Keloid scarring: understanding the genetic basis, advances, and prospects

Dissolving Triamcinolone-Embedded Microneedles for the Treatment of Keloids: A Single-Blinded Intra-Individual Controlled Clinical Trial

INTRODUCTION

Keloids are a prevalent chronic skin disorder with significant psychosocial morbidity. Intralesional corticosteroid injections are the first-line treatment but are painful and require repeated injections by medical professionals. Dissolving microneedles are a novel method of cutaneous drug delivery that induces minimal/no pain and can be self-administered. The objective of the study was to evaluate the efficacy and safety of triamcinolone-embedded dissolving microneedles in treatment of keloids.

METHODS

This was a single-blind, intra-individual controlled two-phase clinical trial of 8-week duration each. Two keloids per subject were selected for (1) once-daily 2-min application with microneedles for 4 weeks, followed by no treatment for the next 4 weeks, or (2) non-intervention as control. Primary outcome was change in keloid volume as assessed by a high-resolution 3D scanner.

RESULTS

There was significant reduction in keloid volume compared with controls after 4 weeks of treatment. This reduction was greater with a higher dosage of triamcinolone used.

CONCLUSIONS

Once-daily application of dissolving triamcinolone-embedded microneedles significantly reduced the volume of keloids. The treatment was safe, can be self-administered and can serve as an alternative for patients unsuitable for conventional treatments.

TRIAL REGISTRATION

Trial Registry: Health Science Authority (Singapore) Clinical Trials Register Registration number: 2015/00440.

Toward understanding scarless skin wound healing and pathological scarring

The efficient healing of skin wounds is crucial for securing the vital barrier function of the skin, but pathological wound healing and scar formation are major medical problems causing both physiological and psychological challenges for patients. A number of tightly coordinated regenerative responses, including haemostasis, the migration of various cell types into the wound, inflammation, angiogenesis, and the formation of the extracellular matrix, are involved in the healing process. In this article, we summarise the central mechanisms and processes in excessive scarring and acute wound healing, which can lead to the formation of keloids or hypertrophic scars, the two types of fibrotic scars caused by burns or other traumas resulting in significant functional or aesthetic disadvantages. In addition, we discuss recent developments related to the functions of activated fibroblasts, the extracellular matrix and mechanical forces in the wound environment as well as the mechanisms of scarless wound healing. Understanding the different mechanisms of wound healing is pivotal for developing new therapies to prevent the fibrotic scarring of large skin wounds.

Stem Cells in Keloid Lesions: A Review

Keloid disorder (KD) is a fibroproliferative condition caused by dysregulated wound healing following wounding of the skin. The pathogenesis of KD has not been fully elucidated and current treatment is unsatisfactory. There is increasing evidence of the role of stem cells in KD. This review discusses the role of embryonic stem (ESC)-like cells and mesenchymal stem cells in the pathogenesis of KD. It is proposed that dysfunction of the ESC-like population localized to the endothelium of the microvessels and perivascular cells within the keloid-associated lymphoid tissues may give rise to the aberrant fibroblasts and myofibroblasts via a mesenchymal stem cell intermediate in keloid lesions, by undergoing an endothelial-to-mesenchymal transition. We also discuss the role of the renin-angiotensin system (RAS), the immune system, and the inflammatory response, on stem cell proliferation and differentiation. The understanding of the precise roles of these stem cells and interplay of the associated regulatory pathways could lead to the development of targeted therapy for this enigmatic and challenging condition. The demonstration of the expression of components of the RAS and cathepsins B, D, and G that constitute bypass loops of the RAS, by the ESC-like population, suggests that the primitive population may be a therapeutic target by modulation of the RAS, using existing medications.

Wound Healing: A Cellular Perspective

Wound healing is one of the most complex processes in the human body. It involves the spatial and temporal synchronization of a variety of cell types with distinct roles in the phases of hemostasis, inflammation, growth, re-epithelialization, and remodeling. With the evolution of single cell technologies, it has been possible to uncover phenotypic and functional heterogeneity within several of these cell types. There have also been discoveries of rare, stem cell subsets within the skin, which are unipotent in the uninjured state, but become multipotent following skin injury. Unraveling the roles of each of these cell types and their interactions with each other is important in understanding the mechanisms of normal wound closure. Changes in the microenvironment including alterations in mechanical forces, oxygen levels, chemokines, extracellular matrix and growth factor synthesis directly impact cellular recruitment and activation, leading to impaired states of wound healing. Single cell technologies can be used to decipher these cellular alterations in diseased states such as in chronic wounds and hypertrophic scarring so that effective therapeutic solutions for healing wounds can be developed.

Keloid research: current status and future directions

INTRODUCTION

Keloids and hypertrophic scars are fibroproliferative disorders of the skin that result from abnormal healing of injured or irritated skin. Multiple studies suggest that genetic, systemic and local factors may contribute to the development and/or growth of keloids and hypertrophic scars. A key local factor may be mechanical stimuli. Here, we provide an up-to-date review of the studies on the roles that genetic variation, epigenetic modifications and mechanotransduction play in keloidogenesis.

METHODS

An English literature review was performed by searching the PubMed, Embase and Web of Science databases with the following keywords: genome-wide association study; epigenetics; non-coding RNA; microRNA; long non-coding RNA (lncRNA); DNA methylation; mechanobiology; and keloid. The searches targeted the time period between the date of database inception and July 2018.

RESULTS

Genetic studies identified several single-nucleotide polymorphisms and gene linkages that may contribute to keloid pathogenesis. Epigenetic modifications caused by non-coding RNAs (e.g. microRNAs and lncRNAs) and DNA methylation may also play important roles by inducing the persistent activation of keloidal fibroblasts. Mechanical forces and the ensuing cellular mechanotransduction may also influence the degree of scar formation, scar contracture and the formation/progression of keloids and hypertrophic scars.

CONCLUSIONS

Recent research indicates that the formation/growth of keloids and hypertrophic scars associate clearly with genetic, epigenetic, systemic and local risk factors, particularly skin tension around scars. Further research into scar-related genetics, epigenetics and mechanobiology may reveal molecular, cellular or tissue-level targets that could lead to the development of more effective prophylactic and therapeutic strategies for wounds/scars in the future.

Genetic influence on scar height and pliability after burn injury in individuals of European ancestry: A prospective cohort study

After similar extent of injury there is considerable variability in scarring between individuals, in part due to genetic factors. This study aimed to identify genetic variants associated with scar height and pliability after burn injury. An exome-wide array association study and gene pathway analysis were performed on a prospective cohort of 665 patients treated for burn injury. Outcomes were scar height (SH) and scar pliability (SP) sub-scores of the modified Vancouver Scar Scale (mVSS). DNA was genotyped using the Infinium^® HumanCoreExome-24 BeadChip. Associations between genetic variants (single nucleotide polymorphisms) and SH and SP were estimated using an additive genetic model adjusting for age, sex, number of surgical procedures and % total body surface area of burn in subjects of European ancestry. No individual genetic variants achieved the cut-off threshold of significance. Gene regions were analysed for spatially correlated single nucleotide polymorphisms and significant regions identified using comb-p software. This gene list was subject to gene pathway analysis to find which biological process terms were over-represented. Using this approach biological processes related to the nervous system and cell adhesion were the predominant gene pathways associated with both SH and SP. This study suggests genes associated with innervation may be important in scar fibrosis. Further studies using similar and larger datasets will be essential to validate these findings.

Gallic acid inhibits fibroblast growth and migration in keloids through the AKT/ERK signaling pathway

Keloids are a fibroproliferative disorder of the skin resulted from abnormal healing of injured or irritated skin and are characterized by the ability to spread beyond the original boundary of the wound. Here, we tested the effect of gallic acid (GA), a plant polyphenol with selective growth inhibitory effects in cancer, on the proliferation and invasion of keloid fibroblasts (KFs) isolated from patients undergoing surgery. GA inhibited KF proliferation, migration, and invasion in parallel with the downregulation of matrix metalloproteinase-1 and -3 and upregulation of tissue inhibitors of metalloproteinase-1. Flow cytometric analysis showed that GA inhibited cell cycle progression and induced apoptosis. The effects of GA on KFs occurred in parallel with the inhibition of AKT and ERK1/2, suggesting that GA acts by suppressing the AKT/ERK signaling pathway. In ex vivo explant cultures of keloid tissues, GA inhibited the migration of KFs to the wound area and suppressed the expression of angiogenic markers concomitant with the inhibition of collagen deposition. These results identify GA as a potential therapeutic agent for the treatment of keloids and suggest a potential mechanism underlying its protective effect.

miR-34 modulates apoptotic gene expression in Ingenol mebutate treated keloid fibroblasts

Keloids are benign skin tumors that develop in individuals who have a positive family history of keloid disorders. Keloids are characterized by a deregulated wound-healing process, atypical fibroblasts with extreme deposition of extracellular matrix components, particularly collagen, increased cell proliferation and associated failure of apoptosis. Recently ingenol-mebutate has been used as a novel agent with anti-proliferative activity on human keloids as an alternative treatment option in patients, once conventional therapies have failed. We hypothesized that microRNAs (miR/miRNA) may be involved in the balance between lesion formation and repair. A comprehensive understanding of the molecular mechanism underlying the Ingenol-mebutate response in keloid fibroblast following Ingenol-mebutate exposure has been established previously. Therefore, the present study analyzed changes in miRNAs and apoptotic gene regulation in Ingenol-mebutate treated keloid fibroblast, by reverse transcription-quantitative polymerase chain reaction and a DNA fragmentation assay. The range of upregulated miRNAs and downregulated genes encoding cell death appeared to be associated with the degree of the morphological alterations in Ingenol-mebutate treated keloids. In particular, the upregulation of miR-34a was detected in keloid fibroblasts during and following Ingenol-mebutate exposure. Keloid fibroblasts that overexpressed miR-34a showed differential expression of genes involved in the apoptotic signaling pathway such as p53. In conclusion, the Ingenol-mebutate treatment used here was effective in reducing keloid fibroblast growth in cell culture experiments and the expression of particular miRNAs modulated the pro-apoptotic gene expression following Ingenol-mebutate treatment.

Coherency image analysis to quantify collagen architecture: implications in scar assessment

An important histological difference between normal, uninjured dermis and scar tissue such as that found in keloid scars is the pattern (morphological architecture) in which the collagen is deposited and arranged. In the uninjured dermis, collagen bundle architecture appears randomly organized (or in a basket weave formation), whereas in pathological conditions such as keloid scar tissue, collagen bundles are often found in whorls or in a hypotrophic scar collagen is more densely packed in a parallel configuration. In the case of skin, a scar disables the dermis, leaving it weaker, stiff and with a loss of optimal functionality. The absence of objective and quantifiable assessments of collagen orientation is a major bottleneck in monitoring progression of scar therapeutics. In this article, a novel quantitative approach for analyzing collagen orientation is reported. The methodology is demonstrated using collagen produced by cells in a model scar environment and examines collagen remodeling post-TGFβ stimulation in vitro. The method is shown to be reliable and effective in identifying significant coherency differences in the collagen deposited by human keloid scar cells. The technique is also compared for analysing collagen architecture in rat sections of normal, scarred skin and tendon tissue. Results demonstrate that the proposed computational method provides a fast and robust way of analyzing collagen orientation in a manner surpassing existing methods. This study establishes this methodology as a preliminary means of monitoring in vitro and in tissue treatment modalities which are expected to alter collagen morphology.

Gene-based evaluation of low-frequency variation and genetically-predicted gene expression impacting risk of keloid formation

Keloids are benign dermal tumors occurring approximately 20 times more often in individuals of African descent as compared to individuals of European descent. While most keloids occur sporadically, a genetic predisposition is supported by both familial aggregation of some keloids and large differences in risk among populations. Despite Africans and African Americans being at increased risk over lighter-skinned individuals, little genetic research exists into this phenotype. Using a combination of admixture mapping and exome analysis, we reported multiple common variants within chr15q21.2-22.3 associated with risk of keloid formation in African Americans. Here we describe a gene-based association analysis using 478 African American samples with exome genotyping data to identify genes containing low-frequency variants associated with keloids, with evaluation of genetically-predicted gene expression in skin tissues using association summary statistics. The strongest signal from gene-based association was located in C15orf63 (P-value = 6.6 × 10^-6 ) located at 15q15.3. The top result from gene expression was increased predicted DCAF4 expression (P-value = 5.5 × 10^-4 ) in non-sun-exposed skin, followed by increased predicted OR10A3 expression in sun-exposed skin (P-value = 6.9 × 10^-4 ). Our findings identify variation with putative roles in keloid formation, enhanced by the use of predicted gene expression to support the biological roles of variation identified only though genetic association studies.

Immunomodulation as Rescue for Chronic Atonic Skin Wounds

Chronic skin wounds, caused by arterial or venous insufficiency or by physical pressure, constitute an increasing medical problem as populations age. Whereas typical wounds are characterized by local inflammation that participates in the healing process, atonic wounds lack inflammatory markers, such as neutrophil infiltration, and generally do not heal. Recently, prominent roles in the immunopathology of chronic wounds were attributed to dysregulations in specific cytokines, chemokines, matrix metalloproteinases (MMPs), and their substrates. Together with the complement system, these molecular players provide necessary defense against infections, initiate angiogenesis, and prepare tissue reconstitution. Here, we review the current state of the field and include the concept that, aside from surgery and stem cell therapy, healing may be enhanced by immunomodulating agents.

Genomic risk variants at 3q22.3 are associated with keloids in a Chinese Han population

A keloid is the process of skin healing, collagen synthesis and metabolism of the loss of normal control in a sustained hyperactive state, resulting in excessive proliferation of collagen fibers. A large-scale genome-wide association study (GWAS) has identified multiple single nucleotide polymorphisms (SNPs) in the 3q22.3 loci that are associated with keloids in a Japanese population. However, the associations of SNPs in 3q22.3 with keloids were not confirmed in a selected Chinese population by a replication study. Thus, in the present study, the relationships between keloids and 3q22.3 were assessed in another independent Chinese Han population, including 309 keloid patients and 1080 control subjects. The results displayed that rs940187 was associated with keloids (OR=1.88, 95% CI 1.27-2.78, P=1.35E^-3) and remained significant after Bonferroni's correction for multiple testing, while rs1511412 showed only a trend association (OR=2.23, 95% CI 1.09-4.55, P=0.02) with keloids. In addition, we subsequently checked the annotation datasets for rs940187 with eQTLs and obtained two hits, trans-proteins SLC7A9 and LEMD3, with significant P values less than 1e-4. In summary, genomic risk variants at 3q22.3 are associated with keloids in a Chinese Han population and contribute to the development and deterioration of the keloids, together with environmental factors.

Genotype-Phenotype Associations of IL6 and PRG4 With Conjunctival Fibrosis After Glaucoma Surgery

Importance

Postsurgical fibrosis is a critical determinant of the long-term success of glaucoma surgery, but no reliable biomarkers are currently available to stratify the risk of scarring.

Objective

To compare the clinical phenotype of patients with conjunctival fibrosis after glaucoma surgery with candidate gene expression tissue biomarkers of fibrosis.

Design, Setting, and Participants

In this cross-sectional study, 42 patients were recruited at the time of glaucoma surgery at the Moorfields Eye Hospital from September 1, 2014, to September 1, 2016. The participants were divided into those with fibrosis and those without fibrosis.

Main Outcomes and Measures

Genotype-phenotype correlations of the IL6 or PRG4 gene and detailed clinical phenotype. The IL6 and PRG4 protein expression in conjunctival tissues was also assessed using in situ immunohistochemical analysis. Central bleb area, maximal bleb area, and bleb height were graded on a scale of 1 to 5 (1 indicating 0%; 2, 25%; 3, 50%; 4, 75%; and 5, 100%). Bleb vascularity was graded on a scale of 1 to 5 (1 indicating avascularity; 2, normal; 3, mild; 4, moderate; and 5, severe hyperemia).

Results

A total of 42 patients were recruited during the study period; 28 participants (67%) had previously undergone glaucoma surgery (fibrotic group) (mean [SD] age, 43.8 [3.6 years]; 16 [57%] female; 22 [79%] white), and 14 participants (33%) had not previously undergone glaucoma surgery (nonfibrotic group) (mean [SD] age, 47.7 [6.9] years; 4 [29%] female; 9 [64%] white). The fibrotic group had marked bleb scarring and vascularization and worse logMAR visual acuity. The mean (SD) grades were 1.4 (0.1) for central bleb area, 1.4 (0.1) for bleb height, and 3.4 (0.2) for bleb vascularity. The IL6 gene was upregulated in fibrotic cell lines (mean, 0.040) compared with nonfibrotic cell lines (mean, 0.011) (difference, 0.029; 95% CI, 0.015-0.043; P = .003). The PRG4 gene was also downregulated in fibrotic cell lines (0.002) compared with nonfibrotic cell lines (mean, 0.109; difference, 0.107; 95% CI, 0.104-0.110; P = .03). The study found a strong correlation between the IL6 gene and the number of glaucoma operations (r = 0.94, P < .001) and logMAR visual acuity (r = 0.64, P = .03). A moderate correlation was found between the PRG4 gene and the number of glaucoma operations (r = -0.72, P = .005) and logMAR visual acuity (r = -0.62, P = .03).

Conclusions and Relevance

IL6 and PRG4 represent potential novel tissue biomarkers of disease severity and prognosis in conjunctival fibrosis after glaucoma surgery. Future longitudinal studies with multiple postoperative measures are needed to validate the effect of these potential biomarkers of fibrosis.

Complete excision of proliferating core in auricular keloids significantly reduces local recurrence: A prospective study

Keloids are mysterious soft‐tissue tumors that are characterized by excessive reparative processes composed of collagen‐forming fibroblasts and inflammatory cells. Generally, complete tumor excision regardless of sufficient margin is considered as a first‐line treatment because they are considered reactive rather than a neoplastic condition. Recently, a specific part of the keloids is being highlighted as an important microstructure for local recurrence, but there has been very little evidence. We conducted a prospective study to evaluate the relationship of recurrence and several clinicopathological parameters with specific focus on surgical resection margin. A total 87 cases of auricular keloids from 71 patients were included. The resection margins were carefully evaluated by an exhaustive grossing method and thorough microstructural assessment. During up to 48.8 months of the follow‐up period, local recurrence has been monitored and documented. The clinicopathological data including symptoms, bilaterality, size, location, prior treatment and operation history, gross type and etiology were collected and analyzed. Positive margin status was significantly related to tumor recurrence (P < 0.0001). Complete excision warrants a lower recurrence of auricular keloids in an Asian population. The most reasonable explanation for this seems to be remnant “proliferating core”, which may serve a key role in local recurrence.

Epidermal Growth Factor (EGF)-Like Repeats and Discoidin I-Like Domains 3 (EDIL3): A Potential New Therapeutic Tool for the Treatment of Keloid Scars

In keloids, the mechanism underlying the excessive accumulation of extracellular matrix after injury of the skin is unclear, and there is no effective treatment because of the incomplete understanding of their pathogenesis; thus, a high recurrence rate is observed. We studied a new marker of keloids to determine a new treatment strategy. First, the keloid gene expression profile (GSE44270) was analyzed (downloaded from the Gene Expression Omnibus database) and the new keloid marker candidate, epidermal growth factor (EGF)-like repeats and discoidin I-like domains 3 (EDIL3) which were upregulated in keloid samples was identified. Knockdown of EDIL3 is known to suppresses angiogenesis by downregulating relevant inhibitory factors that can limit the supply of survival factors to tumor cells from the circulation via the vascular endothelial cells. In keloids, the mechanism of action of EDIL3 may be similar to that in tumors; the inhibition of apoptosis in tumor cells via a reduction in the apoptosis of blood vessels by upregulating an angiogenic factor. To determine whether EDIL3 is involved in keloid formation, we performed knockdown of EDIL3 in keloid fibroblasts in vitro by transfection with anti-EDIL3 small interfering RNA (via microporation). EDIL3 was upregulated in keloid fibroblasts compared with normal fibroblasts in collagen type I, II and III. Our results indicate the control of EDIL3 expression may be a new promising treatment of keloid disease also the molecular targeting of EDIL3 may improve the quality of treatment and reduce the formation of keloids.

Upregulation of microRNA-205 suppresses vascular endothelial growth factor expression-mediated PI3K/Akt signaling transduction in human keloid fibroblasts

Keloid is one of the most frustrating problems related to wounding healing and presents a great challenge in clinic. MicroRNAs (miRs) have shown their potential as a novel therapy for the prevention and treatment of keloid. Vascular endothelial growth factor (VEGF) plays a critical role in the regulation of scar development. In the current study, it was hypothesized that miR-205-5p was capable of suppressing keloid formation by inhibiting the VEGF-mediated wound healing cascade. The expression statuses of miR-205-5p and VEGF in clinical keloid tissues and keloid cell line human keloid fibroblasts (HKF) were detected. Then the direct action of miR-205-5p on VEGF gene was assessed using dual-luciferase assay. Thereafter, orchestrated administrations on HKF with miR-205-5p mimic, specific VEGF siRNA, PI3K agonist (740 Y-P), and PI3K inhibitor (LY294002) were performed to reveal the roles of miR-205-5p and VEGF in keloid formation and further explain the mechanism through which miR-205-5p affected the VEGF-mediated signaling transductions. Our results showed that there was significant low expression of miR-205-5p in keloid tissue specimens and the cell line while the expression of VEGF in keloid tissues was augmented. Moreover, miR-205-5p overexpression dramatically impaired the cell viability, induced the cell apoptosis, and inhibited the cell invasion and migration ability in HKF. Based on the detection of dual luciferase assay and detection at protein level, miR-205-5p antagonized the keloids by directly targeting VEGF expression and subsequently inhibiting PI3K/Akt pathway. The current study is the first one demonstrating that miR-205-5p inhibits the pathogenesis of keloids, indicating the potential of miR-205-5p in the development of therapies for prevention and treatment of keloids.

Cutaneous basal cell carcinoma arising within a keloid scar: a case report

Basal cell carcinomas (BCCs) are one of the most frequent cutaneous malignancies. The majority of BCCs are reported to occur on the auricular helix and periauricular region due to ultraviolet light exposure. Despite the frequency of BCCs, those that develop within scar tissue are rare, and the phenomenon of keloid BCCs has rarely been reported in the literature. Keloid collagen within BCCs is associated with morphoeiform characteristics, ulceration, or necrosis. Extensive keloid collagen is often seen in BCCs of the ear region, a site prone to keloid scarring. This article presents a rare case of a secondary tumor (BCC) which arose on top of a primary tumor (keloid scar) on the right auricle region in a healthy 23-year-old female after an ear piercing 2 years prior. To our knowledge, the tumor described in this case, in contrast to keloidal BCCs, has never been reported in the literature.

NEDD4 single nucleotide polymorphism rs2271289 is associated with keloids in Chinese Han population

Keloids are abnormally raised fibroproliferative lesions that usually occur following cutaneous traumas. Recently, a large-scale genome-wide association study (GWAS) has identified multiple single nucleotide polymorphisms (SNPs) in three genetic loci that are associated with keloids in Japanese population. Subsequently, two reported loci 1q41 (rs873549 and rs1442440) and 15q21.3 (rs2271289) for keloids were confirmed in selected Chinese population. The association of these SNPs with clinical features of keloids, has not yet been studied. To explore the role of these SNPs in the pathogenesis of keloids, we performed a case-controlled study in another independent Chinese Han population to analyze the correlation between 4 SNPs (rs873549, rs2118610, rs1511412, rs2271289) and keloids phenotypes. 309 keloids patients and 1080 control subjects were included. The results showed that, in the dominant mode of inheritance, the minor allele T of SNP rs2271289 had significantly higher odd ratios (ORs) in the severe keloid group compared with both the controls and the mild keloid group. The ORs were maintained after Bonferroni's correction (OR: 4.09, 95% CI: 1.78-9.37, P-value 3.25E-04). The ratio of the severe: mild OR for rs2271289 (dominant model) is (4.73/1.84=2.57). Similar associations in SNP rs2271289 were seen for groups with no family history and multiplesite compared with the control groups. No associations between keloid number, family history or severity relative to the controls were observed for the other three SNPs. Our data support that rs2271289 is strongly associated with severe keloids and might contribute to the complexity of clinical features of keloids.

The molecular basis of hypertrophic scars

Hypertrophic scars (HTS) are caused by dermal injuries such as trauma and burns to the deep dermis, which are red, raised, itchy and painful. They can cause cosmetic disfigurement or contractures if craniofacial areas or mobile region of the skin are affected. Abnormal wound healing with more extracellular matrix deposition than degradation will result in HTS formation. This review will introduce the physiology of wound healing, dermal HTS formation, treatment and difference with keloids in the skin, and it also review the current advance of molecular basis of HTS including the involvement of cytokines, growth factors, and macrophages via chemokine pathway, to bring insights for future prevention and treatment of HTS.

LncRNA expression profiles and validation in keloid and normal skin tissue

Keloid is a type of pathological skin scar. Pathogenesis of keloid is complex and is not fully understood. lncRNA can regulate gene expression on different levels. It also participates in cell cycle regulation and cell proliferation. The present study investigated the potential biological function of lncRNA in keloid. We identified differential expression of lncRNAs and mRNAs between 3 pairs of keloid and normal skin tissue by microarray. Differentially expressed lncRNAs were validated by quantitative reverse transcriptase-PCR (qRT-PCR). Gene ontology (GO) and pathway analysis presented the characteristics of associated protein-coding genes. Additionally, a co-expression network of lncRNA and mRNA was constructed to find potential underlying regulation targets. There were 1,731 lncRNAs constantly upregulated and 782 downregulated, 1,079 mRNAs upregulated and 3,282 downregulated in keloid respectively (fold change ≥ 2.0, p<0.05). We chose, respectively, 3 upregulated and 1 downregulated lncRNA for qRT-PCR and results were consistent with microarray. Moreover, 11 pathways were related with upregulated transcripts and 44 with downregulated in keloid. The co-expression network revealed that one lncRNA was connected with numerous mRNAs, and vice versa. Furthermore, bioinformation analysis suggested that lncRNA CACNA1G-AS1 may be crucial to keloid formation. In conclusion, groups of lncRNAs were aberrantly expressed in keloid compared with normal skin tissue, which indicated that differentially expressed lncRNAs may play a key role in keloid formation. The present study provides new insights into keloid pathology and potential targets for treatment of keloid.

Clinical implications of single- versus multiple-site keloid disorder: a retrospective study in an Asian population

BACKGROUND

There is strong evidence of genetic susceptibility in individuals with keloid disorder. The purpose of this cross-sectional study was to determine the clinical relevance of our proposed variables on the multiplicity of keloids by further investigating the presence of other keloids and a family history.

METHODS

This was a retrospective review, using institutional review board-approved questionnaires, of patients with keloids who were seen at Kangbuk Samsung Hospital between December 2002 and February 2010. Eight hundred sixty-eight patients were included in our study. Comparisons between the 2 groups were made using Mann-Whitney tests for continuous variables and χ2 tests for categorical variables.

RESULTS

In our patient group, younger age of onset and the presence of family history were significantly associated with the occurrence of keloids at multiple sites. The locations of extra-auricular keloids, in order of frequency, included the shoulder; anterior chest, including the breasts; deltoid; trunk and pubic area; upper extremities; lower extremities; and other sites. As compared to secondary keloids, primary keloids were significantly associated with both a lower degree of recurrence and the presence of other keloids. The presence or absence of family history was significantly associated with the presence or absence of other keloids and primary or secondary keloids.

CONCLUSIONS

Keloid disorder is one of the most frustrating problems in wound healing and advances in our understanding of the differences of occurrence at a single site versus multiple sites might help in understanding pathogenesis and improving treatment.

[Therapy of hypertrophic scars and keloids]

Keloids mostly occur between the ages of 10 and 30 years and grow continuously beyond the original margins of the scar. Beside the cosmetic impairment they often lead to pruritus, pain, contractures and decrease in quality of life. Advances in the understanding of the genetics and pathogenesis of hypertrophic scars and keloids have led to new therapeutic options. Nevertheless treatment remains a challenge and there is no single treatment modality which is appropriate for all types of scars. Combined approaches are becoming more widely employed as they are more effective than single treatment modalities. This article gives an overview of hypertrophic scars and keloids, their pathogenesis and recommended therapeutic approaches.

High-mobility Group Box Protein-1, Matrix Metalloproteinases, and Vitamin D in Keloids and Hypertrophic Scars

Keloids and hypertrophic scars represent excessive wound healing involving high production of collagen by skin fibroblasts. This review focuses on the role of high-mobility group box protein-1 (HMGB-1), matrix metalloproteinases (MMPs), and vitamin D in these conditions. Although the role of HMGB-1 in keloids and hypertrophic scars is unclear, the effect of HMGB-1 on fibroblasts suggests a profibrotic role and a potential contribution to excessive scarring. MMPs contribute extensively to wound healing and characteristically degrade the extracellular matrix. MMP-1 is decreased in keloids and hypertrophic scars. However, other MMPs, including MMP-2, have been found to be increased and are thought to possibly contribute to keloid expansion through peripheral extracellular matrix catabolism. Many novel therapeutic approaches to keloids and hypertrophic scars target MMPs and aim to increase their levels and catabolic activity. The higher prevalence of keloids in darker skin types may partially be due to a tendency for lower vitamin D levels. The physiologically active form of vitamin D, 1,25(OH)2D3, inhibits the proliferation of keloid fibroblasts, and correlations between vitamin D receptor polymorphisms, such as the TaqI CC genotype, and keloid formation have been reported. Additionally, vitamin D may exert an antifibrotic effect partially mediated by MMPs. Here, we critically discuss whether keloid and hypertrophic scar formation could be predicted based on vitamin D status and vitamin D receptor polymorphisms. Specifically, the findings identified HMGB-1, MMPs, and vitamin D as potential avenues for further clinical investigation and potentially novel therapeutic approaches to prevent the development of keloids and hypertrophic scars.

Molecular signalings in keloid disease and current therapeutic approaches from natural based compounds

CONTEXT

Keloid is an excessive dermal scar occurring in response to skin injuries. Several therapeutic strategies have been proposed to ease the aggressiveness of keloid scarring. Even though the principle mechanism underlying the disease propagation still remains unidentified, several signaling pathways were highly focused as plausible pathways involving keloid formation, including transforming growth factor-beta 1 (TGF-β1), mitogen-activated protein kinase (MAPK), insulin-like growth factor-I (IGF-I), and integrin pathways. Natural compounds containing multiple bioeffective properties such as quercetin, asiaticoside, Astragalus membranaceus Bunge. (Leguminosae), and Salvia miltiorrhiza Bunge. (Lamiaceae) extracts, curcuminoids, oxymatrine, madecassoside, and Aneilema keisak Hassk. (Commelinaceae) are claimed as candidates for therapeutic treatment against keloid disorder.

OBJECTIVE

This review investigates current mechanisms regarding keloid formation and provides scientific evidence supporting the therapeutic potential of natural compounds.

METHODS

This review obtained and analyzed a number of literature data items from various databases including Pubmed, ScienceDirect, and Elton B. Stephens Company (EBSCO).

RESULT

Several phytochemical compounds are able to suppress keloid scar development through manipulating various components in the complex signaling cascades.

CONCLUSION

The present review may be helpful to future studies that further examine the molecular mechanism of keloid etiology as well as investigate the anti-keloid property in natural compounds.

New approach to the understanding of keloid: psychoneuroimmune-endocrine aspects

The skin is a dynamic and complex organ that relies on the interrelation among different cell types, macromolecules, and signaling pathways. Further, the skin has interactions with its own appendages and other organs such as the sebaceous glands and hair follicles, the kidney, and adrenal glands; systems such as the central nervous system; and axes such as the hypothalamic–pituitary–adrenal axis. These continuous connections give the skin its versatility, and when an injury is caused, some triggers start a cascade of events designed to restore its integrity. Nowadays, it is known that this psychoneuroimmune–endocrine intercommunication modulates both the homeostatic condition and the healing process. In this sense, the skin conditions before a trauma, whether of endogenous (acne) or exogenous origin (injury or surgical incision), could regulate the process of tissue repair. Most skin diseases such as psoriasis and atopic dermatitis, among others, have in their pathophysiology a psychogenic component that triggers integrated actions in the nervous, immune, and endocrine systems. However, fibroproliferative disorders of wound healing, such as hypertrophic scar and keloid, are not yet included in this listing, despite showing correlation with stress, especially with the psychosocial character. This review, by understanding the “brain–skin connection”, presents evidence that allows us to understand the keloid as a psychomediated disease.

Synergistic effect of interleukin-6 and hyaluronic acid on cell migration and ERK activation in human keratinocytes

Wound healing is initiated and progressed by complex integrated process of cellular, physiologic, and biochemical events, such as inflammation, cell migration and proliferation. Interleukin 6 (IL-6) is a multifunctional cytokine, and it could regulate the inflammatory response of wound healing process in a timely manner. Hyaluronic acid (HA) is an essential component of the extracellular matrix, and contributes significantly to cell proliferation and migration. The purpose of this study was to investigate the effects of IL-6 or/and HA on the cell migration process in human keratinocytes. Combining IL-6 and HA significantly increased the cell migration in scratch based wound healing assay. The phosphorylation of extracellular-signal-regulated kinase (ERK) was significantly increased after 1 hr of IL-6 and HA treatment, but the phosphorylation of p38 mitogen-activated protein kinase (MAPK) was not. We also found that significant increase of the NF-κB translocation from cytoplasm into nucleus after 1 hr of IL-6 or/and HA treatments. This study firstly showed that synergistic effects of combining IL-6 and HA on the cell migration of wound healing by activation of ERK and NF-κB signaling. Further studies might be required to confirm the synergistic effects of HA and IL-6 in the animal model for the development of a novel therapeutic mixture for stimulation of wound healing process.

Wound healing: an update

Wounds, both chronic and acute, continue to be a tremendous socioeconomic burden. As such, technologies drawn from many disciplines within science and engineering are constantly being incorporated into innovative wound healing therapies. While many of these therapies are experimental, they have resulted in new insights into the pathophysiology of wound healing, and in turn the development of more specialized treatments for both normal and abnormal wound healing states. Herein, we review some of the emerging technologies that are currently being developed to aid and improve wound healing after cutaneous injury.

Models of abnormal scarring

Keloids and hypertrophic scars are thick, raised dermal scars, caused by derailing of the normal scarring process. Extensive research on such abnormal scarring has been done; however, these being refractory disorders specific to humans, it has been difficult to establish a universal animal model. A wide variety of animal models have been used. These include the athymic mouse, rats, rabbits, and pigs. Although these models have provided valuable insight into abnormal scarring, there is currently still no ideal model. This paper reviews the models that have been developed.

Keloids and non-diabetic kidney disease: similarities and the APOL1-MYH9 haplotype as a possible genetic link

Keloids and non-diabetic kidney disease are both fibrotic processes that disproportionately affect persons of African descent. Despite similarities in these conditions, the authors identified no studies to date investigating a shared genetic etiology. MYH9 and APOL1 are in linkage disequilibrium and have both been associated with non-diabetic kidney disease. MYH9 codes for a non-muscle myosin that is involved in cell adhesion and locomotion and is known to be overexpressed in keloids. Variations in APOL1 confer resistance to subspecies of Trypanosoma brucei, which may explain why otherwise deleterious genetic alterations in this haplotype could have gained prominence. We feel that the pathophysiological and epidemiological overlap between keloids and non-diabetic kidney disease support a common genetic origin and further investigation into keloids and the MYH9-APOL1 haplotype and keloids is warranted. Furthermore, we feel this haplotype might offer insight into thrombosis, stroke and other conditions that disproportionately affect persons of African descent.