Fig. 3. Preconditioning of human SkM with rhSDF-1α before exposure to H₂O₂. hSkM cells (2.5× 10⁴) were incubated with different concentration of rhSDF-1α (10 to 200 ng/ml) for 2 hours, then washed and incubated with 100μM H₂O₂ in free-serum DMEM for another 2 hours. Each point was performed in duplicate. The percentage of viable cells was assessed by MTT reduction test (A). Preconditioned treated cell with 200 ng/ml of rhSDF-1α for 1∼4 hours were assessed by measure of LDH released level in conditioned medium (B). The results were expressed as mean±SD. *p＜0.05 (optimized condition, 200 ng/ml rSDF-1a) as in dose concentration manner in (A), and also with 4 h in time dependent in (B) vs. H₂O₂ stress only.