title: Hematon: a multicellular functional unit in primary hematopoiesis.
abstract: Bone marrow aspirates from healthy donors contain a fraction of low density multicellular spheroids, 100-500 microns in diameter. They are organized in a three-dimensional network consisting of central preadipocytes/adipocytes, mesenchymal and reticular cells, and resident macrophages that are closely associated with myeloid, erythroid and megakaryocyte progenitor cells and with their progenies. These spheroids are 2- to 5- fold more abundant in progenitor cells compared with the whole bone marrow as estimated by monoclonal antibody markers My 10 and T 9, by analysis of granulocyte--macrophage colony forming cells (GM-CFC) and by cytological techniques. They produce terminally differentiated cells in organotypic microcultures. We suggest that a multicellular spheroid may represent the fundamental unit of primary hematopoiesis; we therefore name it hematon. Here we show that the presence of hematons in bone marrow aspirates correlated positively with homeostatic blood cell production: they were present in normal bone marrow (BM) (19/25), and absent in myelodysplasic syndromes (MDPS) (8/21), in acute nonlymphocytic leukemias (ANLL) (3/22) and in chronic myeloid leukemia (CML) (2/28). The hematons were recovered under hematological remission in MDPS and in ANLL, suggesting that they may be dispersed reversibly in certain disease conditions. The hematons represent a unifying model around which the variability in some bone marrow cell functions can be explored.
authors.affiliation: ICIG and SMSIT, Université Paris-Sud, Villejuif, France.
authors.forename: I
authors.initials: I
authors.lastname: Blazsek
authors.forename: J L
authors.initials: JL
authors.lastname: Misset
authors.forename: M
authors.initials: M
authors.lastname: Comisso
authors.forename: G
authors.initials: G
authors.lastname: Mathé
mesh_terms: D001853:Bone Marrow / Q000473:pathology; D001854:Bone Marrow Cells; D002454:Cell Differentiation / Q000187:drug effects; D003115:Colony-Stimulating Factors / Q000494:pharmacology; D006410:Hematopoiesis; D015464:Leukemia, Myelogenous, Chronic, BCR-ABL Positive / Q000473:pathology; D015470:Leukemia, Myeloid, Acute / Q000473:pathology; D009190:Myelodysplastic Syndromes / Q000473:pathology
chemical_list: D003115:Colony-Stimulating Factors