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

// Yuan Kong 1, * , Yang Song 1, 2, * , Yue Hu 1, 2 , Min-Min Shi 1, 2 , Yu-Tong Wang 1 , Yu Wang 1 , Xiao-Hui Zhang 1 , Lan-Ping Xu 1 , Kai-Yan Liu 1 , Hong-Kui Deng 2, 3 , Xiao-Jun Huang 1, 2 1 Peking University People’s Hospital, Peking University Institute of Hematology, Beijing Key Laboratory of Hematopoietic Stem Cell Transplantation, Collaborative Innovation Center of Hematology, Peking University, Beijing, China 2 Peking-Tsinghua Center for Life Sciences, Academy for Advanced Interdisciplinary Studies, Peking University, Beijing, China 3 Key Laboratory of Cell Proliferation and Differentiation of the Ministry of Education, School of Life Sciences, Peking University, Beijing, China * These authors have contributed equally to this work Correspondence to: Xiao-Jun Huang, email: xjhrm@medmail.com.cn Keywords: poor graft function, allotransplant, haematopoietic stem cells, reactive oxygen species Received: February 02, 2016      Accepted: March 31, 2016      Published: April 18, 2016 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 H 2 O 2 . 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-Prkdc scid IL2rg null 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.