Differentiation of fibroblasts to myofibroblasts consists of a phenotypic conversion to α-smooth muscle actin (α-SMA)-positive, highly contractile cells, which secrete proteins of the extracellular matrix (ECM). This differentiation process is crucial for physiological wound healing, as myofibroblasts are responsible for the restoration of damaged tissue and wound closure. Exaggerated, abnormal myofibroblasts activity is associated with the development of fibrosis. TGF-β is the most potent growth factor involved in fibroblasts-to-myofibroblasts conversion. Several studies indicated that the H2O2-generating NADPH oxidase 4 (NOX4) mediates TGF-β-dependent myofibroblasts differentiation during the development of pathological fibrosis in different organs. The profibrotic role of NOX4 has intensively been studied, but its role in physiological skin wound healing has not been described. The hypothesis of this thesis was that NOX4 regulates physiological skin wound healing. In order to investigate this hypothesis, both in vivo and in vitro approaches were applied. Skin wounds were created on the NOX4 KO and WT mice and the time of wound closure, wound size, epithelization, and contraction were determined. Immunohistochemical staining was performed to quantify α-SMA, cellular infiltration, and collagen content in the wounds.