Establishment and characterization of mammary organoids from non-traditional model organisms

Abstract

Mammary organoid (MaO) models are only available for a few traditional model organisms, limiting our ability to investigate mammary gland development and cancer across the diverse taxa of mammals. For example, horses are mammals with a similar mammary anatomy and function as humans, but they have a remarkably low incidence of mammary cancer, making the development of MaOs in non-traditional model organisms attractive, particularly in comparative cancer research. This study established equine mammary organoids (EqMaOs) from mammary gland tissue fragments and evaluated parameters including diameter, budding, and growth stage in non-budding EqMaOs, in cultures with increasing concentrations of epidermal growth factor (EGF), a key growth factor implicated in mammary gland development. Our findings showed that EqMaO diameter is not influenced by EGF concentration, whereas number of EqMaOs with budding and stage in non-budding EqMaOs are positively influenced by increasing EGF concentration. EqMaOs also formed protrusions with putative functions, including organoid fusion and sensory functions. We further characterized EqMaOs by the presence of myoepithelial and luminal cells using immunohistochemistry and used the hormone prolactin to stimulate milk secretion, as illustrated by β-lactoglobulin expression, in these EqMaOs. Additionally, we showed that our method to establish MaOs is widely applicable to additional non-traditional mammalian model organisms such as cat, pig, deer, rabbit, and prairie vole. Collectively, MaO models across species will be a useful tool for comparative developmental and cancer studies.Summary statementMammary organoids can be established from various mammals by embedding mammary tissue fragments into a 3D matrix, providing a high-throughput, physiologically accurate model for comparative studies centered on mammary gland development and cancer.