MFGE8 Acts as a Cell Adhesion Factor for Human-Induced Pluripotent Stem Cells in Embryology

Mouse embryonic fibroblasts (MEFs) have been widely used as feeder cells in embryonic stem cell cultures because they can mimic the embryonic microenvironment. Milk fat globule-epidermal growth factor 8 (MFGE8) is expressed during mouse gonadal development, 10.5-13.5 embryonic, and is also found in MEF-conditioned medium (MEF-CM). Feeder-less culture of human-induced pluripotent stem cells (iPSCs) with MEF-CM significantly decreased the number of adherent cells when an inhibitory antibody against MFGE8 was used. The concentration of mouse MFGE8 in MEF-CM, as measured by an ELISA (Enzyme-Linked Immunosorbent Assay), was 0.16-1.24 μg/mL. Mouse MFGE8 and human MFGE8 have partially different molecular structures. Both the recombinant mouse MFGE8 and human MFGE8 significantly promoted cell adhesion of human iPSCs at medium-added concentrations of 2 μg/mL. This cell adhesion was also strongly inhibited by Arginylglycylaspartic acid (RGD) inhibitors, suggesting that it is dependent on the RGD sequence. The integrin αVβ5 expressed in iPSCs was thought to be involved in binding to the RGD sequence. MEF-CMs have long been an essential bio-derived material for the feeder culture method of iPSC culture. This study demonstrates that MFGE8 in MEF-CM is a functional factor in the promoting of cell adhesion of human iPSCs. Furthermore, the use of MFGE8-containing media demonstrates that iPSCs can be established and cultured while maintaining pluripotency and inducing three germ layer differentiation. The results of this study suggest the possibility of using MFGE8 as a scaffold material suitable for inducing differentiation when reproducing <i>in vivo</i> maturation <i>in vitro</i>.