Hematopoietic capacity of adult human skeletal muscle is negligible

Using experimental mouse models, hematopoietic potential has been shown to exist within skeletal muscle. In humans, the clinical utility of using muscle-derived hematopoietic progenitors remains uncertain. Here, we evaluate the hematopoietic potential of human skeletal muscle. De novo adult muscle contained markedly reduced levels of hematopoietic colony-forming units (hCFU) and negligible responsiveness to hematopoietic ex vivo culture conditions that augment hematopoietic activity of fetal muscle. Neither fetal nor adult muscle yielded significant engraftment in transplanted immune-deficient mice. Although adult muscle possessed 1.5+/-0.9 hCFU/g, similar hematopoietic activity (2.3+/-0.17 hCFU) could also be demonstrated from as little as 3-10 microl of contaminating peripheral blood. We suggest that the clinical utility of adult skeletal muscle as an alternative source of hematopoietic cells in humans appears limited due to the low yield of blood-forming precursors and their lack of responsiveness to ex vivo expansion.