Boras-Granic Kata, Dann Pamela, Wysolmerski John J
Section of Endocrinology and Metabolism Department of Internal Medicine, Yale University School of Medicine TAC S131, Box 208020, New Haven, CT, 06520-8020, USA.
Breast Cancer Res. 2014 Dec 3;16(6):487. doi: 10.1186/s13058-014-0487-6.
Studies have identified multi-potent stem cells in the adult mammary gland. More recent studies have suggested that the embryonic mammary gland may also contain stem/progenitor cells that contribute to initial ductal development. We were interested in determining whether embryonic cells might also directly contribute to long-lived stem cells that support homeostasis and development in the adult mammary gland.
We used DNA-label retention to detect long label-retaining cells in the mammary gland. Mouse embryos were labeled with 5-ethynl-2'-deoxyuridine (EdU) between embryonic day 14.5 and embryonic day 18.5 and were subsequently sacrificed and examined for EdU retention at various intervals after birth. EdU retaining cells were co-stained for various lineage markers and identified after fluorescence activated cell sorting analysis of specific epithelial subsets. EdU-labeled mice were subjected to subsequent 5-bromo-2'-deoxyuridine administration to determine whether EdU-labeled cells could re-enter the cell cycle. Finally, EdU-labeled cells were grown under non-adherent conditions to assess their ability to form mammospheres.
We demonstrate embryonically-derived, long label-retaining cells (eLLRCs) in the adult mammary gland. eLLRCs stain for basal markers and are enriched within the mammary stem cell population identified by cell sorting. eLLRCs are restricted to the primary ducts near the nipple region. Interestingly, long label retaining cells (labeled during puberty) are found just in front of the eLLRCs, near where the ends of the ducts had been at the time of DNA labeling in early puberty. A subset of eLLRCs becomes mitotically active during periods of mammary growth and in response to ovarian hormones. Finally, we show that eLLRCs are contained within primary and secondary mammospheres.
Our findings suggest that a subset of proliferating embryonic cells subsequently becomes quiescent and contributes to the pool of long-lived mammary stem cells in the adult. eLLRCs can re-enter the cell cycle, produce both mammary lineages and self-renew. Thus, our studies have identified a putative stem/progenitor cell population of embryonic origin. Further study of these cells will contribute to an understanding of how quiescent stem cells are generated during development and how fetal exposures may alter future breast cancer risk in adults.
研究已在成年乳腺中鉴定出多能干细胞。最近的研究表明，胚胎乳腺中可能也含有有助于初始导管发育的干细胞/祖细胞。我们感兴趣的是确定胚胎细胞是否也可能直接产生支持成年乳腺内稳态和发育的长寿干细胞。
我们使用DNA标记保留法来检测乳腺中的长时程标记保留细胞。在胚胎第14.5天至胚胎第18.5天之间，用5-乙炔基-2'-脱氧尿苷（EdU）标记小鼠胚胎，随后将其处死，并在出生后的不同时间间隔检查EdU的保留情况。对保留EdU的细胞进行多种谱系标记的共染色，并在对特定上皮亚群进行荧光激活细胞分选分析后进行鉴定。对用EdU标记的小鼠随后给予5-溴-2'-脱氧尿苷，以确定EdU标记的细胞是否能重新进入细胞周期。最后，将EdU标记的细胞在非贴壁条件下培养，以评估它们形成乳腺球的能力。
我们在成年乳腺中证实了胚胎来源的长时程标记保留细胞（eLLRCs）。eLLRCs表达基底标记，并且在通过细胞分选鉴定的乳腺干细胞群体中富集。eLLRCs局限于乳头区域附近的初级导管。有趣的是，长时程标记保留细胞（在青春期标记）位于eLLRCs前方，靠近青春期早期DNA标记时导管末端所在的位置。一部分eLLRCs在乳腺生长期间以及对卵巢激素的反应中进入有丝分裂活跃状态。最后，我们表明eLLRCs存在于初级和次级乳腺球中。
我们的研究结果表明，一部分增殖的胚胎细胞随后进入静止状态，并对成年乳腺中长寿乳腺干细胞库有贡献。eLLRCs可以重新进入细胞周期，产生乳腺谱系并自我更新。因此，我们的研究鉴定出了一个假定的胚胎来源的干细胞/祖细胞群体。对这些细胞的进一步研究将有助于理解在发育过程中静止干细胞是如何产生的，以及胎儿暴露如何改变成年人未来患乳腺癌的风险。
