样生长因子1（IGF - 1）能在乳腺外植体培养物中产生活化的（lacZ(+)）PI - MEC。雌激素和孕激素均未在这些外植体中诱导WAP - Cre表达。这些PI - MEC中WAP - Cre表达的阳性启动子在乳腺球或乳腺上皮的二维培养中均无效，这表明上皮 - 基质相互作用在PI - MEC激活中不可或缺。与PI - MEC一样，来自未孕外植体的lacZ(+)细胞在体外增殖并为乳腺球提供子代，在体内移植后为上皮生长提供子代。在妊娠宿主中，未孕小鼠乳腺外植体中诱导产生的lacZ(+)细胞具有多能性（类似于PI - MEC），可产生由肌上皮和管腔子代组成的lacZ(+)乳腺腺泡结构。这些数据表明，PI - MEC是小叶局限性祖细胞的乳腺上皮亚群，在未孕雌性小鼠经产之前就已存在，并且与经产后观察到的PI - MEC一样，能够增殖、自我更新并产生具有不同上皮细胞命运的子代。
