title: Hematopoietic stem cells under pressure.
abstract: OBJECTIVE
  Hematopoietic stem cells (HSCs) and progenitors are tasked with maintaining hematopoietic homeostasis in the face of numerous insults and challenges, including infection, inflammation, and exsanguination. HSCs possess the remarkable ability to reconstitute the entire hematopoietic system of an organism whose own hematopoietic system has been ablated. This ability is exploited routinely in the clinic via HSC transplantation (HSCT). Here, we focus on the physiological and molecular bottlenecks overcome by HSCs during transplantation.
  
  
  RESULTS
  During transplantation, HSCs encounter a damaged bone marrow niche, characterized molecularly by increases in oxygen concentrations and an altered cytokine milieu. New mechanisms and pathways have been recently implicated during HSCT, including transplanted HSC-dependent secretion of conditioning molecules that facilitate engraftment and pathways that protect HSCs from perturbed organelle homeostasis.
  
  
  CONCLUSIONS
  Better understanding the molecular processes HSCs employ to withstand the stress of transplant will illuminate novel targets for further improving conditioning regimens and engraftment during HSCT.
authors.affiliation: Department of Hematology, St. Jude Children's Research Hospital, Memphis, Tennessee, USA.
authors.forename: Miguel
authors.initials: M
authors.lastname: Ganuza
authors.forename: Shannon
authors.initials: S
authors.lastname: McKinney-Freeman
mesh_terms: D000818:Animals; D002465:Cell Movement; D044127:Epigenesis, Genetic; D005786:Gene Expression Regulation; D006085:Graft Survival; D018380:Hematopoietic Stem Cell Transplantation; D006412:Hematopoietic Stem Cells / Q000166:cytology* / Q000378:metabolism*; D006706:Homeostasis; D006801:Humans; D015388:Organelles / Q000378:metabolism; D018384:Oxidative Stress; D017382:Reactive Oxygen Species; D055153:Stem Cell Niche / Q000187:drug effects / Q000528:radiation effects; D013312:Stress, Physiological; D019172:Transplantation Conditioning / Q000009:adverse effects / Q000379:methods
chemical_list: D017382:Reactive Oxygen Species