Figure 1.

Possible mechanisms contributing to bone marrow niche modulation in aplastic anemia. Patients with aplastic anemia display not only low numbers of hematopoietic stem/progenitor cells (HSPC) but also an altered hematopoietic niche. This might result from immunologic attack and/or genetic defects impairing proliferation and survival in niche cells, or alternatively, from perturbed interactions of these with an unphysiologically diminished HSPC pool. Because of a quantitative MSC impairment in patients with acquired AA, it is tempting to speculate that bone marrow transplantations may yield better results compared to peripheral blood as stem cell source because they provide higher numbers of co-transplanted MSCs and supporting non-hematopoietic cell populations, which may promote niche reconstitution and thereby indirectly support nascent hematopoiesis in AA patients treated with allogeneic transplantations. allo-HCT, allogeneic hematopoietic cell transplantation; AA, aplastic anemia; BM, bone marrow; BMF, bone marrow failure; HSPC, hematopoietic stem and progenitor cells; MSC, mesenchymal stem cells; PB, peripheral blood; SDS, Shwachman-Diamond syndrome.