"Scar" - what is it, definition of the term
The term denotes a permanent alteration of skin or other tissue that forms after a wound has closed, consisting of fibrous connective tissue with a collagen arrangement different from the surrounding area, often showing altered pigmentation and a raised, depressed, or flat surface; this result of the body’s reparative process replaces the original structure to restore integrity while leaving a visible mark.
Detailed information
A cutaneous mark that forms after dermal injury in rodents represents the end point of the wound‑repair cascade. The lesion appears as a raised, fibrous area where the original epithelium has been replaced by scar tissue.
The repair sequence proceeds through four overlapping phases. Hemostasis establishes a clot that seals the wound. Inflammation recruits neutrophils and macrophages, which clear debris and release cytokines. Proliferation generates granulation tissue, driven by fibroblast migration and angiogenesis. Remodeling reorganizes collagen fibers, gradually increasing tensile strength while reducing cellularity.
Microscopically, the lesion contains dense, type III collagen initially, later replaced by type I collagen arranged in parallel bundles. Myofibroblasts persist longer than in uninjured skin, contributing to contractile forces that reshape the defect. Epidermal regeneration may be incomplete, leaving a permanent discontinuity in the surface layer.
Factors that modify the final appearance include:
- Age of the animal – younger subjects exhibit faster re‑epithelialization.
- Nutritional status – protein deficiency delays collagen synthesis.
- Genetic background – certain strains show reduced fibroblast activity.
- Wound dimensions – larger defects increase the likelihood of hypertrophic remodeling.
- Anatomical site – areas under tension, such as the dorsal skin, develop more pronounced fibrous tissue.
In laboratory settings, these lesions serve as standardized models for evaluating:
- Topical and systemic agents that accelerate or inhibit tissue repair.
- Genetic manipulations affecting cytokine signaling or extracellular‑matrix production.
- Biomaterials designed to support cell migration and vascularization.
- Quantitative imaging techniques for monitoring collagen organization in vivo.
Understanding the biology of these dermal marks in rats and mice provides a reliable framework for translating wound‑healing strategies to clinical applications.