Methods of controlling proliferation and differentiation of stem and progenitor cells

An expanded undifferentiated hematopoietic cell population having reduced intracellular cooper content obtained by ex vivo culturing of seeded hematopoietic cells in a culture medium providing said hematopoietic cells with conditions for cell proliferation and in the presence of a transition metal chelator having an affinity for copper,

• wherein said chelator and said proliferation conditions result in (i) prolonged active hematopoietic cell proliferation;
• (ii) prolonged expansion of clonogenic cells;
• and (iii) maintenance of undifferentiated hematopoietic cells in their undifferentiated state,
• thereby inhibiting differentiation while permitting expansion of said hematopoietic cell population in said culture medium,
• and wherein said hematopoietic cells are hence expanded yet not further differentiated as compared to ex vivo seeded hematopoietic cells from which said expanded hematopoietic cell population expanded.