During early embryogenesis, mammary glands are derived from surface ectoderm and their morphogenesis is controlled by mammary stem cells (MaSCs) and epithelial-mesenchymal transition (EMT). Mammary anlagen stage (E13.5–15.5) is an important stage for fetal mice to achieve EMT dependent mammary morphogenesis. And the characteristics of mammary anlagen repopulating cell population (MaRC) should be identified for understanding its stemness at earlier embryonic stage. Here we quantify and characterize MaSCs proportion at mammary anlagen stage. Compared with adult mouse mammary gland, our data revealed that E14.5 mammary anlagen exhibit higher stem cell activities. Then we purified mammary anlagen cell populations depending on the expression levels of CD24 and CD49f in mouse mammary anlagen, and identified an unique MaRC population (Lin-CD24medCD49f+) by real-time PCR, transplantation and mammosphere forming assays. In addition, by comparing with adult MaSC (Lin-CD24+CD29hi) and differentiated mammary anlagen cells, we find that E14.5 mouse MaRC population exhibit gene expression programs related to mesenchymal properties. To further identify the cell types of E14.5 mouse MaRC population, the expressions of K8, K14, K18, e-cadherin, n-cadherin and vimentin in mammary anlagen Lin-CD24medCD49f + cells were detected by immunofluorescence assay. These findings verified that the undifferentiated E14.5 mouse MaRC population is a heterogeneous population with mesenchymal property, which is associated with cell stemness and mammary duct morphogenesis.

在早期胚胎发生过程中，乳腺来源于表面外胚层，其形态发生由乳腺干细胞 (MaSCs) 和上皮间质转化 (EMT) 控制。乳腺原原阶段 (E13.5–15.5) 是胎鼠实现 EMT 依赖性乳腺形态发生的重要阶段。应确定乳腺原原再生细胞群 (MaRC) 的特征，以了解其在早期胚胎阶段的干性。在这里，我们量化和表征了乳腺原原阶段的 MaSCs 比例。与成年小鼠乳腺相比，我们的数据显示 E14.5 乳腺原素表现出更高的干细胞活性。然后我们根据小鼠乳腺原素中 CD24 和 CD49f 的表达水平纯化乳腺原原细胞群，并通过实时 PCR、移植和乳腺球形成分析鉴定了一个独特的 MaRC 群体 (Lin-CD24medCD49f+)。此外，通过与成年 MaSC (Lin-CD24+CD29hi) 和分化的乳腺原原细胞进行比较，我们发现 E14.5 小鼠 MaRC 群体表现出与间充质特性相关的基因表达程序。为了进一步鉴定E14.5小鼠MaRC群体的细胞类型，采用免疫荧光法检测乳腺原原Lin-CD24medCD49f + 细胞中K8、K14、K18、e-cadherin、n-cadherin和vimentin的表达。这些发现证实未分化的 E14.5 小鼠 MaRC 群体是具有间充质特性的异质群体，这与细胞干性和乳腺导管形态发生有关。通过与成年 MaSC (Lin-CD24+CD29hi) 和分化的乳腺原原细胞进行比较，我们发现 E14.5 小鼠 MaRC 群体表现出与间充质特性相关的基因表达程序。为进一步鉴定E14.5小鼠MaRC群体的细胞类型，采用免疫荧光法检测乳腺原原Lin-CD24medCD49f + 细胞中K8、K14、K18、e-cadherin、n-cadherin和vimentin的表达。这些发现证实未分化的 E14.5 小鼠 MaRC 群体是具有间充质特性的异质群体，这与细胞干性和乳腺导管形态发生有关。通过与成年 MaSC (Lin-CD24+CD29hi) 和分化的乳腺原原细胞进行比较，我们发现 E14.5 小鼠 MaRC 群体表现出与间充质特性相关的基因表达程序。为了进一步鉴定E14.5小鼠MaRC群体的细胞类型，采用免疫荧光法检测乳腺原原Lin-CD24medCD49f + 细胞中K8、K14、K18、e-cadherin、n-cadherin和vimentin的表达。这些发现证实未分化的 E14.5 小鼠 MaRC 群体是具有间充质特性的异质群体，这与细胞干性和乳腺导管形态发生有关。5小鼠MaRC群体，免疫荧光法检测乳腺原原Lin-CD24medCD49f + 细胞K8、K14、K18、e-cadherin、n-cadherin和vimentin的表达。这些发现证实未分化的 E14.5 小鼠 MaRC 群体是具有间充质特性的异质群体，这与细胞干性和乳腺导管形态发生有关。5小鼠MaRC群体，免疫荧光法检测乳腺原原Lin-CD24medCD49f + 细胞K8、K14、K18、e-cadherin、n-cadherin和vimentin的表达。这些发现证实未分化的 E14.5 小鼠 MaRC 群体是具有间充质特性的异质群体，这与细胞干性和乳腺导管形态发生有关。