Art -deficient MSCs are resistant to culture stress by serum withdrawal. (a) Light micrographs of ArtΔ/Δ or WT MSCs exposed to serum-free (serum starvation) versus normal (10%) serum (control) culture conditions. Cell cultures were photographed after either 2 or 6 days of serum withdrawal. (b) ArtΔ/Δ and WT MSCs after culture in normal conditions for 6 days. (c) Viability of WT (filled bars) versus ArtΔ/Δ (open bars) MSCs after culture in normal (control) or serum withdrawal (serum starved) conditions for 7 days. Viable cell counts were determined as the number of trypan blue-excluding cells normalized to the normal serum control. (d) Fold reduction in survival of WT (filled bars) or ArtΔ/Δ (open bars) following 7 days of serum withdrawal. Significance in all assays was determined by t-testing (***P < 0.005).