Surgical Wound Healing: The Four Phases of Cell Growth and Tissue Repair

Surgical wound healing progresses through four overlapping phases, each driven by specific cellular activity:

1. Hemostasis (Minutes–Hours)

Platelets aggregate, forming a fibrin clot and releasing PDGF, TGF-β, and EGF—signaling the recruitment of inflammatory cells.

2. Inflammatory Phase (Days 1–5)

Neutrophils arrive first (phagocytosing bacteria and debris), followed by monocytes that become macrophages. Macrophages orchestrate repair by secreting cytokines (IL-1, TNF-α), growth factors (VEGF, FGF), and recruiting fibroblasts. Some fibroblast apoptosis occurs as part of normal turnover.

3. Proliferative Phase (Days 4–21)

Fibroblasts proliferate and synthesize collagen III (early, reticular) then collagen I (mature, tensile). They also produce glycosaminoglycans, proteoglycans, and fibronectin—forming granulation tissue. Angiogenesis (VEGF-driven) restores perfusion. Epithelial cells migrate across the wound bed (re-epithelialization).

4. Remodeling Phase (Weeks–Months–Years)

Collagen III is replaced by collagen I; fibers cross-link and align along tension lines. Myofibroblasts contract the wound. MMPs and TIMPs balance matrix degradation and synthesis. The result is a scar with approximately 80% of the original tensile strength.

Key point: Initial cell death (neutrophils, some fibroblasts) is programmed and necessary—it clears the way for organized repair. Dysregulation (excess inflammation, impaired angiogenesis, diabetes, steroids) leads to chronic wounds or pathological scarring (hypertrophic, keloid).