Bleomycin-Induced Subcutaneous Fibrosis and Autologous Fat Graft Remodeling Assessed by Ultrasonography in a Rat Experimental Model

Radiation-associated soft tissue fibrosis represents a progressive structural remodeling process characterized by extracellular matrix accumulation, septal thickening, and reduced tissue compliance, which complicates reconstructive interventions. Reliable longitudinal experimental frameworks capable of non-invasive structural monitoring remain limited. This study aimed to develop and implement a standardized ultrasonographic protocol for the evaluation of bleomycin-induced subcutaneous fibrosis and to assess remodeling dynamics following autologous fat grafting in a rat model. Twenty-two adult female Wistar rats were included. Subcutaneous fibrosis was induced using submaximal bleomycin administration (1 mg/kg/day for three consecutive days). High-frequency ultrasonography (12 MHz) was performed at baseline (Day 0), post-bleomycin (Day 17), and post-lipofilling (Day 31). A predefined semi-quantitative 0-3 scoring system was applied to characterize global echogenicity, septal thickening, and architectural organization. At Day 17, all animals demonstrated structural alteration with a mean score of 2.15 ± 0.58. At Day 31, the mean score decreased to 1.50 ± 0.50, with complete disappearance of high-grade architectural disorganization (score 3). Focal hypoechoic areas consistent with graft integration were observed in 88.9% of animals without ultrasonographic signs of necrosis or fluid collection. This standardized imaging-based framework enables reproducible longitudinal monitoring of early-stage subcutaneous fibrotic remodeling and provides a non-invasive tool for evaluating regenerative interventions in translational soft tissue engineering research.