Comparison of botulinum toxin type A and aprotinin monotherapy with combination therapy in healing of burn wounds in an animal model

Burns are one of the most common injuries that are complicated by many challenges including infection, severe inflammatory response, excessive expression of proteases, and scar formation. The aim of this study was to investigate the effect of botulinum toxin type A (BO) and aprotinin (AP) separately or in combination (BO-AP) in healing process. Four burn wounds were created in each rat and randomly filled with silver sulfadiazine (SSD), BO, AP and BO-AP. The rats were euthanized after 7, 14, and 28 days, and their harvested wound samples were evaluated by gross pathology, histopathology, gene expression, biochemical testing, and scanning electron microscopy. Both BO and AP significantly reduced expression of interleukin-1β (IL-1β) and transforming growth factor-β1 (TGF-β1) at the 7th post wounding day. Moreover, they inhibited scar formation by reducing the TGF-β1 level and increasing basic fibroblast growth factor (bFGF) at the 28th day. AP by decreasing protease production showed more effective role than BO in wound regeneration. AP increased tissue organization and maturation and improved cosmetic appearance of wounds, at 28 days. The best results gained when combination of BO and AP were used in healing of burn wounds. Treatment by BO-AP significantly subsided inflammation compared to the BO, AP, and SSD treated wounds. Treatment with BO-AP also reduced collagen density and led to minimal scar formation. Combination of botulinum toxin type A and aprotinin considerably increased structural and functional properties of the healing wounds by reducing scar formation and decreasing production of proteases.

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.

Efficacy and possible mechanisms of Botulinum Toxin type A on hypertrophic scarring

BACKGROUND

Clinical observations indicate that Botulinum toxin type A (BTXA) can inhibit the growth and improve the eventual appearance of hypertrophic scarring. However, the molecular mechanism remains unclear.

OBJECTIVE

We used human keloid fibroblasts to investigate the molecular mechanism of BTXA on hypertrophic scarring.

METHODS

Different concentrations of BTXA (0.01, 0.1, 1, and 10 U/L) were used to treat keloid fibroblasts. Changes in cellular morphology, viability, proliferation, cell cycle, and apoptosis were observed by immunofluorescence, MTT assay, and flow cytometry. In addition, real-time qPCR and Western blotting were used to explore the potential molecular mechanisms.

RESULTS

Keloid fibroblast viability decreased with increasing BTXA dose. After BTXA treatment, the volume of keloid fibroblasts cells increased, but the nucleus of cells shrunk. Long thin dendrites were formed as the concentration of BTXA increased. Furthermore, the proliferation and S phase of keloid fibroblasts were inhibited by BTXA. Matrix metalloproteinase (, MMP)-1 and -2 RNA and protein showed high expression, but TGF-β1 and MMP-9 showed low expression than the control.

CONCLUSION

Botulinum toxin type A may promote the healing of scars by inhibiting the proliferation of keloid fibroblasts and regulating the expression of TGF-β1, which could affect the expression of MMP-1 and MMP-2. This study provides theoretical support for the clinical application of BTXA to control hypertrophic scarring.

Botulinum toxin type A affects the transcriptome of cell cultures derived from muscle biopsies of controls and spastic patients

Botulin toxin (BTX) is widely used for treating skeletal muscle spasticity. Experimental reports on BTX treatment were mainly focused on the neuromuscular junction, while relatively little is known about toxin effects on the muscle cell itself. We investigated possible impact of BTX type A on skeletal muscle cell transcriptome by microarray analysis in muscle-derived cell cultures (fibroblasts, myoblasts and myotubes) from controls and spastic patients, and results were then validated at transcript and protein level. BTX-A treatment of control cells induced major changes in the myogenic component of the transcriptome, whereas the same treatment had a negligible effect in the fibrogenic component. BTX-A treatment of cell cultures from spastic patients induced an increased number of genes differentially expressed both in the fibrogenic and myogenic components. Specifically, BTX-A had a major effect on cell cycle-related genes in myoblasts, on muscle contraction-related genes in myotubes, and on extracellular matrix-related genes in fibroblasts from spastic patients. Our findings show that in vitro BTX-A treatment differentially affects transcript expression in muscle cells from spastic patients compared to those from controls suggesting a direct effect of BTX-A on muscle-specific functional pathways.

Botulinum neurotoxin type A: Actions beyond SNAP-25?

Botulinum neurotoxin type A (BoNT/A), the most potent toxin known in nature which causes botulism, is a commonly used therapeutic protein. It prevents synaptic vesicle neuroexocytosis by proteolytic cleavage of synaptosomal-associated protein of 25 kDa (SNAP-25). It is widely believed that BoNT/A therapeutic or toxic actions are exclusively mediated by SNAP-25 cleavage. On the other hand, in vitro and in vivo findings suggest that several BoNT/A actions related to neuroexocytosis, cell cycle and apoptosis, neuritogenesis and gene expression are not necessarily mediated by this widely accepted mechanism of action. In present review we summarize the literature evidence which point to the existence of unknown BoNT/A molecular target(s) and modulation of unknown signaling pathways. The effects of BoNT/A apparently independent of SNAP-25 occur at similar doses/concentrations known to induce SNAP-25 cleavage and prevention of neurotransmitter release. Accordingly, these effects might be pharmacologically significant. Potentially the most interesting are observations of antimitotic and antitumor activity of BoNT/A. However, the exact mechanisms require further studies.