IGF1-mediated human embryonic stem cell self-renewal recapitulates the embryonic niche

Our understanding of signalling pathways that regulate human pluripotent epiblast cells is limited, despite their fundamental biological and clinical importance. In this study, we mined human embryo transcriptomics datasets, and identified expression of transcripts for the insulin and insulin growth factor 1 (IGF1) receptors, along with IGF1 ligand. Human embryos cultured in medium supplemented with IGF1 showed an increase in the proportion of NANOG-expressing pluripotent epiblast progenitor cells. Consequently, we generated a minimal chemically-defined culture medium informed by the signalling environment of the human embryo. We derived several human embryonic stem cell (hESC) lines and reprogrammed fibroblasts to induced pluripotent stem cells (iPSCs) in these conditions. Transcriptome and protein expression analyses confirmed that these hESCs and iPSCs expressed pluripotency-associated genes. Moreover, hESCs and iPSCs retained high viability, the ability to undergo spontaneous and directed differentiation, and a normal karyotype. By contrast, fibroblast growth factor 2 (FGF2) was detrimental to epiblast development and dispensable for hESC cultures maintained in exogenous insulin or IGF1. This is the first example of how integrating signalling insights from human blastocysts can be used to define hESC culture conditions that more closely recapitulate the embryonic niche.