Gene expression in human keloids is altered from dermal to chondrocytic and osteogenic lineage

Familial Spontaneous Keloids: Examining Thoracic Manifestations in Two Brothers

Keloids are complex fibroproliferative disorders with diverse clinical presentations. Spontaneous keloids (SKs) represent a rare subtype that emerges without any known preceding traumatic event. This report presents a case of familial spontaneous keloids appearing on the thoracic region in two brothers with no prior history of trauma or keloid occurrence in other family members. The lesions exhibited progressive growth over several years but responded to cycles of triamcinolone treatment. This case underscores an unusual spontaneous occurrence of keloids in the thoracic region of two siblings, highlighting the potential genetic predisposition in the aetiology of these lesions. Additionally, this instance reinforces the concept that keloids can develop spontaneously without any apparent trauma in the affected area.

RNA-seq unravels distinct expression profiles of keloids and Dupuytren's disease

Keloid scars and Dupuytren's disease are two common, chronic, and incurable fibroproliferative disorders that, among other shared clinical features, may induce joint contractures. We employed bulk RNA sequencing to discern potential shared gene expression patterns and underlying pathological pathways between these two conditions. Our aim was to uncover potential molecular targets that could pave the way for novel therapeutic strategies. Differentially expressed genes (DEGs) were functionally annotated using Gene Ontology (GO) terms and the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways with the Database for Annotation, Visualization, and Integrated Discovery (DAVID). The protein-protein-interaction (PPI) networks were constructed by using the Search Tool for the Retrieval of Interacting Genes (STRING) and Cytoscape. The Molecular Complex Detection (MCODE) plugin was used for downstream analysis of the PPI networks. A total of 1922 DEGs were identified within Dupuytren's and keloid samples, yet no overlapping gene expression profiles were detected. Significantly enriched GO terms were related to skin development and tendon formation in keloid scars and Dupuytren's disease, respectively. The PPI network analysis revealed 10 genes and the module analysis provided six protein networks, which might play an integral part in disease development. These genes, including CDH1, ERBB2, CASP3 and RPS27A, may serve as new targets for future research to develop biomarkers and/or therapeutic agents.

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.

Evidence of inter- and intra-keloid heterogeneity through analysis of dermal fibroblasts: A new insight in deciphering keloid physiopathology

Keloid scars are hypertrophic and proliferating pathological scars extending beyond the initial lesion and without tendency to regression. Usually, keloids are considered and treated as a single entity but clinical observations suggest heterogeneity in keloid morphologies with distinction of superficial/extensive and nodular entities. Within a keloid, heterogeneity could also be detected between superficial and deep dermis or centre and periphery. Focusing on fibroblasts as main actors of keloid formation, we aimed at evaluating intra- and inter-keloid fibroblast heterogeneity by analysing their gene expression and functional capacities (proliferation, migration, traction forces), in order to improve our understanding of keloid pathogenesis. Fibroblasts were obtained from centre, periphery, papillary and reticular dermis from extensive or nodular keloids and were compared to control fibroblasts from healthy skin. Transcriptional profiling of fibroblasts identified a total of 834 differentially expressed genes between nodular and extensive keloids. Quantification of ECM-associated gene expression by RT-qPCR brought evidence that central reticular fibroblasts of nodular keloids are the population which synthesize higher levels of mature collagens, TGFβ, HIF1α and αSMA as compared to control skin, suggesting that this central deep region is the nucleus of ECM production with a centrifuge extension in keloids. Although no significant variations were found for basal proliferation, migration of peripheral fibroblasts from extensive keloids was higher than that of central ones and from nodular cells. Moreover, these peripheral fibroblasts from extensive keloids exhibited higher traction forces than central cells, control fibroblasts and nodular ones. Altogether, studying fibroblast features demonstrate keloid heterogeneity, leading to a better understanding of keloid pathophysiology and treatment adaptation.

The Role of Extracellular Matrix in Wound Healing

BACKGROUND

Extracellular matrix communicates with surrounding cells to maintain skin homeostasis and modulate multiple cellular processes including wound healing.

OBJECTIVE

To elucidate the dynamic composition and potential roles of extracellular matrix in normal skin, wound healing process, and abnormal skin scarring.

MATERIALS AND METHODS

Literature review was performed to identify relevant publications pertaining to the extracellular matrix deposition in normal skin and wound healing process, as well as in abnormal scars.

RESULTS

A summary of the matrix components in normal skin is presented. Their primary roles in hemostasis, inflammation, proliferation, and remodeling phases of wound healing are briefly discussed. Identification of novel extracellular matrix in keloids is also provided.

CONCLUSION

Abnormal scarring remains a challenging condition with unmet satisfactory treatments. Illumination of extracellular matrix composition and functions in wound healing process will allow for the development of targeted therapies in the future.

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.

Risk single-nucleotide polymorphism-mediated enhancer-promoter interaction drives keloids through long noncoding RNA down expressed in keloids

BACKGROUND

Keloids represent one extreme of aberrant dermal wound healing and are characterized by fibroblast hyperproliferation and excessive deposition of extracellular matrix. Genetics is a major factor for predisposition to keloids and genome-wide association study has identified a single-nucleotide polymorphism (SNP) rs873549 at 1q41 as a susceptibility locus. The SNP rs873549, and the SNPs in strong linkage disequilibrium (LD) with rs873549, may be involved in keloid development. However, the functional significance of these SNPs in keloid pathogenesis remains elusive.

OBJECTIVES

To investigate the function and mechanism of SNP rs873549 and the SNPs in strong LD with rs873549 in keloids.

METHODS

SNPs in strong LD with rs873549 were analysed using Haploview. The expression levels of the genes near the susceptibility locus were analysed using quantitative real-time polymerase chain reaction. The interaction between rs1348270-containing enhancer and the long noncoding RNA down expressed in keloids (DEIK) (formerly RP11-400N13.1) promoter in fibroblasts was investigated using chromosome conformation capture. The enhancer activity of the rs1348270 locus was evaluated using luciferase reporter assay. Knockdown experiments were used to explore the function of DEIK in keloids. RNA-Seq was performed to investigate the mechanism by which DEIK regulates the expression of collagens POSTN and COMP.

RESULTS

rs1348270, an enhancer-located SNP in strong LD with rs873549, mediated looping with the promoter of DEIK. The risk variant was associated with decreased enhancer-promoter interaction and DEIK down-expression in keloids. Mechanistically, downregulation of DEIK increased the expression of collagens POSTN and COMP through upregulating BMP2. Furthermore, correlation analysis revealed that DEIK expression was inversely correlated with BMP2, POSTN and COMP expression in both keloid and normal fibroblasts.

CONCLUSIONS

Our findings suggest that the risk variant rs1348270 is located in an enhancer and is associated with the downregulation of DEIK in keloids, and that downregulation of DEIK increases the expression of collagens POSTN and COMP through BMP2 in keloid fibroblasts. These findings will help to provide a more thorough understanding of the role played by genetic factors in keloid development and may lead to new strategies for screening and therapy in keloid-susceptible populations.

Single-cell RNA-seq reveals cellular heterogeneity from deep fascia in patients with acute compartment syndrome

Introduction

High stress in the compartment surrounded by the deep fascia can cause acute compartment syndrome (ACS) that may result in necrosis of the limbs. The study aims to investigate the cellular heterogeneity of the deep fascia in ACS patients by single-cell RNA sequencing (scRNA-seq).

Methods

We collected deep fascia samples from patients with ACS (high-stress group, HG, n=3) and patients receiving thigh amputation due to osteosarcoma (normal-stress group, NG, n=3). We utilized ultrasound and scanning electron microscopy to observe the morphologic change of the deep fascia, used multiplex staining and multispectral imaging to explore immune cell infiltration, and applied scRNA-seq to investigate the cellular heterogeneity of the deep fascia and to identify differentially expressed genes.

Results

Notably, we identified GZMK⁺interferon-act CD4 central memory T cells as a specific high-stress compartment subcluster expressing interferon-related genes. Additionally, the changes in the proportions of inflammation-related subclusters, such as the increased proportion of M2 macrophages and decreased proportion of M1 macrophages, may play crucial roles in the balance of pro-inflammatory and anti-inflammatory in the development of ACS. Furthermore, we found that heat shock protein genes were highly expressed but metal ion-related genes (S100 family and metallothionein family) were down-regulated in various subpopulations under high stress.

Conclusions

We identified a high stress-specific subcluster and variations in immune cells and fibroblast subclusters, as well as their differentially expressed genes, in ACS patients. Our findings reveal the functions of the deep fascia in the pathophysiology of ACS, providing new approaches for its treatment and prevention.

Scleraxis and fibrosis in the pressure-overloaded heart

AIMS

In response to pro-fibrotic signals, scleraxis regulates cardiac fibroblast activation in vitro via transcriptional control of key fibrosis genes such as collagen and fibronectin; however, its role in vivo is unknown. The present study assessed the impact of scleraxis loss on fibroblast activation, cardiac fibrosis, and dysfunction in pressure overload-induced heart failure.

METHODS AND RESULTS

Scleraxis expression was upregulated in the hearts of non-ischemic dilated cardiomyopathy patients, and in mice subjected to pressure overload by transverse aortic constriction (TAC). Tamoxifen-inducible fibroblast-specific scleraxis knockout (Scx-fKO) completely attenuated cardiac fibrosis, and significantly improved cardiac systolic function and ventricular remodelling, following TAC compared to Scx+/+ TAC mice, concomitant with attenuation of fibroblast activation. Scleraxis deletion, after the establishment of cardiac fibrosis, attenuated the further functional decline observed in Scx+/+ mice, with a reduction in cardiac myofibroblasts. Notably, scleraxis knockout reduced pressure overload-induced mortality from 33% to zero, without affecting the degree of cardiac hypertrophy. Scleraxis directly regulated transcription of the myofibroblast marker periostin, and cardiac fibroblasts lacking scleraxis failed to upregulate periostin synthesis and secretion in response to pro-fibrotic transforming growth factor β.

CONCLUSION

Scleraxis governs fibroblast activation in pressure overload-induced heart failure, and scleraxis knockout attenuated fibrosis and improved cardiac function and survival. These findings identify scleraxis as a viable target for the development of novel anti-fibrotic treatments.

Increased expression of bone/cartilage-associated genes and core transcription factors in keloids by RNA sequencing

Fibroblasts in keloids undergo cell identity transition with altered transcriptional characteristics. However, the core transcription factors driving this cellular reprogramming remain largely unknown. Here, we report the results of transcriptional profiling from 48 keloid and 24 control dermal tissues. We identified 1187 upregulated differentially expressed genes (foldchange > 2, false discovery rate < 0.05) in keloids, which were mainly enriched in extracellular matrix organization and bone/cartilage development, with significantly increased expression of bone/cartilage-associated collagens (COL5A1, COL10A1, and COL11A1) and glycoproteins (ACAN, COMP, and SPARC). Deconvolution analysis also revealed significantly increased composition of osteoblasts in keloid dermis. A total of 92 upregulated transcription factors were screened out from differentially expressed genes and mainly enriched in transcription process and skeleton development. Additional sequencing of six keloid individuals with multiple regions and intersection further narrow the list with 10 transcription factors. Finally, AEBP1, CREB3L1, RUNX2, and ZNF469 have been identified as candidate core regulators in promoting the gaining of bone/cartilage-like characteristics in keloids. RNA-sequencing of full-skin keloids consolidated the existence of these four transcription factors. Immunohistochemistry was employed to verify the expression of AEBP1, CREB3L1, RUNX2, and ZNF469 in keloid fibroblasts. In conclusion, we bioinformatically discovered the increased expression of bone/cartilage-associated genes and candidate core transcription factors in keloids. Our findings promise to provide molecular clues to develop novel therapeutic modalities against skin fibrosis.

Tissue chondrification and ossification in keloids with primary report of five cases

Keloid is commonly regarded as a benign skin tumour. Some keloids clinically exhibit hard tissue texture similar to that of cartilage or bone. We hypothesized that the keloid pathological niche environment is likely to induce keloid MSCs towards chondrogenic or osteogenic differentiation and leads to cartilage or bone‐like tissue formation. The differences in tissue ossification, histology, mechanical properties, abnormal extracellular matrices and chondrogenic/osteogenic gene expression among sclerous keloids (SKs), regular keloids (RKs) and normal skins (NKs) were carefully examined. The sporadic ossified islets existed in SK group whereas no ossified/chondrified islet was found in other groups by micro‐CT reconstruction. H&E, Masson trichrome and safranin O staining revealed lacuna‐like structures in SKs, which were featured as bone/cartilage histology. Immunohistochemical staining showed overproduction of osteoprotegerin, type I and III collagen in SK group but similar production level of aggrecan among three groups. The biomechanical analysis demonstrated the weakest compliance of SK tissues. In addition, SK fibroblasts exhibited a relatively slower proliferation rate but higher expression levels of osteogenic and chondrogenic genes among all three groups. These cell populations also showed the strongest potential for lineage transformation. In conclusion, we first reported the presence of ossified and chondrified matrices in some extremely hard keloids in the present study.

Bioinformatics study on different gene expression profiles of fibroblasts and vascular endothelial cells in keloids

Keloid is a benign fibroproliferative skin tumor. The respective functions of fibroblasts and vascular endothelial cells in keloid have not been fully studied. The purpose of this study is to identify the respective roles and key genes of fibroblasts and vascular endothelial cells in keloids, which can be used as new targets for diagnosis or treatment.The microarray datasets of keloid fibroblasts and vascular endothelial cells were obtained from the Gene Expression Omnibus (GEO) database. Differentially expressed genes (DEGs) were screened out. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) were used for functional enrichment analysis. The search tool for retrieval of interacting genes and Cytoscape were used to construct protein-protein interaction (PPI) networks and analyze gene modules. The hub genes were screened out, and the relevant interaction networks and biological process analysis were carried out.In fibroblasts, the DEGs were significantly enriched in collagen fibril organization, extracellular matrix organization and ECM-receptor interaction. The PPI network was constructed, and the most significant module was selected, which is mainly enriched in ECM-receptor interaction. In vascular endothelial cells, the DEGs were significantly enriched in cytokine activity, growth factor activity and transforming growth factor-β (TGF-β) signaling pathway. Module analysis was mainly enriched in TGF-β signaling pathway. Hub genes were screened out separately.In summary, the DEGs and hub genes discovered in this study may help us understand the molecular mechanisms of keloid, and provide potential targets for diagnosis and treatment.

Procollagen C-proteinase enhancer-1 (PCPE-1), a potential biomarker and therapeutic target for fibrosis

The correct balance between collagen synthesis and degradation is essential for almost every aspect of life, from development to healthy aging, reproduction and wound healing. When this balance is compromised by external or internal stress signals, it very often leads to disease as is the case in fibrotic conditions. Fibrosis occurs in the context of defective tissue repair and is characterized by the excessive, aberrant and debilitating deposition of fibril-forming collagens. Therefore, the numerous proteins involved in the biosynthesis of fibrillar collagens represent a potential and still underexploited source of therapeutic targets to prevent fibrosis. One such target is procollagen C-proteinase enhancer-1 (PCPE-1) which has the unique ability to accelerate procollagen maturation by BMP-1/tolloid-like proteinases (BTPs) and contributes to trigger collagen fibrillogenesis, without interfering with other BTP functions or the activities of other extracellular metalloproteinases. This role is achieved through a fine-tuned mechanism of action that is close to being elucidated and offers promising perspectives for drug design. Finally, the in vivo data accumulated in recent years also confirm that PCPE-1 overexpression is a general feature and early marker of fibrosis. In this review, we describe the results which presently support the driving role of PCPE-1 in fibrosis and discuss the questions that remain to be solved to validate its use as a biomarker or therapeutic target.

Single-cell RNA-seq reveals fibroblast heterogeneity and increased mesenchymal fibroblasts in human fibrotic skin diseases

Fibrotic skin disease represents a major global healthcare burden, characterized by fibroblast hyperproliferation and excessive accumulation of extracellular matrix. Fibroblasts are found to be heterogeneous in multiple fibrotic diseases, but fibroblast heterogeneity in fibrotic skin diseases is not well characterized. In this study, we explore fibroblast heterogeneity in keloid, a paradigm of fibrotic skin diseases, by using single-cell RNA-seq. Our results indicate that keloid fibroblasts can be divided into 4 subpopulations: secretory-papillary, secretory-reticular, mesenchymal and pro-inflammatory. Interestingly, the percentage of mesenchymal fibroblast subpopulation is significantly increased in keloid compared to normal scar. Functional studies indicate that mesenchymal fibroblasts are crucial for collagen overexpression in keloid. Increased mesenchymal fibroblast subpopulation is also found in another fibrotic skin disease, scleroderma, suggesting this is a broad mechanism for skin fibrosis. These findings will help us better understand skin fibrotic pathogenesis, and provide potential targets for fibrotic disease therapies.

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.

Keloid tissue analysis discredits a role for myofibroblasts in disease pathogenesis

Myofibroblasts, renowned for their contractility and extracellular matrix production, are widely considered the key effector cells for nearly all scars resulting from tissue repair processes, ranging from normal scars to extreme fibrosis. For example, it is often assumed that myofibroblasts underpin the characteristics of keloid scars, which are debilitating pathological skin scars lacking effective treatments because of a poor understanding of the disease mechanisms. Here, we present primary and published transcriptional and histological evidence that myofibroblasts are not consistently present in primary keloid lesions, and when alpha-smooth muscle actin (αSMA)-positive cells are detected, they are not greater in number or expressing more αSMA than in normal or hypertrophic scars. In conclusion, keloid scars do not appear to require αSMA-positive myofibroblasts; continuing to consider keloids on a quantitative spectrum with normal or hypertrophic scars, with αSMA serving as a biomarker of disease severity, is hindering advancement of understanding and therapy development.

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.

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.

NF-κB activation persists into the remodeling phase of tendon healing and promotes myofibroblast survival

Although inflammation is necessary during the early phases of tissue repair, persistent inflammation contributes to fibrosis. Acute tendon injuries often heal through a fibrotic mechanism, which impedes regeneration and functional recovery. Because inflammation mediated by nuclear factor κB (NF-κB) signaling is implicated in this process, we examined the spatial, temporal, and cell type-specific activation profile of canonical NF-κB signaling during tendon healing. NF-κB signaling was maintained through all phases of tendon healing in mice, including the remodeling phase, and tenocytes and myofibroblasts from the Scleraxis (Scx) lineage were the predominant populations that retained NF-κB activation into the late stages of repair. We confirmed persistent NF-κB activation in myofibroblasts in human tendon scar tissue. Deleting the canonical NF-κB kinase, IKKβ, in Scx-lineage cells in mice increased apoptosis and the deposition of the matrix protein periostin during the late stages of tendon repair, suggesting that persistent NF-κB signaling may facilitate myofibroblast survival and fibrotic progression. Consistent with this, myofibroblasts in human tendon scar samples displayed enhanced prosurvival signaling compared to control tissue. Together, these data suggest that NF-κB may contribute to fibrotic tendon healing through both inflammation-dependent and inflammation-independent functions, such as NF-κB-mediated cell survival.

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.

Small Leucine-Rich Proteoglycans in Skin Wound Healing

Healing of cutaneous wounds is a complex and well-coordinated process requiring cooperation among multiple cells from different lineages and delicately orchestrated signaling transduction of a diversity of growth factors, cytokines, and extracellular matrix (ECM) at the wound site. Most skin wound healing in adults is imperfect, characterized by scar formation which results in significant functional and psychological sequelae. Thus, the reconstruction of the damaged skin to its original state is of concern to doctors and scientists. Beyond the traditional treatments such as corticosteroid injection and radiation therapy, several growth factors or cytokines-based anti-scarring products are being or have been tested in clinical trials to optimize skin wound healing. Unfortunately, all have been unsatisfactory to date. Currently, accumulating evidence suggests that the ECM not only functions as the structural component of the tissue but also actively modulates signal transduction and regulates cellular behaviors, and thus, ECM should be considered as an alternative target for wound management pharmacotherapy. Of particular interest are small leucine-rich proteoglycans (SLRPs), a group of the ECM, which exist in a wide range of connecting tissues, including the skin. This manuscript summarizes the most current knowledge of SLRPs regarding their spatial-temporal expression in the skin, as well as lessons learned from the genetically modified animal models simulating human skin pathologies. In this review, particular focus is given on the diverse roles of SLRP in skin wound healing, such as anti-inflammation, pro-angiogenesis, pro-migration, pro-contraction, and orchestrate transforming growth factor (TGF)β signal transduction, since cumulative investigations have indicated their therapeutic potential on reducing scar formation in cutaneous wounds. By conducting this review, we intend to gain insight into the potential application of SLRPs in cutaneous wound healing management which may pave the way for the development of a new generation of pharmaceuticals to benefit the patients suffering from skin wounds and their sequelae.

Sox9 in mouse urogenital sinus epithelium mediates elongation of prostatic buds and expression of genes involved in epithelial cell migration

Previous studies identified Sox9 as a critical mediator of prostate development but the precise stage when Sox9 acts had not been determined. A genetic approach was used to delete Sox9 from mouse urogenital sinus epithelium (UGE) prior to prostate specification. All prostatic bud types (anterior, dorsolateral and ventral) were stunted in Sox9 conditional knockouts (cKOs) even though the number of prostatic buds did not differ from that of controls. We concluded that Sox9 is required for prostatic bud elongation and compared control male, control female, Sox9 cKO male and Sox9 cKO female UGE transcriptomes to identify potential molecular mediators. We identified 702 sex-dependent and 95 Sox9-dependent genes. Thirty-one genes were expressed in both a sex- and Sox9-dependent pattern. A comparison of Sox9 cKO female vs control female UGE transcriptomes revealed 74 Sox9-dependent genes, some of which also function in cell migration. SOX9 regulates, directly or indirectly, a largely different profile of genes in male and female UGE. Eighty-three percent of Sox9-dependent genes in male UGE were not Sox9-dependent in female UGE. Only 16 genes were Sox9-dependent in the UGE of both sexes and seven had cell migration functions. These results support the notion that Sox9 promotes cell migration activities needed for prostate ductal elongation.

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.

Cardiac Fibroblast to Myofibroblast Phenotype Conversion-An Unexploited Therapeutic Target

Fibrosis occurs when the synthesis of extracellular matrix outpaces its degradation, and over time can negatively impact tissue and organ function. In the case of cardiac fibrosis, contraction and relaxation of the heart can be impaired to the point of precipitating heart failure, while at the same time fibrosis can result in arrhythmias due to altered electrical properties of the myocardium. The critical event in the evolution of cardiac fibrosis is the phenotype conversion of cardiac fibroblasts to their overly-active counterparts, myofibroblasts: cells demarked by their expression of novel markers such as periostin, by their gain of contractile activity, and by their pronounced and prolonged increase in the production of extracellular matrix components such as collagens. The phenotype change is dramatic, and can be triggered by many stimuli, including mechanical force, inflammatory cytokines, and growth factors. This review will explore fibroblast to myofibroblast transition mechanisms and will consider the therapeutic potential of targeting this process as a means to arrest or even reverse cardiac fibrosis.

Understanding Keloid Pathobiology From a Quasi-Neoplastic Perspective: Less of a Scar and More of a Chronic Inflammatory Disease With Cancer-Like Tendencies

Keloids are considered as benign fibroproliferative skin tumors growing beyond the site of the original dermal injury. Although traditionally viewed as a form of skin scarring, keloids display many cancer-like characteristics such as progressive uncontrolled growth, lack of spontaneous regression and extremely high rates of recurrence. Phenotypically, keloids are consistent with non-malignant dermal tumors that are due to the excessive overproduction of collagen which never metastasize. Within the remit of keloid pathobiology, there is increasing evidence for the various interplay of neoplastic-promoting and suppressing factors, which may explain its aggressive clinical behavior. Amongst the most compelling parallels between keloids and cancer are their shared cellular bioenergetics, epigenetic methylation profiles and epithelial-to-mesenchymal transition amongst other disease biological (genotypic and phenotypic) behaviors. This review explores the quasi-neoplastic or cancer-like properties of keloids and highlights areas for future study.

Regeneration of Dermis: Scarring and Cells Involved

There are many studies on certain skin cell specifications and their contribution to wound healing. In this review, we provide an overview of dermal cell heterogeneity and their participation in skin repair, scar formation, and in the composition of skin substitutes. The papillary, reticular, and hair follicle associated fibroblasts differ not only topographically, but also functionally. Human skin has a number of particular characteristics that are different from murine skin. This should be taken into account in experimental procedures. Dermal cells react differently to skin wounding, remodel the extracellular matrix in their own manner, and convert to myofibroblasts to different extents. Recent studies indicate a special role of papillary fibroblasts in the favorable outcome of wound healing and epithelial-mesenchyme interactions. Neofolliculogenesis can substantially reduce scarring. The role of hair follicle mesenchyme cells in skin repair and possible therapeutic applications is discussed. Participation of dermal cell types in wound healing is described, with the addition of possible mechanisms underlying different outcomes in embryonic and adult tissues in the context of cell population characteristics and extracellular matrix composition and properties. Dermal white adipose tissue involvement in wound healing is also overviewed. Characteristics of myofibroblasts and their activity in scar formation is extensively discussed. Cellular mechanisms of scarring and possible ways for its prevention are highlighted. Data on keloid cells are provided with emphasis on their specific characteristics. We also discuss the contribution of tissue tension to the scar formation as well as the criteria and effectiveness of skin substitutes in skin reconstruction. Special attention is given to the properties of skin substitutes in terms of cell composition and the ability to prevent scarring.

Histological evaluation of tendon formation using a scaffold-free three-dimensional-bioprinted construct of human dermal fibroblasts under in vitro static tensile culture

Introduction

Tendon tissue engineering requires scaffold-free techniques for safe and long-term clinical applications and to explore alternative cell sources to tenocytes. Therefore, we histologically assessed tendon formation in a scaffold-free Bio-three-dimensional (3D) construct developed from normal human dermal fibroblasts (NHDFs) using our Bio-3D printer system under tensile culture in vitro.

Methods

Scaffold-free ring-like tissues were constructed from 120 multicellular spheroids comprising NHDFs using a bio-3D printer. Ring-like tissues were cultured in vitro under static tensile-loading with or without in-house tensile devices (tension-loaded and tension-free groups), with increases in tensile strength applied weekly to the tensile-loaded group. After a 4 or 8-week culture on the device, we evaluated histological findings according to tendon-maturing score and immunohistological findings of the middle portion of the tissues for both groups (n = 4, respectively).

Results

Histology of the tension-loaded group revealed longitudinally aligned collagen fibers with increased collagen deposition and spindle-shaped cells with prolonged culture. By contrast, the tension-free group showed no organized cell arrangement or collagen fiber structure. Additionally, the tension-loaded group showed a significantly improved tendon-maturing score as compared with that for the tension-free group at week 8. Moreover, immunohistochemistry revealed tenascin C distribution with a parallel arrangement in the tensile-loading direction at week 8 in the tension-loaded group, which exhibited stronger scleraxis-staining intensity than that observed in the tension-free group at weeks 4 and 8.

Conclusions

The NHDF-generated scaffold-free Bio-3D construct underwent remodeling and formed tendon-like structures under tensile culture in vitro.

Gene Expression of Neurotrophins and Their Receptors in Keloids

The aim of this study was to assess gene expression of neurotrophins and their receptors in keloids. Skin samples of normal skin and keloids were obtained from patients in the control (n = 12) and keloid (n = 12) groups, respectively. Ribonucleic acid was extracted from the skin specimens, purified, evaluated by spectrophotometry, and used to synthesize complementary DNA. Real-time quantitative polymerase chain reaction analysis of 84 human neurotrophin genes and their receptors was performed. Twelve genes, including heat shock 27-kDa protein 1, gastrin-releasing peptide receptor, corticotropin-releasing hormone receptor 2, neuropeptide Y Y2 receptor, interleukin 6 signal transducer, nerve growth factor, metallothionein 3, B-cell chronic lymphocytic leukemia/lymphoma 2, cholecystokinin A receptor, persephin, galanin receptor 2, and fibroblast growth factor receptor 3, were down-regulated in keloid tissue compared with normal skin. The genes 27-kDa heat shock protein 1, gastrin-releasing peptide receptor, corticotropin-releasing hormone receptor 2, nerve growth factor, metallothionein 3, B-cell chronic lymphocytic leukemia/lymphoma 2, and persephin protein were considered priority genes associated with keloid formation.

HtrA1 Is Specifically Up-Regulated in Active Keloid Lesions and Stimulates Keloid Development

Keloids occur after failure of the wound healing process; inflammation persists, and various treatments are ineffective. Keloid pathogenesis is still unclear. We have previously analysed the gene expression profiles in keloid tissue and found that HtrA1 was markedly up-regulated in the keloid lesions. HtrA1 is a serine protease suggested to play a role in the pathogenesis of various diseases, including age-related macular degeneration and osteoarthritis, by modulating extracellular matrix or cell surface proteins. We analysed HtrA1 localization and its role in keloid pathogenesis. Thirty keloid patients and twelve unrelated patients were enrolled for in situ hybridization, immunohistochemical, western blot, and cell proliferation analyses. Fibroblast-like cells expressed more HtrA1 in active keloid lesions than in surrounding lesions. The proportion of HtrA1-positive cells in keloids was significantly higher than that in normal skin, and HtrA1 protein was up-regulated relative to normal skin. Silencing HtrA1 gene expression significantly suppressed cell proliferation. HtrA1 was highly expressed in keloid tissues, and the suppression of the HtrA1 gene inhibited the proliferation of keloid-derived fibroblasts. HtrA1 may promote keloid development by accelerating cell proliferation and remodelling keloid-specific extracellular matrix or cell surface molecules. HtrA1 is suggested to have an important role in keloid pathogenesis.

Caveolin-1 Controls Hyperresponsiveness to Mechanical Stimuli and Fibrogenesis-Associated RUNX2 Activation in Keloid Fibroblasts

Keloids are pathological scars characterized by excessive extracellular matrix production that are prone to form in body sites with increased skin tension. CAV1, the principal coat protein of caveolae, has been associated with the regulation of cell mechanics, including cell softening and loss of stiffness sensing ability in NIH3T3 fibroblasts. Although CAV1 is present in low amounts in keloid fibroblasts (KFs), the causal association between CAV1 down-regulation and its aberrant responses to mechanical stimuli remain unclear. In this study, atomic force microscopy showed that KFs were softer than normal fibroblasts with a loss of stiffness sensing. The decrease of CAV1 contributed to the hyperactivation of fibrogenesis-associated RUNX2, a transcription factor germane to osteogenesis/chondrogenesis, and increased migratory ability in KFs. Treatment of KFs with trichostatin A, which increased the acetylation level of histone H3, increased CAV1 and decreased RUNX2 and fibronectin. Trichostatin A treatment also resulted in cell stiffening and decreased migratory ability in KFs. Collectively, these results suggest a role for CAV1 down-regulation in linking the aberrant responsiveness to mechanical stimulation and extracellular matrix accumulation with the progression of keloids, findings that may lead to new developments in the prevention and treatment of keloid scarring.

Angiopoietin-like 4 induces a β-catenin-mediated upregulation of ID3 in fibroblasts to reduce scar collagen expression

In adult skin wounds, collagen expression rapidly re-establishes the skin barrier, although the resultant scar is aesthetically and functionally inferior to unwounded tissue. Although TGFβ signaling and fibroblasts are known to be responsible for scar-associated collagen production, there are currently no prophylactic treatments for scar management. Fibroblasts in crosstalk with wound keratinocytes orchestrate collagen expression, although the precise paracrine pathways involved remain poorly understood. Herein, we showed that the matricellular protein, angiopoietin-like 4 (ANGPTL4), accelerated wound closure and reduced collagen expression in diabetic and ANGPTL4-knockout mice. Similar observations were made in wild-type rat wounds. Using human fibroblasts as a preclinical model for mechanistic studies, we systematically elucidated that ANGPTL4 binds to cadherin-11, releasing membrane-bound β-catenin which translocate to the nucleus and transcriptionally upregulate the expression of Inhibitor of DNA-binding/differentiation protein 3 (ID3). ID3 interacts with scleraxis, a basic helix-loop-helix transcription factor, to inhibit scar-associated collagen types 1α2 and 3α1 production by fibroblasts. We also showed ANGPTL4 interaction with cadherin-11 in human scar tissue. Our findings highlight a central role for matricellular proteins such as ANGPTL4 in the attenuation of collagen expression and may have a broader implication for other fibrotic pathologies.

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

Keloid disease (KD) is a fibroproliferative cutaneous tumour characterised by heterogeneity, excess collagen deposition and aggressive local invasion. Lack of a validated animal model and resistance to a multitude of current therapies has resulted in unsatisfactory clinical outcomes of KD management. In order to address KD from a new perspective, we applied for the first time a site-specific in situ microdissection and gene expression profiling approach, through combined laser capture microdissection and transcriptomic array. The aim here was to analyse the utility of this approach compared with established methods of investigation, including whole tissue biopsy and monolayer cell culture techniques. This study was designed to approach KD from a hypothesis-free and compartment-specific angle, using state-of-the-art microdissection and gene expression profiling technology. We sought to characterise expression differences between specific keloid lesional sites and elucidate potential contributions of significantly dysregulated genes to mechanisms underlying keloid pathobiology, thus informing future explorative research into KD. Here, we highlight the advantages of our in situ microdissection strategy in generating expression data with improved sensitivity and accuracy over traditional methods. This methodological approach supports an active role for the epidermis in the pathogenesis of KD through identification of genes and upstream regulators implicated in epithelial-mesenchymal transition, inflammation and immune modulation. We describe dermal expression patterns crucial to collagen deposition that are associated with TGFβ-mediated signalling, which have not previously been examined in KD. Additionally, this study supports the previously proposed presence of a cancer-like stem cell population in KD and explores the possible contribution of gene dysregulation to the resistance of KD to conventional therapy. Through this innovative in situ microdissection gene profiling approach, we provide better-defined gene signatures of distinct KD regions, thereby addressing KD heterogeneity, facilitating differential diagnosis with other cutaneous fibroses via transcriptional fingerprinting, and highlighting key areas for future KD research.

Aberrant connective tissue differentiation towards cartilage and bone underlies human keloids in African Americans

Keloids are benign fibroproliferative tumors more frequently found among African Americans. Until now, keloid etiopathogenesis is not fully understood. To characterize keloids in African Americans, we performed transcriptional profiling of biopsies from large chronic keloids, adjacent non-lesional (NL) skin (n=3) and a newly formed keloid lesion using Affymetrix HGU133 2.0 plus arrays. Quantitative RT-PCR (qRT-PCR) and immunohistochemistry (IHC) staining were performed to confirm increased expression of relevant genes. We identified 1202 upregulated and 961 downregulated differentially expressed genes (DEGs) between keloid and NL skin; 1819 up- and 1867 downregulated DEGs between newly formed keloid and NL skin; and 492 up- and 775 downregulated DEGs between chronic and newly formed keloid (fold change >2, false discovery rate <0.05). Many of the top upregulated DEGs between chronic keloid and NL skin and between newly formed keloid and NL skin are involved in bone/cartilage formation including Fibrillin 2 (FBN2), Collagen type X alpha 1, Asporin (ASPN), Cadherin 11 (CDH11), Bone morphogenic protein 1 (BMP1), Secreted phosphoprotein 1 and Runt-related transcription factor 2 (RUNX2). qRT-PCR confirmed significant (P<.05) upregulation of BMP1, RUNX2, CDH11 and FBN2 in chronic keloid compared to NL skin. IHC staining showed increased protein expression of ASPN, CDH11, BMP1 and RUNX2 on chronic and newly formed keloid compared to NL skin. Our study shows that large keloids in African Americans represent a dysplasia of cutaneous connective tissue towards immature cartilage or bone differentiation. The phenotype is potentially regulated by overexpression of RUNX2. This knowledge may give insights to guide the development of better treatment for the disease in the future.

Master regulators in primary skin fibroblast fate reprogramming in a human ex vivo model of chronic wounds

Fibroblasts are important players in regulating tissue homeostasis. In the dermis, they are involved in wound healing where they differentiate into contractile myofibroblasts leading to wound closure. In nonhealing chronic wounds, fibroblasts fail to undertake differentiation. We established and used a human ex vivo model of chronic wounds where fibroblasts can undergo normal myofibroblast differentiation, or take on a nondifferentiable pathological state. At the whole genome scale, we identified the genes that are differentially regulated in these two cell fates. By coupling the search of evolutionary conserved regulatory elements with global gene network expression changes, we identified transcription factors (TF) potentially involved in myofibroblast differentiation, and constructed a network of relationship between these key factors. Among these, we found that TCF4, SOX9, EGR2, and FOXS1 are major regulators of fibroblast to myofibroblast differentiation. Conversely, down-regulation of MEOX2, SIX2, and MAF causes reprogramming of fibroblasts to myofibroblasts even in absence of TGF-β, the natural inducer of myofibroblast differentiation. These results provide insight into the fibroblast differentiation program and reveal a TF network essential for cellular reprogramming. They could lead to the development of new therapeutics to treat fibroblast-related human pathologies.

The Shear Wave Velocity on Elastography Correlates with the Clinical Symptoms and Histopathological Features of Keloids

Background:

Keloids present as red, painful lesions causing serious functional and cosmetic problems; however, there is no consensus regarding tools for objectively evaluating keloids. To demonstrate the utility of shear wave elastography in keloids, we investigated the correlations between clinical symptoms, ultrasound shear wave velocity, and histopathological findings.

Methods:

Three patients with keloids containing both red hypertrophic and mature areas were evaluated using the shear wave velocity and histopathological findings.

Results:

The results indicate that the shear wave velocity is high in active hypertrophic areas and low in mature areas. The areas with high elastography values exhibited numerous fibrillar collagenous matrices forming a whorled pattern with hyalinized tissue on hematoxylin-eosin staining corresponding with metachromasia on toluidine blue staining. In the mature area, the collagen fibers were oriented parallel to each other without metachromasia.

Conclusions:

Shear wave elastography provides quantitative estimates of tissue stiffness that correlate with the clinical symptoms and histopathological findings of the keloid lesions and can be used to assess the activity of keloids.

Protein-protein interaction network of gene expression in the hydrocortisone-treated keloid

OBJECTIVES

In order to explore the molecular mechanism of hydrocortisone in keloid tissue, the gene expression profiles of keloid samples treated with hydrocortisone were subjected to bioinformatics analysis.

METHODS

Firstly, the gene expression profiles (GSE7890) of five samples of keloid treated with hydrocortisone and five untreated keloid samples were downloaded from the Gene Expression Omnibus (GEO) database. Secondly, data were preprocessed using packages in R language and differentially expressed genes (DEGs) were screened using a significance analysis of microarrays (SAM) protocol. Thirdly, the DEGs were subjected to gene ontology (GO) function and KEGG pathway enrichment analysis. Finally, the interactions of DEGs in samples of keloid treated with hydrocortisone were explored in a human protein-protein interaction (PPI) network, and sub-modules of the DEGs interaction network were analyzed using Cytoscape software.

RESULTS

Based on the analysis, 572 DEGs in the hydrocortisone-treated samples were screened; most of these were involved in the signal transduction and cell cycle. Furthermore, three critical genes in the module, including COL1A1, NID1, and PRELP, were screened in the PPI network analysis.

CONCLUSIONS

These findings enhance understanding of the pathogenesis of the keloid and provide references for keloid therapy.

Identification of biomarkers involved in differential profiling of hypertrophic and keloid scars versus normal skin

Among raised dermal scar types, keloid (KS) and hypertrophic scars (HS) are considered to present clinical similarities, but there are no known specific biomarkers that allow both scar types to be easily distinguished. Development and progression of raised dermal scars comprises the activation of several molecular pathways and cell defence mechanisms leading to elevated extracellular matrix component synthesis, delayed apoptosis, altered migration and differentiation. Therefore, the aim here was to identify biomarkers that may differentiate between KS and HS compared to normal skin (NS). To achieve this aim, NS (n = 14), KS (n = 14) and HS (n = 14) biopsies were evaluated using histology by H&E staining. Tissue biopsies and primary fibroblasts (passages 0-4) were employed to assess the gene expression levels of 21 biomarkers selected from our previous microarray studies using qRT-PCR. Finally, protein expression was evaluated using In-Cell Western Blotting in primary fibroblasts (p 0-4). Our results demonstrated that out of the 21 biomarkers screened at mRNA and protein levels, α2β1-integrin, Hsp27, PAI-2, MMP-19 and CGRP showed significantly higher expression (p < 0.05) in KS compared to NS and HS. Additionally, these five key biomarkers were found to be significantly higher (p < 0.05) at mRNA level in KS taken from the sternum, a region known to be subjected to high mechanical forces in the body during the performance of daily movements. In conclusion, our findings offer potential molecular targets in raised dermal scars differentiation. Future targeted research may allow provision of diagnostic and prognostic markers in keloid versus hypertrophic scars.

Genome wide gene expression analysis of the posterior capsule in patients with osteoarthritis and knee flexion contracture

OBJECTIVE

Knee flexion contractures (KFC) are limitations in the ability to fully extend the knee joint. In people with knee osteoarthritis (OA), KFC are common, impair function, and worsen outcomes after arthroplasty. In KFC, the posterior knee capsule is believed to play a key role, but the pathophysiology remains poorly understood. We sought to identify gene expression differences in the posterior knee capsule of patients with OA with and without KFC.

METHODS

Capsule tissue was obtained from the knees of 12 subjects diagnosed with advanced-stage OA at the time of knee arthroplasty surgery. The presence or absence of KFC allocated patients into 2 groups using a case-control design. Genomewide capsular gene expression was compared between the 2 patient groups. Confirmation of differential expression of the corresponding proteins was performed by immunohistochemistry on tissue sections.

RESULTS

There were no significant demographic differences between the patients with OA with KFC and without KFC save for reduced extension in their surgical knee (p<0.01). KFC patients showed a 6.4-fold decrease in CSN1S1 (p=0.017) gene expression and a 3.7-, 2.0-, and 2.6-fold increase in CHAD, Sox9, and Cyr61 gene expression, respectively (p=0.001, 0.004, 0.001, respectively). There were corresponding increases in protein levels for chondroadherin, sex determining region Y-box 9, and casein alphaS1 (all p<0.05). Functional analysis of the differentially expressed genes indicated a strong association with pathways related to the extracellular matrix and to tissue fibrosis.

CONCLUSION

Posterior capsules in endstage OA knees with KFC exhibited differential expression of 4 genes all previously documented to be associated with tissue fibrosis.

A tale of 2 tissues: the overlapping role of scleraxis in tendons and the heart

Tissue integrity in the face of external physical forces requires the production of a strong extracellular matrix (ECM) composed primarily of the protein collagen. Tendons and the heart both withstand large and changing physical forces, and emerging evidence suggests that the transcription factor scleraxis plays a central role in responding to these forces by directly regulating the production of ECM components and (or) by determining the fate of matrix-producing cell types. Thus, despite the highly disparate inherent nature of these tissues, a common response mechanism may exist to govern the development, growth, and remodeling of the ECM in response to external force.

Keloid-derived keratinocytes exhibit an abnormal gene expression profile consistent with a distinct causal role in keloid pathology

Keloids are disfiguring scars that extend beyond the original wound borders and resist treatment. Keloids exhibit excessive extracellular matrix deposition, although the underlying mechanisms remain unclear. To better understand the molecular basis of keloid scarring, here we define the genomic profiles of keloid fibroblasts and keratinocytes. In both cell types, keloid-derived cells exhibit differential expression of genes encompassing a diverse set of functional categories. Strikingly, keloid keratinocytes exhibited decreased expression of a set of transcription factor, cell adhesion, and intermediate filament genes essential for normal epidermal morphology. Conversely, they exhibit elevated expression of genes associated with wound healing, cellular motility, and vascular development. A substantial number of genes involved in epithelial-mesenchymal transition were also up-regulated in keloid keratinocytes, implicating this process in keloid pathology. Furthermore, keloid keratinocytes displayed significantly higher migration rates than normal keratinocytes in vitro and reduced expression of desmosomal proteins in vivo. Previous studies suggested that keratinocytes contribute to keloid scarring by regulating extracellular matrix production in fibroblasts. Our current results show fundamental abnormalities in keloid keratinocytes, suggesting they have a profoundly more direct role in keloid scarring than previously appreciated. Therefore, development of novel therapies should target both fibroblast and keratinocyte populations for increased efficacy.

GENE PROFILING: IMPLICATIONS IN DERMATOLOGY

DNA microarrays are capable of following the level of expression of, virtually, all genes in a human tissue. This has been employed to determine the aberrant gene expression profiles in many skin diseases, including ultraviolet light damage, inflammatory processes and cancers. Because of its accessibility, skin also served as one of the initial targets of basic research using DNA microarrays. Both the epidermis and dermis have been extensively investigated. Development of bed-side uses of DNA arrays, and the concomitant price reduction of the materials and methods of microarray analyses, holds great promise for improved diagnosis, treatment and prevention of dermatologic disorders.

Sox9 plays multiple roles in the lung epithelium during branching morphogenesis

Lung branching morphogenesis is a highly orchestrated process that gives rise to the complex network of gas-exchanging units in the adult lung. Intricate regulation of signaling pathways, transcription factors, and epithelial-mesenchymal cross-talk are critical to ensuring branching morphogenesis occurs properly. Here, we describe a role for the transcription factor Sox9 during lung branching morphogenesis. Sox9 is expressed at the distal tips of the branching epithelium in a highly dynamic manner as branching occurs and is down-regulated starting at embryonic day 16.5, concurrent with the onset of terminal differentiation of type 1 and type 2 alveolar cells. Using epithelial-specific genetic loss- and gain-of-function approaches, our results demonstrate that Sox9 controls multiple aspects of lung branching. Fine regulation of Sox9 levels is required to balance proliferation and differentiation of epithelial tip progenitor cells, and loss of Sox9 leads to direct and indirect cellular defects including extracellular matrix defects, cytoskeletal disorganization, and aberrant epithelial movement. Our evidence shows that unlike other endoderm-derived epithelial tissues, such as the intestine, Wnt/β-catenin signaling does not regulate Sox9 expression in the lung. We conclude that Sox9 collectively promotes proper branching morphogenesis by controlling the balance between proliferation and differentiation and regulating the extracellular matrix.

A snapshot of gene expression signatures generated using microarray datasets associated with excessive scarring

OBJECTIVE

The aim of this study was to examine the gene expression signatures of 2 types of excessive scarring, keloid and hypertrophic scar (HS), through the integrated bioinformatics analysis of multiple published gene expression profile datasets.

METHODS

A literature search of microarray data published in focusing on keloid and HS was performed. The microarray data were reanalyzed to identify the common significantly dysregulated (CSD) genes. The experimental and statistical parameters of the studies were systematically evaluated to reveal any influences on the consensus findings among the studies. Overrepresentation analysis of gene ontology (GO) categories and pathways was used to explore the significantly dysregulated genes functionally associated with the pathogenesis of excessive scarring.

RESULTS

Seven published microarray studies on keloid and 4 studies on HS were identified. A total of 64 CSD genes were identified in keloid; 9 upregulated CSD genes were identified in HS. The 48 consistently dysregulated genes that overlapped in least 1 keloid study and 1 HS study were defined as the CSD genes in excessive scarring. The differences in the variables associated with the study protocols and data management were systematically documented and evaluated. Activated GO categories and pathways related to skeletal development, binding, extracellular matrix-receptor interaction, and adhesion were found to have significance in excessive scarring, implying a common pathological basis for keloid and HS formation. Notably, the GO categories related to cancer and the TGF-beta signaling pathway were significantly enriched in keloids.

CONCLUSIONS

As gene signatures and molecular markers of excessive scarring, the identified CSD genes may be particularly relevant to disease pathogenesis and serve as new therapeutic targets.

Connective tissue growth factor causes EMT-like cell fate changes in vivo and in vitro

Connective tissue growth factor (CTGF) plays an important role in the pathogenesis of chronic fibrotic diseases. However, the mechanism by which paracrine effects of CTGF control the cell fate of neighboring epithelial cells is not known. In this study, we investigated the paracrine effects of CTGF overexpressed in fibroblasts of Col1a2-CTGF transgenic mice on epithelial cells of skin and lung. The skin and lungs of Col1a2-CTGF transgenic mice were examined for phenotypic markers of epithelial activation and differentiation and stimulation of signal transduction pathways. In addition to an expansion of the dermal compartment in Col1a2-CTGF transgenic mice, the epidermis was characterized by focal hyperplasia, and basal cells stained positive for αSMA, Snail, S100A4 and Sox9, indicating that these cells had undergone a change in their genetic program. Activation of phosphorylated p38 and phosphorylated Erk1/2 was observed in the granular and cornified layers of the skin. Lung fibrosis was associated with a marked increase in cells co-expressing epithelial and mesenchymal markers in the lesional and unaffected lung tissue of Col1a2-CTGF mice. In epithelial cells treated with TGFβ, CTGF-specific siRNA-mediated knockdown suppressed Snail, Sox9, S100A4 protein levels and restored E-cadherin levels. Both adenoviral expression of CTGF in epithelial cells and treatment with recombinant CTGF induced EMT-like morphological changes and expression of α-SMA. Our in vivo and in vitro data supports the notion that CTGF expression in mesenchymal cells in the skin and lungs can cause changes in the differentiation program of adjacent epithelial cells. We speculate that these changes might contribute to fibrogenesis.

Chondroitinase injection improves keloid pathology by reorganizing the extracellular matrix with regenerated elastic fibers

Keloids are a proliferative fibrotic disease characterized by abnormal accumulation of extracellular matrix in the dermis. Keloid lesions lack skin plasticity due to deficiencies in elastic fiber formation in the extracellular matrix. The loss of elastic fiber is caused by excessive accumulation of chondroitin sulfate (CS), a sulfated glycosaminoglycan. However, there is no radical cure for keloids. Using a model system, we show herein that treatment of keloid tissues with chondroitinase ABC, an enzyme that specifically digests CS, improves clinical features of keloids. Keloid tissues obtained from patients were grafted on nude mice, and chondroitinase ABC was injected into the grafted keloid tissues. Chondroitinase ABC treatment significantly reduced the volume of keloid implants concomitant with recovery of elastic fiber formation. These results suggest that chondroitinase ABC injection is an effective therapy for keloid.

Common threads in cardiac fibrosis, infarct scar formation, and wound healing

Wound healing, cardiac fibrosis, and infarct scar development, while possessing distinct features, share a number of key functional similarities, including extracellular matrix synthesis and remodeling by fibroblasts and myofibroblasts. Understanding the underlying mechanisms that are common to these processes may suggest novel therapeutic approaches for pathologic situations such as fibrosis, or defective wound healing such as hypertrophic scarring or keloid formation. This manuscript will briefly review the major steps of wound healing, and will contrast this process with how cardiac infarct scar formation or interstitial fibrosis occurs. The feasibility of targeting common pro-fibrotic growth factor signaling pathways will be discussed. Finally, the potential exploitation of novel regulators of wound healing and fibrosis (ski and scleraxis), will be examined.