title: Synergy between erythropoietin and stem cell factor during erythropoiesis can be quantitatively described without co-signaling effects.
abstract: Synergistic interactions between cytokines underlie developmental processes fundamental to tissue and cellular engineering. However, a mechanistic understanding of the cell-specific and population-mediated effects is often lacking. In this study, we have investigated the synergistic generation of erythroid cells in response to erythropoietin (EPO) and stem cell factor (SCF). We have used a quantitative approach to determine if the effects of EPO and SCF superpose in a supra-additive fashion on the cell proliferation rate or on the death rate, suggesting a contribution from a joint cytokine effect (co-signaling). Primary mouse bone marrow hematopoietic cells and the stem cell-like FDCP-mix cell line were used to investigate the effects of EPO and SCF (individually or in combination) on erythroid output. Carboxyfluorescein diacetate succinimidyl ester (CFSE)-based cell-division tracking and mathematical modeling were used to measure cell type-specific proliferation and death rates. We observed a significant synergistic effect of EPO and SCF on the net generation of benzidine positive (erythroid) colony-forming cells, CD71++ (early erythroblasts) cells and TER-119+ (late erythroblasts and reticulocytes) cells in culture. When the observed increases in cell number were decomposed into proliferation and death rates, the cytokines were shown to act independently at different stages of erythroid development; SCF promoted the early proliferation of primitive cells, while EPO primarily promoted the survival of differentiating erythroid progenitor cells. Our analysis demonstrates that EPO and SCF have distinct and predominantly sequential effects on erythroid differentiation. This study emphasizes the necessity to separate proliferation rates from death rates to understand apparent cytokine synergies.
authors.affiliation: Institute of Biomaterials and Biomedical Engineering (IBBME), Terrence Donnelly Centre for Cellular and Biomolecular Research, University of Toronto, 164 College Street, Rm 407, Toronto, ON, Canada M5S 3G9.
authors.forename: Weijia
authors.initials: W
authors.lastname: Wang
authors.forename: Daniel N
authors.initials: DN
authors.lastname: Horner
authors.forename: Wen Li Kelly
authors.initials: WL
authors.lastname: Chen
authors.forename: Peter W
authors.initials: PW
authors.lastname: Zandstra
authors.forename: Julie
authors.initials: J
authors.lastname: Audet
mesh_terms: D000818:Animals; D001854:Bone Marrow Cells / Q000166:cytology*; D002454:Cell Differentiation; D002455:Cell Division; D002460:Cell Line; D002478:Cells, Cultured; D004920:Erythropoiesis; D004921:Erythropoietin / Q000378:metabolism*; D005434:Flow Cytometry; D005452:Fluoresceins; D005456:Fluorescent Dyes; D051379:Mice; D008810:Mice, Inbred C57BL; D039902:Multipotent Stem Cells / Q000166:cytology*; D015398:Signal Transduction; D019089:Stem Cell Factor / Q000378:metabolism*; D013388:Succinimides
chemical_list: C087165:5-(6)-carboxyfluorescein diacetate succinimidyl ester; D005452:Fluoresceins; D005456:Fluorescent Dyes; D019089:Stem Cell Factor; D013388:Succinimides; D004921:Erythropoietin