Serial transplantation demonstrates superior self-renewal of Lin⁻CD34⁺CD38⁻Rho^lo SRCs compared with Lin⁻CD34⁺CD38⁻Rho^hi SRCs. Sorted cell populations were injected intrafemorally into preconditioned primary (1°) mice. After 7 to 10 weeks, the ability of SRCs to repopulate secondary (2°) mice was assessed separately for cells from the primary injected RF (A) and remaining BM (B). Secondary recipients were killed 7 to 10 weeks after transplantation, and human cell engraftment was assessed in the injected RF and remaining BM. Primary mice were injected with Lin⁻CD34⁺CD38⁻Rho^lo cells (•) or Lin⁻CD34⁺CD38⁻Rho^hi cells (○). Bars indicate geometric means. (*) P < .05 versus Lin⁻CD34⁺CD38⁻Rho^hi cells. (C) Southern blot analysis of repopulating clones in representative primary mice that received a transplant of Lin⁻CD34⁺CD38⁻Rho^lo cells and corresponding secondary recipients. Lanes were loaded with DNA obtained from RF or BM of a primary recipient and from the corresponding tissues of 2 secondary recipients injected with cells from the primary RF (*) or remaining BM (**). Self-renewing clones are indicated by arrowheads.