What Causes Scarring?
Scarring occurs as the body's natural healing response to tissue injury, resulting from excessive deposition of extracellular matrix by fibroblasts and myofibroblasts during the wound healing process, primarily modulated by the inflammatory response at the injury site. 1
Fundamental Mechanism of Scar Formation
Scar tissue forms when the dermis is damaged and the body attempts to reestablish dermal integrity. 2 The process involves:
- Fibroblast activation and proliferation at the wound site, leading to excessive collagen deposition 3
- Inflammatory response modulation that drives the wound healing process toward fibrotic tissue formation rather than regeneration 1
- Myofibroblast activity that contracts and deposits extracellular matrix, creating the characteristic dense, disorganized collagen structure of scars 1
The key distinction is that scarring is not necessary for tissue repair—it represents a specific adult wound healing mechanism that differs from the regenerative healing seen in fetal wounds or certain animal models. 1
Specific Causes and Risk Factors
Tissue Injury and Trauma
- Surgical procedures that disrupt tissue integrity 3
- Physical trauma including burns, lacerations, and penetrating injuries 4
- Ulceration from various causes, which always leaves residual scarring 3
Procedural and Iatrogenic Causes
- Surgical manipulation of tissue, including bridle sutures that can cause local bleeding and scar formation 3
- Laser procedures where the dermis between vessels is coagulated, particularly when dermis is largely replaced by vessels 3
- Delayed epithelial healing following procedures like keratectomy, especially with ablation depth beyond 50-75μm 3
- Direct muscle or tissue injury during ophthalmic surgeries including pterygium surgery, blepharoplasty, and scleral buckling 3
Disease-Related Scarring
- Inflammatory skin conditions including lichen sclerosus, which can cause significant scarring and stenosis 3
- Recurrent infections or chronic inflammation that leads to florid scarring 3
- Corneal dystrophies where underlying disease processes recur despite treatment 3
Factors That Worsen Scarring
Critical risk factors that increase scar severity include:
- Delayed re-epithelialization following injury or surgery 3
- Infection at the wound site 3
- Excessive tissue manipulation or repeated trauma 3
- Inadequate anti-inflammatory treatment during the healing phase 3
- Hemorrhage and tissue edema in adjacent structures 3
Clinical Implications
The formation of scar tissue represents inferior tissue compared to uninjured skin, though it successfully restores the barrier between body and environment. 1 Understanding that inflammation drives fibrosis rather than regeneration explains why:
- Early intervention to control inflammation may reduce scarring 1
- Mitomycin-C works by inhibiting cellular proliferation involved in wound healing, though with significant risks including keratocyte depletion and endothelial failure 3
- Residual scarring is permanent once formed, with only transient haze being reversible 3
The spectrum of scarring ranges from stretched (flat) scars to contracted, atrophic, and raised (hypertrophic/keloid) variants, each requiring different management approaches. 5