Botulinum Toxin Type A Inhibits α-Smooth Muscle Actin and Myosin II Expression in Fibroblasts Derived From Scar Contracture

New and Future Developments in Neurotoxins

BACKGROUND

There are 7 known serotypes of botulinum neurotoxins (A through G). Currently, commercially available toxins are those in serotypes A and B. This paper will discuss new toxins on the horizon, developments in prolonging and shortening the duration of outcomes, and novel therapeutic indications on the horizon.

OBJECTIVE

To provide insight into new toxins and new therapeutic modalities surrounding toxins on the horizon.

METHODS

The authors have reviewed the relevant literature and shared their insights and opinions as to future developments in toxin research and potential clinical applications.

CONCLUSION

Botulinum neurotoxin type E's faster onset and shorter duration of effect represent true clinical differentiators. Future development of botulinum neurotoxin type E for aesthetic and therapeutic uses will be in areas where fast onset and short duration of effect are desirable. Current challenges with neuromodulators include the need for frequent treatments and lack of reversal agents. Agents to address both challenges and novel indications, including inhibition of melanogenesis, are being developed.

Using Neuromodulators to Improve Scar Formation, Keloids, Rosacea, and Antiaging

BACKGROUND

Botulinum toxin A (BoNT-A) treatment has many uses in dermatology. Its mechanism of action and long-term effects for scar formation, rosacea, and antiaging are still being investigated.

OBJECTIVE

To conduct a literature review on BoNT-A to further investigate its use in scar formation, rosacea, and antiaging.

METHODS

A literature review was conducted using PubMed on botulinum toxin treatment for scar formation, rosacea, and antiaging. Studies discussing the toxin mechanism of action and treatment algorithm were included. The authors also provided their personal experience in BoNT-A use for these 3 conditions.

RESULTS

The mechanism of action of Botulinum toxin A in improving scar formation, rosacea, and antiaging is now better understood. While it is effective in the short term, little is still known about how frequently treatment needs to be repeated and if there are any long-term effects.

CONCLUSION

While in vitro studies have supporting evidence on the mechanism of action of BoNT-A on scar formation, rosacea, and antiaging, further studies are needed to identify long-term treatment effects.

Alteration of myoepithelial cells during botulinum toxin type A-inhibited salivary secretion

OBJECTIVE

Intraglandular injection of botulinum toxin type A (BoNT/A) effectively treats sialorrhea. Myoepithelial cells (MECs) are essential for salivary secretion. The role of MECs in BoNT/A-inhibited salivary secretion, and its underlying mechanisms remain unknown.

MATERIALS AND METHODS

BoNT/A was injected into rat submandibular glands (SMGs). At 1, 2, 4, 8, and 12 weeks postinjection, salivary flow rate of SMGs was measured. Electron microscopy, immunohistochemistry, immunofluorescence, and Western blot analysis were used to detect morphological and functional changes in MECs and chemical denervation in SMGs.

RESULTS

BoNT/A temporarily decreased salivary secretion in rat SMGs and this inhibitory effect lasted 4 weeks. During the inhibitory period, MECs atrophied and expressed reduced α-smooth muscle actin (α-SMA), vimentin, and phosphorylated myosin light chain 2 (p-MLC2), suggesting that BoNT/A attenuated MEC contractility. Furthermore, BoNT/A cleaved synaptosome-associated protein 25 (SNAP-25) and decreased the expression and activity of acetylcholinesterase (AChE), indicating that BoNT/A-induced chemical parasympathetic denervation of SMGs by cleaving SNAP-25.

CONCLUSIONS

BoNT/A temporarily caused MEC atrophy and decreased MEC contractility in rat SMGs, which contributed to reversible inhibition of salivary secretion. The underlying mechanisms involved temporary parasympathetic denervation caused by SNAP-25 cleavage. These findings provide new insights into the mechanisms of BoNT/A-inhibited salivary secretion.

Current Research of Botulinum Toxin Type A in Prevention and Treatment on Pathological Scars

BACKGROUND

Dermatologists have been looking for ways to improve wound healing and postoperative scar appearance. The safety and efficacy of botulinum toxin type A (BTXA) in the prevention and treatment on pathological scars have become the current research hotspot since it was approved by the US FDA in medical cosmetology in 2002.

PURPOSE

This article aims to provide an overview of the clinical research, limitations, and application prospects of BTXA in the prevention and treatment of traumatic or postoperative pathological scars, which can provide a reference and better understanding of relevant studies.

METHODS

The current research progress was summarized and discussed, with new problems and research ideas being proposed ranging from the molecular mechanism of BTXA in preventing and treating pathological scars to its clinical application via investigation and reference research.

RESULTS

BTXA is effective in relieving itching and pain associated with pathological scars, limiting scar hyperplasia along with preventing scar contracture, but the specific mechanism is still not clear.

CONCLUSION

Most of the clinicians have confirmed the clinical effectiveness of BTXA in the prevention and treatment of pathological scars, yet its mode of action and combination therapy need more research.

Effectiveness of fractional carbon dioxide laser combined with botulinum toxin type A in a rabbit ear model with the underlying mechanism

BACKGROUND

Hypertrophic scar (HS) is a common disease in plastic and cosmetic surgery, with limited treatment options, and is a challenge for clinicians.

OBJECTIVES

This study aimed to evaluate the efficacy of fractional carbon dioxide (CO₂ ) laser combined with botulinum toxin type A (BTXA) in treating HSs in rabbit ears and to provide new strategies for treating HS.

METHODS

Twenty-four New Zealand white rabbits with induced HSs were randomly divided into one control and three treatment groups. After 4 weeks of modeling, BTXA (2.0 U) was injected into the HS of the BTXA and combination groups, whereas a fractional CO₂ laser (combo mode, deep energy: 12.5 mJ; super energy: 90 mJ) was used in the fractional CO₂ laser and combination groups. The laser treatments were repeated after 2 weeks. The HSs in the rabbit ears were observed and photographed 5 weeks after the first treatment. The scar thickness in each group was measured and compared, and the scar elevation index (SEI) was determined using hematoxylin and eosin staining. Collagen content and alignment were observed using Masson's trichrome staining. Western blotting and immunohistochemistry were performed to analyze scar-related protein levels.

RESULTS

Hypertrophic scars were reduced in all treatment groups compared with the control group. The combination group had lower scar thickness, SEI, and expression of scar-related proteins in HSs, with an appearance similar to that of normal rabbit ear skin. Furthermore, the fibroblast content and collagen deposition decreased significantly in the combination group (p < 0.001).

CONCLUSIONS

Fractional CO₂ laser combined with BTXA more effectively reduced HSs by inhibiting fibroblast proliferation, decreasing transforming growth factor-β1 and α- smooth muscle actin expression, and causing collagen remodeling.

Glabridin from Glycyrrhiza glabra Possesses a Therapeutic Role against Keloid via Attenuating PI3K/Akt and Transforming Growth Factor-β1/SMAD Signaling Pathways

Glabridin (Gla) is a typical flavonoid isolated from the Glycyrrhiza glabra with various bioactivities and is a common additive in many cosmetics. In our study, we evaluated the antiscarring effect of Gla from G. glabra in a rabbit ear hyperplastic scar model. Hematoxylin and eosin staining and Masson staining were applied to determine the pathological changes and collagen fibers of scar tissue in rabbits. The results suggested that Gla could reduce rabbit ear scar hyperplasia, inhibit inflammation, and decrease collagen production. Furthermore, the in vitro cell experiments were applied to determine the effects of Gla on human keloid fibroblasts (HKFs), and we observed that Gla suppressed the HKF cells' proliferation via inducing apoptosis. Subsequently, we found that Gla reduced collagen production in HKF cells. The further molecular mechanisms investigations suggested that Gla played a therapeutic role against keloid by attenuating PI3K/Akt and TGFβ1/SMAD pathways. Our study would be beneficial for extending the applications of the known sweet plant of G. glabra.

Efficacy and safety of botulinum toxin type A for postoperative scar prevention and wound healing improvement: A systematic review and meta-analysis

BACKGROUND

Botulinum toxin type A (BTXA) has shown underlying effects for wound healing improvement. New small clinical trials keep emerging every year and updated evidence-based information is warranted. This study aimed to evaluate the efficacy and safety of BTXA for preventing scarring.

METHODS

Four databases were searched to recruit randomized clinical trials (RCTs) which compared the surgical wounds treated with BTXA vs. those treated with placebo or blank control. The outcomes were primarily quantified by measures including the Vancouver Scar Scale (VSS), Visual Analog Scale (VAS), Stony Brook Scar Evaluation Scales (SBSES), modified SBSES (mSBSES), and scar width. Patients' satisfaction and adverse events were also reported.

RESULTS

In total, 16 RCTs involving 671 cases (510 patients) were included. The outcome showed significant superiority of BTXA in VSS (mean difference [MD] = -1.32, 95% confidence interval [CI]: -2.00 to -0.65, p = 0.0001), VAS (MD = 1.29, 95% CI: 1.05-1.52, p < 0.00001), SBSES or mSBSES (MD = -0.18, 95% CI: -0.27 to -0.10, p < 0.0001), scar width (MD = -0.18, 95% CI: -0.27 to -0.10, p < 0.0001), and patients' satisfaction (risk ratio [RR] = 1.25, 95% CI: 1.06-1.49, p = 0.01). No significant difference of adverse events incidence was observed (RR = 1.46 95% CI: 0.64-3.33, p = 0.36).

CONCLUSIONS

Botulinum toxin type A is effective and safe for postoperative scar prevention and wound healing improvement, especially for facial wounds of Asians. Further studies should manage to standardize the treatment algorithm, while mSBSES is recommended for scar assessment.

The effect of botulinum toxin type A in different dilution on the contraction of fibroblast-In vitro study

BACKGROUND

Botulinum toxin type A (BoNT-A) may directly remodel dermal tissues or induce a loss of normal morphology and cytoplasmic retraction and spread. Intradermal injection was claimed to produce a dermo-lifting effect, including midface lifting by using low concentration with variable dilution.

OBJECTIVE

To understand how intradermal BoNT-A achieves tissue lifting, we examined different type of BoNT-A and their effects on dermal fibroblast contraction.

METHODS

Normal human dermal fibroblasts were treated with onabotulinumtoxin (ONA), abobotulinumtoxin (ABO), prabotulinumtoxinA (PRABO), incobotulinumtoxinA (INCO), and letibotulinumtoxin A (LETI) in dilutions used in real-world practice. Fifty fibroblasts per dilution were photographed and measured the length to demonstrate their contraction every 2 hours from baseline (0 hours) to 12 hours post-treatment.

RESULTS

ONA did not significantly decrease fibroblast lengths, at any timepoint or dilution. At 1:7 dilution ratios, ABO decreased fibroblast lengths after 2 hours and significantly after 10-12 hours. At 1:7, 1:8, 1:9, and 1:10 dilution, PRABO decreased length, and most rapidly at 1:7 and 1:8. At 1:6, 1:8, 1:9, and 1:10 dilution, INCO decreased lengths almost immediately. At 1:6 dilution, INCO decreased lengths almost immediately. At 1:7 dilution, INCO decreased lengths after 2-4 hours, while at 1:8, 1:9, and 1:10 dilution, INCO decreased lenghts nearly imediately. LETI decreased lengths at all dilutions except 1:9, with near-immediate effects at 1:6, 1:7, 1:8, and 1:10. At 1:4 dilution, LETI decreased lengths from 1 hour.

CONCLUSIONS

Different commercial preparations of BoNT-A toxins cause different fibroblast contractions in vitro. Product selection and dilution used may affect the clinical outcome of intradermal injection of BoNT-A for face lifting.

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.

Alternative Therapies to Fat Grafting in the Craniofacial Region

Autologous fat grafting is a technique with various applications in the craniofacial region ranging from the treatment of wounds, scars, keloids, and soft tissue deformities. In this review, alternative therapies to fat grafting are discussed. These are composed of established therapies like silicone gel or sheeting, corticosteroids, cryotherapy, and laser therapy. Novel applications of negative pressure wound therapy, botulinum toxin A injection, and biologic agents are also reviewed.

Botulinum toxin type A prevents the phenotypic transformation of fibroblasts induced by TGF‑β1 via the PTEN/PI3K/Akt signaling pathway

Hypertrophic scar (HS) is a common type of dermatosis. Botulinum toxin type A (BTXA) can exert an anti-HS effect; however, the regulatory mechanisms underlying this effect remain unclear. Thus, the aim of this study was to examine the effects of BTXA on phosphatase and tensin homolog deleted on chromosome ten (PTEN) expression and the fibroblast phenotypic transformation induced by transforming growth factor (TGF)-β1, which is an important regulatory factor involved in the process of HS. For this purpose, fibroblasts were treated with various concentrations of BTXA and then treated with 10 ng/ml of TGF-β1 with gradient concentrations of BTXA. The proliferation and apoptosis of fibroblasts were measured by cell counting kit-8 assay (CCK-8) and flow cytometry, respectively. PTEN methylation was analyzed by methylation-specific PCR (MSP) and DNA methyltransferase (DNMT) activity was determined using a corresponding kit. RT-qPCR and western blot analysis were performed to detect the transcription and translation levels. The results revealed that BTXA suppressed the proliferation and increased the apoptosis of fibroblasts treated with TGF-β1 in a dose-dependent manner. BTXA in combination with TGF-β1 suppressed the expression of molecules related to the extracellular matrix (ECM), epithelial-mesenchymal transition (EMT) and apoptosis. BTXA reduced the PTEN methylation level and downregulated the expression levels of methylation-associated genes. BTXA also inhibited the phosphorylation of phosphoinositide 3-kinase (PI3K) and Akt. On the whole, the findings of this study indicate that BTXA may inhibit fibroblast phenotypic transformation by regulating PTEN methylation and the phosphorylation of related pathways. The findings of this study can provide a theoretical basis for HS treatment.

Proteasome inhibitor MG132 inhibits the process of renal interstitial fibrosis

The proteasome inhibitor pathway serves a crucial role in cell cycle progression and apoptosis, and in the activation of transcription factors and cytokines in tumor cells. The aim of the current study was to investigate the effect of the proteasome inhibitor, MG132, on transforming growth factor (TGF)-β1-induced expression of extracellular matrix proteins in rat renal interstitial fibroblasts (NRK-49F cells) and to better elucidate the mechanism by which MG132 functions. The level of connective tissue growth factor (CTGF), α-smooth muscle actin (SMA), fibronectin (FN) and collagen type III (Col III) in the MG132-pretreated groups was significantly decreased compared with groups treated with TGF-β1 alone. MG132 significantly decreased mRNA and the protein levels of fibrosis-associated factors induced by TGF-β1 treatment. The MG132-pretreated groups exhibited lower phosphorylated-mothers against decapentaplegic homolog (p-Smad)2, p-Smad3 and FN protein expression compared with the groups treated with TGF-β1 alone. In conclusion, MG132 reduced mRNA and protein expression of fibrosis-associated factors. It can successfully inhibit the inflammatory reaction induced by TGF-β via the Smad signaling pathway. These results indicate that MG132 appears to have a potent effect in counteracting renal fibrosis. MG132 may be applied in the treatment of patients with chronic kidney disease.

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.

The non-neuronal and nonmuscular effects of botulinum toxin: an opportunity for a deadly molecule to treat disease in the skin and beyond

There is growing evidence that botulinum neurotoxins (BoNTs) exhibit biological effects on various human cell types with a host of associated clinical implications. This review aims to provide an update on the non-neuronal and nonmuscular effects of botulinum toxin. We critically analysed recent reports on the structure and function of cellular signalling systems subserving biological effects of BoNTs. The BoNT receptors and intracellular targets are not unique for neurotransmission. They have been found in both neuronal and non-neuronal cells, but there are differences in how BoNT binds to, and acts on, neuronal vs. non-neuronal cells. The non-neuronal cells that express one or more BoNT/A-binding proteins, and/or cleavage target synaptosomal-associated protein 25, include: epidermal keratinocytes; mesenchymal stem cells from subcutaneous adipose; nasal mucosal cells; urothelial cells; intestinal, prostate and alveolar epithelial cells; breast cell lines; neutrophils; and macrophages. Serotype BoNT/A can also elicit specific biological effects in dermal fibroblasts, sebocytes and vascular endothelial cells. Nontraditional applications of BoNT have been reported for the treatment of the following dermatological conditions: hyperhidrosis, Hailey-Hailey disease, Darier disease, inversed psoriasis, aquagenic palmoplantar keratoderma, pachyonychia congenita, multiple eccrine hydrocystomas, eccrine angiomatous hamartoma, eccrine sweat gland naevi, congenital eccrine naevus, Raynaud phenomenon and cutaneous leiomyomas. Experimental studies have demonstrated the ability of BoNT/A to protect skin flaps, facilitate wound healing, decrease thickness of hypertrophic scars, produce an anti-ageing effect, improve a mouse model of psoriasiform dermatitis, and have also revealed extracutaneous effects of BoNT arising from its anti-inflammatory and anticancer properties. BoNTs have a much wider range of applications than originally understood, and the individual cellular responses to the cholinergic impacts of BoNTs could provide fertile ground for future studies.

Botulinum Toxin in the Field of Dermatology: Novel Indications

Since its approval by the US Food and Drug Administration in 2002 for glabellar wrinkles, botulinum toxin (BTX) has been widely used to correct facial wrinkles. As a result, many consider BTX synonymous with cosmetic dermatology. Recent studies indicate that BTX elicits biological effects on various skin cell types via the modulation of neurotransmitter release, and it seems that BTX has a wider zone of dermatologic influence than originally understood. Clinicians and researchers are now beginning to explore the potential of BTX beyond the amelioration of facial lines and encouraging results are seen with BTX in a variety of skin conditions. In this paper, we review novel dermatological indications of BTX which includes (but not limited to) scar prevention, facial flushing, post-herpetic neuralgia and itch. These areas show great promise, but there is definite need for larger, double-blinded, randomized control trials against established treatments before BTX becomes a clinical reality.

Current progress in understanding the molecular pathogenesis of burn scar contracture

Abnormal wound healing is likely to induce scar formation, leading to dysfunction, deformity, and psychological trauma in burn patients. Despite the advancement of medical care treatment, scar contracture in burn patients remains a challenge. Myofibroblasts play a key role in scar contracture. It has been demonstrated that myofibroblasts, as well as inflammatory cells, fibroblasts, endothelial cells, and epithelial cells, secrete transforming growth factor-β1 (TGF-β1) and other cytokines, which can promote persistent myofibroblast activation via a positive regulation loop. In addition to the cellular contribution, the microenvironments, including the mechanical tension and integrin family, are also involved in scar contracture. Most recently, eukaryotic initiation factor 6 (eIF6), an upstream regulator of TGF-β1, has been demonstrated to be involved in myofibroblast differentiation and contraction in both in vitro fibroblast-populated collagen lattice (FPCL) and in vivo external mechanical stretch models. Moreover, the data showed that P311 could induce the transdifferentiation of epidermal stem cells to myofibroblasts by upregulating TGF-β1 expression, which mediated myofibroblast contraction. In this review, we briefly described the most current progress on the biological function of myofibroblasts in scar contracture and subsequently summarized the molecular events that initiated contracture. This would help us better understand the molecular basis of scar contracture as well as to find a comprehensive strategy for preventing/managing scar contracture.

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.

Combined Treatment with Botulinum Toxin and 595-nm Pulsed Dye Laser for Traumatic Scarring

Traumatic scars on skin covering areas of high movement, especially areas on the face, can be stressful for patients. We report two cases of traumatic scars that occurred on the chin, and that were successfully treated with a combined therapy of 595-nm pulsed dye laser (PDL) and intramuscular injection of botulinum toxin. After the treatment, good cosmetic results were achieved in both patients. The only adverse effect during and after the treatments was mild pain, which resolved within several days without any additional treatment. In conclusion, the combination of 595-nm PDL and intramuscular botulinum toxin injection was shown to be a safe and effective treatment for traumatic scars on the mobile chin area in Korean patients.