<b>Significance:</b> Fractional resurfacing involves producing arrays of microinjuries on the skin, by thermal or mechanical means, to trigger tissue regeneration. Originally developed for cosmetic enhancement, fractional resurfacing induces a broad array of improvements in the structural and functional qualities of the treated skin and is especially effective at returning defective skin to a more normal state. In addition to fascinating questions about the nature of this remarkable regenerative capacity, there may be potential utility in ulcer prevention by halting or even reversing the progressive decline in overall skin quality that usually precedes chronic wound development. <b>Recent Advances:</b> Photoaging and scarring are the two skin defects most commonly treated by fractional resurfacing, and the treatment produces profound and long-lasting improvements in skin quality, both clinically and at the cellular/histologic level. Chronic wounds usually occur in skin that is compromised by various pathologic factors, and many of the defects found in this ulcer-prone skin are similar to those that have seen improvements after fractional resurfacing. <b>Critical Issues:</b> The mechanisms responsible for the regenerative capacity of fractional resurfacing are mostly unknown, as is how ulcer-prone skin, which is usually afflicted by stressors external to the skin tissue itself, would respond to fractional resurfacing. <b>Future Directions:</b> Better understanding of the cellular and molecular mechanisms underlying the unique healing response to fractional resurfacing could reveal fundamental information about adult tissue regeneration, lead to improvements in current applications, as well as new therapies in other pathologic conditions.

Abstract Hypertrophic scars are one of the more difficult problems to treat in our clinical practice. In this review, we cover our approach, from basic science research in our laboratory to the clinical theater on how we approach and treat these patients to improve cosmetic appearance and functional capabilities for patients suffering from hypertrophic scars.

This review aims to investigate the mechanisms underlying the application of ablative fractional CO2 laser in scar treatment and analyze its effects on inflammatory responses, cell proliferation and collagen remodeling during wound healing. It focuses on how the fractional CO2 laser promotes skin repair by modulating molecular mechanisms, thereby effectively improving scar appearance. This review summarizes numerous clinical and experimental studies on ablative fractional CO2 laser treatment, focusing particularly on its regulatory effects on immune cells, fibroblasts, matrix metalloproteinases (MMPs), transforming growth factor-β (TGF-β), heat shock proteins (HSPs), microRNAs (miRNAs), and basic fibroblast growth factor (bFGF) at various stages of repair. The findings demonstrate that ablative fractional CO2 laser significantly improves scars through precise thermal damage and modulation of the tissue repair. Specifically, by precisely regulating key factors such as MMPs, TGF-β, HSPs, miRNAs, and bFGF during the tissue repair phases, it promotes re-epithelialization, neovascularization, and the synthesis and orderly deposition of collagen, thereby balancing antifibrotic and pro-repair effects to improve scar texture and function. The fractional CO2 laser is an effective modality for scar treatment that promotes scar resolution and wound healing through dynamic regulation. It demonstrates significant clinical efficacy for both atrophic and hypertrophic scars, offering new perspectives and approaches for future scar management. This review aims to investigate the mechanisms underlying the application of ablative fractional CO 2 laser in scar treatment and analyze its effects on inflammatory responses, cell proliferation and collagen remodeling during wound healing. It focuses on how the fractional CO 2 laser promotes skin repair by modulating molecular mechanisms, thereby effectively improving scar appearance. Specifically, by precisely regulating key factors such as MMPs, TGF-β, HSPs, miRNAs, and bFGF during the tissue repair phases, it promotes re-epithelialization, neovascularization, and the synthesis and orderly deposition of collagen, thereby balancing antifibrotic and pro-repair effects to improve scar texture and function. The fractional CO 2 laser is an effective modality for scar treatment that promotes scar resolution and wound healing through dynamic regulation. It demonstrates significant clinical efficacy for both atrophic and hypertrophic scars, offering new perspectives and approaches for future scar management. Currently, the dermatological lasers commonly used in clinical practice are primarily divided into two categories: ablative lasers and non-ablative lasers [ 1 ]. Traditional ablative laser resurfacing achieves skin remodeling through complete skin resurfacing. Although effective, it is often accompanied by adverse reactions such as edema, exudation, crusting, pigmentary changes, and scarring. In contrast, non-ablative laser treatments have milder side effects but often require multiple sessions and yield limited efficacy [ 6 – 8 ]. The pulse duration modulates the extent of thermal diffusion; a shorter pulse width helps to precisely confine the injury to the target area, avoiding unnecessary thermal accumulation in surrounding tissues. Furthermore, the spot size and the density of the treatment area (MTZs/cm²) collectively determine the proportion of the epidermal area covered during a single treatment. Balancing these variables is essential for inducing sufficient therapeutic necrosis for tissue remodeling, achieving an optimal balance between recovery speed and therapeutic outcome [ 16 ]. The fractional CO 2 laser has demonstrated effective therapeutic results for both atrophic and hypertrophic scars. clearly observed significant thinning of the stratum corneum in hypertrophic scars after fractional CO₂ laser therapy [ 29 ]. This histological alteration marks the effective alleviation of the hyperkeratotic state of the scar, providing a microstructural explanation for the clinically observed improvement in rough scar texture. The increase in CD31-positive vascular density in the dermis of photoaged human skin at 3 and 5 weeks post-treatment indicates the reconstruction of the vascular network [ 23 ], which has also been corroborated in normal mouse skin models and human scar tissues [ 19 , 21 , 23 ]. Similarly, another study on mature human burn scars observed elevated MMP-1 expression 48 h postoperatively [ 31 ]. This suggests that MMP-1 likely plays a primary role in degrading scar tissue during the early stage following laser treatment. MMP-3, also known as stromelysin-1, is expressed by keratinocytes in the proximal proliferative population near the leading edge during wound healing [ 32 ]. It degrades partially damaged collagen, proteoglycans, elastin, laminin, and fibronectin [ 32 , 36 , 37 ]. Conclusion This review demonstrates that fractional CO 2 laser therapy significantly improves scar quality through precisely controlled thermal injury-induced wound healing mechanisms (inflammation-proliferation-remodeling). Its core mechanisms involve the regulation of molecular pathways—including MMPs, TGF-β, bFGF, HSPs, and miRNAs (Fig. 2 ) (Table 1 )—to stimulate orderly collagen remodeling. Its efficacy in improving scar elasticity, thickness, and symptoms has been well documented. Fig. Building upon this foundation, multi-omics technologies, including spatial transcriptomics, should be further integrated to dissect the three-dimensional molecular regulatory networks of “laser-scar” interactions. This will not only help elucidate the heterogeneous responses of different scar types but also provide a robust theoretical basis for formulating personalized treatment strategies, maximizing therapeutic efficacy across diverse patient populations, and minimizing adverse reactions.

ed skin. Non-responsive skin after a facelift. Fine lines or wrinkles around or under the eyes, forehead or mouth Enlarged oil glands on your nose. You may not be a good candidate for laser skin resurfacing if you have: Active acne. Very dark skin. Deep wrinkles. Excessive or sagging skin. Treatment Details How does laser skin resurfacing work? There are two forms of laser resurfacing. First there’s carbon dioxide (CO2) and erbium lasers. These lasers create a uniform injury to your skin in the treatment area. The other form of laser resurfacing is called fractionated CO2 laser treatment. Fractionated CO2 laser resurfacing involves using the laser to drill numerous narrow columns of holes deep into the layers of your skin, but with the surrounding skin remaining untreated and intact. Advertisement CO2 laser resurfacing CO2 laser resurfacing has been used for years to treat different benign and malignant skin conditions. A newer generation of CO2 laser resurfacing uses very short pulsed light energy (ultrapulsed) or continuous light beams that are delivered in a scanning pattern to very precisely remove thin layers of skin with minimal heat damage to the surrounding structures. CO2 laser resurfacing has been successfully used to treat wrinkles and scars as well as other benign skin growths such as warts , birthmarks, rhinophyma (enlarged oil glands on the nose), and other skin conditions. Recovery time with CO2 laser resurfacing is up to two weeks. Erbium laser resurfacing Erbium laser resurfacing is designed to remove superficial and moderately deep lines and wrinkles on your face and should require only local anesthetic. This laser can also be used on your hands, neck or chest. One of the benefits of erbium laser resurfacing is minimal injury of surrounding tissue. This laser causes fewer side effects than CO2 lasers, such as swelling, bruising and redness, so your recovery time should be more rapid. If you have a darker skin tone, erbium laser resurfacing may be a