L'adipocyte médullaire : une cellule pleine d'avenir.

Abstract

Bien que constituant un element essentiel du micro-environnement de la moelle osseuse, les adipocytes medullaires ont ete peu etudies. Leur nombre varie considerablement au cours du developpement et dans differentes situations pathologiques lors desquelles se produisent des modifications de l' hematopoiese. Cela a laisse supposer un lien privilegie entre adipocytes et hematopoiese, assimile dans un premier temps a un simple role de soutien ou de fourniture d' energie et de precurseurs lipidiques de l' adipocyte vers les cellules hematopoietiques. Le developpement des cultures cellulaires permet aujourd' hui de considerer que l' adipocyte medullaire, par ses proprietes endocrines et, en particulier, sa capacite de secreter la leptine, joue un role direct dans la differenciation et la proliferation des progeniteurs hematopoietiques. Par ailleurs, il existerait une possibilite de conversion phenotypique entre adipocyte medullaire et osteoblaste, refletant l' origine commune de ces deux types cellulaires. Compte tenu de ces proprietes particulieres, on peut s' interroger sur le fait de considerer cette cellule, a cote de l' adipocyte blanc et de l' adipocyte brun, comme un troisieme type d' adipocyte.

Although bone marrow adipocytes are an essential element of the bone marrow microenvironment, they have attracted little interest. Their number varies considerably in the course of development and in different disorders where hematopoiesis is itself subject to variation. A privileged relationship was thus thought to exist between adipocytes and hematopoiesis, and was first considered to be limited to support or provision energy and lipid precursors from adipocytes to the hematopoietic cells. Owing to the development of cell culture, we can now consider that the bone marrow adipocyte, through its endocrine properties and in particular its ability to secrete leptin, plays a direct role in the differentiation and proliferation of hematopoietic progenitors. Moreover, phenotypic conversion may be possible between bone marrow adipocytes and osteoblasts, reflecting the common origin of these two cell types. Taking into account these particular properties, the future should tell us whether this cell should be considered, beside the white and brown adipocyte, as a third type of adipocyte.