Reshaping in vitro Models of Breast Tissue: Integration of Stromal and Parenchymal Compartments in 3D Printed Hydrogels.

Patrícia Barros Da Silva,Mariana Coelho,Sara Carvalheira Neves,Sílvia Joana Bidarra,Cristina Carvalho Barrias

doi:10.3389/fbioe.2020.00494

Abstract

Breast tissue consists of an epithelial parenchyma embedded in stroma, of heterogeneous and complex composition, undergoing several morphological and functional alterations throughout females' lifespan. Improved knowledge on the crosstalk between parenchymal and stromal mammary cells should provide important insights on breast tissue dynamics, both under healthy and diseased states. Here, we describe an advanced 3D in vitro model of breast tissue, combining multiple components, namely stromal cells and their extracellular matrix (ECM), as well as parenchymal epithelial cells, in a hybrid system. To build the model, porous scaffolds were produced by extrusion 3D printing of peptide-modified alginate hydrogels, and then populated with human mammary fibroblasts. Seeded fibroblasts were able to adhere, spread and produce endogenous ECM, providing adequate coverage of the scaffold surface, without obstructing the pores. On a second stage, a peptide-modified alginate pre-gel laden with mammary gland epithelial cells was used to fill the scaffold's pores, forming a hydrogel in situ by ionic crosslinking. Throughout time, epithelial cells formed prototypical mammary acini-like structures, in close proximity with fibroblasts and their ECM. This generated a heterotypic 3D model that partially recreates both stromal and parenchymal compartments of breast tissue, promoting cell-cell and cell-matrix crosstalk. Furthermore, the hybrid system could be easily dissolved for cell recovery and subsequent analysis by standard cellular/molecular assays. In particular, we show that retrieved cell populations could be discriminated by flow cytometry using cell-type specific markers. This integrative 3D model stands out as a promising in vitro platform for studying breast stroma-parenchyma interactions, both under physiological and pathological settings.

Highlights

In the twenty-first century, cancer is expected to rank as the leading cause of death worldwide, and the single most important barrier to increasing life expectancy (GLOBOCAN2018) (Ferlay et al, 2019)
Breast tissue is complex, undergoing various morphological and functional alterations throughout a woman’s lifespan. It is primarily composed of mammary gland epithelial cells and a variety of stromal cell types, which interact in different ways, depending on internal and external stimuli
While this study focused on fibroblasts, which are abundant in breast stroma, other stromal cell types, such as adipocytes, may be explored in future studies

Summary

Introduction

In the twenty-first century, cancer is expected to rank as the leading cause of death worldwide, and the single most important barrier to increasing life expectancy (GLOBOCAN2018) (Ferlay et al, 2019). Breast cancer is the most diagnosed cancer, accounting for almost 1-in-4 cancer cases, and the leading cause of cancer-related deaths These numbers point breast cancer as major health threat for women, calling for the urgent implementation of measures for improved prevention, diagnosis and treatment (Ferlay et al, 2019). Breast tissue is complex, undergoing various morphological and functional alterations throughout a woman’s lifespan It is primarily composed of mammary gland epithelial cells and a variety of stromal cell types, which interact in different ways, depending on internal and external stimuli. Improved knowledge on these interactions would enable a better understanding on the dynamic alterations of breast tissue, underlying both healthy and pathological processes. The importance of non-cellular components, namely the extracellular matrix (ECM) has been emphasized (Weigelt and Bissell, 2008; Arendt et al, 2010; Oskarsson, 2013)

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Conclusion