Fractional Ablative CO2 Laser Treatment Results in Measurable Changes to Collagen and Galectin in Hypertrophic Scars

Burn injuries often lead to hypertrophic scars (HTS), which negatively affect quality of life and skin function. Hypertrophic scars result from abnormal wound healing characterized by excess, disorganized collagen confined to the original wound. Fractional ablative CO₂ laser revision (FLSR) has shown promise in improving burn scar symptoms by inducing micro-wound healing, but its specific mechanism remains unclear. Progress is limited by a lack of standardized, objective metrics to evaluate treatment response. We hypothesized that FLSR would shift HTS collagen structure toward that of normal skin (NS) and reduce galectin-1, a wound-healing molecule elevated in HTS, and that these changes could be quantified. Red Duroc pigs, whose wounds heal similarly to humans, were used to create HTS and NS sites. Each pig had 4 HTS and 2 NS sites. Punch biopsies were collected at postoperative days 49 and 70, corresponding to pre- and post-FLSR timepoints. Fractional ablative CO₂ laser revision was administered on days 49, 56, and 63. Biopsies were paraffin-embedded, sectioned, stained with Picrosirius Red, imaged at 40× (n = 3/tissue), and analyzed using CT-FIRE and CurveAlign software. Metrics included collagen fiber width, length, straightness, angle, number, and overall alignment. Data were compared using 2-way analysis of variance. Before treatment, NS and HTS differed significantly in collagen alignment and width. After treatment, HTS collagen alignment shifted toward NS values, while width differences persisted. Galectin-1 levels decreased in HTS after FLSR. Other parameters showed no significant changes. These findings indicate that FLSR alters collagen alignment and length in HTS and that quantitative collagen metrics provide a valuable, objective method for assessing HTS treatment effectiveness.