Effects of DMSO on a rabbit ear hypertrophic scar model: A controlled randomized experimental study

Oral dextran sulfate sodium administration induces peripheral spondyloarthritis features in SKG mice accompanied by intestinal bacterial translocation and systemic Th1 and Th17 cell activation

BACKGROUND

Spondyloarthritis (SpA) is an autoimmune and autoinflammatory musculoskeletal disease characterised by systemic enthesitis. Recent research has focused on subclinical inflammatory bowel disease (IBD) in SpA pathogenesis. SKG mice, harbouring the Zap70 W163C mutation, increase autoreactive Th17 cells intrinsically, and in a conventional environment, they exhibit spontaneous arthritis with fungal factors. Under SPF conditions, they show SpA features, including enteritis, after peritoneal injection of β-1,3-glucan. This study aimed to clarify whether oral dextran sulfate sodium (DSS) administration, utilised in IBD model mice, can provoke SpA features in SKG mice under SPF conditions, focusing on the relationship between gut microorganisms and SpA pathogenesis.

METHODS

BALB/c and SKG mice were administered oral DSS, and their body weights, arthritis, and enthesitis scores were recorded. In another cohort, antibiotics (meropenem and vancomycin) or an anti-fungal agent (amphotericin B) was administered orally before DSS administration. The splenic Th1 and Th17 cell populations were examined before and after DSS administration using flow cytometry. Furthermore, the amount of circulating bacterial DNA in whole blood was measured by absolute quantitative polymerase chain reaction (qPCR), and the number and characteristics of bacterial species corresponding to these circulating DNA were analysed by next-generation sequencing (NGS).

RESULTS

Ankle enthesitis as a peripheral SpA feature was elicited in half of DSS-administered SKG mice, and none of the BALB/c mice. Pre-administration of antibiotics suppressed enthesitis, whilst an anti-fungal agent could not. Th1 and Th17 cell levels in the spleen increased after DSS administration, and this was suppressed by pre-administration of antibiotics. SKG mice have a larger amount of bacterial DNA in whole blood than BALB/c mice before and 1 day after the initiation of DSS administration. The number of bacterial species in whole blood increased after DSS administration in BALB/c and SKG mice. Some genera and species significantly specific to the DSS-treated SKG mouse group were also detected.

CONCLUSION

Oral DSS administration alone elicited peripheral enthesitis in SKG mice with bacterial translocation accompanied by increased splenic Th1 and Th17 cell levels. Pre-administration of antibiotics ameliorated these DSS-induced SpA features. These findings suggest that intestinal bacterial leakage plays a pivotal role in SpA pathogenesis.

Proteoglycan 4 (PRG4) treatment enhances wound closure and tissue regeneration

The wound healing response is one of most primitive and conserved physiological responses in the animal kingdom, as restoring tissue integrity/homeostasis can be the difference between life and death. Wound healing in mammals is mediated by immune cells and inflammatory signaling molecules that regulate tissue resident cells, including local progenitor cells, to mediate closure of the wound through formation of a scar. Proteoglycan 4 (PRG4), a protein found throughout the animal kingdom from fish to elephants, is best known as a glycoprotein that reduces friction between articulating surfaces (e.g. cartilage). Previously, PRG4 was also shown to regulate the inflammatory and fibrotic response. Based on this, we asked whether PRG4 plays a role in the wound healing response. Using an ear wound model, topical application of exogenous recombinant human (rh)PRG4 hastened wound closure and enhanced tissue regeneration. Our results also suggest that rhPRG4 may impact the fibrotic response, angiogenesis/blood flow to the injury site, macrophage inflammatory dynamics, recruitment of immune and increased proliferation of adult mesenchymal progenitor cells (MPCs) and promoting chondrogenic differentiation of MPCs to form the auricular cartilage scaffold of the injured ear. These results suggest that PRG4 has the potential to suppress scar formation while enhancing connective tissue regeneration post-injury by modulating aspects of each wound healing stage (blood clotting, inflammation, tissue generation and tissue remodeling). Therefore, we propose that rhPRG4 may represent a potential therapy to mitigate scar and improve wound healing.

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.

Tacrolimus action pathways in an ointment base for hypertrophic scar prevention in a rabbit ear model

BACKGROUND

Tacrolimus is used to prevent unaesthetic scars due to its action on fibroblast activity and collagen production modulation.

OBJECTIVES

To evaluate the action pathways, from the histopathological point of view and in cytokine control, of tacrolimus ointment in the prevention of hypertrophic scars.

METHODS

Twenty-two rabbits were submitted to the excision of two 1-cm fragments in each ear, including the perichondrium. The right ear received 0.1% and 0.03% tacrolimus in ointment base twice a day in the upper wound and in the lower wound respectively. The left ear, used as the control, was treated with petrolatum. After 30 days, collagen fibers were evaluated using special staining, and immunohistochemistry analyses for smooth muscle actin, TGF-β and VEGF were performed.

RESULTS

The wounds treated with 0.1% tacrolimus showed weak labeling and a lower percentage of labeling for smooth muscle actin, a higher proportion of mucin absence, weak staining, fine and organized fibers for Gomori's Trichrome, strong staining and organized fibers for Verhoeff when compared to controls. The wounds treated with 0.03% tacrolimus showed weak labeling for smooth muscle actin, a higher proportion of mucin absence, strong staining for Verhoeff when compared to the controls. There was absence of TGF-β and low VEGF expression.

STUDY LIMITATIONS

The analysis was performed by a single pathologist. Second-harmonic imaging microscopy was performed in 2 sample areas of the scar.

CONCLUSIONS

Both drug concentrations were effective in suppressing TGF-β and smooth muscle actin, reducing mucin, improving the quality of collagen fibers, and the density of elastic fibers, but only the higher concentration influenced elastic fiber organization.

Effect of Local and Systemic Dimethylsulfoxide on Peripheral Nerve Repair: A Controlled Randomized Experimental Study

INTRODUCTION

We investigated the possible beneficial effect of dimethylsulfoxide (DMSO) on peripheral nerve repair in rats. Methods: Seventy rats were divided into four groups: control, sham, DMSO-L, and DMSO-IP. Except in the control group, nerve repair was done at the right sciatic nerve. DMSO was administered locally and intraperitoneally for 12 weeks to the DMSO-L and DMSO-IP groups, respectively. No therapeutic agent was administered to the other groups. Nerve regeneration was assessed by behavioral, electrophysiological, histopathological, and immunohistochemical tests. Results: With the exception of S-100 protein expression, all results indicate that DMSO has a beneficial effect on peripheral nerve regeneration. Functional nerve recovery was notably more evident in the DMSO-L than in the DMSO-IP group. Under macroscopic examination, nerve scores of the regeneration area in the DMSO-L group was also better than in the others. Discussion: We believe that DMSO can improve peripheral nerve regeneration in rats.

Effect of artesunate and relation with TGF-β1 and SMAD3 signaling on experimental hypertrophic scar model in rabbit ear

Artesunate (ART) is the derivative of artemisinin isolated from the traditional Chinese medicine qinghao. Although several studies reported the efficiency of artesunate in the treatment of malaria, inhibiting fibroblasts and collagen synthesis, the association between artesunate and scar formation is unclear. The research was designed to study the significance of artesunate (ART) on the expression of transforming growth factor (TGF-β1) and small mother against decapentaplegic (SMAD3) in rabbit's ear hypertrophic scar model. Twenty-four New Zealand white rabbits were randomly divided into six groups: control group, matrix group, low-concentration artesunate group (0.48%), medium-concentration artesunate group (0.96%), high-concentration artesunate group (1.92%) and silicone gel group. Punched defects were established on each rabbit’s ear which resulted in a hypertrophic scar. On the 28th day, topical artesunate creams were applied twice a day except on the control group. On the 56th day, scar samples were collected for histopathology and immunoassay. Hematoxylin and eosin staining, Van Gieson staining, immunohistochemistry and Western blot analysis were done. Amongst the six groups, findings showed that the medium-concentration artesunate group (0.92%) efficiently decreased hypertrophic scar formation and significantly reduced fibroblasts and collagen synthesis. The results had also shown a decrease in the expression of transforming growth factor (TGF-β1) and declined small signal mother against decapentaplegic (Smad3). The overall study shows efficacy and mechanism of artesunate. It concluded that the medium concentration of artesunate (0.92%) could be an effective therapeutic agent for hypertrophic scars.

Growth hormone-releasing peptide 6 prevents cutaneous hypertrophic scarring: early mechanistic data from a proteome study

Hypertrophic scars (HTS) and keloids are forms of aberrant cutaneous healing with excessive extracellular matrix (ECM) deposition. Current therapies still fall short and cause undesired effects. We aimed to thoroughly evaluate the ability of growth hormone releasing peptide 6 (GHRP6) to both prevent and reverse cutaneous fibrosis and to acquire the earliest proteome data supporting GHRP6's acute impact on aesthetic wound healing. Two independent sets of experiments addressing prevention and reversion effects were conducted on the classic HTS model in rabbits. In the prevention approach, the wounds were assigned to topically receive GHRP6, triamcinolone acetonide (TA), or vehicle (1% sodium carboxy methylcellulose [CMC]) from day 1 to day 30 post-wounding. The reversion scheme was based on the infiltration of either GHRP6 or sterile saline in mature HTS for 4 consecutive weeks. The incidence and appearance of HTS were systematically monitored. The sub-epidermal fibrotic core area of HTS was ultrasonographically determined, and the scar elevation index was calculated on haematoxylin/eosin-stained, microscopic digitised images. Tissue samples were collected for proteomics after 1 hour of HTS induction and treatment with either GHRP6 or vehicle. GHRP6 prevented the onset of HTS without the untoward reactions induced by the first-line treatment triamcinolone acetonide (TA); however, it failed to significantly reverse mature HTS. The preliminary proteomic study suggests that the anti-fibrotic preventing effect exerted by GHRP6 depends on different pathways involved in lipid metabolism, cytoskeleton arrangements, epidermal cells' differentiation, and ECM dynamics. These results enlighten the potential success of GHRP6 as one of the incoming alternatives for HTS prevention.

Inhibitory effect of timolol on topical glucocorticoid‑induced skin telangiectasia

The aim of the present study wasto investigate the potential inhibitory effect of timolol on topical glucocorticoid-induced skin telangiectasia. In rabbits, flumethasone ointment was used to induce skin telangiectasia in the inner ear. Subsequently, timolol maleate (0.5%) eye drops (TMEDs) were administered twice daily for 4 weeks. Expression of the antibacterial peptides 37-amino acid peptide (LL-37) and kallikrein-5 (KLK5) was detected using quantitative polymerase chain reaction (PCR) and semi-quantitative reverse transcription-PCR. In patients with facial skin telangiectasia, one cheek of each patient was assigned to a treatment group and the other to a control group. For the treatment group cheeks, topical application of TMEDs was combined with 0.1% tacrolimus ointment once or twice daily for 8 weeks. The control group cheeks were administered with 0.1% tacrolimus ointment alone. Alterations in lesions were recorded by dermoscopy, and the L, a and b values of lesions were measured, based on the Commission Internationale de l'Éclairage system, with a chromameter prior to and at 1, 2, 4 and 8 weeks following treatment. The results indicated that erythema, papules and telangiectasia were significantly diminished following 4 weeks of treatment with TMEDs in rabbits. Notably, the expression of LL-37 and KLK5 mRNA was increased in the negative control group; however, it was decreased in the trial and blank groups. Clinical and dermoscopy images demonstrated that erythema was reduced in the 2 groups for 1 week, and that telangiectasia in the treatment group was markedly reduced compared with the control group at 4 weeks. The difference of the L and a values of lesions between the treatment and control group was significant (P<0.05). Overall, the present results suggested that the abnormal expression of LL-37 may be one of the mechanisms underlying the pathogenesis of facial corticosteroid addiction dermatitis (FCAD) and TMEDs may inhibit the mRNA expression of LL-37 by downregulating KLK5; in this regard, TMEDs may serve a role in attenuating telangiectasia, which may be beneficial in improving the telangiectasia symptoms of FCAD.