Hypertrophic scars cause impaired skin appearance and function, seriously affecting physical and mental health. Due to medical ethics and clinical accessibility, the collection of human scar specimens is frequently restricted, and the establishment of scar experimental animal models for scientific research is urgently needed. The four most commonly used animal models of hypertrophic scars have the following drawbacks: the rabbit ear model takes a long time to construct; the immunodeficient mouse hypertrophic scar model necessitates careful feeding and experimental operations; female Duroc pigs are expensive to purchase and maintain, and their large size makes it difficult to produce a significant number of models; and mouse scar models that rely on tension require special skin stretch devices, which are often damaged and shed, resulting in unstable model establishment. Our group overcame the shortcomings of previous scar animal models and created a new mouse model of hypertrophic scarring induced by suture anchoring at the wound edge.

We utilized suture anchoring of incisional wounds to impose directional tension throughout the healing process, restrain wound contraction, and generate granulation tissue, thus inducing scar formation. Dorsal paired incisions were generated in mice, with wound edges on the upper back sutured to the rib cage and the wound edges on the lower back relaxed as a control. Macroscopic manifestation, microscopic histological analysis, mRNA sequencing, bioinformatics, and in vitro cell assays were also conducted to verify the reliability of this method.

Compared with those in relaxed controls, the fibrotic changes in stretched wounds were more profound. Histologically, the stretched scars were hypercellular, hypervascular, and hyperproliferative with disorganized extracellular matrix deposition, and displayed molecular hallmarks of hypertrophic fibrosis. In addition, the stretched scars exhibited transcriptional overlap with mechanically stretched scars, and human hypertrophic and keloid scars. Phosphatidylinositol 3-kinase-serine/threonine-protein kinase B signaling was implicated as a profibrotic mediator of apoptosis resistance under suture-induced tension.

This straightforward murine model successfully induces cardinal molecular and histological features of pathological hypertrophic scarring through localized suture tension to inhibit wound contraction. The model enables us to interrogate the mechanisms of tension-induced fibrosis and evaluate anti-scarring therapies.

Despite being a stable component of burn rehabilitation at later stages of recovery, exercise training is not commonly provided during the acute phase of burns. A lack of evidence surrounding its efficacy and safety in severely burned adults has hampered its implementation in acute burn care. The aim of this study was to investigate the capacity of early exercise training to modulate parameters of postburn muscle wasting and quality of life.

Adults <65 years of age with burns ≥40% total burn surface area (TBSA) were randomly allocated to either receive early exercise (n = 29) in addition to standard care or standard care alone (n = 29). Early exercise involved resistance and aerobic training, which commenced as early as possible and lasted for a duration of 6 to 12 weeks, in line with burn center length of stay. Ultrasound-derived quadriceps muscle layer thickness (QMLT) and rectus femoris cross-sectional area (RF-CSA), lower limb muscle force, Eurocol Quality of Life-5 Dimensions and Burn Specific Health Scale Brief (BSHS-B) were assessed 6 and 12 weeks after baseline. Mixed models were fitted to compare between-group changes over time.

A total of 58 adults [42 (95% confidence interval 40–45) years old; 40–94% TBSA range, 86% previously mechanically ventilated] participated in this study. Exercise commenced 7 days [IQR (interquartile range) 5–9] after burn center admission with an attendance rate of 93%. Allocation to the exercise group had a protective effect on the loss of muscle size from baseline to 6 weeks of follow-up (QMLT: β-coefficient: 0.05 cm, p = 0.010; RF-CSA: β-coefficient: 0.05 cm², p = 0.045), and resulted in an improved recovery from 6 to 12 weeks (QMLT: β-coefficient: 0.04 cm, p = 0.01; RF-CSA: β-coefficient: 0.06 cm², p < 0.001). Muscle force increased significantly more in the exercise group than in the control group (β-coefficient: 3.102 N, p < 0.001) between 6 and 12 weeks. Besides a marginally significant effect for the BSHS-B domains ‘affect’ and ‘interpersonal relationships’ between 6 and 12 weeks, no benefits were observed in the other assessed quality-of-life measures. No serious adverse events were reported in the exercise group.

The results of this study support the use of early exercise training as a feasible and efficacious therapeutic strategy to manage burn-related changes in muscle size and strength in adults with acute severe burn injury.

From the perspective of aesthetic surgery and regenerative medicine, the precision of surgical instruments is critical for preventing aesthetic complications during procedures such as skin debridement and the removal of unwanted tissues, as well as for better regeneration. Femtosecond lasers (fs-lasers) can achieve micrometer-level tissue removal. However, an uneven skin texture can cause the laser to defocus, leading to iatrogenic injury and hindering clinical application. Overcoming the defocusing tendency of fs-lasers is therefore crucial for their clinical use.

Our self-developed fs-laser microfabrication platform was used to implement a focus-corrected method based on 2D interpolation for uneven skin surfaces, using different laser powers and velocities for linear, planar, and 3D scanning of porcine skin. Leveraging the identified dose–response relationship, the optimized device and parameters were used for precise tissue ablation in an in vivo rat experiment. The structural integrity and viability of the remaining skin were evaluated histologically.

Our study revealed that focus-corrected fs-laser ablation enabled controllable micrometer-level removal of target skin tissues. The depth of tissue removal was correlated with the fs-laser single-pulse energy. Unlike other laser devices, the scanning velocity did not affect the ablation depth, as the focusing mechanism of the focus-corrected fs-laser restricts ablation beyond the focal point. Appropriate fs-laser parameters for parallel linear scanning enabled tissue removal in various 3D shapes. Increased depth of field, increased single-pulse energy, and faster scanning velocity enabled precise, rapid, and safe ablation of skin tissue in the rat model. Histological and biochemical analyses demonstrated that focus-corrected fs-laser debridement did not damage the surrounding collagen structure or cell viability of the wound.

We demonstrated that focus-corrected fs-laser ablation enables micron-scale skin removal with minimal collateral damage. By selectively adjusting single-pulse energy for depth-specific ablation and operation at the maximum permissible scanning velocity, this technique enables precise skin removal in the desired shape, offering an innovative and ultrahigh-precision surgical approach for skin as well as other tissues or organ surgery.