Retrovirally transduced muscle-derived cells contribute to hematopoiesis at very low levels in the nonhuman primate model

In vitro and in vivo evaluation of the haematopoietic potential of skeletal muscle in a non-human primate model

This study was aimed at evaluating the in vitro and in vivo haematopoietic potential in macaque skeletal muscle cells. Biopsy samples showed the presence of CD34(+) (7.6%), CD90(+) (8.4%), CD117(+), CD31(+), side population (SP) cells (7-10%) and a low number of CD45(+) cells. In clonogenic and long-term culture-initiating cell assays, no haematopoietic potential could be detected in either total mononuclear cells or SP cells. Regarding in vivo studies, two animals were transplanted with unfractionated fresh muscle cells after lethal irradiation. Both animals died early after transplant without any evidence of haematopoietic reconstitution. In two other monkeys, harvested muscle cells were frozen and secondarily marked using a green fluorescent protein (GFP)-lentiviral vector. After sublethal irradiation, both animals were transplanted with GFP-expressing muscle cells followed by a bone marrow rescue. Both animals had haematopoietic reconstitution at days 22 and 25, but no GFP-expressing haematopoietic cells could be detected by flow cytometry, either in the blood or in clonogenic cells from marrow aspirates. Using PCR assays, GFP(+) cells were detected in a single marrow sample of one animal at 41 days after transplantation. These results strongly suggest that as opposed to murine muscle, the non-human primate skeletal muscle does not harbour cells with a straightforward haematopoietic potential.