Expression Profiles of lncRNAs and circRNAs in Keloid

hsa_circ_0037722 Drives Keloid Formation by Interacting with miR-140-3p and NR2F2

Keloids can invade normal skin tissues to lead to itching, pain, hemorrhaging and suppuration, thereby affecting the mental health of patients. circRNAs can participate in keloids formation, but the role of hsa_circ_0037722 in keloids is still unknown. The goal of our study was to reveal the role of hsa_circ_0037722 in keloids. The levels of hsa_circ_0037722, miR-140-3p and NR2F2 in keloids was confirmed by qRT-PCR. Cell experiments were applied to assess the effect of hsa_circ_0037722/miR-140-3p/NR2F2 axis on keloids formation. In addition, the correlation among hsa_circ_0037722, miR-140-3p and NR2F2 was confirmed by luciferase assay. hsa_circ_0037722 and NR2F2 were upregulated in keloids tissues and keloids fibroblasts, whereas miR-140-3p was downregulated in keloids tissues and keloids fibroblasts. The abilities of proliferation and metastasis of keloids fibroblasts were impaired by silencing hsa_circ_0037722. However, miR-140-3p inhibitor or NR2F2 overexpression could restore the inhibitory function of hsa_circ_0037722 knockdown in keloid fibroblasts due to their targeting relationship. Taken together, hsa_circ_0037722 can facilitate keloids formation by interacting with miR-140-3p to relieve the suppression of miR-140-3p for NR2F2. The findings of this study may provide a novel idea for developing molecular targeted therapies for keloid.

Defining a Unique Gene Expression Profile in Mature and Developing Keloids

Keloids are benign, fibroproliferative dermal tumors that typically form owing to abnormal wound healing. The current standard of care is generally ineffective and does not prevent recurrence. To characterize keloid scars and better understand the mechanism of their formation, we performed transcriptomic profiling of keloid biopsies from a total of 25 subjects of diverse racial and ethnic origins, 15 of whom provided a paired nonlesional sample, a longitudinal sample, or both. The transcriptomic signature of nonlesional skin biopsies from subjects with keloids resembled that of control skin at baseline but shifted to closely match that of keloid skin after dermal trauma. Peripheral keloid skin and rebiopsied surrounding normal skin both showed upregulation of epithelial-mesenchymal transition markers, extracellular matrix organization, and collagen genes. These keloid signatures strongly overlapped those from healthy wound healing studies, usually with greater perturbations, reinforcing our understanding of keloids as dysregulated and exuberant wound healing. In addition, 219 genes uniquely regulated in keloids but not in normal injured or uninjured skin were also identified. This study provides insights into mature and developing keloid signatures that can act as a basis for further validation and target identification in the search for transformative keloid treatments.

Long Non-Coding RNA uc003jox.1 Promotes Keloid Fibroblast Proliferation and Invasion Through Activating the PI3K/AKT Signaling Pathway

The pathogenesis of keloids is complex and unclear, and the treatment of this condition remains challenging. The long non-coding RNA uc003jox.1 is highly expressed in keloid tissues compared with in normal skin tissues. We assessed the role of uc003jox.1 in keloid fibroblasts and its underlying mechanism, focusing on the phosphoinositide 3-kinase (PI3K)/protein kinase B (AKT) pathway. Keloid fibroblasts were transfected with a small interfering RNA targeting uc003jox.1. Colony formation, transwell, and flow cytometry assays were conducted to evaluate the proliferation, invasion, and apoptosis of keloid fibroblasts, respectively. The interaction between uc003jox.1 and the PI3K/AKT pathway was explored by using polymerase chain reaction and western blotting. Knockdown of uc003jox.1 markedly suppressed keloid fibroblast proliferation, clone-forming activity, and invasion, as well as promoted apoptosis. Silencing of uc003jox.1 decreased the phosphorylation levels of PI3K, AKT, and mammalian target of rapamycin and increased both the mRNA and protein expression levels of phosphatase and tensin homolog. Our in vitro results suggest that the long non-coding RNA uc003jox.1 can be used as a biomarker for keloid fibroblasts and that its expression is closely related to the proliferation and invasion of keloid fibroblasts through the PI3K/AKT/mammalian target of rapamycin pathway. Thus, uc003jox.1 shows potential as a treatment target for keloids.

IncRNA MIAT Accelerates Keloid Formation by miR-411-5p/JAG1 Axis

The long non-coding RNA (lncRNA) myocardial infarction-associated transcript (MIAT) regulates the biological functions of many kinds of cells. The aim of this study is to explore the mechanism of MIAT and how it affects keloid progression. The expressions of MIAT, JAG1, and miR-411-5p in keloid tissues and keloid fibroblasts (KEL FIBs) were quantified by conducting Western blot and quantitative reverse transcription polymerase chain reaction analyses. The influences of MIAT, JAG1, and miR-411-5p on the abilities of KEL FIBs to proliferate, migrate, and invade were assessed by means of the CCK-8, wound healing, and Transwell experiments. To determine the binding relationship among MIAT, JAG1, and miR-411-5p, we performed luciferase reporter and RIP experiments. In keloid tissues and KEL FIBs, MIAT and JAG1 were upregulated while miR-411-5p was downregulated. Knocking-down MIAT or JAG1 significantly inhibited proliferation, migration and invasion. On the contrary, suppressing miR-411-5p expression produced an opposite effect. With regard to mechanisms, MIAT sponged miR-411-5p, which targeted JAG1. MIAT accelerates keloid formation by modulating the miR-411-5p/JAG1 axis.

CircCOL5A1 inhibits proliferation, migration, invasion, and extracellular matrix production of keloid fibroblasts by regulating the miR-877-5p/EGR1 axis

BACKGROUND

Circular RNA (circRNA) has been proved to mediate the biological functions of fibroblasts to participate in the regulation of keloid formation. However, the role of circCOL5A1 in keloid formation remains to be further confirmed.

METHODS

Primary keloid fibroblasts were isolated form keloid tissues. The expression of circCOL5A1, microRNA (miR)- 877-5p, and early growth response 1 (EGR1) were determined by quantitative real-time PCR. Transfection experiments were carried out to explore the effects of circCOL5A1, miR-877-5p, and EGR1 on cell functions. Cell proliferation, migration, invasion and apoptosis were detected using cell counting kit 8 assay, colony formation assay, transwell assay and flow cytometry. The protein levels of apoptosis markers, extracellular matrix (ECM) markers and EGR1 were measured by western blot analysis. The mechanism of circCOL5A1 was confirmed by RNA pull-down assay, dual-luciferase reporter assay and RIP assay.

RESULTS

Our data showed that circCOL5A1 was upregulated in keloid tissues and fibroblasts. Silencing of circCOL5A1 had an inhibition effect on proliferation, migration, invasion and ECM production, while had a promotion effect on apoptosis in keloid fibroblasts. MiR-877-5p could be sponged by circCOL5A1, and its overexpression could repress the biological functions of keloid fibroblasts. The rescue experiments showed that miR-877-5p inhibitor could reverse the suppressive effect of circCOL5A1 knockdown on the biological functions of keloid fibroblasts. In addition, EGR1 was a target of miR-877-5p, and its expression was positively regulated by circCOL5A1. The inhibition effect of miR-877-5p on the biological functions of keloid fibroblasts could be abolished by EGR1 overexpression.

CONCLUSION

In summary, circCOL5A1 facilitates keloid fibroblast proliferation, migration, invasion and ECM production through the miR-877-5p/EGR1 axis, thereby potentially promoting keloid formation.

Keloid Patient Plasma-Derived Exosomal hsa_circ_0020792 Promotes Normal Skin Fibroblasts Proliferation, Migration, and Fibrogenesis via Modulating miR-193a-5p and Activating TGF-β1/Smad2/3 Signaling

Background

Keloids are fibroproliferative disorders, which seriously affect the quality of life of patients with keloids. Additionally, circRNAs are enriched within exosomes derived from human blood samples, whereas their relationship with keloids remains largely unknown. It has been reported that hsa_circ_0020792 was abnormally upregulated in keloid tissues. However, the role of keloid patient plasma-derived exosomal hsa_circ_0020792 in the formation and development of keloids is not well understood.

Methods

Exosomes were isolated from the peripheral blood plasma of the patients with keloids (keloid patient-Exo) and healthy controls (Healthy control-Exo). The hsa_circ_0020792 and miR-193a-5p levels in keloid patient-Exo and healthy control-Exo, as well as in keloid fibroblasts and normal skin fibroblasts (NFs) were evaluated by RT-qPCR.

Results

The level of hsa_circ_0020792 was remarkably increased in keloid patient-Exo and keloid fibroblasts compared with that in Healthy control-Exo and NFs, respectively. In addition, keloid patient-Exo obviously enhanced the viability, migration, and extracellular matrix (ECM) synthesis, but reduced the apoptosis of NFs. Moreover, keloid patient-Exo notably promoted the fibrogenesis of NFs, as characterized by enhanced TGF-β signaling, increased expressions of phosphorylated Smad2/3. However, downregulation of hsa_circ_0020792 markedly reversed the promoting effects of keloid patient-Exo on cell growth, migration, and myofibroblast activation and fibrogenesis. Furthermore, downregulation of hsa_circ_0020792 significantly reduced the viability, migration, and fibrogenesis in NFs, whereas these phenomena were reversed by miR-193a-5p inhibitor.

Conclusion

Collectively, keloid patient plasma-derived exosomal hsa_circ_0020792 could promote the proliferation, migration, and fibrogenesis of NFs via modulating miR-193a-5p and activating TGF-β1/Smad2/3 signaling.

Circ_0057452 sponges miR-7-5p to promote keloid progression through upregulating GAB1

Increasing evidence has shown that circular RNAs (circRNAs) play critical roles in various diseases, including keloid. The purpose of this study was to investigate the role of circ_0057452 and related action mechanisms during the development of keloid. The expression levels of circ_0057452, microRNA-7-5p (miR-7-5p) and GRB2 associated binding protein 1 (GAB1) mRNA were determined by quantitative real-time PCR (qRT-PCR). Cell proliferation was evaluated using methylthiazolyldiphenyl-tetrazolium bromide (MTT) and 5-Ethynyl-2'-deoxyuridine (Edu) assays. Flow cytometry analysis was utilized to determine cell cycle distribution and cell apoptosis. Western blot assay was used to measure apoptosis-related, collagen synthesis-related, and GAB1 protein levels. Cell migration and invasion were detected by wound healing assay and transwell assay. The interaction between miR-7-5p and circ_0057452 or GAB1 was confirmed by dual-luciferase reporter, RNA pull-down, and RNA Immunoprecipitation (RIP) assays. Circ_0057452 and GAB1 were upregulated in keloid tissues and keloid fibroblasts (KFs), while miR-7-5p was downregulated. Circ_0057452 knockdown or miR-7-5p overexpression inhibited the proliferation, migration, invasion, and collagen synthesis and induced cell cycle arrest and apoptosis of KFs. MiR-7-5p was targeted by circ_0057452, and its inhibition overturned the effects of circ_0057452 knockdown. In addition, GAB1 was a target of miR-7-5p, and GAB1 upregulation abolished the role of miR-7-5p overexpression and circ_0057452 knockdown in KFs. Circ_0057452 regulated the expression of GAB1 by adsorbing miR-7-5p in KFs. Circ_0057452 knockdown suppressed keloid development by regulating miR-7-5p/GAB1 axis, which might provide a promising therapeutic target for keloid.

Circular RNAs: Emerging players in the pathogenesis of keloid

Circular RNAs (circRNAs) are a new type of non-coding RNAs originating from precursor messenger RNAs. Recent research has confirmed that circRNAs play a significant role in various biological and pathological processes, including cell viability, migration, and apoptosis. Emerging studies have demonstrated that the deregulated circRNA-miRNA-mRNA interaction network plays a key role in the development of many diseases. Increasing evidence has highlighted the role of ncRNAs (mainly miRNAs and lncRNAs) in the pathogenesis of keloids. Recently, several publications also indicated that circRNAs contribute to keloid development. The discovery of circRNAs changed the current understanding of the biology of keloids It is crucial to elucidate a circRNA-miRNA-mRNA network to understand the pathological mechanism of keloids. In the present review, we summarize the aberrant expression of regulatory roles of circRNAs in keloids. We discuss the potential clinical application of circRNAs in the diagnosis and treatment of keloids.

circRNA: Regulatory factors and potential therapeutic targets in inflammatory dermatoses

The skin is the largest organ of the human body and acts as the first line of defence against injury and infection. Skin diseases are among the most common health problems and are associated with a considerable burden that encompasses financial, physical and mental consequences for patients. Exploring the pathogenesis of skin diseases can provide insights into new treatment strategies. Inflammatory dermatoses account for a large proportion of dermatoses and have a great impact on the patients' body and quality of life. Therefore, it is important to study their pathogenesis and explore effective treatment. Circular RNAs (circRNAs) are a special type of RNA molecules that play important regulatory roles in several diseases and are involved in skin pathophysiological processes. This review summarizes the biogenesis, properties and functions of circRNAs as well as their roles in the pathogenesis of inflammatory dermatoses, including psoriasis, lupus erythematosus, atopic dermatitis, lichen planus and severe acne and their potential as therapeutic targets.

Circular RNA hsa_circ_0043688 serves as a competing endogenous RNA for microRNA-145-5p to promote the progression of Keloids via Fibroblast growth factor-2

Background

Keloids are benign fibroproliferative skin tumors. Circular RNA (circRNA) hsa_circ_0043688 has been exhibited to the freakishly expressed in keloid tissues. Here, we aimed to investigate the regulatory network of hsa_circ_0043688 in the pathological process of keloid.

Methods

Hsa_circ_0043688, microRNA‐145‐5p (miR‐145‐5p), and Fibroblast growth factor‐2 (FGF2) level were detected using RT‐qPCR. Cell viability, proliferation, apoptosis, invasion, and migration were investigated using Cell Counting Kit‐8 (CCK‐8), 5‐ethynyl‐2′‐deoxyuridine (EdU), flow cytometry, transwell, and wound healing assays, respectively. Western blot analysis of protein levels of FGF2, CyclinD1, Collagen I, and Collagen III. After the prediction of Circinteractome and Starbase, their interaction was verified based on a dual‐luciferase reporter and RIP assays.

Results

Increased hsa_circ_0043688 and FGF2, and decreased miR‐145‐5p in keloids samples and fibroblasts were found. Also, hsa_circ_0043688 absence hindered proliferation, invasion, migration, and boost apoptosis of keloid fibroblasts. In mechanism, hsa_circ_0043688 modulated FGF2 content via sponging miR‐145‐5p.

Conclusion

Hsa_circ_0043688 knockdown inhibited cell growth and metastasis of keloid fibroblasts via miR‐145‐5p/FGF2, providing a new mechanism to understand the keloid progression.

CircSLC8A1 targets miR-181a-5p/HIF1AN pathway to inhibit the growth, migration and extracellular matrix deposition of human keloid fibroblasts

BACKGROUND

Circular RNAs (circRNAs) are identified as important regulators in human diseases, including keloid. The purpose of this study is to reveal the role and molecular mechanism of circSLC8A1 in keloid formation.

METHODS

Expression of circSLC8A1, microRNA (miR)-181a-5p, and hypoxia inducible factor 1 alpha inhibitor (HIF1AN) were detected by quantitative real-time PCR. Protein expression of extracellular matrix (ECM) deposition markers and HIF1AN was detected by western blot analysis. Furthermore, the interaction between miR-181a-5p and circSLC8A1 or HIF1AN was confirmed by dual-luciferase reporter assay, RIP assay and RNA pull-down assay.

RESULTS

Expression of circSLC8A1 was downregulated in keloid tissues and HKFs. Overexpression of circSLC8A1 suppressed HKFs proliferation, migration, ECM deposition, and promoted apoptosis. MiR-181a-5p is targeted by circSLC8A1, and its mimic reversed the effect of circSLC8A1 on the biological function of HKFs. HIF1AN was a target of miR-181a-5p, and it was positively regulated by circSLC8A1. Knockdown of HIF1AN also reversed the negatively regulation of circSLC8A1 on the biological functions of HKFs.

CONCLUSION

Our data showed that circSLC8A1 regulates the miR-181a-5p/HIF1AN axis to restrain HKFs biological functions, confirming that circSLC8A1 might serve as a novel therapeutic target for keloids.

Circ_0084443 Inhibits Wound Healing Via Repressing Keratinocyte Migration Through Targeting the miR-17-3p/FOXO4 Axis

Keratinocyte migration is a crucial process during skin wound healing, and circular RNAs are associated with keratinocyte migration. The purpose of our study was to clarify the role of circ_0084443 in wound healing. The levels of circ_0084443, microRNA (miR)-17-3p, and forkhead box protein O4 (FOXO4) were examined by quantitative reverse transcription-PCR. Cell migration was detected via wound scratch assay or transwell assay. The protein expression was measured using western blot. The binding analysis between miR-17-3p and circ_0084443 or FOXO4 was determined by dual-luciferase reporter assay and RNA Immunoprecipitation assay. TGF-β1 decreased the levels of circ_0084443 and FOXO4 while increased the miR-17-3p expression in keratinocytes by a concentration-dependent manner. Circ_0084443 acted as a miR-17-3p sponge and circ_0084443 overexpression alleviated TGF-β1-induced migration of keratinocytes by sponging miR-17-3p. FOXO4 was a target for miR-17-3p. The downregulation of miR-17-3p suppressed cell migration in TGF-β1-induced cells by increasing the FOXO4 level. Circ_0084443 positively regulated the FOXO4 expression by sponging miR-17-3p. Circ_0084443 suppressed the TGFβ signaling pathway by affecting the miR-17-3p/FOXO4 axis. These results exhibited that circ_0084443 suppressed the TGF-β1-induced keratinocyte migration by regulating the miR-17-3p/FOXO4 axis, suggesting the application potential of circ_0084443 in wound-healing-related diseases.

Single-cell RNA-seq reveals lineage-specific regulatory changes of fibroblasts and vascular endothelial cells in keloids

Keloids are a benign dermal fibrotic disorder with features similar to malignant tumors. keloids remain a therapeutic challenge and lack medical therapies, which is partially due to the incomplete understanding of the pathogenesis mechanism. We performed single-cell RNA-seq of 28,064 cells from keloid skin tissue and adjacent relatively normal tissue. Unbiased clustering revealed substantial cellular heterogeneity of keloid tissue, which included 21 clusters assigned to 11 cell lineages. We observed significant expansion of fibroblast and vascular endothelial cell subpopulations in keloids, reflecting their strong association with keloid pathogenesis. Comparative analyses were performed to identify the dysregulated pathways, regulators and ligand-receptor interactions in keloid fibroblasts and vascular endothelial cells. Our results highlight the roles of transforming growth factor beta and Eph-ephrin signaling pathways in both the aberrant fibrogenesis and angiogenesis of keloids. Critical regulators probably involved in the fibrogenesis of keloid fibroblasts, such as TWIST1, FOXO3 and SMAD3, were identified. TWIST1 inhibitor harmine could significantly suppress the fibrogenesis of keloid fibroblasts. In addition, tumor-related pathways were activated in keloid fibroblasts and vascular endothelial cells, which may be responsible for the malignant features of keloids. Our study put insights into the pathogenesis of keloids and provides potential targets for medical therapies.

The epigenetics of keloids

Keloid scarring is a fibroproliferative disorder of the skin with unknown pathophysiology, characterised by fibrotic tissue that extends beyond the boundaries of the original wound. Therapeutic options are few and commonly ineffective, with keloids very commonly recurring even after surgery and adjunct treatments. Epigenetics, defined as alterations to the DNA not involving the base-pair sequence, is a key regulator of cell functions, and aberrant epigenetic modifications have been found to contribute to many pathologies. Multiple studies have examined many different epigenetic modifications in keloids, including DNA methylation, histone modification, microRNAs and long non-coding RNAs. These studies have established that epigenetic dysregulation exists in keloid scars, and successful future treatment of keloids may involve reverting these aberrant modifications back to those found in normal skin. Here we summarise the clinical and experimental studies available on the epigenetics of keloids, discuss the major open questions and future perspectives on the treatment of this disease.

Epigenetic regulation of cellular functions in wound healing

Stringent spatiotemporal regulation of the wound healing process involving multiple cell types is associated with epigenetic mechanisms of gene regulation, such as DNA methylation, histone modification and chromatin remodelling, as well as non-coding RNAs. Here, we discuss the epigenetic changes that occur during wound healing and the rapidly expanding understanding of how these mechanisms affect healing resolution in both acute and chronic wound milieu. We provide a focussed overview of current research into epigenetic regulators that contribute to wound healing by specific cell type. We highlight the role of epigenetic regulators in the molecular pathophysiology of chronic wound conditions. The understanding of how epigenetic regulators can affect cellular functions during normal and impaired wound healing could lead to novel therapeutic approaches, and we outline questions that can provide guidance for future research on epigenetic-based interventions to promote healing. Dissecting the dynamic interplay between cellular subtypes involved in wound healing and epigenetic parameters during barrier repair will deepen our understanding of how to improve healing outcomes in patients affected by chronic non-healing wounds.

Circular RNA CircCOL5A1 Sponges the MiR-7-5p/Epac1 Axis to Promote the Progression of Keloids Through Regulating PI3K/Akt Signaling Pathway

Keloids, as a result of abnormal wound healing in susceptible individuals, are characterized by the hyper-proliferation of fibroblasts and exaggerated deposition of extracellular matrix. Current surgical and therapeutic modalities provide limited satisfactory results. Growing evidence has highlighted the roles of circRNAs in acting as miRNA sponges. However, up to date, the regulatory mechanism of circRNAs in the pathological process of keloids has rarely been reported. In this study, cell proliferation, cell migration, flow cytometry, western blotting, fluorescence in situ hybridization, dual-luciferase activity, and immunohistochemistry assays were applied to explore the roles and mechanisms of the circCOL5A1/miR-7-5p/Epac1 axis in the keloid. The therapeutic potential of circCOL5A1 was investigated by establishing keloid implantation models. The RT-qPCR result revealed that circCOL5A1 expression was obviously higher in keloid tissues and keloid fibroblasts. Subsequent cellular experiments demonstrated that circCOL5A1 knockdown repressed the proliferation, migration, extracellular matrix (ECM) deposition, whereas promoted cell apoptosis, through the PI3K/Akt signaling pathway. Furthermore, RNA-fluorescence in situ hybridization (RNA-FISH) illustrated that both circCOL5A1 and miR-7-5p were located in the cytoplasm. The luciferase reporter gene assay confirmed that exact binding sites were present between circCOL5A1 and miR-7-5p, as well as between miR-7-5p and Epac1. Collectively, the present study revealed that circCOL5A1 functioned as competing endogenous RNA (ceRNA) by adsorbing miR-7-5p to release Epac1, which contributed to pathological hyperplasia of keloids through activating the PI3K/Akt signaling pathway. Our data indicated that circCOL5A1 might serve as a novel promising therapeutic target and represent a new avenue to understand underlying pathogenesis for keloids.

Identification of differentially expressed circular RNAs in keloid and normal skin tissue by high-throughput sequencing

Keloid is a kind of pathological skin scar with unclear molecular pathology. Circular RNAs (circRNAs) are involved in the occurrence and development of many diseases; however, their relationship with keloid is not well understood. To investigate the involvement of dysregulated circRNAs in keloid. Thirty-seven keloids and 37 normal skin tissues were collected, and the changes of circRNAs, microRNAs (miRNAs) and mRNAs in 3 keloids and 3 normal samples by high-throughput sequencing were detected first. Based on the circRNA-miRNA-mRNA interaction network construction, gene ontology and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis combining several signaling pathways associated with keloid formation and progression, the circRNAs required further verification were screened out. The expression levels of the selected circRNAs were verified in 37 keloids and 37 normal skin tissues using quantitative real-time polymerase chain reaction (QPCR). The interaction of candidate circRNA and its predicted binding miRNA was tested by dual-luciferase reporter gene experiment. Compared with normal controls, there was an average of 120 and 12 circRNAs, 44 and 63 miRNAs, 656 and 156 mRNAs were upregulated and downregulated, respectively, in keloids. According to the analysis of bioinformation, six circRNAs were picked out. The QPCR validation results of two upregulated circRNAs (hsa_circ_0001320 and circCOL5A1) were consistent with previous sequencing results. The interaction between hsa_circ_0001320 and miR-574-5p was confirmed. This study makes it clear that the abnormal expression of circRNAs may be related to the pathological process of keloid.

Epigenetic modification mechanisms involved in keloid: current status and prospect

Keloid, a common dermal fibroproliferative disorder, is benign skin tumors characterized by the aggressive fibroblasts proliferation and excessive accumulation of extracellular matrix. However, common therapeutic approaches of keloid have limited effectiveness, emphasizing the momentousness of developing innovative mechanisms and therapeutic strategies. Epigenetics, representing the potential link of complex interactions between genetics and external risk factors, is currently under intense scrutiny. Accumulating evidence has demonstrated that multiple diverse and reversible epigenetic modifications, represented by DNA methylation, histone modification, and non-coding RNAs (ncRNAs), play a critical role in gene regulation and downstream fibroblastic function in keloid. Importantly, abnormal epigenetic modification manipulates multiple behaviors of keloid-derived fibroblasts, which served as the main cellular components in keloid skin tissue, including proliferation, migration, apoptosis, and differentiation. Here, we have reviewed and summarized the present available clinical and experimental studies to deeply investigate the expression profiles and clarify the mechanisms of epigenetic modification in the progression of keloid, mainly including DNA methylation, histone modification, and ncRNAs (miRNA, lncRNA, and circRNA). Besides, we also provide the challenges and future perspectives associated with epigenetics modification in keloid. Deciphering the complicated epigenetic modification in keloid is hopeful to bring novel insights into the pathogenesis etiology and diagnostic/therapeutic targets in keloid, laying a foundation for optimal keloid ending.

Circ_0008450 downregulates Runx3 to promote the proliferation and epithelial-mesenchymal transition of human keratinized epithelial cells

Keloid is an extremely common and often overlooked benign neoplastic disease, but its consequences should not be underestimated. Therefore, a deep exploration of the pathological mechanism of keloid becomes very essential. After 22 samples were collected from each patient's keloid tissues and normal skin tissues, circ_0008450 and Runx3 expression was tested by qRT-PCR. When primary human keratinized epithelial cells were transfected by sh-circ_0008450 or sh-Runx3, cell proliferation, apoptosis, migration, and EMT process were assessed by CCK-8, BrdU assay, apoptosis assay, migration assay, and Western blot. Finally, transfection was performed to explore the effect of circ_0008450 on the TGF-β/Smad signal pathway by adopting western blot. Circ_0008450 was highly expressed in keratinized epithelial tissues. After the transfection of sh-circ_0008450 into primary human keratinized epithelial cells, cell proliferation, migration, and EMT process were inhibited, and apoptosis was stimulated. Moreover, circ_0008450 silence-induced above changes were partly reversed by transfecting sh-Runx3. In addition, transfecting sh-circ_0008450 could repress TGF-β/Smad pathway, while transfecting sh-Runx3 activated the above pathway. Circ_0008450 down-regulated Runx3 to promote the proliferation and EMT process of human keratinized epithelial cells. This discovery may be related to the activation of the TGF-β/Smad pathway.

Effects of the circ_101238/miR-138-5p/CDK6 axis on proliferation and apoptosis keloid fibroblasts

The formation of keloid scars is normally induced by cutaneous injuries, however, the detailed mechanisms underlying keloid formation remain largely unknown. The present study aimed to investigate the effects of circular RNA_101238 (circ_101238) on the proliferation and apoptosis of keloid fibroblasts and to identify the underlying molecular mechanisms of these effects. Reverse transcription-quantitative (RT-q)PCR was performed to determine the expression levels of circ_101238, microRNA (miRNA/miR)-138-5p and cyclin-dependent kinase 6 (CDK6) in keloids and normal skin tissues. Following transfection with short hairpin (sh)-circ_101238, LV-circ_101238, miR-138-5p mimics, miR-138-5p inhibitors and small interfering (si)-CDK6, cell proliferation was assessed using a cell counting kit-8 assay. Furthermore, cell apoptosis was evaluated via flow cytometric analysis, while a dual-luciferase assay was performed to confirm interactions between circ_101238, miR-138-5p and CDK6. The expression levels of the proliferation marker, CDK6 and apoptosis marker, caspase-3 were determined via RT-qPCR and western blot analyses. The results demonstrated that expression levels of circ_101238 and CDK6 were significantly increased in keloid samples, while miR-138-5p expression was reduced in comparison to normal skin. Furthermore, circ_101238 was demonstrated to bind miR-138-5p, which subsequently targeted CDK6. Proliferative activity and CDK6 expression were significantly decreased in keloid fibroblasts following transfection with sh-circ_101238 or miR-138-5p mimics, while cell apoptosis was markedly increased. Furthermore, co-transfection with miR-138-5p mimics reversed the effects caused by overexpression of circ_101238. Treatment of keloid fibroblasts with si-CDK6 counteracted the biological behavior changes induced by miR-138-5p inhibitors. Additionally, transfection with LV-CDK6 reversed the effects caused by miR-138-5p mimics. Taken together, the results of the present study demonstrated that circ_101238 was upregulated in keloid tissues in comparison with normal tissues and that circ_101238 knockdown inhibited cell proliferation, while promoting apoptosis of keloid fibroblasts via the miR-138-5p/CDK6 axis. These results suggest that circ_101238 may serve as a promising therapeutic candidate for keloid therapy and that circ_101238/miR-138-5p/CDK6 signaling has the potential to regulate the growth of keloid fibroblasts.

Circular RNA: A novel potential biomarker for skin diseases

Circular RNA (circRNA) has been classified as noncoding RNA with a covalent closed continuous loop, the 3'and 5' ends of which are normally joined together to increase its own stability. More recently, circRNA has been shown to encode proteins and may be involved in the regulation of gene transcription. This provides more evidence for the involvement of circRNA in disease progression. Accumulating investigations have found that the expression of many circRNAs is abnormal in plenty of skin diseases such as malignant melanoma, psoriasis, and abnormal wound healing. Herein, in addition to the summary of recent studies on the nuclear export, N⁶-methyladenosine (m⁶A) modification, degradation, and other biogenesis and properties of circRNA, we highlight the importance of circRNAin skin diseases. Although their exact roles and mechanisms in most skin disease remain preliminary, circRNAs have potential applications as diagnostic biomarkers and novel therapeutic targets for skin diseases due to its structural and functional properties (stability, specificity and sensitivity), which is worthy of deeper exploration and greater research efforts.