Distinct requirements for optimal growth and In vitro expansion of human CD34(+)CD38(-) bone marrow long-term culture-initiating cells (LTC-IC), extended LTC-IC, and murine in vivo long-term reconstituting stem cells
Recently, primitive human bone marrow (BM) progenitors supporting hematopoiesis in extended (>60 days) long-term BM cultures were identified. Such extended long-term culture-initiating cells (ELTC-IC) are of the CD34(+)CD38(-) phenotype, are quiescent, and are difficult to recruit into proliferation, implicating ELTC-IC as the most primitive human progenitor cells detectable in vitro. However, it