From Wound to Scar: Scarring Explained—Pathophysiology of Wound Healing

Wound healing is a multi-stage process that tries to restore the morphology and function of damaged tissue. Physiological wound healing is divided into many stages that overlap and partly parallel each other. Cytokines and growth factors produced by cells in the wound environment and the wound itself regulate the finely adjusted processes. After an injury, a fibrin coagulum is used to seal the wound temporarily. Neutrophil granulocytes and monocytes/macrophages are recruited and travel to clear pathogens and debris. Finally, macrophages promote fibroblast migration, proliferation, and angiogenesis. Wound contracture speeds wound closure by filling the tissue defect and forming a new extracellular matrix. The defect is reepithelialized at the same time. A wide range of local problems and underlying systemic conditions can impede the wound-healing process. In this situation, the healing process is generally locked in the inflammatory phase, with the granulation phase occurring only rarely. Consequently, despite all treatment efforts, a chronic wound does not heal in an acceptable amount of time. This healing condition is characterized by inflammation, tissue damage caused by increased protease activity and free oxygen radicals, and fibroblast proliferation weakness (senescence). In this chapter, the basics of wound healing and its distinctive phases are explained. Furthermore, the difference between acute and chronic wounds is discussed. Finally, we introduce hyperspectral imaging as tool for non-invasive wound, skin, and scar evaluation.