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Hématologie

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Tissus adipeux, cellules hématopoïétiques et hématopoïèse Volume 17, issue 1, Février 2011

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Authors
Université de Toulouse, UPS, UMR 5241 métabolisme, plasticité et mitochondrie, Toulouse, CNRS, UMR 5241 Métabolisme, Plasticité et Mitochondrie, Toulouse, Laboratoire d’hématologie, CHU de Toulouse

The metabolic and endocrine role of white adipose tissue (WAT) has give rise to numerous studies. Since a few years, the identification of an abundant and various hematopoietic population in this tissue brought us to draw a parallel with the bone marrow. Located within hematopoietic tissue in adults, medullar adipose tissue is supposed to play a key role in the control of hematopoiesis. There are indeed narrow relationships between medullar fat cells and hematopoietic cells that were extensively studied. In contrast, the study of hematopoiesis in extramedullar WAT is very recent. We demonstrated the existence in this tissue of a functional hematopoietic stem cells population, presenting however specific properties towards their medullar counterparts. As in the bone marrow, the microenvironment in WAT is composed of stromal and fat cells and seems to play a role on mature and immature hematopoietic cells. The recent data thus suggest that the extra-medullar WAT could present a real hematopoietic function, whose physiological importance remains to be determined. In summary, the knowledge on each of these tissues is not of the same order. Indeed, while hematopoiesis in the bone marrow is very well studied and described, the medullar fat cells and the yellow bone marrow are still little known. On the contrary while extra-medullar white adipose cells have been fully investigated, their links and relations with hematopoietic cells still remain to be specified. This capacity of adipose tissues in mammals to assume both a metabolic role and possibly an immune function via the production of hematopoietic cells could result from the evolution of the fat body, a common ancestral structure present in insects.