Comparative Analysis of iPSC and Mammary Tissue-Derived Lactogenic Organoids as Models for Human Lactation

Introduction: Human lactation is a critical process for infant health, governed by the transport of nutrients across epithelial barriers via specialized membrane transport proteins. Modeling this process has been constrained by the limited availability and ethical concerns of human tissue. To address these challenges, we developed two distinct organoid models: one derived from human induced pluripotent stem cells (iPSCs) and the other from mammary tissue obtained via mammoplasty. Both models were induced into a lactogenic state using a combination of hormones and growth factors, and their functional characteristics were assessed. Methods: iPSCs were differentiated into mammary-like organoids using a 40-day stepwise protocol and further stimulated with lactogenic factors. Mammary tissue was digested, dispersed and similarly induced into a lactogenic state. Both models were characterized using mammary markers, including milk protein, CK14, CK18, E-cadherin, and estrogen receptor. Functional analysis, such as calcium transport by the secretory pathway pump SPCA2, will be conducted to assess physiological relevance. Results: The expression of both basal (CK14) and luminal (CK18) markers was observed in organoids derived from iPSCs and mammoplasty tissue. However, the polarity of the luminal marker was inverted in the iPSC-derived organoids, with luminal cells located at the periphery and basal cells occupying the interior of the organoids. In contrast, mammoplasty-derived organoids exhibited correct polarity. Robust expression of lactogenic markers occurred upon lactogenic induction in both organoid types, although weak expression of these markers was also detected in the non-lactating mammoplasty tissue. This unexpected observation may be attributed to the tissue source being from a donor who had given birth four years prior, potentially retaining remnants of milk-producing luminal cells. Conclusion: This comparative study highlights the strengths and limitations of distinct organoid models in studying human lactation. iPSCs offer an ethically sound, renewable and scalable source with broad applicability, whereas tissue-derived organoids retain donor-specific characteristics and provide immediate functional relevance and physiological complexity. Together, these models represent a complementary approach to advancing our understanding of lactation and developing targeted nutritional interventions for maternal-infant health. National Institutes of Health/NICHD 5UC2HD113036 This abstract was presented at the American Physiology Summit 2025 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.