ABSTRACT
Epigenetic memory in induced pluripotent stem cells, which is related to the somatic cell type of origin of the stem cells, might lead to variations in the differentiation capacities of the pluripotent stem cells. In this context, induced pluripotent stem cells from human CD34(+) hematopoietic stem cells might be more suitable for hematopoietic differentiation than the commonly used fibroblast-derived induced pluripotent stem cells. To investigate the influence of an epigenetic memory on the ex vivo expansion of induced pluripotent stem cells into erythroid cells, we compared induced pluripotent stem cells from human neural stem cells and human cord blood-derived CD34(+) hematopoietic stem cells and evaluated their potential for differentiation into hematopoietic progenitor and mature red blood cells. Although genome-wide DNA methylation profiling at all promoter regions demonstrates that the epigenetic memory of induced pluripotent stem cells is influenced by the somatic cell type of origin of the stem cells, we found a similar hematopoietic induction potential and erythroid differentiation pattern of induced pluripotent stem cells of different somatic cell origin. All human induced pluripotent stem cell lines showed terminal maturation into normoblasts and enucleated reticulocytes, producing predominantly fetal hemoglobin. Differences were only observed in the growth rate of erythroid cells, which was slightly higher in the induced pluripotent stem cells derived from CD34(+) hematopoietic stem cells. More detailed methylation analysis of the hematopoietic and erythroid promoters identified similar CpG methylation levels in the induced pluripotent stem cell lines derived from CD34(+) cells and those derived from neural stem cells, which confirms their comparable erythroid differentiation potential.
Subject(s)
Cell Differentiation , Erythroid Cells/cytology , Fetal Blood/cytology , Hematopoietic Stem Cells/cytology , Induced Pluripotent Stem Cells/cytology , Neural Stem Cells/cytology , Biomarkers/metabolism , DNA Methylation , Epigenomics , Erythroid Cells/metabolism , Fetal Blood/metabolism , Fibroblasts/cytology , Fibroblasts/metabolism , Gene Expression Profiling , Hematopoietic Stem Cells/metabolism , Humans , Induced Pluripotent Stem Cells/metabolism , Neural Stem Cells/metabolism , RNA, Messenger/genetics , Real-Time Polymerase Chain Reaction , Reverse Transcriptase Polymerase Chain ReactionABSTRACT
This study compared airway responsiveness in vitro, as measured in isolated bronchi, with responsiveness in vivo in patients with COPD and smokers with normal lung function. In 9 patients with COPD (mean (range) FEV, 55 (30-78) %predicted) and 8 smokers with normal lung function (FEV1 101 (89-117) %predicted), who underwent surgery for lung cancer, responses to inhaled histamine and salbutamol were assessed before surgery. Bronchial specimens of 1-4 mm internal diameter were studied in the organ bath and histamine concentration-response curves assessed. All patients with COPD and none of the control individuals were hyperresponsive to inhaled histamine. Five patients with COPD and no control patient showed a bronchodilator response to salbutamol. Opposite to these findings, bronchial rings in the organ bath demonstrated a rightward shift of histamine concentration-response curves in COPD compared to controls, (p < 0.005). Accordingly, pED50 but not Emax differed statistically (p = 0.0016) between groups, mean+/-SEM values of pED50 in COPD (controls) being 4.67+/-0.08 (5.29+/-0.15) and of Emax 672+/-86 (772+/-120) mg. Patients with COPD showing hyperresponsiveness to inhaled histamine demonstrated lower responsiveness of their isolated bronchi compared to smokers with normal lung function. This suggests that in vivo hyperresponsiveness is based on other mechanisms than alterations in smooth muscle physiology.
