Effect of hyperbaric oxygen on the process of hypertrophic scar formation in rabbit ears

Could hyperbaric oxygen be an effective therapy option for pathological scars? A systematic review and meta-analysis

BACKGROUND

Hyperbaric oxygen (HBO) therapy involves breathing pure oxygen or a high oxygen concentration above atmospheric (ATM) pressure in an enclosed chamber. Studies on pathological scars have demonstrated that HBO can inhibit the formation of pathological scars.

OBJECTIVE

To evaluate the efficacy of HBO in the treatment of pathological scars via meta-analysis.

METHODS

Searches were run on various databases, including the Cochrane, Embase, PubMed, Web of Science, and CNKI databases. A comparative study was conducted on patients with pathological scars treated with or without HBO. We used RevMan 5.4 software to determine the recurrence rate, treatment satisfaction, and Vancouver Scar Scale(VSS) score in the pathological scar.

RESULTS

A total of 543 publications were identified; after screening, four were selected for review, including one randomized controlled trial (RCT), one controlled clinical trial (CCT), and two retrospective cohort studies. Meta-analysis results showed that HBO treatment reduced the pathological scar recurrence rate after surgery and radiotherapy (OR = 0.26, 95% CI: 0.13-0.52, p = 0.0001). Patients had higher satisfaction after HBO therapy (OR = 4.45, 95% CI: 1.49-13.30, p = 0.007). The Vancouver scar scale (VSS) score of patients with pathological scars was significantly improved in the HBO group (SMD: -3.82, 95% CI: -6.07to -0.49, p = 0.02).

CONCLUSIONS

HBO treatment decreased the recurrence rate of pathological scars after surgery and radiotherapy, increased patient satisfaction, and reduced the VSS score, thus providing a new way to treat pathological scar hyperplasia. However, evaluation of the longer-term effects of HBO treatment requires further comprehensive studies, including more RCTs.

In Vivo Models for Hypertrophic Scars—A Systematic Review

Backgroundand Objectives: Hypertrophic scars following surgeries or burns present a serious concern for many patients because these scars not only lead to an aesthetical but also to a functional and psychological burden. Treatment of hypertrophic scars is challenging because despite various treatment options, a low level of evidence hinders preference of any specific treatment plan. To properly identify new therapeutic approaches, the use of in vivo models remains indispensable. A gold standard for hypertrophic scars has not been established to date. This review aims at giving a comprehensive overview of the available in vivo models. Materials and Methods: PubMed and CINAHL were queried for currently existing models. Results: Models with mice, rats, rabbits, pigs, guinea pigs and dogs are used in hypertrophic scar research. Rodent models provide the advantage of ready availability and low costs, but the number of scars per animal is limited due to their relatively small body surface, leading to a high number of test animals which should be avoided according to the 3Rs. Multiple scars per animal can be created in the guinea pig and rabbit ear model; but like other rodent models, these models exhibit low transferability to human conditions. Pig models show a good transferability, but are cost-intensive and require adequate housing facilities. Further, it is not clear if a currently available pig model can deliver clinical and histological features of human hypertrophic scars concurrently. Conclusions: None of the analyzed animal models can be clearly recommended as a standard model in hypertrophic scar research because the particular research question must be considered to elect a suitable model.

A Review of Hypertrophic Scar and Keloid Treatment and Prevention in the Pediatric Population: Where Are We Now?

Significance: This body of work gives a concise and comprehensive overview for the clinician and scientist on the latest treatment modalities for hypertrophic scars (HTS) and keloids in the pediatric population, as well as the most promising methods of prevention currently being investigated. This review will serve as a guide to the clinician for treatment selection and as an efficient tool for the scientist to achieve a comprehensive overview of the scientific literature to guide their future experiments aimed at pathologic scar prevention. Recent Advances: Current studies in the literature suggest carbon dioxide (CO₂) laser and E-light (bipolar radiofrequency, intense pulsed light, and cooling) are two of the most effective treatment modalities for HTS, while surgical excision+CO₂ laser+triamcinolone injection was one of the most successful treatments for keloids. In animal models, drug impregnated electrospun nanofiber dressings offer encouraging results for HTS prevention, while Kelulut honey showed promising results for keloid prevention. Critical Issues: Treatment outcome reproducibility is hindered by small cohorts of patients, inadequate-follow up, and variability in assessment tools. Prevention studies show multiple ways of achieving the same result, yet fall short of complete prevention. Furthermore, some studies that have purported full prevention have not been validated. Future Directions: To establish a standard of care, large clinical trials of the most successful modalities in small cohorts are needed. The key for prevention will be validation in animal models of the most successful methods, followed by translational and clinical studies.

Evaluation of the effect of hyperbaric oxygen therapy on hypertrophic scar formation in a rabbit ear model: An experimental study

Hypertrophic scar is a disease with complicated treatment methods. Although there are numerous studies in the literature definitive therapy has not been reported yet. In this study, we aimed to evaluate the short and long-term effects of HBOT on hypertrophic scar formation in a rabbit ear model. A total of 20 male New Zealand rabbits weighing 2.1 to 2.4 kg were used in this study. The rabbits in group 2 were exposed to hyperbaric oxygen treatment for 7 days starting from the first day following biopsy punch, while no extra treatment was applied to the rabbits in group 1. Macroscopic scar thickness, histopathological parameters and HI were assessed in both of the 30th day and 60th day scars. Scar thickness was found significantly less in the scars of the rabbits exposed to HBOT (P < .05). And less dermal hypertrophy was also found in HI results of group 2.(P ≈ .022) There were differences between groups in terms of inflammation, vascularization and density of collagen fibrils. HBOT applied for 7 days from the first day of wound formation has both short and long-term effects on the triggering factors of hypertrophic scar, especially on inflammation.

The therapeutic effect of Interleukin-18 on hypertrophic scar through inducing Fas ligand expression

OBJECTIVE

Among downstream interleukin-18 (IL-18) targets, Fas ligand (FasL) in particular, has been strongly implicated in many conditions. Our study aims to explore the role of IL-18 in hypertrophic scar through enhancing FasL expression.

METHODS

IL-18 expression in hypertrophic scar tissues and normal tissues were explored by immunohistochemistry, qRT-PCR and Western blotting, and the expression of IL-18 in normal skin fibroblasts and hypertrophic scar fibroblasts by immunofluorescence. Hypertrophic scar fibroblasts treated with recombinant human IL-18 (rhIL-18) were assessed with MTT, Annexin V-FITC/PI, qRT-PCR, ELISA and western blotting. In the hypertrophic scar of rabbit ears, rhIL-18 was injected to determine histological changes with HE and Masson staining. Additionally, the scars were rated based on contour and overall severity using a visual analog scale scores (VAS).

RESULTS

IL-18 was decreased in hypertrophic scar tissues and fibroblasts compared to normal skin tissues and fibroblasts, respectively. Decreased proliferation and increased apoptosis of hypertrophic scar fibroblasts were found after rhIL-18 treatment with enhanced expression of FasL, sFasL FADD, Caspase-8, Caspase-9 and Caspase-3 in a dose-dependent manner. The VAS and thickness of scars in rabbit ears was decreased as time went on after rhIL-18 treatment, with decreases in scar elevation index (SEI) and the increases in FasL expression.

CONCLUSION

IL-18 curbs proliferation and promotes apoptosis of hypertrophic scar fibroblasts by enhancing FasL expression. IL-18is a potential target for treatment of hypertrophic scar.