Expression of HO-1 in wound fibroblasts in time. Fibroblast populations isolated from the wound area (see “Materials and methods”) were analyzed for HO-1 expression levels (left y-axis; mean fluorescence intensity) and percentage HO-1⁺ cells (right y-axis) using flow cytometry. After initial decrease, HO-1 expression is elevated and peaks after 15 days, after which it decreased and returned to control levels (left y-axis). After wounding, the population of infiltrated HO-1⁺ cells swiftly increased, peaked after 15 days, and returned to control levels at day 60, after which it slowly increased again (right y-axis).