Stage‐specific regulation of Gremlin1 on the differentiation and expansion of human urinary induced pluripotent stem cells into endothelial progenitors

Abstract

Human urinary induced pluripotent stem cells (hUiPSCs) produced from exfoliated renal epithelial cells present in urine may provide a non‐invasive source of endothelial progenitors for the treatment of ischaemic diseases. However, their differentiation efficiency is unsatisfactory and the underlying mechanism of differentiation is still unknown. Gremlin1 (GREM1) is an important gene involved in cell differentiation. Therefore, we tried to elucidate the roles of GREM1 during the differentiation and expansion of endothelial progenitors. HUiPSCs were induced into endothelial progenitors by three stages. After differentiation, GREM1 was obviously increased in hUiPSC‐induced endothelial progenitors (hUiPSC‐EPs). RNA interference (RNAi) was used to silence GREM1 expression in three stages, respectively. We demonstrated a stage‐specific effect of GREM1 in decreasing hUiPSC‐EP differentiation in the mesoderm induction stage (Stage 1), while increasing differentiation in the endothelial progenitors' induction stage (Stage 2) and expansion stage (Stage 3). Exogenous addition of GREM1 recombinant protein in the endothelial progenitors' expansion stage (Stage 3) promoted the expansion of hUiPSC‐EPs although the activation of VEGFR2/Akt or VEGFR2/p42/44MAPK pathway. Our study provided a new non‐invasive source for endothelial progenitors, demonstrated critical roles of GREM1 in hUiPSC‐EP and afforded a novel strategy to improve stem cell‐based therapy for the ischaemic diseases.

Pathological angiogenesis and inflammation in tissues

“…Among them, VEGF-A/VEGFR2 interaction is the most prominent in the VEGF signaling pathway (Song et al 2018). VEGF-A binding to VEGFR2 induces receptor dimerization and autophosphorylation at specific tyrosine kinase residues, including Tyr1054 and Tyr1059 within the kinase domain of VEGFR2 (Jin et al 2018;Chen et al 2020). VEGF-A induces the activation of diverse signaling pathways, including the phospholipase C-γ (PLC-γ)/protein kinase C (PKC) pathway via VEGFR2 Tyr1175 phosphorylation (Simons et al 2016) and the phosphoinositide 3-kinase (PI3K)/Akt pathway via VEGFR2 Tyr1175/1173 phosphorylation (Wang et al 2019b).…”