Differentiation of Mature Eosinophils From Human Embryonic and Induced Pluripotent Stem Cells.

Abstract 1594

Eosinophils are multifunctional leukocytes implicated in the pathogenesis of numerous inflammatory processes. As the major effectors, eosinophils function in a variety of biological responses, allergic diseases and helminth infections. It is generally accepted human eosinophils develop through a pathway initially sharing common feature with basophils. However, there lacks a clear chart for early development of human eosinophils, such as during embryonic or fetal stages. We recently established an efficient method for producing eosinophils from human embryonic and induced pluripotent stem cells (hESC/iPSCs). By a two-step induction, we first generated multipotential hematopoietic progenitors by co-culturing hESC/iPSCs with mouse AGM-derived stromal cells for 2 weeks. Then, total co-culture cells were transferred into suspension culture favoring eosinophil development with addition of IL-3 and other factors (SCF, IL-6, TPO, Flt-3 ligand) . The maturation of hESC/iPSC -derived eosinophils was shown in a time-dependent manner, first co-expressing eosinophil-and basophil-specific markers [eosinophil peroxidase (EPO), and 2D7, respectively], then the portion of eosinophil markers gradually increased while that of basophil markers decreased (EPO+ cells from 56.4% at day 7 to 94.4% at day 21, while 2D7+ cells from 62.8% to 25.7%, respectively), typically mimicking the development of eosinophils from human adult hematopoietic progenitors. By flowcytometric analysis, an eosinophil-specific surface marker, Siglec-8, was also expressed on these hESC/iPSC-derived eosinophils in a time-dependent manner (from 10.8% at day 7 to 91.3% at day 21), paralleling to those with EPO. The expression of eosinophil-specific granule cationic proteins (EPO, MBP, ECP, EDN) and IL-5 receptor mRNA was also detected by RT-PCR. Furthermore, transmission electron microscopy (TEM) observation confirmed the eosinophil property. Eosinophils derived from hiPSCs hold similar characteristics as those from hESCs. The function of hES/hiPSC-derived eosinophils is being under investigation. Our study provides an experimental model for exploring early genesis of eosinophils, especially in uncovering the mechanisms controlling the development of the initial innate immune system of human being in normal and diseased individuals.