Three-dimensional culture models of mammary gland

Abstract

The mammary gland is a complex tissue comprised of a branching network of ducts embedded within an adipocyte-rich stroma. The ductal epithelium is a bi-layer of luminal and myoepithelial cells, the latter being in contact with a basement membrane. During pregnancy, tertiary branching occurs and lobuloalveolar structures, which produce milk during lactation, form in response to hormonal and cytokine signals. Postlactational regression is characterized by extensive cell death and tissue remodeling. These complex developmental events have been difficult to mimic in cell culture although many useful culture models exist. Recently, considerable advances in three-dimensional modelling of the mammary gland have been made with the use of collagen and other biomaterials for the study of branching morphogenesis and tumorigenesis, techniques which may enable rapid advances in our understanding of both basic biology and the study of cancer therapeutics.

Keywords: adipocytes; cell culture; cell-lines; epithelium; extracellular matrix; mammary gland; models; scaffolds; tissue engineering.

Figure 1

Structure of the mouse mammary gland. (A) Carmine alum stained whole mount of mammary gland from 6 week virgin mouse showing branched ductal structure embedded in a fat pad. The growing ends of the ducts terminate in terminal end buds (×3). (B) H&E stained section of paraffin embedded tissue showing a bifurcated TEB (×60).

Figure 2

Formation of acini in different matrices. (A–C) Mammary epithelial cells (EpH4) adopt the correct polarity in Matrigel™ but not in collagen gel preparations. (A) Tissue section from virgin mammary gland showing bi-layered epithelium. (B) EpH4 cells in Matrigel. (C) EpH4 cells in Collagen gel. Antibody staining: Green, cytokeratin, a marker of myoepithelial cells; red, aquaporin 5, a marker of polarized cells that is expressed on the luminal face; blue, DAPI (nucleus—DNA). (D–F) KIM-2 cells form acini when cultured in Matrigel. (D) Nuclear staining (DAPI); (E) E-Cadherin (red) showing cell adhesions. (F) phase contrast. Scale bars = 10 µm.