Ex vivo–expanded BM HSCs are in both Endoglin-positive and -negative fractions. After 10 days of culture of total BM cells, 6000 sorted Endoglin⁺ and 2.4 × 10⁴ Endoglin^- cells or 3000 Lin^-Endoglin^- and 3000 Lin^-Endoglin⁺ cells were transplanted together with 2 × 10⁵ CD45.1 competitor cells into lethally irradiated CD45.1 mice (n = 4). Shown are peripheral blood engraftment at 4 weeks (left) and 4 months (right) after transplantation. Different numbers of sorted Endoglin⁺ Endoglin^- cells were used because after culture there were 3 times more Endoglin^- cells (76% of the total) than Endoglin⁺ cells (26%). Error bars indicate SEM.