The Northwestern Abdominoplasty Scar Model: A Novel Human Model for Scar Research and Therapeutics

Pharmaceutical Prophylaxis of Scarring with Emphasis on Burns: A Review of Preclinical and Clinical Studies

Significance: The worldwide estimate of burns requiring medical attention each year is 11 million. Each year in the United States, ∼486,000 burn injuries receive medical attention, including 40,000 hospitalizations. Scars resulting from burns can be disfiguring and impair functions. The development of prophylactic drugs for cutaneous scarring could improve the outcomes for burns, traumatic lacerations (>6 million/year treated in U.S. emergency rooms), and surgical incisions (∼250 million/year worldwide). Antiscar pharmaceuticals have been estimated to have a market of $12 billion. Recent Advances: Many small molecules, cells, proteins/polypeptides, and nucleic acids have mitigated scarring in animal studies and clinical trials, but none have received Food and Drug Administration (FDA) approval yet. Critical Issues: The development of antiscar pharmaceuticals involves the identification of the proper dose, frequency of application, and window of administration postwounding for the indicated wound. Risks of infection and impaired healing must be considered. Scar outcome needs to be evaluated after scars have matured. Future Directions: Once treatments have demonstrated safety and efficacy in rodent and/or rabbit and porcine wound models, human testing can begin, such as on artificially created wounds on healthy subjects and on bilateral-surgical wounds, comparing treatments versus vehicle controls on intrapatient-matched wounds, before testing on separate cohorts of patients. Given the progress made in the past 20 years, FDA-approved drugs for improving scar outcomes may be expected.

A Systematic Review Comparing Animal and Human Scarring Models

Introduction

A reproducible, standardised model for cutaneous scar tissue to assess therapeutics is crucial to the progress of the field. A systematic review was performed to critically evaluate scarring models in both animal and human research.

Method

All studies in which cutaneous scars are modelling in animals or humans were included. Models that were focused on the wound healing process or those in humans with scars from an existing injury were excluded. Ovid Medline^® was searched on 25 February 2019 to perform two near identical searches; one aimed at animals and the other aimed at humans. Two reviewers independently screened the titles and abstracts for study selection. Full texts of potentially suitable studies were then obtained for analysis.

Results

The animal kingdom search yielded 818 results, of which 71 were included in the review. Animals utilised included rabbits, mice, pigs, dogs and primates. Methods used for creating scar tissue included sharp excision, dermatome injury, thermal injury and injection of fibrotic substances. The search for scar assessment in humans yielded 287 results, of which 9 met the inclusion criteria. In all human studies, sharp incision was used to create scar tissue. Some studies focused on patients before or after elective surgery, including bilateral breast reduction, knee replacement or midline sternotomy.

Discussion

The rabbit ear scar model was the most popular tool for scar research, although pigs produce scar tissue which most closely resembles that of humans. Immunodeficient mouse models allow for in vivo engraftment and study of human scar tissue, however, there are limitations relating to the systemic response to these xenografts. Factors that determine the use of animals include cost of housing requirements, genetic traceability, and ethical concerns. In humans, surgical patients are often studied for scarring responses and outcomes, but reproducibility and patient factors that impact healing can limit interpretation. Human tissue use in vitro may serve as a good basis to rapidly screen and assess treatments prior to clinical use, with the advantage of reduced cost and setup requirements.

Comparison of a Novel Silicone Gel Wound Dressing vs Bacitracin After Follicular Unit Extraction Hair Transplantation

BACKGROUND

Follicular unit extraction (FUE) hair transplantation subjects are excellent candidates to assess wound dressings. The wound surface area is large and adequately delineated to allow randomization, while in-patient split scalp designs allow patients to serve as their own controls.

OBJECTIVES

This randomized, single-blinded, split-scalp comparison trial compares a novel, film-forming silicone gel-Stratamed (SM; Stratpharma AG, Basel, Switzerland)-to Bacitracin (Bac; McKesson Medical-Surgical Inc., Richmond, VA) in subjects undergoing FUE.

METHODS

Twenty subjects were randomized to receive SM and Bac on alternating sides of the scalp. Primary outcome measures included blinded clinician assessments of edema, erythema, crusting, healing response and outcome preference. Secondary measures included subject-reported assessments of pain and pruritis as well as FaceQ scores taken at post-FUE days two through six.

RESULTS

Twenty subjects were enrolled. Nineteen completed the trial. All subjects were non-smokers, and none had medical comorbidities expected to impact wound healing. An average of 1778 follicles per subject were harvested. No adverse events were reported, and all subjects healed by day 7. Healing response and outcome preference were significantly higher at day 1 in the SM group and by day 7, both groups were similar. There were no significant differences between groups for edema, erythema, or crusting. There were no significant differences between groups for subject-reported outcomes of pain, pruritis, or FACE-Q scores. When asked which product they preferred using, 44% of subjects preferred using SM versus 22% who preferred Bac.

CONCLUSIONS

The SM wound dressing was well-tolerated in patients undergoing FUE. SM may speed the healing response in the early phase of wound healing.

LEVEL OF EVIDENCE 2

The Northwestern Abdominoplasty Scar Model: A Tool for High-Throughput Assessment of Scar Therapeutics

Significance: Scar management is an important concern in plastic surgery. Scar models that best mimic in vivo human scarring are essential for understanding scar development and progression, assessing the efficacy of therapeutics, and providing reliable and valid research outcomes. Recent Advances: In 2016, Lanier et al. proposed a new in vivo patient model, the Northwestern Abdominoplasty Scar Model, that overcomes the prior limitations of both animal and human models, with greater representativeness of the human scarring process, expedited recruitment, smaller sample requirements, and greater flexibility in the types and number of interventions that can be studied simultaneously. Critical Issues: Existing animal models suffer from limitations that impede generalization to human scars. Human scar studies are difficult to conduct and rarely used due to recruitment difficulties, ethical concerns regarding purposeful wounding, and inherent variability based on location, type of scar, and the heterogeneity of the host response between humans. Although overcoming many of these hurdles, the Northwestern Abdominoplasty Scar Model still has a few limitations. In addition, there remains a need for further study of and comparison between the Northwestern Abdominoplasty Scar Model and existing human and animal models, to inspire more widespread acceptance of a standardized human scar model. Future Directions: The Northwestern Abdominoplasty Scar Model is a critical stepping stone toward better human scar models. This model hopefully will inspire other in vivo patient models utilizing elective surgery to overcome recruitment and ethical concerns.

Comparison of Aesthetic Quality of the Final Scar in Abdominoplasty with Conventional and Mini Inverted t-Scar

Background and objectives: Abdominoplasty is one of the most commonly performed cosmetic procedures. The excess skin in the conventional abdominoplasty is transversely excised and a single horizontal scar is formed. The mini inverted t-scar abdominoplasty is a modification of the “Fleur-de-lis” technique and involves the use of a small vertical incision in comparison to the long vertical incision. The aim of this technique is to lower the position of the final abdominal scar instead of addressing the horizontal laxity. In this study, we have compared the aesthetic satisfaction, width and the position of the scar with conventional abdominoplasty and mini inverted t-scar abdominoplasty. Materials and Methods: Thirty patients undergoing abdominoplasty and breast reconstruction with transverse rectus abdominis flap (TRAM) and deep inferior epigastric flap (DIEP) were included in the study. In 15 patients, abdominal closure with the conventional transverse scar was performed. In the remaining 15 patients, closure with a mini inverted t-scar was performed. Scar width, scar height and satisfaction scores were evaluated in both groups. Results: Scar widths, scar heights and patients’ and as well as surgeons’ satisfaction scores were better in the mini inverted t-scar group than the conventional group. Conclusions: The visibility of the vertical scar alone should not be a reason to avoid mini inverse t-scar abdominoplasty. Mini inverted t-scar can be an option to achieve a better hidden high-quality scar.