Botulinum Toxin Type A and the Prevention of Hypertrophic Scars on the Maxillofacial Area and Neck: A Meta-Analysis of Randomized Controlled Trials

Investigating the impact of botulinum toxin type a on the migration of normal human dermal fibroblasts: An in vitro wound healing assay

BACKGROUND

Botulinum toxin A (BoNT-A) is widely utilized in the management of hypertrophic and keloid scars. One proposed mechanism for scar prevention involves the inhibition of fibroblast migration in scars by BoNT-A. However, the data regarding the effect of BoNT-A on the migration of normal human dermal fibroblasts (NHDF) is limited.

OBJECTIVES

The aim of this study was to investigate the inhibitory effect of different types and dilutions of BoNT-A on the migration of NHDF.

METHODS

In vitro scratch wound assay, NHDF cells were cultured, incubated, and subjected to scratching using a sterile tip. Subsequently, the scratched NHDF monolayer was treated with different types of BoNT-A, including onabotulinumtoxinA (ONA), incobotulinumtoxinA (INCO), prabotulinumtoxinA (PRABO), or letibotulinumtoxinA (LETI), at varying concentrations of 10, 20, 25, 40, 50, and 100 units/milliliter (U/mL). Additionally, abobotulinumtoxinA (ABO) was administered at concentrations of 33, 50, 66, 71, 100, 150, 300, and 500 U/mL. Normal saline solution (NSS) served as a negative control. The extent of NHDF migration was evaluated by comparing each dilution of BoNT-A with the controls using high-content imaging at the 48-h time point. Furthermore, the viability of the of NHDF was assessed.

RESULTS

The concentrations of 25, 40, and 50 U/mL of ONA (p < 0.001) and 25 U/mL of LETI (p < 0.05) demonstrated significantly inhibited NHDF migration in comparison to the control group. Conversely, all dilutions of PRABO, INCO, and ABO exhibited comparable NHDF migration to that of the control group. Regarding NHDF viability, no significant decrease was observed across any of the BoNT-A types and dilutions.

CONCLUSION

Different types and dilutions of BoNT-A demonstrated variable inhibitory effects on NHDF migration in vitro. The selection of BoNT-A formulation may significantly impact the clinical outcome of scar prevention related to fibroblast migration.

Botulinum toxin type A inhibits M1 macrophage polarization by deactivation of JAK2/STAT1 and IκB/NFκB pathway and contributes to scar alleviation in aseptic skin wound healing

The non-neuronal and non-muscular effects of botulinum toxin type A (BTXA) on scar reduction has been discovered. This study was designed to investigate the effects of BTXA on macrophages polarization during the early stage of skin repair. A skin defect model was established on the dorsal skin of SD rats. BTXA was intracutaneous injected into the edge of wound immediately as the model was established. Histological examinations were performed on scar samples. Raw 264.7 was selected as the cell model of recruited circulating macrophages, and was induced for M1 polarization by LPS. Identify the signaling pathways that primarily regulated M1 polarization and respond to BTXA treatment. Application of BTXA at early stage of injury significantly reduced the scar diameter without delaying wound closure. BTXA treatment improved fiber proliferation and arrangement, and inhibited angiogenesis in scar granular tissue. The number of M1 macrophages and the levels of pro-inflammation were decreased after treated with BTXA in scar tissues. LPS activated JAK2/STAT1 and IκB/NFκB pathways were downregulated by BTXA, as well as LPS induced M1 polarization. At early stage of skin wound healing, injection of BTXA effectively reduced the number of M1 macrophages and the levels of pro-inflammatory mediators which contributes to scar alleviation. BTXA resisted the M1 polarization of macrophages induced by LPS via deactivating the JAK2/STAT1 and IκB/NFκB pathways.

Pharmacotherapy for Keloids and Hypertrophic Scars

Keloids (KD) and hypertrophic scars (HTS), which are quite raised and pigmented and have increased vascularization and cellularity, are formed due to the impaired healing process of cutaneous injuries in some individuals having family history and genetic factors. These scars decrease the quality of life (QOL) of patients greatly, due to the pain, itching, contracture, cosmetic problems, and so on, depending on the location of the scars. Treatment/prevention that will satisfy patients' QOL is still under development. In this article, we review pharmacotherapy for treating KD and HTS, including the prevention of postsurgical recurrence (especially KD). Pharmacotherapy involves monotherapy using a single drug and combination pharmacotherapy using multiple drugs, where drugs are administered orally, topically and/or through intralesional injection. In addition, pharmacotherapy for KD/HTS is sometimes combined with surgical excision and/or with physical therapy such as cryotherapy, laser therapy, radiotherapy including brachytherapy, and silicone gel/sheeting. The results regarding the clinical effectiveness of each mono-pharmacotherapy for KD/HTS are not always consistent but rather scattered among researchers. Multimodal combination pharmacotherapy that targets multiple sites simultaneously is more effective than mono-pharmacotherapy. The literature was searched using PubMed, Google Scholar, and Online search engines.

Acne-induced pathological scars: pathophysiology and current treatments

Acne is a common chronic inflammatory dermatosis that can lead to pathological scars (PSs, divided into hypertrophic scars and keloids). These kinds of abnormal scars seriously reduce the quality of life of patients. However, their mechanism is still unclear, resulting in difficult clinical prevention, unstable treatment effects and a high risk of recurrence. Available evidence supports inflammatory changes caused by infection as one of the keys to abnormal proliferation of skin fibroblasts. In acne-induced PSs, increasing knowledge of the immunopathology indicates that inflammatory cells directly secrete growth factors to activate fibroblasts and release pro-inflammatory factors to promote the formation of PSs. T helper cells contribute to PSs via the secretion of interleukin (IL)-4 and IL-13, the pro-inflammatory factors; while regulatory T cells have anti-inflammatory effects, secrete IL-10 and prostaglandin E2, and suppress fibrosis production. Several treatments are available, but there is a lack of combination regimens to target different aspects of acne-induced PSs. Overall, this review indicates that the joint involvement of inflammatory response and fibrosis plays a crucial role in acne-induced PSs, and also analyzes the interaction of current treatments for acne and PS.

Early postoperative interventions in the prevention and management of thyroidectomy scars

Thyroidectomy scars, located on the exposed site, can cause distress in patients. Owing to the cosmetic importance of thyroidectomy scars, many studies have been conducted on its prevention and treatment. Scar formation factors mainly include inflammatory cell infiltration, angiogenesis, fibroblast proliferation, secretion of cytokines such as transforming growth factor (TGF)-β1, and mechanical tension on the wound edges. Anti-scar methods including topical anti-scar agents, skin tension-bearing devices, and local injections of botulinum toxin, as well as lasers and phototherapies, that target these scar formation factors have been developed. However, current studies remain fragmented, and there is a lack of a comprehensive evaluation of the impacts of these anti-scar methods on treating thyroidectomy scars. Early intervention is a crucial but often neglected key to control hyperplastic thyroidectomy scars. Therefore, we review the currently adopted early postoperative strategies for thyroidectomy scar reduction, aiming to illustrate the mechanism of these anti-scar methods and provide flexible and comprehensive treatment selections for clinical physicians to deal with thyroidectomy scars.

Experimental study on the effect and mechanism of adipose stem cell-derived exosomes combined with botulinum toxin A on skin trauma in rats

BACKGROUND

Adipose stem cell-derived exosomes (ADSC-EXO) and botulinum toxin type A (BTX-A) individually showed a therapeutic effect on skin wound repair.

AIMS

This study investigated their synergistic effect on promoting skin wound healing in vitro and in vivo and the underlying molecular events.

METHODS

ADSCs were isolated from Sprague-Dawley (SD) rats to obtain ADSC-EXO by ultrafiltration and ultracentrifugation and were confirmed using nanoparticle tracking analysis and transmission electron microscopy. Human skin fibroblasts (HSF) were cultured and treated with or without ADSC-EXO, BTX-A, or their combination. Changes in cell phenotypes and protein expression were analyzed using different in vitro assays, and a rat skin wound model was used to assess their in vivo effects.

RESULTS

The isolated ADSC-EXO from primarily cultured ADSCs had a circular vesicle shape with a 30-180 nm diameter. Treatment of HSF with ADSC-EXO and/or BTX-A significantly accelerated HSF migration in vitro and skin wound healing in a rat model. Moreover, ADSC-EXO plus BTX-A treatment dramatically induced VEGFA expression but reduced COL III and COL I levels in vivo. ADSC-EXO and/or BTX-A treatment significantly upregulated TGF-β3 expression on Day 16 after surgery but downregulated TGF-β1 expression, suggesting that ADSC-EXO plus BTX-A promoted skin wound healing and reduced inflammatory cell infiltration.

CONCLUSIONS

The ADSC-EXO plus BTX-A treatment demonstrated a synergistic effect on skin wound healing through upregulation of VEGF expression and the TGF-β3/TGF-β1 and COL III/COL I ratio.

Successful Topical Application of Botulinum Toxin After Microneedling Versus Microneedling Alone for the Treatment of Atrophic Post Acne Scars: A Prospective, Split-face, Controlled Study

BACKGROUND

Acne scars are a source of cosmetic concern for most of the patients.

OBJECTIVE

We sought to compare the clinical efficacy and safety of topical botulinum toxin A (BTX-A) application immediately after microneedling (Mn) versus Mn with saline in the treatment of atrophic acne scars.

METHODS

Forty patients with atrophic acne scars (rolling, boxcar, and mixed types) were enrolled in a split-face study; microneedling was performed on both sides of the face followed by an application of topically diluted botulinum toxin on one side (Side A) and saline on the other (Side B) for two sessions both two weeks apart. Evaluation was done at baseline, two and four weeks after the session. Follow-up was performed after six months. The assessments included blinded clinical assessment and patient's satisfaction.

RESULTS

After the treatment, acne scars in (Side A) showed 70 percent overall improvement versus zero percent in Side B (P<0.0001). A statistically highly significant reduction of acne scars severity occurred in (Side A) (P=0.0008). Patient's satisfaction was higher in (Side A) (P<0.0001). No serious side effects were reported.

CONCLUSION

Microneedling delivery of BTX-A could be simple, safe, and innovative modality improving the appearance and decrease the depth of atrophic acne scars.

Emerging off-label esthetic uses of botulinum toxin in dermatology

Botulinum toxin is a neurotoxic protein produced by Clostridium botulinum, the bacterium responsible for botulism. Botulinum toxin was first used for therapeutic indications in the 1970s for the treatment of strabismus. With greater understanding of its underlying physiology and safety profile, the use of botulinum toxin has now expanded to a range of cosmetic and medical indications. We performed a systematic review of current literature on the applications of botulinum toxin on off-label esthetic uses. Electronic databases were searched for original published studies including randomized trials, observational or cohort studies, as well as relevant case reports. To add to the body of evidence, our review summarizes and synthesizes key study characteristics, results, and level of evidence for each use case. Although the body of evidence remains weak, there is increasing support for the use of botulinum toxin in emerging off-label esthetic uses of botulinum toxin in dermatology.

Combination Treatment of Intra/Perilesional Botulinum Toxin-A Injection and Ablative Fractional Laser for Better Clinical Outcomes of Hypertrophic Fibrotic Thyroidectomy Scars Following Fractional Ablative Laser Resurfacing

BACKGROUND

Recent reports have shown that intralesional botulinum toxin type-A (BTX-A) works on scar cosmesis.

OBJECTIVE

To evaluate the clinical efficacy of combination treatment of laser and BTX-A injection and compare the effects of conventional intralesional injection and intra- and perilesional BTX-A injection on fibrotic thyroidectomy scars.

METHODS

Patients with fibrotic thyroidectomy scars showing insufficient responses to previous ablative fractional laser (AFL) treatment were enrolled. Combination treatment with AFL and BTX-A injection was performed. Patients who received intra/perilesional BTX-A injections were classified into group A. Group B was patients in whom the injection was performed only intralesionally. The improvement was assessed based on the Vancouver Scar Scale (VSS).

RESULTS

A total of 24 patients was included. Statistically significant improvement in pliability and total VSS score after the combination treatment were observed in overall patient group. Subgroup analysis demonstrated that pliability, height, and total VSS improved significantly in group A. In group B, only pliability significantly improved.

CONCLUSION

BTX-A injection combined with AFL can provide better relief for the previously treated fibrotic thyroidectomy scars. Injection of BTX-A not only into the scar itself, but also into perilesional muscles that can exert tension on the scar site may provide additional benefit in flattening scar height.

Evaluation of the efficiency and safety of botulinum toxin A injection on improving facial scars: A protocol for systematic review and meta-analysis

BACKGROUND

Botulinum toxin A injection is an established method of treatment. Clinical practitioners use it widely in their practice to prevent the occurrence of facial scars. However, the effectiveness and safeness of has not been comprehensively established. The objective of the current systematic review is to evaluate the efficacy and safety of using botulinum toxin A injection to improve facial scars.

METHODS AND ANALYSIS

This systematic review involves browsing a number of electronic databases to search for related articles. The search will include databases in both English (PubMed, EMBASE, Web of Science, Spocus, and Cochrane Central Register of Controlled Trials) and Chinese (WanFang database, China Nation Knowledge Infrastructure, and VIP database), the periods of searching will be from inception till the 15th of September 2020. Completing the search in databases allows to consider randomized controlled studies that compares botulinum toxin A interventions to any comparison interventions in those who have facial scars. The review will be inclusive of papers in both languages, English and Chinese. The independent screening of studies for eligibility is conducted by 2 independent authors. Discussion was used to resolve discrepancies between the authors. The Cochrane Risk of Bias Tool V.2.0 is adopted for evaluating the methodological quality of each study. Data extraction was performed by 2 independent authors. For dichotomous outcomes, the were expressed as relative risk (RR) with 95% confidence intervals (CI). For continuous outcomes the results were expressed as the mean difference (MD) or standardized mean difference (SMD) with 95% CI. The statistical analysis of the present study is carried out in RevMan 5.3 software.

RESULTS

This study will output a comprehensive synthesis of existing evidence in relation to botulinum toxin A. Moreover, the results will also provide an interpretation of the effectiveness and safety of botulinum toxin A.

CONCLUSION

The present review contributes to the existing body of knowledge by adding more evidence to evaluate if botulinum toxin A is effective and safe to be used as an intervention for improving facial scars.

OSF REGISTRATION NUMBER

DOI 10.17605/OSF.IO/94TXP (https://osf.io/94TXP/).

Keloids: a review of therapeutic management

Keloid scar formation arises from a disorganized fibroproliferative collagen response that extends beyond the original wound margins because of excessive production of extracellular matrix (ECM). Despite treatment options for keloid scars including medical and surgical therapies, such as intralesional steroid injection and surgical excision, the recurrence rate remains high. Herein we consolidate recently published narrative reviews, systematic reviews, and meta-analyses to provide an overview of updated treatment recommendations for keloidal scar formation. PubMed search engine was used to access the MEDLINE database to investigate updates regarding keloid incidence and treatment. More than 100 articles were reviewed. Keloid management remains a multimodal approach. There continues to be no gold standard of treatment that provides a consistently low recurrence rate; however, the increasing number of available treatments and synergistic combinations of these treatments (i.e., laser-based devices in combination with intralesional steroids, or 5-fluorouracil (5-FU) in combination with steroid therapy) is showing favorable results. Future studies could target the efficacy of novel treatment modalities (i.e., autologous fat grafting or stem cell-based therapies) for keloid management. This review article provides updated treatment guidelines for keloids and discusses insight into management to assist patient-focused, evidence-based clinical decision making.

Efficacy and Safety of Botulinum Toxin Type A in Preventing Postoperative Scars and Improving the Cosmetic Appearance of Scars: A Systematic Review and Meta-Analysis

BACKGROUND

Scars with poor cosmesis that develop after wound healing may affect normal life.

OBJECTIVE

To assess the efficacy and safety of botulinum toxin type A (BTXA) in preventing postoperative hypertrophic scars or keloids.

METHODS

A systematic review was performed by searching the PubMed, Cochrane Library, and EMBASE databases from their inception date up to February 2020 for randomized controlled trials (RCTs) evaluating the efficacy of BTXA in preventing hypertrophic scars or keloids. The primary outcome measures included the Vancouver Scar Scale (VSS) score, Visual Analog Scale (VAS) score, scar width, patient satisfaction, and adverse events.

RESULTS

Twelve RCTs involving 497 cases (372 patients) were included. The meta-analysis showed significant differences in the VAS score (weighted mean difference [WMD] = 1.31, 95% CI = 1.06 to 1.55, P < .00001), VSS score (WMD = -1.02, 95% CI = -1.72 to -0.32, P = .004), scar width (WMD = -0.18, 95% CI = -0.29 to -0.08, P = .0008), and patient satisfaction (relative risk = 1.25, 95% CI = 1.06-1.49, P = .01). Four studies reported trivial adverse events.

CONCLUSIONS

This meta-analysis showed that BTXA was more effective than the control treatment in preventing postoperative scars and improving the cosmetic appearance of facial scars for East Asians, and no serious adverse events were found during the follow-up period. However, there was insufficient evidence to support the use of BTXA for the prevention of scars in patients from other ethnic groups and regions or scars in non-facial areas.

Appropriate Timing of Early Postoperative Botulinum Toxin Type A Injection for Thyroidectomy Scar Management: A Split-Scar Study

BACKGROUND

Botulinum toxin type A (BTxA) injection is effective for surgical scar prevention. Although some studies have aimed to confirm the efficacy of BTxA injection at different time points, none has been conducted to determine the most appropriate timing of injection for scar management. The authors predicted that the injection of BTxA at different times during the wound healing process would cause differing scar quality improvement and clarify unknown molecular mechanisms.

METHODS

The study included adults who underwent thyroidectomy. All patients received paralesional BTxA injections on the day of the surgery on either the right or left side of the operative site. The same dose was injected on the noninjected side by means of the same method after 2 weeks. At 2, 4, 12, and 24 weeks postoperatively, the modified Stony Brook Scar Evaluation Scale, visual analogue scale, and erythema index were used for objective, subjective, and quantitative evaluations of the scar. At week 24 postoperatively, a quantitative scar assessment was performed with respect to the erythema index, skin elasticity, melanin index, and friction.

RESULTS

On objective evaluation of the scar and patient satisfaction at 24 weeks postoperatively, the operation-day injection side showed better outcomes than the 2-week-postoperative injection side. These differences were significant from postoperative week 4. In the final quantitative scar assessment at postoperative week 24, significant improvements were observed in the erythema index and skin elasticity.

CONCLUSION

These results suggest that immediate postoperative BTxA injection is more effective for thyroidectomy scar management in terms of erythema, skin elasticity, and patient satisfaction.

CLINICAL QUESTION/LEVEL OF EVIDENCE

Therapeutic, II.

The use of botulinum toxin in keloid scar management: a literature review

INTRODUCTION

Administration of botulinum toxin is an increasingly popular procedure in the medical and aesthetic field. There is emerging evidence that it can influence fibroblast activity and minimise tension around the scar by virtue of muscular chemoimmobilisation. This review aims to explore the current evidence base behind the treatment of keloid scars with botulinum toxin.

METHODS

A detailed literature review was conducted using PubMed Medline, Embase and Web of Science databases. Manuscripts were appraised and classified in accordance with the Joanna Briggs Institute Levels of Evidence by an independent consultant in evidence synthesis. The results of this search are presented in descending order of evidence for botulinum toxin as a primary management agent as well as a secondary adjunct following extralesional keloid excision.

DISCUSSION

On the basis of level 1 evidence, botulinum toxin appears to be equivalent to triamcinolone in producing a short-term reduction in keloidal volume, height and vascularity. A number of level 1 and 2 studies also suggest that botulinum toxin may be particularly helpful in alleviating symptoms of keloid associated pain and itch. There are currently limited studies appraising the value of botulinum toxin in the postoperative management of keloid scars.

CONCLUSION

Botulinum toxin may represent a promising agent in the management of keloid scars. However, further research involving large-scale studies with comparative designs and long-term follow-up is warranted to delineate the value of this therapeutic modality in scar management protocols.

Botulin Toxin Use in Scars/Keloids Treatment

Botulinum toxin (BTX) is a neurotoxin protein derived from the Clostridium botulinum bacterium that inhibits the release of acetylcholine at the neuromuscular junction level whose effects has been used for many years to treat a variety of muscular/neuromuscular conditions and more recently also for cosmetic use.

BTX has experimented in some dermatological conditions which include scar prevention and treatment with good results The complex mechanism underlying those results is not completely understood but several mechanisms were proposed release inhibition of different substances like (TGF)-β, substance P, calcitonin gene-related peptide (CGRP) and glutamate thus modulating cutaneous inflammation and wound healing.

We analysed the published data on BTX off label applications on scars and keloids retrieved from PubMed.

[Postoperative care and options for scar treatment in eyelid surgery]

Oculoplastic surgery places special demands on postoperative care because of the functional importance of the eyelids for the ocular surface. We present an overview of postoperative care after surgical eyelid interventions. All options, limits and the scientific evidence are discussed with a special focus on the treatment of postoperative edema, analgesia, infection prophylaxis and scar treatment.

Cosmetic camouflage improves quality of life among patients with skin disfigurement: A systematic review

This study systematically reviewed the impact of cosmetic camouflage use on different psychosocial outcomes in patients with disfiguring skin disorders. Electronic databases and reference lists were searched in February 2018 for studies reporting the impact of cosmetic camouflage on different quality of life (QoL) outcomes. Eighteen studies met the inclusion criteria: six randomized controlled trials, two quasi-experimental studies, nine single group 'before and after' interventions, and one comparative study with single post-intervention measurement. Quality appraisal of included studies was undertaken using the Joanna Briggs critical appraisal tools. While the studies varied in design, those included in this review indicated significant improvement in QoL after the use of cosmetic camouflage. The mean reduction in Dermatological Life Quality Index scores ranged from 1.4 to 6.4 signifying improvement in QoL of participants after treatment with cosmetic camouflage. Cosmetic camouflage can be an effective therapy in improving QoL among patients with skin disfigurement.

Personal Technique of Microinfiltration With Botulin Toxin: The SINB Technique (Superficial Injection Needling Botulinum)

The superficial injection needling botulinum (SINB) technique is the dermal injection of microdoses of botulin toxin, not by traditional syringe but with needling technique that consists in multiple microdroplets by electrical device. The intention is to decrease sweat and sebaceous gland activity to improve skin texture and sheen and to target the superficial layer of muscles that find attachment to the undersurface of the dermis causing visible rhytides. The technique is for treatment of face and neck by the injection of the botulin toxin into the dermis or in subdermal plane to improve skin texture, smoothen horizontal creases, and decrease vertical banding of the neck as well as to achieve better apposition of the platysma to the jawline and neck, improving contouring of the cervicomental angle. The botox solution is hyperconcentrated when compared to traditional dilution or compared to microbotox or mesobotox. Furthermore, the injection technique is different because spreading superficial microdroplets are not performed, but small, homogeneous, and controlled amounts of solution are injected. Each 0.8-mL syringe contains 50 units of onabotulinumtoxinA. The solution is delivered intradermally, using an electrical needling pen and setting the depth penetration of the needles at 3 to 3.5 mm. The 2 conjugated techniques play a 2-fold action on the skin. The technique was applied to a group of 63 patients dealing with face, forehead, cheekbones, and neck.

A Randomized, Placebo-Controlled, Double-Blind, Prospective Clinical Trial of Botulinum Toxin Type A in Prevention of Hypertrophic Scar Development in Median Sternotomy Wound

BACKGROUND

Linear hypertrophic scar is a common surgical problem that can be difficult to manage, especially for the median sternotomy scar. Botulinum toxin type A (BTA) is widely used in cosmetic surgery and has been shown to improve scar quality recently. The aim of this study was to evaluate the efficacy of BTA injected in the early postoperative of median sternotomy on preventing scar formation.

METHODS

In this prospective randomized controlled trial, 19 consecutive patients who underwent median sternotomy were enrolled. The median sternotomy wound in each patient was divided into the upper half and the lower half. Both halves of the wound were randomized to receive the treatment with either BTA or normal saline. At 6-month follow-up, scars were assessed using the Vancouver Scar Scale, scar widths were measured, and patients were asked to evaluate their overall satisfaction.

RESULTS

Seventeen patients with median sternotomy wounds completed the entire study. At 6-month follow-up, the mean Vancouver Scar Scale score for the BTA-treated group was 3.44 ± 1.68 and for the normal saline control group was 6.29 ± 2.39, and there was a statistically significant difference between the two groups (P < 0.05). There were also significant improvements in scar width and patient satisfaction for the BTA-treated halves of the wounds (P < 0.05).

CONCLUSIONS

The study demonstrates that early postoperative BTA injection can decrease scar formation and reduce scar width in median sternotomy wounds, and the overall appearance is more satisfactory.

LEVEL OF EVIDENCE I

This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

The Cellular Response of Keloids and Hypertrophic Scars to Botulinum Toxin A: A Comprehensive Literature Review

BACKGROUND

Keloids and hypertrophic scars are conditions of pathologic scarring characterized by fibroblast hyperproliferation and excess collagen deposition. These conditions significantly impact patients by causing psychosocial, functional, and aesthetic distress. Current treatment modalities have limitations. Clinical evidence indicates that botulinum toxin A (BoNT-A) may prevent and treat keloids and hypertrophic scars.

OBJECTIVE

To examine investigated cellular pathways involved in BoNT-A therapeutic modulation of keloids and hypertrophic scars.

METHODS

The authors searched PubMed, Embase, and Web of Science for basic science articles related to botulinum toxin therapy, scarring, fibroblasts, keloids, and hypertrophic scars.

RESULTS

Eleven basic science articles involving keloids and hypertrophic scars were reviewed.

DISCUSSION

BoNT-A may reduce skin fibrosis by decreasing fibroblast proliferation, modulating the activity of transforming growth factor-β, and reducing transcription and expression of profibrotic cytokines in keloid-derived and hypertrophic scar-derived dermal fibroblasts. BoNT-A may modulate collagen deposition, but there is a paucity of evidence regarding specific mechanisms of action.

CONCLUSION

Overall, BoNT-A has the potential to prevent or treat pathologic scars in patients with a known personal or family history of keloids and hypertrophic scars, which may improve patient psychosocial distress and reduce clinic visits and health care costs. Variability in keloid and hypertrophic scar response to BoNT-A may be due to interexperiment differences in dosing, tissue donors, and assay sensitivity.

New Uses of AbobotulinumtoxinA in Aesthetics

BotulinumtoxinA (BoNT-A) is now widely established for the main approved indication of reducing glabellar lines, and is also widely used off-label to improve the appearance of wrinkles and lines in other parts of the face. The number of aesthetic procedures continues to increase as the patient population becomes more diverse, in particular with increasing numbers of people of color and men. Further developments in treatment may continue to expand the audience for BoNT-A by making procedures more comfortable and by delivering a more natural, less static appearance. These may be achieved through use of combinations of BoNT-A with other aesthetic procedures, tailoring the dose of toxin to the patient's muscle mass or by using novel injection and application techniques. Beyond amelioration of facial lines, encouraging results have been seen with the use of BoNT-A to improve the appearance of hypertrophic and keloid scars and even to prevent them. Studies have been conducted with scars in various parts of the body and further research is ongoing. Dermatological and other medical uses for BoNT-A are also active areas of research. Injections of BoNT-A have been shown to reduce signs and symptoms of acne, rosacea, and psoriasis, to reduce neuromuscular pain, and to bring about significant improvements in a number of rare diseases that are caused or exacerbated by hyperhidrosis. This paper reviews these new uses for BoNT-A, looking at the rationale for their use and discussing the results of published case studies and clinical trials. These areas have shown great promise to date, but more and larger clinical studies will be required before these treatments become a clinical reality. To this end details are also provided of clinical trials currently listed in the main clinical trials database to highlight research areas of particular interest.