The Expression of <i>Wnt5a</i> Gene Throughout Definitive Endoderm Induction Process in Induced Pluripotent Stem Cells

Abstract

Background: Induced pluripotent stem cells (iPSCs) have the ability to proliferate indefinitely and differentiate into three germ layers of ectoderm, mesoderm, and endoderm. Definitive induction is the first and the most delicate stage of differentiation of various iPSC-derived organs. It has been found that the Wnt signaling pathway implicates in embryogenesis, organogenesis, and cell communication. Objectives: In the present study, we aimed to investigate the expression pattern of the Wnt5a gene as an indicator of non-canonical Wnt signaling activity during definitive endoderm induction of iPSCs. Methods: Human iPSCs (RSCB0042) were acquired from Royan stem cell bank of Royan Institute (Tehran, Iran). The iPSCs were cultured on a feeder layer of mitomycin-inactivated mouse embryonic fibroblasts (MEF), and iPSC colonies were collected for embryoid body (EB) generation by suspension culture method. Then endoderm induction step was performed using a series of small molecules. The quantitative real-time PCR was used to assess the mRNA expression of wnt5a, Nanog, OCT4, SOX17, and FOXA2 genes. Results: The production of efficient EBs confirmed by a decrease in Nanog and Oct4 gene expression and the success of DE (definite endoderm) induction step was confirmed by a high expression level of DE specific genes, Sox17, and FoxA2. A significant upregulation of Wnt5a in EB samples and a minor decrease at day 4 was observed. However, the differentiation process followed by an incremental fashion in Wnt5a mRNA expression starting from day 4 of differentiation among the samples of days 6 and 8 (DE stage). Conclusions: Our results suggest that Wnt5a is more activated at the later steps of endoderm induction rather than the early steps, which may be due to the stimulation of canonical Wnt signaling. Finding the expression level of Wnt5a could rise insights for developing more efficient differentiation induction protocols.