Evidence of two distinct functionally specialized fibroblast lineages in breast stroma

Abstract

BackgroundThe terminal duct lobular unit (TDLU) is the most dynamic structure in the human breast and the putative site of origin of human breast cancer. Although stromal cells contribute to a specialized microenvironment in many organs, this component remains largely understudied in the human breast. We here demonstrate the impact on epithelium of two lineages of breast stromal fibroblasts, one of which accumulates in the TDLU while the other resides outside the TDLU in the interlobular stroma.MethodsThe two lineages are prospectively isolated by fluorescence activated cell sorting (FACS) based on different expression levels of CD105 and CD26. The characteristics of the two fibroblast lineages are assessed by immunocytochemical staining and gene expression analysis. The differentiation capacity of the two fibroblast populations is determined by exposure to specific differentiating conditions followed by analysis of adipogenic and osteogenic differentiation. To test whether the two fibroblast lineages are functionally imprinted by their site of origin, single cell sorted CD271low/MUC1high normal breast luminal epithelial cells are plated on fibroblast feeders for the observation of morphological development. Epithelial structure formation and polarization is shown by immunofluorescence and digitalized quantification of immunoperoxidase-stained cultures.ResultsLobular fibroblasts are CD105high/CD26low while interlobular fibroblasts are CD105low/CD26high. Once isolated the two lineages remain phenotypically stable and functionally distinct in culture. Lobular fibroblasts have properties in common with bone marrow derived mesenchymal stem cells and they specifically convey growth and branching morphogenesis of epithelial progenitors.ConclusionsTwo distinct functionally specialized fibroblast lineages exist in the normal human breast, of which the lobular fibroblasts have properties in common with mesenchymal stem cells and support epithelial growth and morphogenesis. We propose that lobular fibroblasts constitute a specialized microenvironment for human breast luminal epithelial progenitors, i.e. the putative precursors of breast cancer.Electronic supplementary materialThe online version of this article (doi:10.1186/s13058-016-0769-2) contains supplementary material, which is available to authorized users.

CD26 expression is attenuated by TGF‐β and SDF‐1 autocrine signaling on stromal myofibroblasts in human breast cancers

“…Distinct fibroblast populations with inherent functional diversity exist in stroma of human breast and skin tissues as well as various human tumors . CD26 expression has been demonstrated to serve as a marker for stratification of the stromal cell type in human breast and skin tissues . CD105/endoglin, a coreceptor for TGF‐β family members, is also expressed on a subset of stromal myofibroblasts at the invasive borders of human colon carcinomas .…”

“…45 Moreover, CD26 low CD105 high fibroblasts with myofibroblast-related characteristics are abundant in the terminal duct lobular unit of the human breast, while interlobular ducts are rich in CD26 high CD105 low fibroblasts. 38 Collectively, these observations indicate the importance of CD26 and CD105 expressions for identifying the particular fibroblast lineages in human mammary tissues including those of breast cancer.…”

“…Distinct fibroblast populations with inherent functional diversity exist in stroma of human breast 38 and skin 39,40 tissues as well as various human tumors. [41][42][43] CD26 expression has been demonstrated to serve as a marker for stratification of the stromal cell type in human breast and skin tissues.…”

“…[41][42][43] CD26 expression has been demonstrated to serve as a marker for stratification of the stromal cell type in human breast and skin tissues. 38,39,44 CD105/endoglin, a coreceptor for TGF-β family members, is also expressed on a subset of stromal myofibroblasts at the invasive borders of human colon carcinomas. 45 Moreover, CD26 low CD105 high fibroblasts with myofibroblast-related characteristics are abundant in the terminal duct lobular unit of the human breast, while interlobular ducts are rich in CD26 high CD105 low fibroblasts.…”

A pleiotropic role for FGF signaling in mammary gland stromal fibroblasts

“…Stromal fibroblasts are important regulators of mammary epithelial morphogenesis (Hammer et al, 2017;Koledova et al, 2016;Morsing et al, 2016;Peuhu et al, 2017). Therefore, we investigated the role of FGF2 signaling in fibroblasts in epithelial branching morphogenesis using 3D cultures of mammary organoids alone, fibroblasts alone, and co-cultures of organoids with fibroblasts.…”