CFU-F content and niche activity of MSCs is reversed by switching culture conditions.

<p>(A) Schematic illustration of experimental scheme. MSCs that had been passage cultured in stimulatory or non-stimulatory conditions were switched to the other conditions or to 3^rd medium for additional 2 passages, then analyzed for CFU-F or co-cultured with HSCs for 5days. (B) Effects of switching culture on the CFU-F content of MSCs. Shown are the mean numbers of CFU-F for 500 MSC cells in each culture condition with error bar representing SEM. Large and small colonies were separately counted (n = 6 for each group). (C, D) Effects of switching culture on hematopoietic supporting activity of MSCs. MSCs that had been passaged under stimulatory or non-stimulatory condition were switched to 3^rd medium (C) or to the other condition (D), followed by co-culture with CD34⁺ cells for additional 5 days. Shown are the numbers of primitive hematopoietic cell population (CD34⁺CD90⁺) after co-culture under each indicated switched culture conditions with error bars representing SEM (n = 6; ***, p < .0001).