The Sympathetic Nervous Influence on Hematopoiesis Up To Date.

Hematopoiesis is a tightly regulated process taking place in specialized bone marrow structures called hematopoietic niches. In these structures, hematopoietic stem cells produce all hematopoietic lineages by their self-renewal and differentiation abilities. Sympathetic nerve fibers, entering the bone marrow in association with blood vessels, regulate on a circadian basis the hematopoietic stem cells and leukocytes migration in and out the bone marrow. This cellular traffic, that is mainly regulated by beta-adrenergic receptors expressed on mesenchymal stem cells, is needed to maintain an efficient hematopoietic niche and for immunosurveillance against infections. Both alpha- and beta-adrenergic receptors seem involved in the regeneration of hematopoiesis after myeloablative treatments. Likewise, the effects of psychogenic stress and of ageing on the hematopoietic system are also mediated by adrenergic signals. Yet, the exact mechanisms regulating hematopoietic regeneration and the differentiation ratio between lymphoid and myeloid cells are still obscure. A comprehensive understanding of the adrenergic influence on hematopoiesis holds the potential for novel therapeutic approaches in a variety of hematological diseases.