N‐acetyl‐L‐cysteine improves bone marrow endothelial progenitor cells in prolonged isolated thrombocytopenia patients post allogeneic hematopoietic stem cell transplantation

Abstract

Prolonged isolated thrombocytopenia (PT) is a serious complication following allogeneic hematopoietic stem cell transplantation (allo-HSCT). According to murine studies, endothelial progenitor cells (EPCs) play a crucial role in the regulation of hematopoiesis and thrombopoiesis in the bone marrow (BM) microenvironment. We previously showed that the reduced frequency of BM EPCs was an independent risk factor for the occurrence of PT following allo-HSCT. However, the functional role of BM EPCs and methods to improve the impaired BM EPCs in PT patients are unknown. In the current case-control study, we investigated whether the BM EPCs in PT patients differed from those in good graft function patients. Moreover, we evaluated whether N-acetyl-L-cysteine (NAC, a reactive oxygen species [ROS] scavenger) could enhance BM EPCs from PT patients in vitro and in vivo. The PT patients exhibited dysfunctional BM EPCs characterized by high levels of ROS and apoptosis and decreased migration and angiogenesis capabilities. In vitro treatment with NAC improved the quantity and function of the BM EPCs cultivated from the PT patients by downregulating the p38 MAPK pathway and rescued the impaired BM EPCs to support megakaryocytopoiesis. Furthermore, according to the results of a preliminary clinical study, NAC is safe and effective in PT patients. In summary, these results suggested that the reduced and dysfunctional BM EPCs are involved in the occurrence of PT. The defective BM EPCs in the PT patients can be quantitatively and functionally improved by NAC, indicating that NAC is a promising therapeutic approach for PT patients following allo-HSCT.

Dysfunctional Bone Marrow Mesenchymal Stem Cells in Patients with Poor Graft Function after Allogeneic Hematopoietic Stem Cell Transplantation

“…The definitions of PGF and GGF were consistent with those of previous studies [9][10][11][12][13][14]24,26,27]. PGF was defined as hypoplastic or aplastic BM with 2 or 3 of the following: neutrophil count .5 £ 10 9 /L, platelet count 20 £ 10 9 /L, and/or hemoglobin concentration 70 g/L for at least 3 consecutive days after day +28 post-HSCT or in accordance with the platelet, RBC ), pre-HSCT cycles of chemotherapy ( §1 cycle), disease status at HSCT, and BM microenvironment evaluated time after allo-HSCT ( §5 days).…”

“…Poor graft function (PGF), characterized by pancytopenia, is a severe complication of allogeneic hematopoietic stem cell transplantation (allo-HSCT) [1][2][3]. However, the exact pathogenesis of PGF remains unclear, and effective treatment options for PGF are limited [1][2][3][4].…”

“…Poor graft function (PGF), characterized by pancytopenia, is a severe complication of allogeneic hematopoietic stem cell transplantation (allo-HSCT) [1][2][3]. However, the exact pathogenesis of PGF remains unclear, and effective treatment options for PGF are limited [1][2][3][4]. Murine studies demonstrated that effective hematopoiesis in the bone marrow (BM) depends on the interaction between HSCs and the specific BM microenvironment [5][6][7][8].…”

Impairment of bone marrow endothelial progenitor cells in acute graft‐versus‐host disease patients after allotransplant

“…BM trephine biopsies (BMBs) were obtained from the posterior superior iliac spine of the patients with or without aGVHD and healthy donors. As previously described (Duan et al , ; Kong et al , ,b), the immunofluorescence staining of EPCs in the BMBs were performed with the mouse anti‐human CD34 (Becton Dickinson) and rabbit anti‐human CD133 (Abcam, Cambridge, MA, USA) antibodies. The goat anti‐rabbit 555 and donkey anti‐mouse 488 (Invitrogen, Carlsbad, CA, USA) antibodies were added at RT for 1 h. 4′,6‐Diamidino‐2‐phenylindole (DAPI) was applied to stain the nuclei, and the prepared slides were analysed under a Leica TCS SP8 microscope (Leica Microsystems, Wetzlar, Germany).…”

“…In this regard, EPCs improved the quality and quantity of transplanted haematopoietic stem cells (HSCs) in mice (Qiao et al , ). More recently, we reported that impaired BM EPCs contribute to the occurrence of poor graft function (PGF) and prolonged isolated thrombocytopenia (PT) after allo‐HSCT in humans (Kong et al , , , ; Shi et al , ). We further found that disruption of the BM EPCs may hamper the differentiation progress from HSCs to megakaryocytes, resulting in the occurrence of corticosteroid‐resistant immune thrombocytopenia (ITP), indicating that immune‐mediated platelet destruction is not the sole pathogenic mechanism of corticosteroid‐resistant ITP (Kong et al , ).…”