Colony-forming unit fibroblastic assay of passage 0 bone marrow-derived mesenchymal stem cells isolated and expanded under normoxia or hypoxia. (A-J) Plastic-adherent bone marrow-derived mesenchymal stem cells were isolated and expanded under hypoxia or normoxia and formed colonies that were stained with crystal violet for visualization. Dishes seeded with cells from donor Z01 were excluded because of a lack of colony formation. (K, L) Colony counts and diameters were measured and are reported as mean ± standard error of the mean, and P values are listed. Representative photomicrographs of adherent cells from donor Y19 formed under hypoxic (M) and normoxic (N) culture.