Cutaneous Scarring: Basic Science, Current Treatments, and Future Directions

The Biology of Extracellular Matrix Proteins in Hypertrophic Scarring

Significance: Hypertrophic scars (HTS) are a fibroproliferative disorder that occur following deep dermal injury and affect up to 72% of burn patients. These scars result in discomfort, impaired mobility, disruption of normal function and cosmesis, and significant psychological distress. Currently, there are no satisfactory methods to treat or prevent HTS, as the cellular and molecular mechanisms are complex and incompletely understood. This review summarizes the biology of proteins in the dermal extracellular matrix (ECM), which are involved in wound healing and hypertrophic scarring. Recent Advances: New basic research continues toward understanding the diversity of cellular and molecular mechanisms of normal wound healing and hypertrophic scarring. Broadening the understanding of these mechanisms creates insight into novel methods for preventing and treating HTS. Critical Issues: Although there is an abundance of research conducted on collagen in the ECM and its relationship to HTS, there is a significant gap in understanding the role of proteoglycans and their specific isoforms in dermal fibrosis. Future Directions: Exploring the biological roles of ECM proteins and their unique isoforms in HTS, mature scars, and normal skin will further the understanding of abnormal wound healing and create a more robust understanding of what constitutes dermal fibrosis. Research into the biological roles of ECM protein isoforms and their regulation during wound healing warrants a more extensive investigation to identify their distinct biological functions in cellular processes and outcomes.

Distinct inflammatory macrophage populations sequentially infiltrate bone‐to‐tendon interface tissue after ACL reconstruction surgery in mice

Macrophages are important for repair of injured tissues, but their role in healing after surgical repair of musculoskeletal tissues is not well understood. We used single‐cell RNA sequencing (RNA‐seq), flow cytometry, and transcriptomics to characterize functional phenotypes of macrophages in a mouse anterior cruciate ligament reconstruction (ACLR) model that involves bone injury followed by a healing phase of bone and fibrovascular interface tissue formation that results in bone‐to‐tendon attachment. We identified a novel “surgery‐induced” highly inflammatory CD9+ IL1+ macrophage population that expresses neutrophil‐related genes, peaks 1 day after surgery, and slowly resolves while transitioning to a more homeostatic phenotype. In contrast, CX3CR1+ CCR2+ macrophages accumulated more slowly and unexpectedly expressed an interferon signature, which can suppress bone formation. Deletion of Ccr2 resulted in an increased amount of bone in the surgical bone tunnel at the tendon interface, suggestive of improved healing. The “surgery‐induced macrophages” identify a new cell type in the early phase of inflammation related to bone injury, which in other tissues is dominated by blood‐derived neutrophils. The complex patterns of macrophage and inflammatory pathway activation after ACLR set the stage for developing therapeutic strategies to target specific cell populations and inflammatory pathways to improve surgical outcomes. © 2022 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

Amniotic fluid derived stem cells promote skin regeneration and alleviate scar formation through exosomal miRNA-146a-5p via targeting CXCR4

BACKGROUND AND OBJECTIVES

Regenerative medicine is promising in wound healing. Exosomes derived from human amniotic fluid derived stem cells(hAFS) have become an important area of research for many diseases as a key paracrine factor,but its effects in wound healing remains unknown. In this study, we investigated the possible role and possible mechanisms of hAFS in skin wound healing.

METHODS

hAFS were isolated from human amniotic fluid via routine amniocentesis. The mice were randomly divided into 2 groups: control group and hAFS group treated with 1.25×10⁶ hAFS cells. immunohistochemistry staining was performed for histological analysis and qRT-PCR for assessment of gene levels. Luciferase Reporter Assay was performed for verification of target gene.

RESULTS

Our results demonstrated that hAFS accelerated wound closure. hAFS alleviated scar formation via promoting ECM remodeling, upregulating molecular of immune response, enhancing anti-fibrotic activity and decreasing the secretion of inflammation-associated cytokines through exosomal miRNA-146a-5p via targeting CXCR4.

CONCLUSIONS

Taken together, hAFS was a promising cell source for wound healing. The findings in this study provide vital references and pave the way for future research.

Regenerative Approaches for Chronic Wounds

Chronic skin wounds are commonly found in older individuals who have impaired circulation due to diabetes or are immobilized due to physical disability. Chronic wounds pose a severe burden to the health-care system and are likely to become increasingly prevalent in aging populations. Various treatment approaches exist to help the healing process, although the healed tissue does not generally recapitulate intact skin but rather forms a scar that has inferior mechanical properties and that lacks appendages such as hair or sweat glands. This article describes new experimental avenues for attempting to improve the regenerative response of skin using biophysical techniques as well as biochemical methods, in some cases by trying to harness the potential of stem cells, either endogenous to the host or provided exogenously, to regenerate the skin. These approaches primarily address the local wound environment and should likely be combined with other modalities to address regional and systemic disease, as well as social determinants of health. Expected final online publication date for the Annual Review of Biomedical Engineering, Volume 24 is June 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Scar formation from the perspective of complexity science: a new look at the biological system as a whole

A burn wound is a complex systemic disease at multiple levels. Current knowledge of scar formation after burn injury has come from traditional biological and clinical studies. These are normally focused on just a small part of the entire process, which has limited our ability to sufficiently understand the underlying mechanisms and to predict systems behaviour. Scar formation after burn injury is a result of a complex biological system-wound healing. It is a part of a larger whole. In this self-organising system, many components form networks of interactions with each other. These networks of interactions are typically non-linear and change their states dynamically, responding to the environment and showing emergent long-term behaviour. How molecular and cellular data relate to clinical phenomena, especially regarding effective therapies of burn wounds to achieve minimal scarring, is difficult to unravel and comprehend. Complexity science can help bridge this gap by integrating small parts into a larger whole, such that relevant biological mechanisms and data are combined in a computational model to better understand the complexity of the entire biological system. A better understanding of the complex biological system of post-burn scar formation could bring research and treatment regimens to the next level. The aim of this review/position paper is to create more awareness of complexity in scar formation after burn injury by describing the basic principles of complexity science and its potential for burn care professionals.

Approaches for Regenerative Healing of Cutaneous Wound with an Emphasis on Strategies Activating the Wnt/β-Catenin Pathway

Significance: In adult mammals, spontaneous repair of a cutaneous wound occurs slowly and leaves a scar with skin adnexa deficiencies. To accelerate cutaneous wound-healing rates and avoid scar formation, current studies have focused on regenerative therapies. Recent Advances: Emerging therapeutics for regenerative wound healing often focus on the use of growth factors and stem cells. However, these therapeutic approaches have limited routine clinical use due to high costs and technical requirements. Critical Issue: Understanding the molecular mechanisms involved in the signaling pathways for cutaneous wound healing and neogenic synthesis of the skin components is important for identification of novel targets for the development of regenerative wound-healing agents. Future Directions: The Wnt/β-catenin pathway is a well-known key player for enhancement of the overall healing process involving tissue regeneration via crosstalk with other signaling pathways. Strategies that activate the Wnt/β-catenin pathway via modulation of the pathway-controlling regulatory factors could provide effective therapeutic approaches for regenerative wound healing.

Subcutaneous injection of an immunologically tolerated protein up to 5 days before skin injuries improves wound healing

Oral tolerance blocks the development of specific immune responses to proteins ingested by the oral route. One of the first registries of oral tolerance showed that guinea pigs fed corn became refractory to hypersensitivity to corn proteins. Mice fed with chow containing corn are tolerant to zein, and parenteral injection of zein plus adjuvant blocks immunization to unrelated proteins injected concomitantly and reduces unspecific inflammation. Extensive and prolonged inflammatory infiltrate in the wound bed is one of the causes of pathological wound healing. Previous research shows that intraperitoneal injection of zein concomitant with skin injuries reduces the inflammatory infiltrate in the wound bed and improves wound healing. Herein, we tested if one subcutaneous injection of zein before skin injury improves wound healing. We also investigated how long the effects triggered by zein could improve skin wound healing. Mice fed zein received two excisional wounds on the interscapular skin under anesthesia. Zein plus Al(OH)₃ was injected at the tail base at 10 min, or 3, 5, or 7 days before skin injuries. Wound healing was analyzed at days 7 and 40 after injury. Our results showed that a zein injection up to 5 days before skin injury reduced the inflammatory infiltrate, increased the number of T-cells in the wound bed, and improved the pattern of collagen deposition in the neodermis. These findings could promote the development of new strategies for the treatment and prevention of pathological healing using proteins normally found in the common diet.

Clinical status of hospitalized keloid cases from 2013 to 2018

OBJECTS

Keloids are intractable scar diseases and sometimes undergo hospitalization. This study aims to represent current status of keloid management in a national sample of hospitalized scar cases.

METHODS

Data of scar-diagnosed cases admitted in 1064 China's tertiary hospitals between 2013 and 2018, were obtained from the Hospital Quality Monitoring System (HQMS) database. Variables analyzed include sex, age, nationality, occupation, hospital department, accompanied symptoms at admission, surgical treatment, length of stay (LOS), and hospitalization cost. The potential risk factors of keloid diagnosis among scar cases were preliminarily identified through the Cochran-Mantel-Haenszel tests and univariate regression analyses.

RESULTS

This study identified 177,586 scar cases including 21,777 keloid cases and 155,809 non-keloid scar cases. The prevalence of scars in the HQMS database was gradually decreased from 0.123% in 2013 to 0.075% in 2018. We found a preponderances of males (54.32%), adults (61.52%), Han nationality (93.38%), and students (17.35%) in scar cases, among whom keloid cases accounted for growing proportions increasing from 9.2% in 2013 to 15.1% in 2018. Comparing non-keloid scar cases, keloid cases consisted of more women (59.1% VS 43.8%), office staffs (13.08% VS 6.75%) and retirees (5.16% VS 2.65%), and less Zhuang (0.79% VS 1.40%) and Hui nationalities (0.76% VS 1.00%), and showed lower incidence of accompanied symptoms (4.51% VS 47.96%) and higher rate of receiving operations (57.96% VS 50.28%, P < 0.001). Both the LOS and cost per hospitalization were lower in keloid cases. Furthermore, the adult and older women, Han and Uyghur nationalities, office staffs and retirees, and admitted in otolaryngology and dermatology departments, were potential predictors of keloid diagnosis among hospitalized scar cases.

CONCLUSION

When viewed at the national level, keloid occupies an important part in scar management in Chinese tertiary hospitals. Demographic and clinical differences between keloids and other scars facilitate understanding and promoting of individualized anti-scar therapeutic strategies.

IR-808 loaded nanoethosomes for aggregation-enhanced synergistic transdermal photodynamic/photothermal treatment of hypertrophic scars

Synergistic transdermal photodynamic therapy (PDT)/photothermal therapy (PTT) has emerged as a novel strategy for improving hypertrophic scar (HS) therapeutic outcomes. Herein, a near-infrared heptamethine cyanine dye, named IR-808, has been selected as the desirable photosensitizer owing to its PDT and PTT properties. Benefitting from the transdermal delivery ability of ethosomes (ESs), IR-808 loaded nanoethosomes (IR-808-ES) have been prepared as a novel nanophotosensitizer for the transdermal PDT/PTT of HSs. The special structure of IR-808 aggregate distribution in the ES lipid membrane enhances ROS generation and hyperthermia. The in vitro experiments indicate that the IR-808-ES enhances the PDT/PTT efficacy for inducing the HS fibroblast (HSF) apoptosis via the intrinsic mitochondrial pathway. Furthermore, the in vivo transdermal delivery studies reveal that the IR-808-ES efficiently delivers IR-808 into HSFs in the HS tissue. Systematic assessments in the rabbit ear HS models demonstrate that the enhanced PDT/PTT performance of the IR-808-ES has remarkable therapeutic effects on improving the HS appearance, promoting HSF apoptosis and remodeling collagen fibers. Therefore, the IR-808-ES integrates both the transdermal delivery ability and the aggregation-enhanced PDT/PTT effect, and these features endow the IR-808-ES with significant potential as a novel nanophotosensitizer for the transdermal phototherapy of HSs in the clinical field.

Roles of cutaneous cell-cell communication in wound healing outcome: An emphasis on keratinocyte-fibroblast crosstalk

Tissue repair is a very complex event and involves a continuously orchestrated sequence of signals and responses from platelets, fibroblasts, epithelial, endothelial and immune cells. The details of interaction between these signals, which are mainly growth factors and cytokines, have been widely discussed. However, it is still not clear how activated cells at wound sites lessen their activities after epithelialization is completed. Termination of the wound healing process requires a fine balance between extracellular matrix (ECM) deposition and degradation. Maintaining this balance requires highly accurate epithelial-mesenchymal communication and correct information exchange between keratinocytes and fibroblasts. As it has been reported in the literature, a disruption in epithelialization during the process of wound healing increases the frequency of developing chronic wounds or fibrotic conditions, as seen in a variety of clinical cases. Conversely, the potential stop signal for wound healing should have a regulatory role on both ECM synthesis and degradation to reach a successful wound healing outcome. This review briefly describes the potential roles of growth factors and cytokines in controlling the early phase of wound healing and predominantly explores the role of releasable factors from epithelial-mesenchymal interaction in controlling during and the late stage of the healing process. Emphasis will be given on the crosstalk between keratinocytes and fibroblasts in ECM modulation and the healing outcome following a brief discussion of the wound healing initiation mechanism. In particular, we will review the termination of acute dermal wound healing, which frequently leads to the development of hypertrophic scarring.

Safety and Ease of Sheath Insertion During Endovascular Treatment Via the Common Femoral Artery After Endarterectomy With Autologous Repair: A Retrospective Cohort Study

Background Endovascular treatment (EVT) using the common femoral artery (CFA) for access after endarterectomy (EA) may result in sheath insertion difficulties because of subcutaneous scar tissue, as well as difficulties with hemostasis. We evaluated the safety of CFA access and the ease of sheath insertion over time after EA. Method We included 19 patients (21 limbs, 40 cases) in whom the CFA was used after EA with autologous repair as an access route in EVT for peripheral arterial disease in our institution from January 2013 to December 2020. Nine limbs underwent simple closure repair and 12 underwent autologous patch repair. Difficult sheath insertions were defined as those in which additional devices (stiff guidewire or a smaller diameter sheath for dilation) were used for scheduled sheath insertion. The inability to insert a sheath with the scheduled diameter was defined as a failed sheath insertion. We evaluated the EVT timing after EA for difficult sheath insertions, and whether the CFA was repaired with simple closure or autologous patch repair during EA surgery. Results There were 10 (25%) difficult sheath insertions, with one (2.5%) failure. The rate of difficult sheath insertions peaked from 6 months to 1 year after EA and gradually decreased (47% from 6 months to 3 years, 14% thereafter). There were more statistically significant difficult sheath insertions with simple closure repair (50%) than with autologous patch repair (12%) (P = 0.018). Hemostasis devices were used in 90% of EVT cases. The median maximum sheath diameter was 6 Fr (mean = 5.8 Fr). None of the cases required surgical procedures to achieve hemostasis after EVT. Conclusion EVT may be performed safely using the CFA after EA. The difficulty of sheath insertion may differ depending on the EVT timing after EA; it was more difficult with simple closure than with autologous patch repair, possibly related to scar formation.

Anti-Aging β-Klotho Gene-Activated Scaffold Promotes Rejuvenative Wound Healing Response in Human Adipose-Derived Stem Cells

Wound healing requires a tight orchestration of complex cellular events. Disruption in the cell-signaling events can severely impair healing. The application of biomaterial scaffolds has shown healing potential; however, the potential is insufficient for optimal wound maturation. This study explored the functional impact of a collagen-chondroitin sulfate scaffold functionalized with nanoparticles carrying an anti-aging gene β-Klotho on human adipose-derived stem cells (ADSCs) for rejuvenative healing applications. We studied the response in the ADSCs in three phases: (1) transcriptional activities of pluripotency factors (Oct-4, Nanog and Sox-2), proliferation marker (Ki-67), wound healing regulators (TGF-β3 and TGF-β1); (2) paracrine bioactivity of the secretome generated by the ADSCs; and (3) regeneration of basement membrane (fibronectin, laminin, and collagen IV proteins) and expression of scar-associated proteins (α-SMA and elastin proteins) towards maturation. Overall, we found that the β-Klotho gene-activated scaffold offers controlled activation of ADSCs' regenerative abilities. On day 3, the ADSCs on the gene-activated scaffold showed enhanced (2.5-fold) activation of transcription factor Oct-4 that was regulated transiently. This response was accompanied by a 3.6-fold increase in the expression of the anti-fibrotic gene TGF-β3. Through paracrine signaling, the ADSCs-laden gene-activated scaffold also controlled human endothelial angiogenesis and pro-fibrotic response in dermal fibroblasts. Towards maturation, the ADSCs-laden gene-activated scaffold further showed an enhanced regeneration of the basement membrane through increases in laminin (2.1-fold) and collagen IV (8.8-fold) deposition. The ADSCs also expressed 2-fold lower amounts of the scar-associated α-SMA protein with improved qualitative elastin matrix deposition. Collectively, we determined that the β-Klotho gene-activated scaffold possesses tremendous potential for wound healing and could advance stem cell-based therapy for rejuvenative healing applications.

Prospective, Randomized, Double-Blind, Placebo-Controlled Study on Efficacy of Copaiba Oil in Silicone-Based Gel to Reduce Scar Formation

Introduction

Scars are the end result of a biologic and natural process of wound repair after injury, surgery, acne, illness, burns, and infection. When skin is damaged, a fast and coordinated body response is triggered by four highly integrated and overlapping phases including homeostasis, inflammation, proliferation, and tissue remodeling. Healing of a skin wound may result in an abnormal scar if the balance among these four phases is lost during the healing process. Various topical treatments have been used for their ability to reduce unsightly scar formation. Recently, studies have shown improvement in scar appearance after treating with silicone gels containing natural herbal ingredients. The aim of this study is to evaluate the efficacy of a novel silicone-based gel containing copaiba oil (Copaderm) for prevention and/or appearance reduction of different types of abnormal scars.

Methods

This study was designed as a prospective, randomized, double-blind, placebo-controlled trial involving 42 patients with abnormal scars, divided into two groups. Each group received either a topical scar formulation consisting of copaiba oil in silicone gel or a placebo gel twice a day for 84 days. Assessments of the scars were performed at 0, 28, and 84 days following the onset of topical application using three methods: a clinical assessment using the Manchester Scar Scale, a photographic assessment to establish before and after treatment improvements, and at the end of the study period, patients completed a final satisfaction questionnaire.

Results

Of the original 42 patients, 32 completed the evaluation. There was a significant difference with respect to the overall score of the Manchester Scar Scale between the two groups from baseline to 84 days (P < 0.05). All patients with copaiba oil in silicone gel achieved improvement of their scars, based on overall score at 84 days. A visible scar reduction was observed with photographic assessment. Eighty-nine percent of subjects (n = 16) with copaiba oil in silicone gel rated as being satisfied or very satisfied after 84 days of treatment.

Conclusion

Our findings support the hypothesis that copaiba oil in silicone-derivative gel was able obtain significant improvement in color, contour, distortion, and texture for different types of scar through the Manchester Scar Scale analysis. These findings contribute to reducing abnormal scar formation during the healing process.

Systemic Immunosuppression for Prevention of Recurrent Tendon Adhesions

Background:

The recovery for patients after tendon repair is frequently limited by development of tendon adhesions. This scar tissue formation is dependent on immune system activation. Tacrolimus has unique properties that may contribute to the prevention of overactive scarring by inhibition of inflammatory cytokines.

Methods:

Herein, we present a case using systemic immunosuppression to prevent recurrent adhesion accumulation in a patient with a prior spaghetti wrist injury. Tacrolimus began 1 week before repeat-secondary tenolysis surgery, and it continued for 3 months postoperative. Dosing was tapered to a serum level between 5 and 8 µg/L.

Results:

The 27-year-old male patient suffered a volar wrist laceration transecting all flexor tendons and volar wrist nerves. He underwent immediate repair but had a poor outcome despite early range of motion therapy. A primary tenolysis only improved his average arc of finger motion from 72 to 95 degrees. Secondary tenolysis augmented with systemic tacrolimus improved his arc of finger motion from 95 to 202 degrees. Mechanistically, tacrolimus prevents proper function of activated T and B cells. This results in decreased proliferation, angiogenesis, and cytoskeletal organization of fibroblasts on inflammation and integrin adhesions, and it potentially explains the reduced tendon molecule adhesions seen in this patient.

Conclusions:

Tacrolimus may be effective in reducing motion, limiting tendon adhesions. The novel use of this medication resulted in the return of near-normal hand function in a patient placed on low-dose tacrolimus after primary tenolysis had failed.

Clinical Translation of Scarless 0.33-mm Core Microbiopsy for Molecular Evaluation of Human Skin

BACKGROUND

Skin scarring can occur after punch biopsies, prohibiting their routine utilization, especially in the central face.

OBJECTIVES

This paper describes a scarless, 0.33-mm-diameter skin microbiopsy for molecular analysis of skin.

METHODS

This is was single-center, randomized, prospective study with 15 patients receiving no biopsy or biopsy on the left or right nasolabial fold. Six blinded raters assessed participant photos at baseline, 1 month, and 3 months post biopsy to evaluate for a visualized scar. Patient and Observer Scar Assessment Scale was completed. Additionally, biopsies from various skin regions of body along with arm skin after treatment with a single Erbium-YAG laser were processed for molecular analysis.

RESULTS

No patients exhibited scar formation based on evaluation of photographs and patient feedback. There was no mark at the biopsy site 7 days post-procedure. Optical coherence tomography showed a complete closing of the biopsy-punch wound 48 hours post-biopsy. One month post-biopsy, photography reviewers were unable to identify a scar, on average, 90% of the time at 3-month follow-up. Microbiopsies from various anatomical regions were successfully extracted for histology, electron microscopy, and gene expression analysis. Selected skin rejuvenation markers in the biopsies from Erbium-YAG-treated forearm skin resulted in significant gene upregulation in extracellular matrix molecules at 1 month posttreatment compared with untreated skin.

CONCLUSIONS

A core microbiopsy of 0.33 mm can be extracted reproducibly for histological, ultrastructural, and gene expression analysis without scarring. This allows repeated sampling for assessment of skin treatments and diseases, including aesthetics and wound-healing progress.

Synergic Effect of Botulinum Toxin Type A and Triamcinolone Alleviates Scar Pruritus by Modulating Epidermal Hyperinnervation: A Preliminary Report

BACKGROUND

Patients often experience scar-related pruritus, which adversely affects quality of life. Triamcinolone acetonide (TAC) is widely used to treat pathologic scars, and botulinum toxin type A (BTX-A) reportedly improves scarring and associated discomfort.

OBJECTIVES

The aim of this study was to investigate the clinical efficacy of combining TAC and BTX-A to reduce scar itch; potential mechanisms were investigated via an animal model.

METHODS

For the clinical study, each scar on a patient was divided into 2 equal parts, with one part receiving TAC/BTX-A and the other TAC alone. Therapeutic interventions were administered over 3 sessions at 4-week intervals. Itch intensity was measured on a visual analog scale before each therapeutic intervention (V1, V2, V3) and 4 weeks after the last intervention (V4). For the animal model, rats were allocated into 5 groups: control, untreated burn, TAC, BTX-A, and TAC/BTX-A. We evaluated alloknesis in the right hind paw and analyzed possible molecular mechanisms.

RESULTS

In humans, TAC/BTX-A significantly reduced scar itch compared with TAC alone at V4 (P = 0.04). In rats, post-burn itch was mitigated at 4 weeks after treatment with TAC, BTX-A, and TAC/BTX-A (P = 0.03, P = 0.0054, and P = 0.0053, respectively). TAC/BTX-A significantly decreased the density of intraepidermal nerve fibers post-burn relative to the untreated burn (P = 0.0008). TAC/BTX-A downregulated the expressions of nerve growth factor and protein transient receptor potential vanilloid subtype 1.

CONCLUSIONS

TAC/BTX-A therapy exhibited enhanced and sustained clinical efficacy in relieving scar itch, possibly via modulating epidermal innervation and expression of transient receptor potential vanilloid subtype 1 .

LEVEL OF EVIDENCE: 2

A critical review on the potential role of adipose-derived stem cells for future treatment of hypertrophic scars

INTRODUCTION

Adipose-derived stem cells (ASCs) have recently gained researchers' interest as a solution to various diseases and conditions, including hypertrophic scar. This literature review aims to elucidate ASCs as a potential solution to alleviate hypertrophic scar in human subjects.

METHODS

Literature search was done in databases which includes PubMed, MEDLINE, and ProQuest using terms 'adipose derived stem cells', 'adipose cells', 'fat graft', 'fat grafting', 'autologous fat graft', 'fat injection', 'lipofilling', 'scar management', 'scar treatment', 'burn scar', and 'wound management'. The included articles which were published during year 2000-November 2020 must describe the use of ASCs or fat grafting or lipofilling as an attempt to alleviate hypertrophic scar.

REMARKS

Clinically, ASCs improve hypertrophic scars in terms of scar color, elasticity, texture, thickness, and size. Histologically, ASCs promotes healthy tissue regeneration, reduction in fibroblasts, and reorganisation of collagen, resembling those of normal skin. In terms of molecular aspects, ASCs alleviates hypertrophic scars through direct differentiation and paracrine mechanisms.

CONCLUSION

Adipose-derived stem cells, emerge to be a potential solution for alleviating hypertrophic scar, as demonstrated in various studies. However, there has been no studies conducted in human subjects to investigate the effect of ASCs on hypertrophic scar.

A Trifecta of New Insights into Ovine Footrot for Infection Drivers, Immune Response, and Host-Pathogen Interactions

Footrot is a polymicrobial infectious disease in sheep causing severe lameness, leading to one of the industry's largest welfare problems. The complex etiology of footrot makes in situ or in vitro investigations difficult. Computational methods offer a solution to understanding the bacteria involved and how they may interact with the host, ultimately providing a way to identify targets for future hypothesis-driven investigative work. Here, we present the first combined global analysis of bacterial community transcripts together with the host immune response in healthy and diseased ovine feet during a natural polymicrobial infection state using metatranscriptomics. The intratissue and surface bacterial populations and the most abundant bacterial transcriptomes were analyzed, demonstrating that footrot-affected skin has reduced diversity and increased abundances of not only the causative bacterium Dichelobacter nodosus but also other species such as Mycoplasma fermentans and Porphyromonas asaccharolytica. Host transcriptomics reveals the suppression of biological processes related to skin barrier function, vascular functions, and immunosurveillance in unhealthy interdigital skin, supported by histological findings that type I collagen (associated with scar tissue formation) is significantly increased in footrot-affected interdigital skin compared to outwardly healthy skin. Finally, we provide some interesting indications of host and pathogen interactions associated with virulence genes and the host spliceosome, which could lead to the identification of future therapeutic targets.

Glibenclamide Nanocrystal-Loaded Bioactive Polymeric Scaffolds for Skin Regeneration: In Vitro Characterization and Preclinical Evaluation

Skin restoration following full-thickness injury poses significant clinical challenges including inflammation and scarring. Medicated scaffolds formulated from natural bioactive polymers present an attractive platform for promoting wound healing. Glibenclamide was formulated in collagen/chitosan composite scaffolds to fulfill this aim. Glibenclamide was forged into nanocrystals with optimized colloidal properties (particle size of 352.2 nm, and polydispersity index of 0.29) using Kolliphor as a stabilizer to allow loading into the hydrophilic polymeric matrix. Scaffolds were prepared by the freeze drying method using different total polymer contents (3-6%) and collagen/chitosan ratios (0.25-2). A total polymer content of 3% at a collagen/chitosan ratio of 2:1 (SCGL3-2) was selected based on the results of in vitro characterization including the swelling index (1095.21), porosity (94.08%), mechanical strength, rate of degradation and in vitro drug release. SCGL3-2 was shown to be hemocompatible based on the results of protein binding, blood clotting and percentage hemolysis assays. In vitro cell culture studies on HSF cells demonstrated the biocompatibility of nanocrystals and SCGL3-2. In vivo studies on a rat model of a full-thickness wound presented rapid closure with enhanced histological and immunohistochemical parameters, revealing the success of the scaffold in reducing inflammation and promoting wound healing without scar formation. Hence, SCGL3-2 could be considered a potential dermal substitute for skin regeneration.

Hyaluronic acid-fibrin hydrogels show improved mechanical stability in dermo-epidermal skin substitutes

Human plasma-derived bilayered skin substitutes have been successfully used by our group in different skin tissue engineering applications. However, several issues associated with their poor mechanical properties were observed, and they often resulted in rapid contraction and degradation. In this sense, hydrogels composed of plasma-derived fibrin and thiolated-hyaluronic acid (HA-SH, 0.05-0.2% w/v) crosslinked with poly(ethylene glycol) diacrylate (PEGDA, 2:1, 6:1, 10:1 and 14:1 mol of thiol to moles of acrylate) were developed to reduce the shrinking rates and enhance the mechanical properties of the plasma-derived matrices. Plasma/HA-SH-PEGDA hydrogels showed a decrease in the contraction behaviour ranging from 5% to 25% and an increase in Young's modulus. Furthermore, the results showed that a minimal amount of the added HA-SH was able to escape the plasma/HA-SH-PEGDA hydrogels after incubation in PBS. The results showed that the increase in rigidity of the matrices as well as the absence of adhesion cellular moieties in the second network of HA-SH/PEGDA, resulted in a decrease in contraction in the presence of the encapsulated primary human fibroblasts (hFBs), which may have been related to an overall decrease in proliferation of hFBs found for all hydrogels after 7 days with respect to the plasma control. The metabolic activity of hFB returned to the control levels at 14 days except for the 2:1 PEGDA crosslinking ratio. The metabolic activity of primary human keratinocytes (hKCs) seeded on the hydrogels showed a decrease when high amounts of HA-SH and PEGDA crosslinker were incorporated. Organotypic skins formed in vitro after 21 days with plasma/HA-SH-PEGDA hydrogels with an HA content of 0.05% w/v and a 2:1 crosslinking ratio were up to three times thicker than the plasma controls, evidencing a reduction in contraction, while they also showed better and more homogeneous keratin 10 (K10) expression in the supra-basal layer of the epidermis. Furthermore, filaggrin expression showed the formation of an enhanced stratum corneum for the constructs containing HA. These promising results indicate the potential of using these biomimetic hydrogels as in vitro skin models for pharmaceutical products and cosmetics and future work will elucidate their potential functionality for clinical treatment.

Efficacy and safety of pulsed dye laser for the treatment of surgical scars: a systematic review and meta-analysis

Various clinical trials have explored whether the pulsed dye laser (PDL) method is safe to treat scars, especially surgical scars. However, comprehensive evidence confirming the exact outcomes of PDL for treating surgical scars is lacking. The efficacy and safety of PDL in the treatment of surgical scars were determined through a review of several studies. The PubMed, Embase, Cochrane Library, and Web of Science databases were searched, and the main clinical outcomes were Vancouver Scar Scale (VSS) scores in terms of pigmentation, vascularity, pliability, and height. Review Manager 5.4 software was used for statistical analyses of the data; we chose a standardized mean difference (SMZ) to present the results with 95% confidence interval (CI). Overall, seven randomized controlled trials were used for this meta-analysis, all of these papers used 585 nm or 595 nm PDL with 7 mm or 10 mm spot size and a fluence of 3.5 to 10 J/cm² for treating surgical scars; besides, the pulse duration ranged from 450 μs to 10 ms. We found that PDL significantly resulted in decreased VSS scores (P = 0.02) in four aspects: pigmentation (P = 0.0002), vascularity (P < 0.00001), pliability (P = 0.0002), and height (P = 0.0002). Moreover, scar improvement was similar when using 585 nm and 595 nm PDL in terms of pigmentation (P = 0.76), vascularity (P = 0.34), pliability (P = 0.64), and height (P = 0.57). Furthermore, our review indicated that PDL has no obvious adverse effects for most people, except transitory erythema and purpura. The meta-analysis showed that both 585 nm and 595 nm PDL therapy can effectively reduce the VSS score, suggesting that PDL can be a safe and effective method for the treatment of surgical scars.

A Scarless Healing Tale: Comparing Homeostasis and Wound Healing of Oral Mucosa With Skin and Oesophagus

Epithelial tissues are the most rapidly dividing tissues in the body, holding a natural ability for renewal and regeneration. This ability is crucial for survival as epithelia are essential to provide the ultimate barrier against the external environment, protecting the underlying tissues. Tissue stem and progenitor cells are responsible for self-renewal and repair during homeostasis and following injury. Upon wounding, epithelial tissues undergo different phases of haemostasis, inflammation, proliferation and remodelling, often resulting in fibrosis and scarring. In this review, we explore the phenotypic differences between the skin, the oesophagus and the oral mucosa. We discuss the plasticity of these epithelial stem cells and contribution of different fibroblast subpopulations for tissue regeneration and wound healing. While these epithelial tissues share global mechanisms of stem cell behaviour for tissue renewal and regeneration, the oral mucosa is known for its outstanding healing potential with minimal scarring. We aim to provide an updated review of recent studies that combined cell therapy with bioengineering exporting the unique scarless properties of the oral mucosa to improve skin and oesophageal wound healing and to reduce fibrotic tissue formation. These advances open new avenues toward the ultimate goal of achieving scarless wound healing.

Efficacy of combined treatment with intense pulsed light and fractional erbium:YAG Laser in scar prevention: A randomized split wound trial

Various methods have been used for scar prevention; however, the optimal method remains unclear. We investigated the efficacy of combinational intense pulsed light (IPL)/fractional erbium-doped yttrium aluminum garnet (Er:YAG) laser treatment in early wound healing. This was a prospective, randomized, controlled split wound trial. Scars were divided into three sites: the combined IPL/fractional Er:YAG treatment, fractional Er:YAG laser treatment, and untreated control sites. Treatment was conducted in three sessions: at removal of stitches and after 4 and 8 weeks. Treatment efficacy was evaluated using the Patient Observer Scar Assessment Scale (POSAS) and Vancouver Scar Scale (VSS) scores. The erythema index (EI) and melanin index (MI) were measured. In the total POSAS score, the IPL/fractional Er:YAG site showed steady and significant improvement, in contrast to the other sites. At week 8, the combined treatment sites had better POSAS scores than the fractional Er:YAG laser alone sites (p = 0.001) and the control sites (p = 0.000). The effect of combinational treatment was maintained until the follow-up period by comparing the Er:YAG (p = 0.015) and control sites (p = 0.007). In terms of VSS scores, the IPL/fractional Er:YAG combined treatment sites had consistent improvement at week 8 (p = 0.005) and week 20 (p = 0.02) compared to that at week 4, while the other sites showed no such improvement. In conclusion, the combination of IPL and Er:YAG showed more favorable effects on scar prevention than Er:YAG or no treatment. IPL/Er:YAG therapy could be an effective and safe strategy in the early wound healing process for reducing scar formation.

Wound dressings: curbing inflammation in chronic wound healing

Chronic wounds represent an economic burden to healthcare systems worldwide and a societal burden to patients, deeply impacting their quality of life. The incidence of recalcitrant wounds has been steadily increasing since the population more susceptible, the elderly and diabetic, are rapidly growing. Chronic wounds are characterised by a delayed wound healing process that takes longer to heal under standard of care than acute (i.e. healthy) wounds. Two of the most common problems associated with chronic wounds are inflammation and infection, with the latter usually exacerbating the former. With this in mind, researchers and wound care companies have developed and marketed a wide variety of wound dressings presenting different compositions but all aimed at promoting healing. This makes it harder for physicians to choose the correct therapy, especially given a lack of public quantitative data to support the manufacturers’ claims. This review aims at giving a brief introduction to the clinical need for chronic wound dressings, focusing on inflammation and evaluating how bio-derived and synthetic dressings may control excess inflammation and promote healing.

Light emitting diode-red light for reduction of post-surgical scarring: Results from a dose-ranging, split-face, randomized controlled trial

Scarring has significant esthetic and functional consequences for patients. A need exists for anti-scarring therapeutics. Light emitting diode-red light (LED-RL) has been shown to modulate skin fibrosis. The aim of this study is to evaluate the safety and efficacy of LED-RL to reduce post-operative scarring. Cutaneous Understanding of Red-light Efficacy on Scarring was a randomized, mock-controlled, single-blind, dose-ranging, split-face phase II clinical trial. Starting 1 week post-surgery, patients received LED-RL irradiation and temperature-controlled mock therapy to incision sites at fluences of 160, 320 or 480 J/cm2 , triweekly for 3 weeks. Efficacy was assessed at 1, 3 and 6-12 months. The primary endpoint was difference in scar pliability between LED-RL-treated and control sites. Secondary outcomes included Patient and Observer Scar Assessment Scale, collagen and water concentration, and adverse events. There were no significant differences in scar pliability between treated and control scars. At certain fluences, treated scars showed greater improvements in observer rating and scar pliability, reflected by greater reductions in induration, from baseline to 6 months compared to control scars. Treatment-site adverse events included blistering (n = 2) and swelling (n = 1), which were mild and resolved without sequelae. LED-RL phototherapy is safe in the early postoperative period and may reduce scarring.

Nanomaterials in Skin Regeneration and Rejuvenation

Skin is the external part of the human body; thus, it is exposed to outer stimuli leading to injuries and damage, due to being the tissue mostly affected by wounds and aging that compromise its protective function. The recent extension of the average lifespan raises the interest in products capable of counteracting skin related health conditions. However, the skin barrier is not easy to permeate and could be influenced by different factors. In the last decades an innovative pharmacotherapeutic approach has been possible thanks to the advent of nanomedicine. Nanodevices can represent an appropriate formulation to enhance the passive penetration, modulate drug solubility and increase the thermodynamic activity of drugs. Here, we summarize the recent nanotechnological approaches to maintain and replace skin homeostasis, with particular attention to nanomaterials applications on wound healing, regeneration and rejuvenation of skin tissue. The different nanomaterials as nanofibers, hydrogels, nanosuspensions, and nanoparticles are described and in particular we highlight their main chemical features that are useful in drug delivery and tissue regeneration.

Dehydrated Human Amniotic Membrane Inhibits Myofibroblast Contraction through the Regulation of the TGFβ‒SMAD Pathway In Vitro

Excessive fibrosis affects more than 100 million patients yearly, leading to the accumulation of extracellular matrix that compromises tissue architecture and impedes its function. Intrinsic properties of the amniotic membrane have alluded to its potential to inhibit excessive fibrosis; therefore, this study aimed to investigate the effects of dehydrated human amnion/chorion membrane (dHACM) on dermal fibroblasts and their role in fibrotic pathways. Human dermal fibroblasts were stimulated with TGFβ1, triggering myofibroblast-like characteristics in vitro. Subsequent addition of dHACM in the continued presence of TGFβ1 inhibited downstream signaling, leading to a reduction in the expression of known fibrotic and extracellular matrix genes. In addition, dHACM decreased alpha-smooth muscle actin, a stress filament responsible for contractile activity in scarring. The functional outcome of these effects was observed in an ex vivo model for cellular contraction. Hyperactivation of TGFβ signaling increased the contractile capacity of myofibroblasts embedded within a collagen substrate. Simultaneous addition of dHACM treatment prevented the marked contraction, which is likely a direct result of the inhibition of TGFβ signaling mentioned earlier. These observations may support the use of dHACM in the regulation of fibroblast activity as it relates to tissue fibrosis.

Preventing Engrailed-1 activation in fibroblasts yields wound regeneration without scarring

Skin scarring, the end result of adult wound healing, is detrimental to tissue form and function. Engrailed-1 lineage-positive fibroblasts (EPFs) are known to function in scarring, but Engrailed-1 lineage-negative fibroblasts (ENFs) remain poorly characterized. Using cell transplantation and transgenic mouse models, we identified a dermal ENF subpopulation that gives rise to postnatally derived EPFs by activating Engrailed-1 expression during adult wound healing. By studying ENF responses to substrate mechanics, we found that mechanical tension drives Engrailed-1 activation via canonical mechanotransduction signaling. Finally, we showed that blocking mechanotransduction signaling with either verteporfin, an inhibitor of Yes-associated protein (YAP), or fibroblast-specific transgenic YAP knockout prevents Engrailed-1 activation and promotes wound regeneration by ENFs, with recovery of skin appendages, ultrastructure, and mechanical strength. This finding suggests that there are two possible outcomes to postnatal wound healing: a fibrotic response (EPF-mediated) and a regenerative response (ENF-mediated).

In-vivo imaging of melanoma with simultaneous dual-wavelength acoustic-resolution-based photoacoustic/ultrasound microscopy

Melanoma is a common, highly fatal skin cancer. Photoacoustic imaging can achieve highly sensitive and high-contrast detection of melanin molecules in tissues, also inheriting the high penetration depth and high spatial resolution characteristics of ultrasound imaging, thus it is a very promising non-invasive diagnostic tool for early melanoma. In this work, we built an acoustic-resolution-based photoacoustic microscopy system, using 1064 nm/532 nm pulsed light to observe melanoma in the back of a mouse with simultaneous photoacoustic/ultrasound imaging. Through the fusion of multi-modal images, accurate positioning of melanoma and its surrounding normal tissues were realized. This work will further promote the application of photoacoustic imaging in the clinical diagnosis of early melanoma.

Petite miracles: insight into the nano-management of scarless wound healing

Scars affect millions of patients worldwide, yet their treatment efficacy and options clinically remain limited. In recent years, increased understanding of scar formation pathways leading to developments in nanotechnology have opened many opportunities for scar detection, prevention, and treatment due to the nanoscale features and therapeutic delivery capabilities of such technologies. Led by nanoparticles (NPs) and nanofibers, these novel strategies can aid in reducing scar contracture, improving wound-healing efficacy, and advancing progress towards scarless wound healing.

Electrochemical treatment of ex vivo human abdominal skin and potential use in scar management: A pilot study

INTRODUCTION

Scar treatments aim to address pathologic collagen deposition; however, they can be expensive or difficult to control. Electrochemical therapy (ECT) offers a simple alternative treatment. The purpose of this study is to examine the acid-base and histological changes in ex vivo human abdominal skin following ECT.

METHODS

Forty-two ex vivo human panniculus tissue sections collected from six individuals were tumesced with normal saline. ECT was performed by inserting two platinum needle electrodes connected to a DC power supply into each specimen. Voltage was varied (3-6 V) and applied for 5 minutes. Each specimen was sectioned across both electrode insertion sites and immediately stained with pH sensitive dye. The width of dye color change for each dosimetry pair was calculated. Hematoxylin and eosin staining was used to evaluate samples.

RESULTS AND DISCUSSION

ECT caused a spatially localised and dose-dependent increased area of acidic and basic pH around the anode and cathode, respectively. A significantly greater mean width of pH change was generated at the cathode compared to the anode in all treatment groups. Histological evaluation displayed broad condensation and hyalinisation of dermal collagen.

CONCLUSION

ECT triggered dermal pH alterations and changed the underlying structural framework of the specimen. This technology may serve as a low-cost, minimally invasive local soft-tissue remodeling technique with potential application in scar management.

LEVEL OF EVIDENCE

5.

LAY SUMMARY

Electrochemical therapy is a novel treatment that causes spatially selective dermal injury in areas of interest. This study measures the effects of electrochemical therapy when applied to abdominal skin. Electrochemical therapy appears to have beneficial effects by causing a highly localised reduction in collagen content or local softening of tissue, which is consistent with other studies on scar therapies, including chemexfoliation, radiofrequency technologies, and lasers. However, electrochemical therapy can be performed at a fraction of the costs of these aforementioned modalities.

Effects of Fractional CO2 Laser Treatment on Subglottic Scar in a Rabbit Model

OBJECTIVE

The objective of this study was to investigate the effects of fractional CO₂ laser on subglottic scar.

STUDY DESIGN

Randomized controlled animal study.

SETTING

Academic medical center.

METHODS

Subglottic scar was induced in 12 New Zealand white rabbits via an endoscopic brush technique. This was followed by an open airway surgery that included vertical division of the cricoid and proximal trachea. Eight rabbits underwent fractional CO₂ laser treatment of the scar via a Lumenis Ultrapulse Deep FX handpiece. Four rabbits underwent the open surgical approach without laser treatment. Bronchoscopy was performed at weeks 1, 2, 4, and 8. The animals were euthanized and laryngotracheal complexes harvested 12 weeks postsurgery. Immunohistochemistry was performed to determine the collagen composition of treated and untreated scars.

RESULTS

All 12 subjects survived to the study endpoint with no significant respiratory complications, despite 10 of 12 developing some degree of lateral tracheal narrowing. The median ratio of type I collagen to type III collagen in the laser group (1.57) was significantly more favorable than that of the untreated group (2.84; P = .03).

CONCLUSION

Treatment with fractional CO₂ laser appears to have similar effects on subglottic scars as with cutaneous scars, improving the ratio of type I to type III collagen. Additionally, we developed an open airway approach in the rabbit model to deliver fractional CO₂ laser treatment to the subglottis without introducing respiratory complications or compromising survival.

When is the right time to remove staples after an elective cesarean delivery?: a randomized control trial

Objective: To determine if there are differences in scar healing and cosmetic outcome between early and late metal staples removal after cesarean delivery.Study design: Randomized controlled trial, in which patients undergoing a scheduled nonemergent cesarean delivery were randomly assigned to early staples removal versus late staples removal. Outcome assessors were blinded to group allocation. Scars were evaluated 8 weeks after cesarean delivery. Primary outcome measures were Patient and Observer Scar Assessment Scale (POSAS) scores. Secondary outcome measures included surgical site infection, wound disruption, hematoma, or seroma.Results: During the study period, 104 patients were randomized. There were no between-group differences in maternal demographics. Both groups had similar indications for cesarean delivery and similar rate of previous one or more cesarean delivery. Patient and Observer Scar Assessment Scale were similar for patients (p = .932) and for physician observer (p = .529). No significant differences were demonstrated between the groups in the rate of surgical site infection or wound disruption.Conclusions: Removal of stainless steel staples on postoperative 4 versus postoperative 8 after cesarean delivery showed similar outcome without significant effect on incision healing. Therefore, timing of removal staples after cesarean delivery could be performed based on patients and surgeon preference.

Candidate rejuvenating factor GDF11 and tissue fibrosis: friend or foe?

Growth differentiation factor 11 (GDF11 or bone morphogenetic protein 11, BMP11) belongs to the transforming growth factor-β superfamily and is closely related to other family member-myostatin (also known as GDF8). GDF11 was firstly identified in 2004 due to its ability to rejuvenate the function of multiple organs in old mice. However, in the past few years, the heralded rejuvenating effects of GDF11 have been seriously questioned by many studies that do not support the idea that restoring levels of GDF11 in aging improves overall organ structure and function. Moreover, with increasing controversies, several other studies described the involvement of GDF11 in fibrotic processes in various organ setups. This review paper focuses on the GDF11 and its pro- or anti-fibrotic actions in major organs and tissues, with the goal to summarize our knowledge on its emerging role in regulating the progression of fibrosis in different pathological conditions, and to guide upcoming research efforts.

Assessment of progressive alterations in collagen organization in the postoperative conjunctiva by multiphoton microscopy

Glaucoma filtration surgery (GFS) commonly fails due to excessive fibrosis. As collagen structure aberrations is implicated in adverse fibrotic progression, this study aims to uncover collagen organization alterations during postoperative scarring. Via quantitative second harmonic generation/two photon excitation multiphoton imaging, we reveal the scar development and phenotype in the mouse model of conjunctival scarring. We also show that multiphoton imaging corroborated the collagen ultrastructure anomaly characteristic of the SPARC-/- mouse postoperative conjunctiva. These data improve our understanding of postoperative conjunctival scarring and further enhance the utility of this model for the development of anti-fibrotic therapeutics for GFS.

A multiscale hybrid mathematical model of epidermal-dermal interactions during skin wound healing

Following injury, skin activates a complex wound healing programme. While cellular and signalling mechanisms of wound repair have been extensively studied, the principles of epidermal-dermal interactions and their effects on wound healing outcomes are only partially understood. To gain new insight into the effects of epidermal-dermal interactions, we developed a multiscale, hybrid mathematical model of skin wound healing. The model takes into consideration interactions between epidermis and dermis across the basement membrane via diffusible signals, defined as activator and inhibitor. Simulations revealed that epidermal-dermal interactions are critical for proper extracellular matrix deposition in the dermis, suggesting these signals may influence how wound scars form. Our model makes several theoretical predictions. First, basal levels of epidermal activator and inhibitor help to maintain dermis in a steady state, whereas their absence results in a raised, scar-like dermal phenotype. Second, wound-triggered increase in activator and inhibitor production by basal epidermal cells, coupled with fast re-epithelialization kinetics, reduces dermal scar size. Third, high-density fibrin clot leads to a raised, hypertrophic scar phenotype, whereas low-density fibrin clot leads to a hypotrophic phenotype. Fourth, shallow wounds, compared to deep wounds, result in overall reduced scarring. Taken together, our model predicts the important role of signalling across dermal-epidermal interface and the effect of fibrin clot density and wound geometry on scar formation. This hybrid modelling approach may be also applicable to other complex tissue systems, enabling the simulation of dynamic processes, otherwise computationally prohibitive with fully discrete models due to a large number of variables.

WITHDRAWN: Petite miracles: insight into the nano-management of scarless wound healing

This article has been withdrawn at the request of the author(s) and/or editor. The Publisher apologizes for any inconvenience this may cause. The full Elsevier Policy on Article Withdrawal can be found at https://www.elsevier.com/about/our-business/policies/article-withdrawal.

Wound Repair, Scar Formation, and Cancer: Converging on Activin

Wound repair is a highly regulated process that requires the interaction of various cell types. It has been shown that cancers use the mechanisms of wound healing to promote their own growth. Therefore, it is of importance to identify common regulators of wound repair and tumor formation and to unravel their functions and mechanisms of action. An exciting example is activin, which acts on multiple cell types in wounds and tumors, thereby promoting healing, but also scar formation and tumorigenesis. Here, we summarize current knowledge on the role of activin in these processes and highlight the therapeutic potential of activin or activin antagonists for the treatment of impaired healing or excessive scarring and cancer, respectively.

Activation of TRPA1 nociceptor promotes systemic adult mammalian skin regeneration

Adult mammalian wounds, with rare exception, heal with fibrotic scars that severely disrupt tissue architecture and function. Regenerative medicine seeks methods to avoid scar formation and restore the original tissue structures. We show in three adult mouse models that pharmacologic activation of the nociceptor TRPA1 on cutaneous sensory neurons reduces scar formation and can also promote tissue regeneration. Local activation of TRPA1 induces tissue regeneration on distant untreated areas of injury, demonstrating a systemic effect. Activated TRPA1 stimulates local production of interleukin-23 (IL-23) by dermal dendritic cells, leading to activation of circulating dermal IL-17-producing γδ T cells. Genetic ablation of TRPA1, IL-23, dermal dendritic cells, or γδ T cells prevents TRPA1-mediated tissue regeneration. These results reveal a cutaneous neuroimmune-regeneration cascade triggered by topical TRPA1 activators that promotes adult mammalian tissue regeneration, presenting a new avenue for research and development of therapies for wounds and scars.

Lower donor-site morbidity using QT autografts for ACL reconstruction

PURPOSE

Comparing scar cosmesis and regional hypoesthesia at the incision site between quadriceps tendon (QT), bone-patellar tendon-bone (BPTB), and hamstring tendon (HT) for anterior cruciate ligament (ACL) reconstruction.

METHODS

Ninety patients undergoing ACL reconstruction with QT, HT or BPTB were evaluated at 1-year post-op. Scar cosmesis was assessed using the patient and observer scar assessment scale (POSAS) and length of the incision. Sensory outcome was analyzed by calculating the area of hypoesthesia around the scar. The classical ACL reconstruction functional follow-up was measured using the Lysholm score and KOOS.

RESULTS

Concerning QT versus BPTB group, QT patients have a significantly lower mean POSAS (24.8 ± 6.3 vs. 39.6 ± 5.8; p < 0.0001), shorter mean incision (2.8 ± 0.4 cm vs. 6.4 ± 1.3 cm; p < 0.0001), lower extent of hypoesthesia (8.7 ± 5.1 cm² vs. 88.2 ± 57 cm²; p < 0.0001), and better Lysholm score (90.1 ± 10.1 vs. 82.6 ± 13.5; n.s.). No significant difference was seen in KOOS (90.7 ± 7.2 vs. 88.4 ± 7.0; n.s.). Concerning QT versus HT group, no significant difference was found regarding mean POSAS score (24.8 ± 6.3 vs. 31.8 ± 6.2; n.s.), mean length of the incision (2.8 ± 0.4 cm vs. 2.5 ± 0.6 cm; n.s.), KOOS (90.7 ± 7.2 vs. 89.8 ± 8.2; n.s.) and mean Lysholm score (90.1 ± 10.1 vs. 87.8 ± 0.6; n.s.). The mean measured area of hypoesthesia was significantly higher in the HT group (70.3 ± 77.1 cm² vs. 8.7 ± 5.1 cm²; p < 0.0001).

CONCLUSION

Quadriceps tendon harvesting technique has the safest incision by causing less sensory loss compared to BPTB and HT. It also has the advantage of a short incision with more cosmetic scar compared to BPTB, with no difference compared to HT. However, no significant difference in terms of functional outcome was shown between the three autografts. These findings provide surgeons evidence about their clinical practice and help with graft choice decisions.

LEVEL OF EVIDENCE

III.

Evaluation of wound healing effect of alginate film containing Aloe vera gel and cross-linked with zinc chloride

PURPOSE

To develop a new wound dressing composed of alginate and Aloe vera gel and cross-linked with zinc ions.

METHODS

The aloe-alginate film was characterized using scanning electron microscopy (SEM), swelling profile, mechanical properties, polysaccharide content and X-ray diffraction (XRD). Thirty Wistar rats were divided in two groups a) treated with aloe-alginate film and b) control (treated with sterile gauze). Wound contraction measurements and hystological analysis were performed on 7th, 14th and 21st days after wound surgery.

RESULTS

The aloe-alginate film presented adequated mechanical resistance and malleability for application as wound dressing. There was no statistical difference in wound contraction between two groups. Histological assay demonstrated that aloe-alginate film presented anti-inflammatory activity, stimulated angiogenesis on proliferative phase and a more significant increased in collagen type I fibers and decreased type III fibers which promoted a mature scar formation when compared to control.

CONCLUSIONS

The aloe-alginate film showed adequate physicochemical characteristics for wound dressing applications. The in vivo assay demonstrated that aloe-alginate film enhanced the healing process of incisional skin wounds.

Nanoparticle-Based Therapeutic Approach for Diabetic Wound Healing

Diabetes mellitus (DM) is a common endocrine disease characterized by a state of hyperglycemia (higher level of glucose in the blood than usual). DM and its complications can lead to diabetic foot ulcer (DFU). DFU is associated with impaired wound healing, due to inappropriate cellular and cytokines response, infection, poor vascularization, and neuropathy. Effective therapeutic strategies for the management of impaired wound could be attained through a better insight of molecular mechanism and pathophysiology of diabetic wound healing. Nanotherapeutics-based agents engineered within 1-100 nm levels, which include nanoparticles and nanoscaffolds, are recent promising treatment strategies for accelerating diabetic wound healing. Nanoparticles are smaller in size and have high surface area to volume ratio that increases the likelihood of biological interaction and penetration at wound site. They are ideal for topical delivery of drugs in a sustained manner, eliciting cell-to-cell interactions, cell proliferation, vascularization, cell signaling, and elaboration of biomolecules necessary for effective wound healing. Furthermore, nanoparticles have the ability to deliver one or more therapeutic drug molecules, such as growth factors, nucleic acids, antibiotics, and antioxidants, which can be released in a sustained manner within the target tissue. This review focuses on recent approaches in the development of nanoparticle-based therapeutics for enhancing diabetic wound healing.

Fibroblast Heterogeneity in and Its Implications for Plastic and Reconstructive Surgery: A Basic Science Review

Fibroblasts’ integral role in tissue development, maintenance, and disease represents a fast-growing field of basic science research. Although fibroblasts were long thought to be a homogeneous cell population, recent research has illuminated the unforeseen complexity of these cells, giving rise to the rapidly expanding research field of “fibroblast heterogeneity.” Fibroblasts play a critical role in states of tissue fibrosis such as skin scarring, which affects hundreds of millions of patients annually and causes severe aesthetic, developmental, and functional morbidity. Beyond scarring, major organ fibrosis is an enormous public health concern responsible for nearly half of all deaths in the United States. Because fibrosis is a conserved response to tissue damage in all organs, the study of fibroblasts throughout the body may help us to understand their role in the conditions most relevant to plastic and reconstructive surgery—for instance, skin scarring (eg, from burns, traumatic lacerations, or surgical incisions), “pathological” scarring (hypertrophic scars, keloids), and capsular contracture. Here, we present a basic science review of fibroblast heterogeneity in wound healing, cancer, organ fibrosis, and human dermal architecture. The field of fibroblast heterogeneity is young, and many of the insights discussed have yet to be translated clinically. However, plastic surgeons stand in a unique position to bridge these discoveries into clinical realities. We hope this information can spur readers to consider both what questions in plastic surgery can be studied from the lens of fibroblast heterogeneity, and how these preclinical insights can be translated to improving care of our patients.