In vitro and in vivo hematopoietic potential of human stem cells residing in muscle tissue

Objective We studied the in vitro and in vivo hematopoietic potential of human stem cells residing in muscle tissue collected from adults with head and neck cancer. Materials and Methods Adherent muscle cells were cultured in F12 medium with 10% fetal bovine serum and transplanted into immunodeficient mice. Results On day 12 we obtained a median of 500,000 adherent cells per gram muscle sample. Thy-1, endoglin, HER2/neu, and P1H12 were expressed in the majority of cells. CD34, VEGFR2, c-kit, VCAM-1, and CXCR4 were expressed in 0.5–1.5%, 1–5%, 1–15%, 9–15%, and 30% of cells, respectively. Immunodeficient mice transplanted with fresh muscle cells or less than 500,000 cultured cells showed little or no human engraftment. In mice transplanted with more than 500,000 cultured cells, up to 14% human CD45+ hematopoietic cells (including myeloid and lymphoid subsets) were detected by flow cytometry. Engraftment was confirmed by polymerase chain reaction, Southern blotting, and DNA sequencing. Liver, muscle, and spleen evaluated for human DNA were positive in the majority of mice showing hematopoietic engraftment in the bone marrow. In vivo hematopoietic engraftment potential was maintained in cultured CD45− muscle cells transduced with the green fluorescence protein gene. Conclusions Human stem cells residing in muscle tissue can generate multilineage hematopoiesis in immunodeficient mice. Surprisingly, this hematopoietic potential increased in cultured versus fresh cells from muscle tissue.