Bone marrow stromal cells from β-thalassemia patients have impaired hematopoietic supportive capacity

Abstract

BACKGROUND. The human bone marrow (BM) niche contains a population of mesenchymal stromal cells (MSCs) that provide physical support and regulate hematopoietic stem cell (HSC) homeostasis. β-Thalassemia (BT) is a hereditary disorder characterized by altered hemoglobin beta-chain synthesis amenable to allogeneic HSC transplantation and HSC gene therapy. Iron overload (IO) is a common complication in BT patients affecting several organs. However, data on the BM stromal compartment are scarce. METHODS. MSCs were isolated and characterized from BM aspirates of healthy donors (HDs) and BT patients. The state of IO was assessed and correlated with the presence of primitive MSCs in vitro and in vivo. Hematopoietic supportive capacity of MSCs was evaluated by transwell migration assay and 2D coculture of MSCs with human CD34 + HSCs. In vivo, the ability of MSCs to facilitate HSC engraftment was tested in a xenogenic transplant model, whereas the capacity to sustain human hematopoiesis was evaluated in humanized ossicle models. RESULTS. We report that, despite iron chelation, BT BM contains high levels of iron and ferritin, indicative of iron accumulation in the BM niche. We found a pauperization of the most primitive MSC pool caused by increased ROS production in vitro which impaired MSC stemness properties. We confirmed a reduced frequency of primitive MSCs in vivo in BT patients. We also discovered a weakened antioxidative response and diminished expression of BM niche–associated genes in BT-MSCs. This caused a functional impairment in MSC hematopoietic supportive capacity in vitro and in cotransplantation models. In addition, BT-MSCs failed to form a proper BM niche in humanized ossicle models. CONCLUSION. Our results suggest an impairment in the mesenchymal compartment of BT BM niche and highlight the need for novel strategies to target the niche to reduce IO and oxidative stress before transplantation. FUNDING. This work was supported by the SR-TIGET Core grant from Fondazione Telethon and by Ricerca Corrente.

Transfusion independence after repeated haploidentical hematopoietic cell transplants in a patient with congenital dyserythropoietic anemia type II and hemosiderosis

“…A healthy BM microenvironment is of paramount importance in allowing and sustaining hematopoietic cell engraftment after HCT. Chronically transfused patients such as ours with significant BM hemosiderosis have impaired hematopoietic supportive capacity and are at increased risk for graft failure . Despite eventual successful engraftment after a third HCT resulting in transfusion independence, our case underscores the risks associated with performing a haploidentical HCT in an older pediatric patient with CDA and severe chronic iron overload.…”

Intra-bone marrow co-transplantation of umbilical cord mesenchymal stem cells promotes the engraftment of umbilical cord blood stem cells in iron overload NOD/SCID mice

“…A weakened antioxidative response and diminished expression of bone marrow niche-associated genes in the MSC were found. This caused a functional impairment in MSC hematopoietic supportive capacity in vitro and in vivo [17]. Since the beneficial effects of MSC were hampered by iron overload, we, therefore, replenished the MSC pool by IBM co-transplantation of MSC with HSC.…”

Bone Marrow-Derived Mesenchymal Stromal Cells: A Novel Target to Optimize Hematopoietic Stem Cell Transplantation Protocols in Hematological Malignancies and Rare Genetic Disorders

“…A condition of iron overload has been identified in the BM niche of BT patients causing a significant upregulation of ROS level in BT-MSCs. The exposure of BT-MSCs to increasing doses of iron revealed an inappropriate antioxidant response, which is responsible for the pauperization of the most primitive MSC fraction [174]. In addition, β-thalassemia-mesenchymal stromal cells (BT-MSCs) express lower level of hematopoietic supportive factors compared to controls, that negatively affect their ability to attract HSPCs in vitro, to sustain HSPC expansion and primitive phenotype in 2D co-culture model, to favor HSPC engraftment and immunological reconstitution in xenogenic transplant models, and to form a proper BM niche in vivo [174] (Figure 6).…”

“…The exposure of BT-MSCs to increasing doses of iron revealed an inappropriate antioxidant response, which is responsible for the pauperization of the most primitive MSC fraction [174]. In addition, β-thalassemia-mesenchymal stromal cells (BT-MSCs) express lower level of hematopoietic supportive factors compared to controls, that negatively affect their ability to attract HSPCs in vitro, to sustain HSPC expansion and primitive phenotype in 2D co-culture model, to favor HSPC engraftment and immunological reconstitution in xenogenic transplant models, and to form a proper BM niche in vivo [174] (Figure 6). These results highlight a profound defect in the BM niche of BT patients, which may explain the increased risk of graft rejection and mixed chimerism observed after HSTC [175,176] and prove the need to treat the BM niche with the aim of reducing oxidative stress, thus potentially ameliorating transplantation outcome.…”