Fibroblast-induced mammary epithelial branching depends on fibroblast contractility.

Epithelial branching morphogenesis is an essential process in living organisms, through which organ-specific epithelial shapes are created. Interactions between epithelial cells and their stromal microenvironment instruct branching morphogenesis but remain incompletely understood. Here, we employed fibroblast-organoid or fibroblast-spheroid co-culture systems and time-lapse imaging to reveal that physical contact between fibroblasts and epithelial cells and fibroblast contractility are required to induce mammary epithelial branching. Pharmacological inhibition of ROCK or non-muscle myosin II, or fibroblast-specific knock-out of Myh9 abrogate fibroblast-induced epithelial branching. The process of fibroblast-induced branching requires epithelial proliferation and is associated with distinctive epithelial patterning of yes associated protein (YAP) activity along organoid branches, which is dependent on fibroblast contractility. Moreover, we provide evidence for the in vivo existence of contractile fibroblasts specifically surrounding terminal end buds (TEBs) of pubertal murine mammary glands, advocating for an important role of fibroblast contractility in branching in vivo. Together, we identify fibroblast contractility as a novel stromal factor driving mammary epithelial morphogenesis. Our study contributes to comprehensive understanding of overlapping but divergent employment of mechanically active fibroblasts in developmental versus tumorigenic programs.

3D Cell Culture: Techniques For and Beyond Organoid Applications.

In the rapidly evolving landscape of cell biology and biomedical research, three-dimensional (3D) cell culture has contributed not only to the diversification of experimental tools available but also to their improvement toward greater physiological relevance. 3D cell culture has emerged as a revolutionary technique that bridges the long-standing gap between traditional two-dimensional (2D) cell culture and the complex microenvironments found in living organisms. By providing conditions for establishing critical features of in vivo environment, such as cell-cell and cell-extracellular matrix interactions, 3D cell culture enables proper tissue-like architecture and differentiated function of cells. Since the early days of 3D cell culture in the 1970s, the field has witnessed remarkable progress, with groundbreaking discoveries, novel methodologies, and transformative applications. One particular 3D cell culture technique has caught the attention of many scientists and has experienced an unprecedented boom and enthusiastic application in both basic and translational research over the past decade - the organoid technology. This book chapter provides an introduction to the fundamental concepts of 3D cell culture including organoids, an overview of 3D cell culture techniques, and an overview of methodological- and protocol-oriented chapters in the book 3D Cell Culture.

Fibroblast-Epithelium Co-culture Methods Using Epithelial Organoids and Cell Line-Derived Spheroids.

Fibroblasts are an integral cell type of mammary gland stroma, which plays crucial roles in development, homeostasis, and tumorigenesis of mammary epithelium. Fibroblasts produce and remodel extracellular matrix proteins and secrete a plethora of paracrine signals, which instruct both epithelial and other stromal cells of the mammary gland through mechanisms, which have not been fully understood. To enable deciphering of the intricate fibroblast-epithelial interactions, we developed several 3D co-culture methods. In this chapter, we describe methods for establishment of various types of embedded 3D co-cultures of mammary fibroblasts with mammary epithelial organoids, mammary tumor organoids, or breast cancer spheroids to investigate the role of fibroblasts in mammary epithelial development, morphogenesis, and tumorigenesis. The co-culture types include dispersed, aggregated, and transwell cultures.

Differentiation of Fibroblasts to Adipocytes in 3D for a Co-culture with Mammary Organoids and Immunohistological Analysis.

Mammary epithelial ducts, the main functional compartment of the mammary gland, are embedded in an adipocyte-rich stroma, which is essential for proper mammary gland development, function, and tissue homeostasis. Moreover, the adipocyte compartment has an important role in cancer progression. To better understand cell-to-cell interactions and the role of the adipocytes in the mammary gland, development of proper in vitro models which realistically mimic in vivo conditions has been essential. In this chapter, we describe a simple and effective method for generating mammary gland adipocytes from mammary fibroblasts and their subsequent co-culture with mammary epithelial organoids to further investigate the role of adipocytes in epithelial development and morphogenesis.

Organotypic 3D Cell Culture of the Embryonic Lacrimal Gland.

Ectodermal organ development, including lacrimal gland, is characterized by an interaction between an epithelium and a mesenchyme. Murine lacrimal gland is a good model to study non-stereotypical branching morphogenesis. In vitro cultures allow the study of morphogenesis events with easy access to high-resolution imaging. Particularly, embryonic lacrimal gland organotypic 3D cell cultures enable the follow-up of branching morphogenesis thanks to the analysis of territories organization by immunohistochemistry. In this chapter, we describe a method to culture primary epithelial fragments together with primary mesenchymal cells, isolated from embryonic day 17 lacrimal glands.

Static 3D Osteoblast Cell Culture on 3D Printed Titanium Scaffolds.

In vitro cell cultures are a very useful tool for the validation of biomaterial cytocompatibility, especially for bone tissue engineering scaffolds and bone implants. In this chapter, a protocol for a static three-dimensional osteoblast cell culture on titanium scaffolds and subsequent analysis of osteogenic capacity is presented. The protocol is explained for additively manufactured titanium scaffolds, but it can be extrapolated to other scaffolds with similar size and structure, while differing in composition or manufactured technology. Additionally, the protocol can be used for culture of other adherent cell types beyond osteoblast cells such as mesenchymal stem cells.