Site-specific gene expression profiling as a novel strategy for unravelling keloid disease pathobiology

Finite Element Analysis of the Stress Changes Associated With the Growth of Acne Keloids

Background

Almost half of all spontaneously occurring keloids are acne keloids on the anterior chest. These keloids often grow in a crab-claw shape due to predominant tractional stresses on the scar; such stresses are risk factors for keloid growth/progression. To understand the relationship between acne keloid growth and mechanical stress, we conducted finite element analysis (FEA), measured the long/short dimensions of photographed acne keloids, and subjected acne keloids to microscopy.

Methods

FEA was conducted on 10 identically shaped ellipsoidal keloids whose long-axis length rose from 5 to 50 mm in 5-mm increments. They were embedded in the skin and subjected to traction. The stress on the keloid and its surrounding tissues was determined. Dimensions of 220 acne keloids were measured. Electron/light microscopy was conducted on the center, margins, and surrounding tissues of chest acne keloids.

Results

FEA showed that as the keloid "grew," the tractional stress centered on its core, then became evenly distributed, and then focused increasingly on the tractioned keloid margin, especially its shallow dermis. This is associated with increasing stress in the surrounding tissues at the keloid margin. Clinical dimension measurements showed that acne keloids remained round until 4-5 mm, after which they elongated rapidly. Electron microscopy showed that in the surrounding skin, fragments of keratinocyte, fibrin, and numerous cell fragments were observed just below the epidermal basement membrane.

Conclusions

Keloid-prone acne should be treated with steroid tape or other keloid therapy when it reaches 4-5 mm in diameter.

Increased Susceptibility to Mechanical Stretch Drives the Persistence of Keloid Fibroblasts: An Investigation Using a Stretchable PDMS Platform

BACKGROUND

Keloids are a common fibrotic disease of the skin, with the pathological hallmark of excessive extracellular matrix synthesis due to abnormal fibroblast activity. Since keloids clinically arise in areas of high mechanical tension, the mechanotransductory pathway may be attributed to its pathogenesis. We aimed to establish a preclinical platform to elucidate the underlying mechanism of keloid development and its clinical persistence.

METHODS

We fabricated a mechanically stretchable polydimethylsiloxane cell culture platform; with its mimicry of the in vivo cyclic stretch of skeletal muscles, cells showed higher proliferation compared with conventional modalities.

RESULTS

In response to mechanical strain, TGF-β and type 1 collagen showed significant increases, suggesting possible TGF-β/Smad pathway activation via mechanical stimulation. Protein candidates selected by proteomic analysis were evaluated, indicating that key molecules involved in cell signaling and oxidative stress were significantly altered. Additionally, the cytoskeletal network of keloid fibroblasts showed increased expression of its components after periodic mechanical stimulation.

CONCLUSIONS

Herein, we demonstrated and validated the existing body of knowledge regarding profibrotic mechanotransduction signaling pathways in keloid fibroblasts. Cyclic stretch, as a driving force, could help to decipher the tension-mediated biomechanical processes, leading to the development of optimized therapeutic targets.

Enhanced bioenergetic cellular activity with metabolic switch to aerobic glycolysis in Keloid and Folliculitis Keloidalis Nuchae

Keloid scars and folliculitis keloidalis nuchae (FKN) are benign fibroproliferative dermal lesions of unknown aetiology and ill-defined treatment, which typically present in genetically susceptible individuals. Their pathognomonic hallmarks include local aggressive invasive behaviour plus high recurrence post-therapy. In view of this, we investigated proliferative and key parameters of bioenergetic cellular characteristics of site-specific keloid-derived fibroblasts (intra(centre)- and peri(margin)-lesional) and FKN compared to normal skin and normal flat non-hypertrophic scar fibroblasts as negative controls.The results showed statistically significant (P < 0.01) and variable growth dynamics with increased proliferation and migration in keloid fibroblasts, while FKN fibroblasts showed a significant (P < 0.001) increase in proliferation but similar migration profile to controls. A statistically significant metabolic switch towards aerobic glycolysis in the fibroblasts from the disease conditions was noted. Furthermore, an increase in basal glycolysis with a concomitant increase in the cellular maximum glycolytic capacity was also demonstrated in perilesional keloid and FKN fibroblasts (P < 0.05). Mitochondrial function parameters showed increased oxidative phosphorylation in the disease conditions (P < 0.05) indicating functional mitochondria. These findings further suggest that Keloids and FKN demonstrate a switch to a metabolic phenotype of aerobic glycolysis. Increased glycolytic flux inhibition is a potential mechanistic basis for future therapy.

Revealing the pathogenesis of keloids based on the status: Active vs inactive

Recently, the pathomechanisms of keloids have been extensively researched using transcriptomic analysis, but most studies did not consider the activity of keloids. We aimed to profile the transcriptomics of keloids according to their clinical activity and location within the keloid lesion, compared with normal and mature scars. Tissue samples were collected (keloid based on its activity (active and inactive), mature scar from keloid patients and normal scar (NS) from non-keloid patients). To reduce possible bias, all keloids assessed in this study had no treatment history and their location was limited to the upper chest or back. Multiomics assessment was performed by using single-cell RNA sequencing and multiplex immunofluorescence. Increased mesenchymal fibroblasts (FBs) was the main feature in keloid patients. Noticeably, the proportion of pro-inflammatory FBs was significantly increased in active keloids compared to inactive ones. To explore the nature of proinflammatory FBs, trajectory analysis was conducted and CCN family associated with mechanical stretch exhibited higher expression in active keloids. For vascular endothelial cells (VECs), the proportion of tip and immature cells increased in keloids compared to NS, especially at the periphery of active keloids. Also, keloid VECs highly expressed genes with characteristics of mesenchymal activation compared to NS, especially those from the active keloid center. Multiomics analysis demonstrated the distinct expression profile of active keloids. Clinically, these findings may provide the future appropriate directions for development of treatment modalities of keloids. Prevention of keloids could be possible by the suppression of mesenchymal activation between FBs and VECs and modulation of proinflammatory FBs may be the key to the control of active keloids.

Immune cells and associated molecular markers in dermal fibrosis with focus on raised cutaneous scars

Raised dermal scars including hypertrophic, and keloid scars as well as scalp-associated fibrosing Folliculitis Keloidalis Nuchae (FKN) are a group of fibrotic raised dermal lesions that mostly occur following cutaneous injury. They are characterized by increased extracellular matrix (ECM) deposition, primarily excessive collagen type 1 production by hyperproliferative fibroblasts. The extent of ECM deposition is thought to be proportional to the severity of local skin inflammation leading to excessive fibrosis of the dermis. Due to a lack of suitable study models, therapy for raised dermal scars remains ill-defined. Immune cells and their associated markers have been strongly associated with dermal fibrosis. Therefore, modulation of the immune system and use of anti-inflammatory cytokines are of potential interest in the management of dermal fibrosis. In this review, we will discuss the importance of immune factors in the pathogenesis of raised dermal scarring. The aim here is to provide an up-to-date comprehensive review of the literature, from PubMed, Scopus, and other relevant search engines in order to describe the known immunological factors associated with raised dermal scarring. The importance of immune cells including mast cells, macrophages, lymphocytes, and relevant molecules such as cytokines, chemokines, and growth factors, antibodies, transcription factors, and other immune-associated molecules as well as tissue lymphoid aggregates identified within raised dermal scars will be presented. A growing body of evidence points to a shift from proinflammatory Th1 response to regulatory/anti-inflammatory Th2 response being associated with the development of fibrogenesis in raised dermal scarring. In summary, a better understanding of immune cells and associated molecular markers in dermal fibrosis will likely enable future development of potential immune-modulated therapeutic, diagnostic, and theranostic targets in raised dermal scarring.

Keloidal Collagen May Be Produced Directly by αSMA-positive Cells: Morphological Analysis and Protein Shotgun Analysis

Keloids are fibroproliferative lesions caused by abnormal dermal wound healing. Keloidal collagen (KC) is a pathognomic feature of keloids, but the mechanism by which it forms is unknown. This study aimed to evaluate the histopathology of KC and thereby gain clues into how it forms.

Methods

The cross-sectional study cohort consisted of a convenience series of patients with keloids who underwent surgical excision. Skin pieces (3 mm²) were collected from the keloid center and nearby control skin. Histopathology was conducted with light and electron microscopy and immunohistochemistry. KC composition was analyzed with protein shotgun analysis.

Results

Microscopic analyses revealed the ubiquitous close association between KC and αSMA-positive spindle-shaped cells that closely resembled myofibroblasts. Neither KC nor the spindle-shaped cells were observed in the control tissues. Compared with control skin, the collagen fibers in the KC were overall thinner, their diameter varied more, and their spacing was irregular. These features were particularly pronounced in the collagens in the vicinity of the spindle-shaped cells. Protein shotgun analysis did not reveal a specific collagen in KC but showed abnormally high abundance of collagens I, III, VI, XII, and XIV.

Conclusions

These findings suggest that KC may be produced directly by myofibroblasts rather than simply being denatured collagen fibers. Because collagens VI and XII associate with myofibroblast differentiation, and collagen XIV associates with local mechanical stress, these collagens may reflect, and perhaps contribute to, the keloid-specific local conditions that lead to the formation of KC.

Gentiopicroside Ameliorates Diabetic Renal Tubulointerstitial Fibrosis via Inhibiting the AT1R/CK2/NF-κB Pathway

Renal tubulointerstitial fibrosis (TIF), characterized by epithelial-to-mesenchymal transition (EMT) of renal tubular epithelial cells, is the typical pathological alteration in diabetic nephropathy. Gentiopicroside (GPS), a natural compound with anti-inflammatory activity, has been demonstrated to alleviate glomerulosclerosis, whereas whether GPS inhibits TIF via regulating inflammation remains unclear. In this study, diabetic db/db mice and high glucose (HG)-stimulated renal tubular epithelial cells (NRK-52E) were applied to explore the effects and mechanisms of GPS on TIF. The results in vivo showed that GPS effectively improves glycolipid metabolism disorder, renal dysfunction, and TIF. In particular, GPS treatment reversed the abnormal expressions of EMT marker proteins including elevated α-smooth muscle actin and vimentin and decreased E-cadherin in the kidney of db/db mice. Moreover, GPS treatment also inhibited protein expressions of angiotensinⅡ type 1 receptor (AT1R) and CK2α and the activation of the NF-κB pathway. Importantly, the aforementioned effects of GPS acted in vivo were further observed in vitro in HG-stimulated NRK-52E cells, which were independent of its effects on glucose and lipid-lowering activity but were reversed by AT1R over-expression. Together, our results indicate that GPS that directly inhibits the CK2/NF-κB inflammatory signaling pathway via AT1R may also contribute to the amelioration of TIF in diabetes.

Downregulated cytotoxic CD8+ T-cell identifies with the NKG2A-soluble HLA-E axis as a predictive biomarker and potential therapeutic target in keloids

Keloids are an abnormal fibroproliferative wound-healing disease with a poorly understood pathogenesis, making it difficult to predict and prevent this disease in clinical settings. Identifying disease-specific signatures at the molecular and cellular levels in both the blood circulation and primary lesions is urgently needed to develop novel biomarkers for risk assessment and therapeutic targets for recurrence-free treatment. There is mounting evidence of immune cell dysregulation in keloid scarring. In this study, we aimed to profile keloid scar tissues and blood cells and found that downregulation of cytotoxic CD8+ T cells is a keloid signature in the peripheral blood and keloid lesions. Single-cell RNA sequencing revealed that the NKG2A/CD94 complex was specifically upregulated, which might contribute to the significant reduction in CTLs within the scar tissue boundary. In addition, the NKG2A/CD94 complex was associated with high serum levels of soluble human leukocyte antigen-E (sHLA-E). We subsequently measured sHLA-E in our hospital-based study cohort, consisting of 104 keloid patients, 512 healthy donors, and 100 patients with an interfering disease. The sensitivity and specificity of sHLA-E were 83.69% (87/104) and 92.16% (564/612), respectively, and hypertrophic scars and other unrelated diseases exhibited minimal interference with the test results. Furthermore, intralesional therapy with triamcinolone combined with 5-fluorouracil drastically decreased the sHLA-E levels in keloid patients with better prognostic outcomes, while an incomplete reduction in the sHLA-E levels in patient serum was associated with higher recurrence. sHLA-E may effectively serve as a diagnostic marker for assessing the risk of keloid formation and a prognostic marker for the clinical outcomes of intralesional treatment.

Classification of Distinct Endotypes in Human Skin Scarring: S.C.A.R.-A Novel Perspective on Dermal Fibrosis

Significance: Skin scarring is a permanent, irreversible end point of cutaneous injury. However, not everyone will acquire the same exact scar type. Skin scarring is generally recognized as complex with significant variability in individuals' scar type and response to treatment. Despite these tangible differences in treatment response, to date there has been no simplified approach in defining spectrum of skin scarring in relation to prediction and outcome post-treatment. Thus, in this study we propose that skin scarring consists of distinct endotypes, which is characterized by their specific pathology. Four distinct scar endotypes can be observed: (1) Stretched (flat), (2) Contracted, (3) Atrophic (depressed), and (4) Raised scarring, which can be abbreviated to S.C.A.R. endotypes. Each of these endotypes can certainly include subphenotypes and each phenotype can be present in more than one endotype. To define these endotypes, we also present a structured approach in assessment of all relevant parameters in skin scar evaluation including clinical (scar symptoms and signs) and nonclinical parameters (device measurements of structural, mechanical, and physiological properties of scars as well as gene and protein laboratory studies). Recent Advances: Scars can be phenotypically characterized based on a multitude of parameters assessed; however, not all scar types will share all the same characteristics. This leads to the question of whether skin scarring is a single disease entity with varying phenotypic characteristics or should be classed as several disease entities that have certain similar parameters. We suggest the latter and propose distinct scarring phenotypes arise mainly owing to genetic and environmental susceptibilities associated with the development of each specific scar endotype. Characteristic features of skin scarring, however, can be objectively and quantitively evaluated and used as an aid in the theranostic goal-directed management of scarring. Critical Issues: The concept of identifying different endotypes is key in formulating personalized treatments with improved outcomes beyond what is achieved with current nonspecific approaches in scar management. This approach has gained interest and significant traction in several other medical conditions including asthma, rheumatoid arthritis, and atopic dermatitis. Future Directions: To begin identifying distinct endotypic features in skin scarring, it is important to have a better understanding of underlying pathological mechanisms leading to further insight into the heterogeneous nature of skin scarring endotypes. This approach may lead to improved theranostic outcomes and further understanding of the pathophysiology of the complex nature of human skin scarring.

EVALUATION OF BLOOD OXYGEN SATURATION OF HIGH JUMPERS BASED ON ISOKINETIC TEST

ABSTRACT Introduction: An isokinetic test refers to the test of the force of a muscle or muscle group during centripetal and centrifugal movements at a constant speed in the whole range of joint motion by means of a isokinetic force tester. Objective: To explore the application of the knee centripetal flexor and extensor muscle groups in the blood oxygen saturation of high jumpers. Methods: Eighteen teenage female high jumper athletes above level 2 in a city sports school were selected. Their ages was 16.89±1.02 years old; height, 168.31±6.32cm; weight, 55.36±6.75kg. Results: At 60° S and 120° S test speed, the peak moment of the extensor muscle group on the same side of the knee was significantly greater than that of the flexor muscle group (P<0.05), while at 240° S test speed, it was the opposite. There was a significant difference in the peak moment of the flexor muscle group on the left and right side of the knee (P<0.01). Conclusions: The function of the dynamic muscle strength test system is one of the methods of studying the human muscle function. and can be used to test and evaluate the general strength of athletes. Level of evidence II; Therapeutic studies - investigation of treatment results.

Scalp and serum profiling of frontal fibrosing alopecia reveals scalp immune and fibrosis dysregulation with no systemic involvement

BACKGROUND

Frontal fibrosing alopecia (FFA) is a progressive, scarring alopecia of the frontotemporal scalp that poses a substantial burden on quality of life. Large-scale global profiling of FFA is lacking, preventing the development of effective therapeutics.

OBJECTIVE

To characterize FFA compared to normal and alopecia areata using broad molecular profiling and to identify biomarkers linked to disease severity.

METHODS

This cross-sectional study assessed 33,118 genes in scalp using RNA sequencing and 350 proteins in serum using OLINK high-throughput proteomics. Disease biomarkers were also correlated with clinical severity and a fibrosis gene set.

RESULTS

Genes differentially expressed in lesional FFA included markers related to Th1 (IFNγ/CXCL9/CXCL10), T-cell activation (CD2/CD3/CCL19/ICOS), fibrosis (CXCR3/FGF14/FGF22/VIM/FN1), T-regulatory (FOXP3/TGFB1/TGFB3), and Janus kinase/JAK (JAK3/STAT1/STAT4) (Fold changes [FCH]>1.5, FDR<.05 for all). Only one protein, ADM, was differentially expressed in FFA serum compared to normal (FCH>1.3, FDR<.05). Significant correlations were found between scalp biomarkers (IL-36RN/IL-25) and FFA severity, as well as between JAK/STAT and fibrosis gene-sets (r>.6; P <.05).

LIMITATIONS

This study was limited by a small sample size and predominantly female FFA patients.

CONCLUSION

Our data characterize FFA as an inflammatory condition limited to scalp, involving Th1/JAK skewing, with associated fibrosis and elevated T-regulatory markers, suggesting the potential for disease reversibility with JAK/STAT inhibition.

The Role of AKR1B10 in Physiology and Pathophysiology

AKR1B10 is a human nicotinamide adenine dinucleotide phosphate (NADPH)-dependent reductase belonging to the aldo-keto reductase (AKR) 1B subfamily. It catalyzes the reduction of aldehydes, some ketones and quinones, and interacts with acetyl-CoA carboxylase and heat shock protein 90α. The enzyme is highly expressed in epithelial cells of the stomach and intestine, but down-regulated in gastrointestinal cancers and inflammatory bowel diseases. In contrast, AKR1B10 expression is low in other tissues, where the enzyme is upregulated in cancers, as well as in non-alcoholic fatty liver disease and several skin diseases. In addition, the enzyme's expression is elevated in cancer cells resistant to clinical anti-cancer drugs. Thus, growing evidence supports AKR1B10 as a potential target for diagnosing and treating these diseases. Herein, we reviewed the literature on the roles of AKR1B10 in a healthy gastrointestinal tract, the development and progression of cancers and acquired chemoresistance, in addition to its gene regulation, functions, and inhibitors.

Multifaceted array-based keloidal gene expression profiling reveals specific MDFI upregulation in keloid lesions

BACKGROUND

Keloid lesions are characterized by mesenchymal cell proliferation and excessive extracellular matrix deposition. Previous microarray analyses have been performed to investigate the mechanism of keloid development. However, the molecular pathology that contributes to keloid development remains obscure.

AIM

To explore the underlying essential molecules of keloids using microarrays.

METHODS

We performed microarray analyses of keloid and nonlesional skin tissues both in vivo and in vitro. Gene expression levels were compared between tissues and cells. Quantitative reverse transcription (qRT)-PCR and immunohistochemical staining were used to determine the expression levels of molecules of interest in keloid tissues.

RESULTS

Several common molecules were upregulated in both keloid tissues and keloid-lesional fibroblasts. PTPRD and NTM were upregulated both in vivo and in vitro. The genes MDFI and ITGA4 were located at the centre of the gene coexpression network analysis using keloid tissues. qRT-PCR revealed significant expression levels of PTPRD and MDFI in keloid tissues. Immunopathological staining revealed that MDFI-positive cells, which have fibroblast characteristics, were located in the keloid-associated lymphoid tissue (KALT) portion of the keloid tissue.

CONCLUSION

Our gene expression profiles of keloids could distinguish the difference between lesional tissue and cultured lesional fibroblasts, and MDFI was found to be commonly expressed in both tissues and cells. Thus, MDFI-positive cells, which were located in the KALT, may play an important role in keloid pathogenesis and thus might be useful for in vitro keloid studies.

Hypertrophic scars and keloids: Overview of the evidence and practical guide for differentiating between these abnormal scars

Although hypertrophic scars and keloids both generate excessive scar tissue, keloids are characterized by their extensive growth beyond the borders of the original wound, which is not observed in hypertrophic scars. Whether or not hypertrophic scars and keloids are two sides of the same coin or in fact distinct entities remains a topic of much debate. However, proper comparison between the two ideally occurs within the same study, but this is the exception rather than the rule. For this reason, the goal of this review was to summarize and evaluate all publications in which both hypertrophic scars and keloids were studied and compared to one another within the same study. The presence of horizontal growth is the mainstay of the keloid diagnosis and remains the strongest argument in support of keloids and hypertrophic scars being distinct entities, and the histopathological distinction is less straightforward. Keloidal collagen remains the strongest keloid parameter, but dermal nodules and α-SMA immunoreactivity are not limited to hypertrophic scars alone. Ultimately, the current hypertrophic scars-keloid differences are mostly quantitative in nature rather than qualitative, and many similar abnormalities exist in both lesions. Nonetheless, the presence of similarities does not equate the absence of fundamental differences, some of which may not yet have been uncovered given how much we still have to learn about the processes involved in normal wound healing. It therefore seems pertinent to continue treating hypertrophic scars and keloids as separate entities, until such a time as new findings more decisively convinces us otherwise.

Keloid disorder: Fibroblast differentiation and gene expression profile in fibrotic skin diseases

Keloid disorder, a group of fibroproliferative skin diseases, is characterized by unremitting accumulation of the extracellular matrix (ECM) of connective tissue, primarily collagen, to develop cutaneous tumors on the predilection sites of skin. There is a strong genetic predisposition for keloid formation, and individuals of African and Asian ancestry are particularly prone. The principal cell type responsible for ECM accumulation is the myofibroblast derived from quiescent resident skin fibroblasts either through trans-differentiation or from keloid progenitor stem cells with capacity for multi-lineage differentiation and self-renewal. The biosynthetic pathways leading to ECM accumulation are activated by several cytokines, but particularly by TGF-β signalling. The mechanical properties of the cellular microenvironment also play a critical role in the cell's response to TGF-β, as demonstrated by culturing of fibroblasts derived from keloids and control skin on substrata with different degrees of stiffness. These studies also demonstrated that culturing of fibroblasts on tissue culture plastic in vitro does not reflect their biosynthetic capacity in vivo. Collectively, our current understanding of the pathogenesis of keloids suggests a complex network of interacting cellular, molecular and mechanical factors, with distinct pathways leading to myofibroblast differentiation and activation. Keloids can serve as a model system of fibrotic diseases, a group of currently intractable disorders, and deciphering of the critical pathogenetic steps leading to ECM accumulation is expected to identify targets for pharmacologic intervention, not only for keloids but also for a number of other, both genetic and acquired, fibrotic diseases.

RNA Sequencing Keloid Transcriptome Associates Keloids With Th2, Th1, Th17/Th22, and JAK3-Skewing

Keloids are disfiguring, fibroproliferative growths and their pathogenesis remains unclear, inhibiting therapeutic development. Available treatment options have limited efficacy and harbor safety concerns. Thus, there is a great need to clarify keloid pathomechanisms that may lead to novel treatments. In this study, we aimed to elucidate the profile of lesional and non-lesional keloid skin compared to normal skin. We performed gene (RNAseq, qRT-PCR) and protein (immunohistochemistry) expression analyses on biopsy specimens obtained from lesional and non-lesional skin of African American (AA) keloid patients compared to healthy skin from AA controls. Fold-change≥2 and false-discovery rate (FDR)<0.05 was used to define significance. We found that lesional versus normal skin showed significant up-regulation of markers of T-cell activation/migration (ICOS, CCR7), Th2- (IL-4R, CCL11, TNFSF4/OX40L), Th1- (CXCL9/CXCL10/CXCL11), Th17/Th22- (CCL20, S100As) pathways, and JAK/STAT-signaling (JAK3) (false-discovery rate [FDR]<0.05). Non-lesional skin also exhibited similar trends. We observed increased cellular infiltrates in keloid tissues, including T-cells, dendritic cells, mast cells, as well as greater IL-4rα+, CCR9+, and periostin+ immunostaining. In sum, comprehensive molecular profiling demonstrated that both lesional and non-lesional skin show significant immune alternations, and particularly Th2 and JAK3 expression. This advocates for the investigation of novel treatments targeting the Th2 axis and/or JAK/STAT-signaling in keloid patients.

Genomics of Human Fibrotic Diseases: Disordered Wound Healing Response

Fibrotic disease, which is implicated in almost half of all deaths worldwide, is the result of an uncontrolled wound healing response to injury in which tissue is replaced by deposition of excess extracellular matrix, leading to fibrosis and loss of organ function. A plethora of genome-wide association studies, microarrays, exome sequencing studies, DNA methylation arrays, next-generation sequencing, and profiling of noncoding RNAs have been performed in patient-derived fibrotic tissue, with the shared goal of utilizing genomics to identify the transcriptional networks and biological pathways underlying the development of fibrotic diseases. In this review, we discuss fibrosing disorders of the skin, liver, kidney, lung, and heart, systematically (1) characterizing the initial acute injury that drives unresolved inflammation, (2) identifying genomic studies that have defined the pathologic gene changes leading to excess matrix deposition and fibrogenesis, and (3) summarizing therapies targeting pro-fibrotic genes and networks identified in the genomic studies. Ultimately, successful bench-to-bedside translation of observations from genomic studies will result in the development of novel anti-fibrotic therapeutics that improve functional quality of life for patients and decrease mortality from fibrotic diseases.

Inflammation as an orchestrator of cutaneous scar formation: a review of the literature

Inflammation is a key phase in the cutaneous wound repair process. The activation of inflammatory cells is critical for preventing infection in contaminated wounds and results in the release of an array of mediators, some of which stimulate the activity of keratinocytes, endothelial cells, and fibroblasts to aid in the repair process. However, there is an abundance of data suggesting that the strength of the inflammatory response early in the healing process correlates directly with the amount of scar tissue that will eventually form. This review will summarize the literature related to inflammation and cutaneous scar formation, highlight recent discoveries, and discuss potential treatment modalities that target inflammation to minimize scarring.

Mast Cells in Skin Scarring: A Review of Animal and Human Research

Mast cells (MCs) are an important immune cell type in the skin and play an active role during wound healing. MCs produce mediators that can enhance acute inflammation, stimulate re-epithelialisation as well as angiogenesis, and promote skin scarring. There is also a link between MCs and abnormal pathological cutaneous scarring, with increased numbers of MCs found in hypertrophic scars and keloid disease. However, there has been conflicting data regarding the specific role of MCs in scar formation in both animal and human studies. Whilst animal studies have proved to be valuable in studying the MC phenomenon in wound healing, the appropriate translation of these findings to cutaneous wound healing and scar formation in human subjects remains crucial to elucidate the role of these cells and target treatment effectively. Therefore, this perspective paper will focus on evaluation of the current evidence for the role of MCs in skin scarring in both animals and humans in order to identify common themes and future areas for translational research.

Correlation between serum IL 37 levels with keloid severity

BACKGROUND

Keloids are dermal fibroproliferative disorders that characterized by over deposition of components of the extracellular matrix. Interleukin 37 (IL-37) is known by its ability to inhibit the proliferation of keloid fibroblasts by inhibiting extracellular matrix production induced by transforming growth factor β (TGF-β). Thus, Il-37 is suggested to be used as an early preventive treatment for keloids.

AIMS

This study aimed to evaluate the correlation between serum levels of IL37 level and the keloid severity.

PATIENTS/METHODS

This is a cross-sectional analytic study involving thirty-two patients diagnosed clinically as having Keloid. An assessment of keloid severity was conducted by using Vancouver Scar Scale (VSS). Blood samples were collected from every patient to measure and assess the serum levels of IL37.

RESULTS

A negative correlation was found between IL37 level and the keloid severity (P = .0001; r = -.737). Also, there was a nonsignificant correlation between IL37 levels in patient with keloid and age, gender, duration of lesions, and family history.

CONCLUSION

Lower level of plasma IL 37 could be an indicator of the severity of Keloids.

The role of macrophages in the formation of hypertrophic scars and keloids

Numerous studies have shown that macrophages can orchestrate the microenvironment from the early stage of wound healing to the later stages of scar formation. However, few reviews have highlighted the significance of macrophages during the formation of abnormal scars. The purpose of this review was to outline the polarization of macrophages from early to late stage of pathological scar formation, focusing on spatiotemporal diversity of M1 and M2 macrophages. In this review, the role of macrophages in the formation of hypertrophic scars and keloids is summarized in detail. First, an increased number of M2 cells observed before injuries are significantly associated with susceptibility to abnormal scar pathogenesis. Second, decreased expression of M1 at the early stage and delayed expression of M2 at the late stage results in pathological scar formation. Third, M2 cells are highly expressed at both the margin and the superficial region, which is consistent with the invasive property of keloids. Finally, this review helps to characterize strategies for the prediction and prevention of pathological scar formation.

Cartilage-like composition of keloid scar extracellular matrix suggests fibroblast mis-differentiation in disease

Following wound damage to the skin, the scarring spectrum is wide-ranging, from a manageable normal scar through to pathological keloids. The question remains whether these fibrotic lesions represent simply a quantitative extreme, or alternatively, whether they are qualitatively distinct. A three-way comparison of the extracellular matrix (ECM) composition of normal skin, normal scar and keloids was performed using quantitative discovery-based proteomics. This approach identified 40 proteins that were significantly altered in keloids compared to normal scars, and strikingly, 23 keloid-unique proteins. The major alterations in keloids, when functionally grouped, showed many changes in proteins involved in ECM assembly and fibrillogenesis, but also a keloid-associated loss of proteases, and a unique cartilage-like composition, which was also evident histologically. The presence of Aggrecan and Collagen II in keloids suggest greater plasticity and mis-differentiation of the constituent cells. This study characterises the ECM of both scar types to a depth previously underappreciated. This thorough molecular description of keloid lesions relative to normal scars is an essential step towards our understanding of this debilitating clinical problem, and how best to treat it.

The Interplay of Mechanical Stress, Strain, and Stiffness at the Keloid Periphery Correlates with Increased Caveolin-1/ROCK Signaling and Scar Progression

BACKGROUND

Fibroproliferative disorders result in excessive scar formation, are associated with high morbidity, and cost billions of dollars every year. Of these, keloid disease presents a particularly challenging clinical problem because the cutaneous scars progress beyond the original site of injury. Altered mechanotransduction has been implicated in keloid development, but the mechanisms governing scar progression into the surrounding tissue remain unknown. The role of mechanotransduction in keloids is further complicated by the differential mechanical properties of keloids and the surrounding skin.

METHODS

The authors used human mechanical testing, finite element modeling, and immunohistologic analyses of human specimens to clarify the complex interplay of mechanical stress, strain, and stiffness in keloid scar progression.

RESULTS

Changes in human position (i.e., standing, sitting, and supine) are correlated to dynamic changes in local stress/strain distribution, particularly in regions with a predilection for keloids. Keloids are composed of stiff tissue, which displays a fibrotic phenotype with relatively low proliferation. In contrast, the soft skin surrounding keloids is exposed to high mechanical strain that correlates with increased expression of the caveolin-1/rho signaling via rho kinase mechanotransduction pathway and elevated inflammation and proliferation, which may lead to keloid progression.

CONCLUSIONS

The authors conclude that changes in human position are strongly correlated with mechanical loading of the predilection sites, which leads to increased mechanical strain in the peripheral tissue surrounding keloids. Furthermore, increased mechanical strain in the peripheral tissue, which is the site of keloid progression, was correlated with aberrant expression of caveolin-1/ROCK signaling pathway. These findings suggest a novel mechanism for keloid progression.

Hypoxia-Induced Epithelial-To-Mesenchymal Transition Mediates Fibroblast Abnormalities via ERK Activation in Cutaneous Wound Healing

Previous studies described the involvement of extracellular signal-related kinase (ERK) in systemic fibrotic diseases, but the role of ERK in cutaneous scarring is unknown. Although hypoxia drives tissue fibrosis by activating hypoxia-inducible factor-1α (HIF-1α), the specific roles of hypoxia and associated ERK phosphorylation in abnormal fibroblast activity during cutaneous scarring are unclear. Here, we investigated whether pathologic myofibroblast-like keloid fibroblast activity is promoted by hypoxia-induced epithelial-mesenchymal transition mediated by ERK activation. ERK phosphorylation was significantly increased in keloid tissue and fibroblasts. Human dermal fibroblasts cultured under hypoxia (1% O₂) expressed phosphorylated ERK and exhibited activation of p38 mitogen-activated protein kinase signaling. Hypoxic human dermal fibroblasts showed increased protein and mRNA levels of epithelial-mesenchymal transition markers. Furthermore, administration of an ERK inhibitor (SCH772984) reduced the hypoxia-induced elevation of collagen type I levels in human dermal fibroblasts. Therefore, ERK may be a promising therapeutic target in profibrogenic diseases.

STAT3 signalling pathway is implicated in keloid pathogenesis by preliminary transcriptome and open chromatin analyses

Keloids are wounding-induced fibroproliferative human tumor-like skin scars of complex genetic makeup and poorly defined pathogenesis. To reveal dynamic epigenetic and transcriptome changes of keloid fibroblasts, we performed RNA-seq and ATAC-seq analysis on an early passage keloid fibroblast cell strain and its paired normal control fibroblasts. This keloid strain produced keloid-like scars in a plasma clot-based skin equivalent humanized keloid animal model. RNA-seq analysis reveals gene ontology terms including hepatic fibrosis, Wnt-β-catenin, TGF-β, regulation of epithelial-mesenchymal transition (EMT), STAT3 and adherens junction. ATAC-seq analysis suggests STAT3 signalling is the most significantly enriched gene ontology term in keloid fibroblasts, followed by Wnt signalling (Wnt5) and regulation of the EMT pathway. Immunohistochemistry confirms that STAT3 (Tyr705 phospho-STAT3) is activated and β-catenin is up-regulated in the dermis of keloid clinical specimens and keloid skin equivalent implants from the humanized mouse model. A non-linear dose-response of cucurbitacin I, a selective JAK2/STAT3 inhibitor, in collagen type I expression of keloid-derived plasma clot-based skin equivalents implicates a likely role of STAT3 signalling in keloid pathogenesis. This work also demonstrates the utility of the recently established humanized keloid mouse model in exploring the mechanism of keloid formation.

Multi-dimensional models for functional testing of keloid scars: In silico, in vitro, organoid, organotypic, ex vivo organ culture, and in vivo models

Keloid scars are described as benign fibro-proliferative dermal outgrowths that commonly occur in pigmented skin post cutaneous injury, and continue to grow beyond the boundary of the original wound margin. There is a lack of thorough understanding of keloid pathogenesis and thus keloid therapeutic options remain ill-defined. In view of the poor response to current therapy and high recurrence rates, there is an unmet need in improving our knowledge and therefore in identifying targeted and effective treatment strategies in management of keloids. Keloid research however, is hampered by a lack of relevant animal models as keloids do not spontaneously occur in animals and are unique to human skin. Therefore, developing novel animal models and nonanimal models for functional evaluation of keloid cells and tissue for better understanding their pathobiology and response to putative candidate therapies are essential. Here, we present the key concepts and relevant emerging research on two-dimensional and three-dimensional cell and tissue models for functional testing of keloid scars. We will describe in detail current models including in vitro mono- and co-cultures, multi-cellular spheroids (organoids) and organotyopic cultures, ex vivo whole skin keloid tissue organ culture models as well as in vivo human patient models. Finally, we discuss the role played by time as the fourth dimension in a novel model that involves sequential temporal biopsies of human patients with keloids (a so called 4D in vivo human model). The use of these unique models will no doubt prove pivotal in identification of new drug targets as well as biomarkers, in functional testing of emerging novel therapeutics, and in enhancing our understanding of keloid disease biology.

The Differential Expression of miRNAs and a Preliminary Study on the Mechanism of miR-194-3p in Keloids

The aim of this study was to detect abnormally expressed microRNA (miRNA) in keloids and to study their functions. The differential expression of miRNAs in keloids and normal tissue was detected by gene microarray. MiRNA expression was verified by real-time PCR. A luciferase reporter gene assay, western blot, and real-time PCR were used to detect the effect of miR-194-3p on RUNX2. An MTT assay and a transwell assay were used to detect the effect of miR-194-3p in both primary cultured fibroblasts and HKF cells. Related proteins were analysed by western blot and real-time PCR. The expression of miR-194-3p was lower in keloids, and MiR-194-3p was shown to target RUNX2 directly. MiR-194-3p inhibited the proliferation and migration of fibroblasts through the inhibition of CDK4 and MMP2. MiR-194-3p and RUNX2 may become new targets for the prevention and treatment of keloids.

Tension enhances cell proliferation and collagen synthesis by upregulating expressions of integrin αvβ3 in human keloid-derived mesenchymal stem cells

AIMS

Keloids are a dermal fibrotic disease whose etiology remains totally unknown and for which there is no successful treatment. Mechanical tension, in addition, is closely associated with the germination and development of keloids. In this study, we investigated the influence of human keloid-derived mesenchymal stem cells (KD-MSCs) on cell proliferation, collagen synthesis, and expressions of integrin αvβ3 under tension.

MAIN METHODS

KD-MSCs and human normal skin-derived mesenchymal stem cells (NS-MSCs) were isolated and cultured in stem cell medium with a gradual increase in the serum concentration. Cell proliferation and collagen synthesis were detected by Cell Counting Kit-8 (CCK-8) assay and hydroxyproline content analysis under tension respectively. We investigated the messenger RNA expressions of nine integrin subunits, including integrin units α2, α3, α5, αv, α8, α10, α11, β1, and β3, in KD-MSCs stimulated with tension. Identification of differentially expressed genes was performed by Western blot analysis and immunocytochemistry staining.

KEY FINDINGS

We obtained high-purity KD-MSCs and NS-MSCs using the culture method of decreasing serum concentration gradient gradually. Furthermore, we found that tension enhances cell proliferation and collagen synthesis and promotes expressions of integrin αvβ3 in KD-MSCs. In addition, blocking experiments showed that increased integrin αvβ3 expression affects cell proliferation and collagen synthesis of KD-MSCs under tension.

SIGNIFICANCE

Our results suggest that integrin αvβ3 receptor may be sensitive molecules of mechanical tension and could contribute to the occurrence and development of keloids. It could lead to novel targets for therapeutic intervention, treatment, and prevention of recurrence for keloid disorders.

Expressions of stemness markers in keloid tissue

Background: Keloid is an abnormal wound healing process that extends beyond the site of injury. Keloid and tumor’s shared similarity of recurrence suggesting a shared underlying mechanism that involves stemness. Octamer-binding transcription factor-4 (Oct-4) and aldehyde dehydrogenase-1 (ALDH1) are stem cell stemness markers. This study aimed to analyze Oct-4 and ALDH1 expressions in keloid tissues.Methods: Samples were obtained from keloid tissue excisions from three keloid patients and post-circumcision preputial skin from three healthy donors (normal control) in accordance with the local ethical committee regulation. Total RNA was isolated using TriPure Isolation kit (Ameritech), and expressions of Oct4 and ALDH1 mRNA in keloid and preputial skin were determined by quantitative reverse transcription–polymerase chain reaction (qRT-PCR) using Livak method.Results: The qRT-PCR analysis revealed the expressions of Oct4 and ALDH1 in keloid and preputial skin tissues. Keloid tissues exhibited lower expression levels of Oct-4 and ALDH1 than the preputial skin. The difference was statistically insignificant.Conclusion: Keloid tissues express Oct-4 and ALDH1 as stemness markers, and the stemness characteristics of keloid might be similar to a normal skin.

Facial Plastic Surgery Controversies: Keloids

There are more than 11 million people in the world affected with keloids. Nevertheless, there is a lack of agreement in keloid management. Moreover, keloid research has left gaps in the understanding of its pathogenesis. Six questions are answered by 3 clinical scientists in an attempt to address common keloid controversies.

Identification of a novel mutation in the mechanoreceptor-encoding gene CXCR1 in patients with keloid

Keloids are skin fibroproliferative tumors characterized by locally invasive growth of fibroblasts and excessive collagen deposition. The objective of this study is to investigate the molecular basis of the keloid scar by studying the mutation of related genes. We performed gene screening of mechanoreceptors by quantitative polymerase chain reaction (qPCR), Sanger sequencing to detect the CXCR1gene mutation, and immuno-histochemistry to determine CXCR1 protein expression. Among the genes encoding mechanoreceptors, the expression of CXCR1 mRNA was significantly higher in keloid scar tissues than in the surrounding tissues of normal controls (P < 0.05). Sequencing analysis identified a novel missense mutation, c.574G > A (p.Gly192Glu). Immunohistochemistry showed heightened protein expression of CXCR1 in keloid scars as compared to controls. Our findings indicate that CXCR1 gene mutation and altered protein expression are associated with keloid scar development. Identification of the CXCR1 gene mutation might provide insights into the molecular mechanism underlying keloid scar and underscores the potential importance of mechanoreceptors in keloid scar pathogenesis.

Treatment of limb wounds of horses with orf virus IL-10 and VEGF-E accelerates resolution of exuberant granulation tissue, but does not prevent its development

Bandaging of limb wounds in horses leads to formation of exuberant granulation tissue (EGT) that retards healing due to protracted inflammation, aberrant vascularisation and delayed epithelialisation. EGT is not observed if wounds are left undressed or when wounds are on the body. A previous study showed that short-term administration of proteins derived from orf virus dampened inflammation and promoted epithelialisation of open wounds in horses. Here, we investigated the impact of orf virus interleukin-10 and vascular endothelial growth factor-E on the development and resolution of EGT. Excisional wounds were created on the forelimb of four horses, and bandages were maintained until full healing to induce EGT formation. Matching body wounds were created to ensure EGT was limited to the limb, and to differentiate the effects of the viral proteins on normal healing and on EGT formation. Viral proteins or the hydrogel vehicle control were administered topically to site-matched wounds at day 1, with repeat administration at day 8. Wound healing and EGT formation were monitored macroscopically. Wound margin samples were harvested at 2, 7 and 14 days, and at full healing, with histology used to observe epithelialisation, immunofluorescence used to detect inflammatory cells, angiogenesis and cell death, and qPCR to measure expression of genes regulating inflammation and angiogenesis. Limb wounds developed EGT, and exhibited slower healing than body wounds. Viral protein treatment did not accelerate healing at either location nor limit EGT formation in limb wounds. Treatment of limb wounds did however increase epithelialisation and angiogenesis, without dampening inflammatory cell infiltration or gene expression. The healed wounds also had less occlusion and death of blood vessels and fewer epidermal rete ridges following viral protein treatment. These findings indicate that the viral protein treatment does not suppress wound inflammation or EGT formation, but does promote vascular and epidermal repair and EGT resolution.