Human breast organoid models for lactation research

The human mammary gland is the major organ involved in lactation. In the mammary gland, alveoli secrete milk and myoepithelial cells contract to propel the milk through branched structures called ducts and eventually to the nipple. It is through this process of lactation that infants receive milk, which is essential for proper infant growth and development. The lactation process is comprised of sophisticated interactive networks at the cellular level that are not well understood. Whereas the majority of published mammary gland lactation studies have relied on mouse mammary glands, recent advancements in techniques to study mammary glands enable in vitro reproduction of lactation using human-representative frameworks. Currently, the 3D breast organoid is the state-of-the-art model in human mammary gland research, utilizing induced pluripotent stem cells (iPSCs) or processed patient-derived breast tissues embedded in a special matrix that are then able to grow into complex structures that recapitulate aspects of native human breast tissue. Gaining comprehensive biological insight into the process of lactation through these breast tissue-mimetic 3D models is essential for further studies on lactation-associated human mammary gland diseases, human milk composition, and potential solutions to challenges in maternal milk accessibility. In this short review, the benefits and potential utility of 3D breast organoids in understanding the underlying science of lactation and advancing further human mammary gland studies are discussed.