WERF Endometriosis Phenome and Biobanking Harmonisation Project for Experimental Models in Endometriosis Research (EPHect-EM-Organoids): endometrial organoids as an emerging technology for endometriosis research.

The aetiology of endometriosis remains poorly understood. In vitro model systems provide the opportunity to identify the mechanisms driving disease pathogenesis using human cells. Three-dimensional models, particularly organoid systems, have revolutionized how we study epithelial biology and are powerful tools for modelling endometriosis. As an emerging model system, it is important to define protocols and identify the remaining challenges surrounding endometrial organoid culture to increase reproducibility and scientific rigour in endometriosis research. The World Endometriosis Research Foundation (WERF) established an international working group comprised of experts using in vitro approaches for the study of endometriosis. This working group harmonized protocols and documentation of existing and emerging organoid systems to maximize comparison and replication across the field and guide specific research hypotheses testing. This evaluation of organoid protocols, limitations, challenges, and alternative approaches assessed both published and grey literature papers across several disciplines pertinent to endometriosis research. Recommendations for protocol and documentation harmonization are presented, and we created the first-ever decision tree diagram to guide and facilitate the selection of existing models best suited for specific areas of endometriosis research. Rigorous and systematic assessment of emerging organoid systems, recognizing the inferential strengths and limitations of these approaches, is vital for endometriosis research. This comprehensive review of the benefits, limitations, and utilization of organoid models, as well as the consequent integration of protocols and documentation, will contribute to the scientific knowledge base by maximizing the reproducibility, comparability, and interpretation of research studies in endometriosis. Additionally, these newly developed protocols and documentation should serve as a resource for, and facilitate collaboration between, endometriosis investigators using organoids in their research methods.