Increased reactive oxygen species and exhaustion of quiescent CD34-positive bone marrow cells may contribute to poor graft function after allotransplants.

Yuan Kong,Kai-Yan Liu,Yu Wang,Xiao-Hui Zhang,Yue Hu,Xiao-Jun Huang,Lan-Ping Xu,Hong-Kui Deng,Min-Min Shi,Yu-Tong Wang,Yang Song

doi:10.18632/oncotarget.8810

Yuan Kong, Kai-Yan Liu + Show 9 more

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https://doi.org/10.18632/oncotarget.8810

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Abstract

Poor graft function (PGF) is a fatal complication following allogeneic haematopoietic stem cell transplantation. However, the underlying mechanism is unclear. Effective cross-talk between haematopoietic stem cells (HSCs) and bone marrow microenvironment is important for normal haematopoiesis. Normal HSCs reside in a hypoxic bone marrow microenvironment that protects them from oxidative stress that would otherwise inhibit their self-renewal and results in bone marrow failure. Whether an increased level of reactive oxygen species (ROS) causes PGF following allotransplant is unclear. Using a prospective case-pair study, we identified increased levels of ROS in CD34+ bone marrow cells in subjects with PGF. Elevated ROS levels was associated with an increased frequency of DNA strand breaks, apoptosis, exhaustion of quiescent CD34+ cells and defective colony-forming unit plating efficiency, particularly in the CD34+CD38− fraction. Up-regulated intracellular p53, p21, caspase-3 and caspase-9 levels (but not p38) were detected in CD34+ cells, particularly in the CD34+CD38− fraction. To further study the potential role of ROS levels in post-transplant haematopoiesis, CD34+ bone marrow cells from subjects with good graft function were treated with H2O2. This increased ROS levels resulting in defective CD34+ cells, an effect partially reversed by N-acetyl-L-cysteine. Moreover, CD34+ bone marrow cells from the donors to subjects with poor or good graft function exhibited comparable haematopoietic reconstitution capacities in the xeno-transplanted NOD-PrkdcscidIL2rgnull mice. Thus, even if the transplanted donors' bone marrow CD34+ cells are functionally normal pre-transplant, ROS-induced apoptosis may contribute to the exhaustion of CD34+ bone marrow cells in subjects with PGF following allotransplant.

Highlights

Poor graft function is an important, often fatal complication following allogeneic haematopoietic stem cell transplant [1,2,3,4]
We recently reported that the transplanted donor CD34-positive cells were quantitatively normal www.impactjournals.com/oncotarget in subjects with poor graft function, but the frequency of bone marrow CD34-positive cells were dramatically reduced and bone marrow endosteal, vascular microenvironment were impaired in subjects with poor graft function compared with those with good graft function posttransplant [2, 3], raising the question whether bone marrow CD34-positive cells in subjects with poor graft function are functionally impaired posttransplant, or the transplanted donors’ CD34-positive cells are already defective pretransplant
Subjects with poor graft function had significantly lower numbers of CD34-positive cells (Figure 1A; 0.21 ± 0.06×10E+6 vs. 1.09±0.18×10E+6; P=0.002) and CD34-positive, CD38-negative cells (Figure 1A; 0.07±0.03×10E+6 vs. 0.84±0.15×10E+6; P=0.0008) in the G0 phase compared with subjects with good graft function

Summary

Introduction

Poor graft function is an important, often fatal complication following allogeneic haematopoietic stem cell transplant [1,2,3,4]. The etiology of poor graft function is complex and includes many factors such as bone marrow toxic drugs, infections, graft-versus-host disease (GvHD) and an impaired bone marrow microenvironment [2, 3, 5,6,7,8,9]. Interactions between haematopoietic stem and progenitor cells and the bone marrow microenvironment are important in maintaining normal haematopoiesis [10,11,12,13]. What drives the bone marrow CD34-positive cells impairing functionally posttransplant and its molecular mechanisms remain to be elucidated in poor graft function

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