No blood from muscle?

Villejuif, France -

The concept of cellular plasticity has attracted many followers, as well as many critics. On the one hand, papers used to be published suggesting various forms of transdifferentiation, for example neurons becoming blood cells, or hematopoietic stem cells becoming cardiomyocytes. On the other hand, some scientists (especially our friend from Stanford) have been known to go on extended rants about transdifferentiation being non-existant.

In a recent paper (Haond et al. In vitro and in vivo evaluation of the haematopoietic potential of skeletal muscle in a non-human primate model. Bone Marrow Transplant. 2007 Nov 26;) the hematopoietic ability of skeletal muscle from monkeys was assessed.

Muscle biopsy extracted cells appeared to contain a population that represented 7-10% of the mononuclear population that resembled stem cells based on expression of phenotypic markers (CD34, CD90, CD31), receptors (c-kit), and functional properties (drug efflux).

Unfortunately these cells did not possess hematopoietic ability in vitro. Transplanting lethally irradiated animals with the putative stem cell population did not result in hematopoietic reconstitution.

The authors concluded that primate muscle does not have cells that possess hematopoietic activity.

On the flip side of the coin, at least in mouse, it appears that hematopoietic stem cells have the ability to differentiate into muscle (Abedi et al. Haematopoietic stem cells participate in muscle regeneration. Br J Haematol. 2007 Sep;138(6):792-801).