Exercise mediated regulation of medullary and extramedullary hematopoiesis

Abstract

<p>Bone marrow is the major site of adult hematopoiesis. Bone marrow cells exert control over the hematopoietic stem cells that reside in the niche; osteoblasts act as positive regulators while adipocytes act as negative regulators. Levels of circulating hematopoietic cytokines also regulate hematopoiesis. In this study, we demonstrate that an endurance exercise training program results in several changes that act to induce hematopoiesis. Bone marrow-derived mesenchymal stem cell differentiation is skewed away from adipogenesis and towards osteogenesis in exercise trained animals. As a result, the bone marrow cavity is remodeled during the training period and acts to facilitate hematopoiesis. Hematopoietic cytokine gene expression levels also increase in exercise trained skeletal muscle. These changes translate into increased bone marrow and blood hematopoietic stem and progenitor cell content. This study draws a link between exercise training, bone marrow niche regulation, skeletal muscle derived hematopoietic cytokines, and the regulation of hematopoiesis.</p>