In vitro generation of mature neutrophils from human induced pluripotent stem cells (iPSCs) requires hematopoietic progenitor development followed by myeloid differentiation. The purpose of our studies was to extensively characterize this process, focusing on the critical window of development between hemogenic endothelium, hematopoietic stem/progenitor cells (HSPCs), and myeloid commitment, to identify associated regulators and markers that might enable the stem cell field to improve the efficiency and efficacy of iPSC hematopoiesis. We utilized a 4-stage differentiation protocol involving: embryoid body (EB) formation (Stage-1); EB culture with hematopoietic cytokines (Stage-2); HSPC expansion (Stage-3); and neutrophil maturation (Stage-4). CD34+CD45- putative hemogenic endothelial cells were observed in Stage-3 cultures, and expressed VEGFR-2/Flk-1/KDR and VE-cadherin endothelial markers, GATA-2, AML1/RUNX1, and SCL/TAL1 transcription factors, and endothelial/HSPC-associated microRNAs miR-24, miR-125a-3p, miR-126/126*, and miR-155. Upon further culture, CD34+CD45- cells generated CD34+CD45+ HSPCs that produced hematopoietic CFUs. Mid-Stage-3 CD34+CD45+ HSPCs exhibited increased expression of GATA-2, AML1/RUNX1, SCL/TAL1, C/EBPα, and PU.1 transcription factors, but exhibited decreased expression of HSPC-associated microRNAs, and failed to engraft in immune-deficient mice. Mid-stage-3 CD34-CD45+ cells maintained PU.1 expression and exhibited increased expression of hematopoiesis-associated miR-142-3p/5p and a trend towards increased miR-223 expression, indicating myeloid commitment. By late Stage-4, increased CD15, CD16b, and C/EBPε expression were observed, with 25-65% of cells exhibiting morphology and functions of mature neutrophils. These studies demonstrate that hematopoiesis and neutrophil differentiation from human iPSCs recapitulates many features of embryonic hematopoiesis and neutrophil production in marrow, but reveals unexpected molecular signatures that may serve as a guide for enhancing iPSC hematopoiesis.
Overall design: miRNA expression profiles were analyzed in iNC-01-3 and iNC-01-4 induced pluripotent stem cell lines at day 0 (undifferentiated iPSCs), day 18 of differentiation (embryoid bodies), and in 3 FACS-sorted cell populations at day 22 of differentiation (CD34+CD45- cells, CD34+CD45+ cells, and CD34-CD45+ cells). Comparative CT analysis was normalized to U6 snRNA and RNU48 control RNAs relative to expression in undifferentiated iPSCs. Data includes 2 files for each sample, one for the card A array and one for the card B array. This includes a total of 32 data files consisting of: 5 replicates for undifferentiated iPSCs (10 files), 2 replicates for EB (4 files), 3 replicates for CD34+CD45- (6 files), 3 replicates for CD34+CD45+ (6 files), and 3 replicates for CD34-CD45+ (6 files).
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