Morally relevant features warranting ethical oversight in human stem cell-based embryo models

Stem cell-based embryo models provide innovative ways to explore the principles of human development but also pose new challenges for regulation. Recent guidelines have argued for case-by-case evaluation of stem cell-based embryo model research but it is still unclear what exactly such oversight should consider. Here we argue that effective review requires the identification of a set of attributes by which to evaluate research proposals. To define these, the underlying ethical values and morally relevant biological features present in embryo models must be identified to enable the practical implementation of oversight. We propose that developmental stage, tissue/organ integrity, fetal potential and the capacity to form neural circuits should be used together for evaluation purposes. We also highlight the importance of the wider context, including the proposed uses of embryo models, public perception and individual researcher responsibilities, and thus provide a general framework for regulatory consideration of human embryo model research.