Apoptosis of human erythroid colony‐forming cells is decreased by stem cell factor and insulin‐like growth factor I as well as erythropoietin

Abstract

To clarify the manner by which erythropoietin (EP), stem cell factor (SCF), or insulin-like growth factor I (IGF-I) regulate erythropoiesis, apoptosis of human erythroid progenitor cells was investigated. Human burst-forming units-erythroid (BFU-E) partially purified from peripheral blood were cultured for 6 days to generate erythroid colony-forming cells (ECFC), which consist mainly of colony-forming units-erythroid (CFU-E). The cells were labeled with [3H]thymidine, incubated in serum-free liquid media, at 37 degrees C, for 16 h, and the pattern of DNA breakdown was analyzed by agarose gel electrophoresis. When these cells were incubated without EP, 70% of the total cellular DNA was broken down into DNA fragments of less than 5 kilobases and nuclear condensation and fragmentation, characteristic of apoptosis, were evident. While EP greatly reduced the amount of DNA breakdown to 23%, SCF and IGF-I each reduced the amount of DNA breakdown to 38-46% and, when added together, to 24%. Dose-response experiments with SCF and IGF-I showed a dose-dependent reduction in DNA fragmentation at concentrations that stimulate colony formation in serum-free semisolid cultures. Finally, assays of ECFC performed by the plasma clot method, after serum-free liquid culture, at 37 degrees C, for 16 h, demonstrated marked protection of erythroid colony-forming capacity by SCF or IGF-I in the absence of EP, as well as by EP itself. These data indicate that human erythroid progenitor cells undergo apoptosis which is reduced by SCF and IGF-I as well as EP and suggest that the control of apoptosis by each of these factors has a prominent role in the regulation of erythropoiesis.

Regulation of Cell Growth and Apoptosis by Adrenomedullin

“…Various stimuli, such as serum deprivation, radiation, chemotherapeutic agents and antioxidants, induce apoptosis in many cell types (57-60), whereas growth factors and cytokines may modulate apoptosis triggered by such environmental signals (61)(62)(63)(64)(65)(66). Within individual growth factors, the potency for inducing cell division is not always equal to that for antagonizing apoptosis whereas some growth factors may induce cell division without antagonizing apoptosis, or vice versa, and thus these two effects are considered discrete cell-survival factors.…”

Janus kinase 2 (V617F) mutation status, signal transducer and activator of transcription-3 phosphorylation and impaired neutrophil apoptosis in myelofibrosis with myeloid metaplasia

“…11 Under physiological conditions, important regulatory cytokines such as erythropoietin, stem cell factor (SCF) and GM-CSF function, at least in part, by inhibiting apoptosis that would otherwise occur in normal marrow progenitor cells. 12 According to current understanding, many of these cytokines regulate apoptosis through a series of steps that sequentially involve activation of receptor-associated JAK kinases, phosphorylation of cytoplasmic signal transducer and activator of transcription (STAT) proteins on specific tyrosine residues, dimerization and nuclear translocation of the phosphorylated STAT molecules and transactivation of genes that encode antiapoptotic polypeptides such as Bcl-2, Bcl-x L and Mcl-1. 7,13,14 For example, GM-CSF-induced activation of signaling through STAT3 has been implicated in Mcl-1 upregulation and delayed apoptosis in normal human neutrophils.…”

Initiation of erythropoiesis by BFU-E cells

“…BFU-Es circulate in blood, home to marrow, and have limited but random movement inside the marrow space where they divide and differentiate in response to growth factors produced by macrophages [1][2][3]. After BFU-Es divide and differentiate they become colony forming units-erythroid (CFU-Es).…”