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

In the face and neck, keloid scar distribution is related to skin thickness and stiffness changes associated with movement

Keloid scars tend to occur in high-tension sites due to mechanical stimuli that are involved in their development. To date, a detailed analysis of keloid distribution focused specifically on facial and neck areas has not been reported, and limited literature exists as to the related mechanical factors. To rectify this deficiency of knowledge, we first quantified the facial and neck keloid distribution observed clinically in 113 patients. Subsequently, we performed a rigorous investigation into the mechanical factors and their associated changes at these anatomic sites in healthy volunteers without a history of pathologic scarring. The association between keloid-predilection sites and sebaceous gland-dense and acne-prone sites was also examined. To assess skin stretch, thickness and stiffness, VECTRA, ultrasound and indentometer were utilised. Baseline skin stiffness and thickness were measured, as well as the magnitude of change in these values associated with facial expression and postural changes. Within the face and neck, keloids were most common near the mandibular angle (41.3%) and lateral submental (20.0%) regions. These areas of increased keloid incidence were not associated with areas more dense in sebaceous glands, nor linked consistently with acne-susceptible regions. Binomial logistic regression revealed that changes in skin stiffness and thickness related to postural changes significantly predicted keloid distribution. Skin stiffness and thickness changes related to prolonged mechanical forces (postural changes) are most pronounced at sites of high keloid predilection. This finding further elucidates the means by which skin stretch and tension are related to keloid development. As a more detailed analysis of mechanical forces on facial and neck skin, this study evaluates the nuances of multiple skin-mechanical properties, and their changes in a three-dimensional framework. Such factors may be critical to better understanding keloid progression and development in the face and neck.

Understanding the Mechanical Forces on the Sacrum Can Help Optimize Flap-based Pilonidal Sinus Reconstruction

Background

Pilonidal sinus can be treated with excision and flap reconstruction, but treatment is often complicated by wound dehiscence, infection, and recurrence. Understanding the mechanical forces on the sacrococcygeal area during posture change could help guide optimal flap choice.

Methods

Sixteen volunteers underwent measurements of skin-stretching, pressure, and shear stress on the sacrum when sitting relative to standing. Skin-stretching was measured by drawing a 4 × 4 cm square on the sacrum and measuring the vertical, horizontal, and diagonal axes. Pressure and shear stress was measured at six sacral points with a device. The data analysis highlighted the potential of the superior gluteal artery perforator (SGAP) flap for dissipating mechanical forces. Ten pilonidal sinus cases treated with SGAP flaps were retrospectively reviewed for 6-month outcomes.

Results

Sitting is associated with high stretching tension in the horizontal direction [estimated marginal mean (95% confidence intervals) = 17.3% (15.4%-22.6%)]. The lower sacrum experienced the highest pressure [106.6 (96.6-116.5) mm Hg] and shear stress [11.6 (9.7-13.5) N] during sitting. The transposed SGAP flap was deemed to be optimal for releasing the horizontal tension and providing sufficient subcutaneous tissue for ameliorating pressure/shear stress during sitting. It also has high blood flow and can therefore be used with large lesions. Moreover, its donor site is above the high-pressure/stress lower sacrum. Retrospective analysis showed that no patients experienced complications.

Conclusions

Sitting is associated with high mechanical forces on the sacrococcygeal skin. The transposed SGAP flap may ameliorate these forces and thereby reduce the risk of complications of pilonidal sinus reconstruction for large defects.

Low-Frequency Ultrasound Sensitive Piezo1 Channels Regulate Keloid-Related Characteristics of Fibroblasts

Keloids are benign fibroproliferative tumors that severely diminish the quality of life due to discomfort, dysfunction, and disfigurement. Recently, ultrasound technology as a noninvasive adjuvant therapy is developed to optimize treatment protocols. However, the biophysical mechanisms have not yet been fully elucidated. Here, it is proposed that piezo-type mechanosensitive ion channel component 1 (Piezo1) plays an important role in low-frequency sonophoresis (LFS) induced mechanical transduction pathways that trigger downstream cellular signaling processes. It is demonstrated that patient-derived primary keloid fibroblasts (PKF), NIH 3T3, and HFF-1 cell migration are inhibited, and PKF apoptosis is significantly increased by LFS stimulation. And the effects of LFS is diminished by the application of GsMTx-4, the selective inhibitor of Piezo1, and the knockdown of Piezo1. More importantly, the effects of LFS can be imitated by Yoda1, an agonist of Piezo1 channels. Establishing a patient-derived xenograft keloid implantation mouse model further verified these results, as LFS significantly decreased the volume and weight of the keloids. Moreover, blocking the Piezo1 channel impaired the effectiveness of LFS treatment. These results suggest that LFS inhibits the malignant characteristics of keloids by activating the Piezo1 channel, thus providing a theoretical basis for improving the clinical treatment of keloids.

Targeting Nuclear Mechanics Mitigates the Fibroblast Invasiveness in Pathological Dermal Scars Induced by Matrix Stiffening

Pathological dermal scars such as keloids present significant clinical challenges lacking effective treatment options. Given the distinctive feature of highly stiffened scar tissues, deciphering how matrix mechanics regulate pathological progression can inform new therapeutic strategies. Here, it is shown that pathological dermal scar keloid fibroblasts display unique metamorphoses to stiffened matrix. Compared to normal fibroblasts, keloid fibroblasts show high sensitivity to stiffness rather than biochemical stimulation, activating cytoskeletal-to-nuclear mechanosensing molecules. Notably, keloid fibroblasts on stiff matrices exhibit nuclear softening, concomitant with reduced lamin A/C expression, and disrupted anchoring of lamina-associated chromatin. This nuclear softening, combined with weak adhesion and high contractility, facilitates the invasive migration of keloid fibroblasts through confining matrices. Inhibiting lamin A/C-driven nuclear softening, via lamin A/C overexpression or actin disruption, mitigates such invasiveness of keloid fibroblasts. These findings highlight the significance of the nuclear mechanics of keloid fibroblasts in scar pathogenesis and propose lamin A/C as a potential therapeutic target for managing pathological scars.

The effects of systemic diseases, genetic disorders and lifestyle on keloids

Keloid are a fibroproliferative disorder caused by abnormal healing of skin, specifically reticular dermis, when subjected to pathological or inflammatory scars demonstrating redness, elevation above the skin surface, extension beyond the original wound margins and resulting in an unappealing cosmetic appearance. The severity of keloids and risk of developing keloids scars are subjected to elevation by other contributing factors such as systemic diseases, general health conditions, genetic disorders, lifestyle and natural environment. In particular, recently, daily physical work interpreted into mechanical force as well as the interplay between mechanical factors such as stress, strain and stiffness have been reported to strongly modulate the cellular behaviour of keloid formation, affect their location and shape in keloids. Herein, we review the extensive literature on the effects of these factors on keloids and the contributing predisposing mechanisms. Early understanding of these participating factors and their effects in developing keloids may raise the patient awareness in preventing keloids incidence and controlling its severity. Moreover, further studies into their association with keloids as well as considering strategies to control such factors may help clinicians to prevent keloids and widen the therapeutic options.

Postoperative Scar Management Protocol for Asian Patients

BACKGROUND

Postoperative scar formation remains a morbidity for patients even with the advent of minimally invasive techniques. Furthermore, the significant difference between the Asian and Caucasian skin results in poorer postoperative scar outcomes in Asians, supporting the need for an evidence-based scar management protocol.

METHODS

Following a literature review of the PubMed and the Cochrane databases over the past 10 years, we constructed a novel postoperative scar management protocol for the Asian skin, utilized in a Singaporean tertiary healthcare institution.

RESULTS

We describe a timeline-based scar protocol from the point of skin closure to a minimum of 1 year of follow-up. We support the use of intraoperative botulinum toxin for selected high-risk individuals upon skin closure with a follow-up regimen in the postoperative setting. For recalcitrant keloids, we have described a multimodal therapy comprising elements of intralesional steroids, botulinum toxin, lasers, surgery, and radiotherapy.

CONCLUSIONS

A consolidated postoperative scar management protocol provides the necessary guidance for improved scar outcomes in the Asian skin. There is inherent potential in expanding the protocol to include post-traumatic and burn wounds or support other skin types including the Caucasian skin.

NO LEVEL ASSIGNED

This journal requires that authors assign a level of evidence to each submission to which Evidence-Based Medicine rankings are applicable. This excludes Review Articles, Book Reviews, and manuscripts that concern Basic Science, Animal Studies, Cadaver Studies, and Experimental Studies. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

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.

Positive feedback loops between fibroblasts and the mechanical environment contribute to dermal fibrosis

Dermal fibrosis is characterized by excessive deposition of extracellular matrix in the dermis and affects millions of people worldwide and causes limited movement, disfigurement and psychological distress in patients. Fibroblast dysfunction of plays a central role in the pathogenesis of dermal fibrosis and is controlled by distinct factors. Recent studies support the hypothesis that fibroblasts can drive matrix deposition and stiffening, which in turn can exacerbate the functional dysregulation of fibroblasts. Ultimately, through a positive feedback loop, uncontrolled pathological fibrosis develops. This review aims to summarize the phenomenon and mechanism of the positive feedback loop in dermal fibrosis, and discuss potential therapeutic targets to help further elucidate the pathogenesis of dermal fibrosis and develop therapeutic strategies. In this review, fibroblast-derived compositional and structural changes in the ECM that lead to altered mechanical properties are briefly discussed. We focus on the mechanisms by which mechanical cues participate in dermal fibrosis progression. The mechanosensors discussed in the review include integrins, DDRs, proteoglycans, and mechanosensitive ion channels. The FAK, ERK, Akt, and Rho pathways, as well as transcription factors, including MRTF and YAP/TAZ, are also discussed. In addition, we describe stiffness-induced biological changes in the ECM on fibroblasts that contribute to the formation of a positive feedback loop. Finally, we discuss therapeutic strategies to treat the vicious cycle and present important suggestions for researchers conducting in-depth research.

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.

Congress Report on the Second World Congress of Global Scar Society with Scar Academy and Japan Scar Workshop

Pathological scars (including keloids, hypertrophic scars, and scar contractures) are present with high severity among certain populations, particularly in Asians and Africans who are highly prone to develop scars. Understanding the patho-mechanism that underlies scarring, such as mechanosignaling, systemic, and genetic factors, as well as optimal surgical techniques and integrated noninvasive therapeutic methods can guide clinicians to develop treatment protocols that can overcome these issues. This report summarizes a congress at Pacifico Yokohama (Conference Center) on December 19, 2021 involving researchers and clinicians from diverse disciplines who convened to discuss current clinical, preclinical, and most recent research advances in understanding pathological scarring, keloid and hypertrophic scar management, and research progress in wound healing. Presenters described the advances in scar therapies, understanding scarring mechanisms, and scar prevention and assessments tools. Moreover, presenters addressed the challenges during the COVID-19 pandemic and using telemedicine in management of scar patients.

Involvement of caveolin-1 in skin diseases

The skin is the outermost layer and largest organ in the human body. Since the skin interfaces with the environment, it has a variety of roles, including providing a protective barrier against external factors, regulating body temperature, and retaining water in the body. It is also involved in the immune system, interacting with immune cells residing in the dermis. Caveolin-1 (CAV-1) is essential for caveolae formation and has multiple functions including endocytosis, lipid homeostasis, and signal transduction. CAV-1 is known to interact with a variety of signaling molecules and receptors and may influence cell proliferation and migration. Several skin-related disorders, especially those of the inflammatory or hyperproliferative type such as skin cancers, psoriasis, fibrosis, and wound healing, are reported to be associated with aberrant CAV-1 expression. In this review, we have explored CAV-1 involvement in skin physiology and skin diseases.

Role of Inflammasomes in Keloids and Hypertrophic Scars-Lessons Learned from Chronic Diabetic Wounds and Skin Fibrosis

Keloids and hypertrophic scars are pathological cutaneous scars. They arise from excessive wound healing, which induces chronic dermal inflammation and results in overwhelming fibroblast production of extracellular matrix. Their etiology is unclear. Inflammasomes are multiprotein complexes that are important in proinflammatory innate-immune system responses. We asked whether inflammasomes participate in pathological scarring by examining the literature on scarring, diabetic wounds (also characterized by chronic inflammation), and systemic sclerosis (also marked by fibrosis). Pathological scars are predominantly populated by anti-inflammatory M2 macrophages and recent literature hints that this could be driven by non-canonical inflammasome signaling. Diabetic-wound healing associates with inflammasome activation in immune (macrophages) and non-immune (keratinocytes) cells. Fibrotic conditions associate with inflammasome activation and inflammasome-induced transition of epithelial cells/endothelial cells/macrophages into myofibroblasts that deposit excessive extracellular matrix. Studies suggest that mechanical stimuli activate inflammasomes via the cytoskeleton and that mechanotransduction-inflammasome crosstalk is involved in fibrosis. Further research should examine (i) the roles that various inflammasome types in macrophages, (myo)fibroblasts, and other cell types play in keloid development and (ii) how mechanical stimuli interact with inflammasomes and thereby drive scar growth. Such research is likely to significantly advance our understanding of pathological scarring and aid the development of new therapeutic strategies.

Hemodynamics and Vascular Histology of Keloid Tissues and Anatomy of Nearby Blood Vessels

Keloids are red' invasive scars that are driven by chronic inflammation in the reticular dermis. The role of blood vessels in keloid behavior remains poorly understood. In the present study with 32 keloid patients, we examined the hemodynamics of keloid tissue, the anatomy of the blood vessels feeding and draining the keloids, and the vascular histology of keloids.

Methods

Ten patients with large anterior chest keloids underwent near-infrared spectroscopy, which measured regional saturation of oxygen and total hemoglobin index in the keloid and surrounding skin. Another 10 patients with large chest keloids and three healthy volunteers underwent multidetector-low computed tomography. The extirpated chest keloids of 12 patients were subjected to histology with optical, CD31 immunohistochemical, and electron microscopy.

Results

All keloids had a low regional saturation of oxygen and a high total hemoglobin index, which is indicative of blood congestion. Multidetector-low computed tomography revealed dilation of the arteries and veins that were respectively feeding and draining the keloid leading edge. Hematoxylin-eosin staining and CD31 immunohistochemisty revealed considerable neovascularization in the keloid leading edge but not in the center. Electron microscopy showed that the lumens of many vessels in the keloid center appeared to be occluded or narrowed.

Conclusions

Keloids seem to be congested because of increased neovascularization and arterial inflow at the leading edge and blocked outflow due to vascular destruction in the center. The surrounding veins seem to expand in response to this congested state. Methods that improve the blood circulation in keloids may be effective therapies.

Biomechanical Regulatory Factors and Therapeutic Targets in Keloid Fibrosis

Keloids are fibroproliferative skin disorder caused by abnormal healing of injured or irritated skin and are characterized by excessive extracellular matrix (ECM) synthesis and deposition, which results in excessive collagen disorders and calcinosis, increasing the remodeling and stiffness of keloid matrix. The pathogenesis of keloid is very complex, and may include changes in cell function, genetics, inflammation, and other factors. In this review, we aim to discuss the role of biomechanical factors in keloid formation. Mechanical stimulation can lead to excessive proliferation of wound fibroblasts, deposition of ECM, secretion of more pro-fibrosis factors, and continuous increase of keloid matrix stiffness. Matrix mechanics resulting from increased matrix stiffness further activates the fibrotic phenotype of keloid fibroblasts, thus forming a loop that continuously invades the surrounding normal tissue. In this process, mechanical force is one of the initial factors of keloid formation, and matrix mechanics leads to further keloid development. Next, we summarized the mechanotransduction pathways involved in the formation of keloids, such as TGF-β/Smad signaling pathway, integrin signaling pathway, YAP/TAZ signaling pathway, and calcium ion pathway. Finally, some potential biomechanics-based therapeutic concepts and strategies are described in detail. Taken together, these findings underscore the importance of biomechanical factors in the formation and progression of keloids and highlight their regulatory value. These findings may help facilitate the development of pharmacological interventions that can ultimately prevent and reduce keloid formation and progression.

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.

The Most Current Algorithms for the Treatment and Prevention of Hypertrophic Scars and Keloids: A 2020 Update of the Algorithms Published 10 Years Ago

BACKGROUND

In 2010, this Journal published my comprehensive review of the literature on hypertrophic scars and keloids. In that article, I presented evidence-based algorithms for the prevention and treatment of these refractory pathologic scars. In the ensuing decade, substantial progress has been made in the field, including many new randomized controlled trials. To reflect this, I have updated my review.

METHODS

All studies were evaluated for methodologic quality. Baseline characteristics of patients were extracted along with the interventions and their outcomes. Systematic reviews, meta-analyses, and comprehensive reviews were included if available.

RESULTS

Risk factors that promote hypertrophic scar and keloid growth include local factors (tension on the wound/scar), systemic factors (e.g., hypertension), genetic factors (e.g., single-nucleotide polymorphisms), and lifestyle factors. Treatment of hypertrophic scars depends on scar contracture severity: if severe, surgery is the first choice. If not, conservative therapies are indicated. Keloid treatment depends on whether they are small and single or large and multiple. Small and single keloids can be treated radically by surgery with adjuvant therapy (e.g., radiotherapy) or multimodal conservative therapy. For large and multiple keloids, volume- and number-reducing surgery is a choice. Regardless of the treatment(s), patients should be followed up over the long term. Conservative therapies, including gel sheets, tape fixation, topical and injected external agents, oral agents, and makeup therapy, should be administered on a case-by-case basis.

CONCLUSIONS

Randomized controlled trials on pathologic scar management have increased markedly over the past decade. Although these studies suffer from various limitations, they have greatly improved hypertrophic scar and keloid management. Future high-quality trials are likely to improve the current hypertrophic scar and keloid treatment algorithms further.

Skin biomechanics: a potential therapeutic intervention target to reduce scarring

Pathological scarring imposes a major clinical and social burden worldwide. Human cutaneous wounds are responsive to mechanical forces and convert mechanical cues to biochemical signals that eventually promote scarring. To understand the mechanotransduction pathways in cutaneous scarring and develop new mechanotherapy approaches to achieve optimal scarring, the current study highlights the mechanical behavior of unwounded and scarred skin as well as intra- and extracellular mechanisms behind keloid and hypertrophic scars. Additionally, the therapeutic interventions that promote optimal scar healing by mechanical means at the molecular, cellular or tissue level are extensively reviewed. The current literature highlights the significant role of fibroblasts in wound contraction and scar formation via differentiation into myofibroblasts. Thus, understanding myofibroblasts and their responses to mechanical loading allows the development of new scar therapeutics. A review of the current clinical and preclinical studies suggests that existing treatment strategies only reduce scarring on a small scale after wound closure and result in poor functional and aesthetic outcomes. Therefore, the perspective of mechanotherapies needs to consider the application of both mechanical forces and biochemical cues to achieve optimal scarring. Moreover, early intervention is critical in wound management; thus, mechanoregulation should be conducted during the healing process to avoid scar maturation. Future studies should either consider combining mechanical loading (pressure) therapies with tension offloading approaches for scar management or developing more effective early therapies based on contraction-blocking biomaterials for the prevention of pathological scarring.

Dysregulation of DPP4-CXCL12 Balance by TGF-β1/SMAD Pathway Promotes CXCR4+ Inflammatory Cell Infiltration in Keloid Scars

Purpose

Recent studies have confirmed the important role of chronic inflammation in keloid; however, mechanism of chronic inflammation in keloid tissue remains largely unclear, especially the dynamic of infiltrated inflammatory cells.

Patients and Methods

Tissue and blood samples collected from keloid patients and healthy subjects were studied by immunohistochemistry and flow cytometry. Fibroblasts from keloid scars and normal skin were isolated by enzymic digestion.

Results

We found that CXCL12 expression was elevated which was correlated with decreased dipeptidyl peptidase-4 (DPP4) expression in keloid scars relative to mature scars. In vitro studies suggested that autocrine transforming growth factor β1 (TGF-β1) in keloid-derived fibroblasts negatively regulated DPP4 expression which inhibited the reduction of extracellular CXCL12 levels by DPP4. Furthermore, immunofluorescence showed that most fibroblasts in keloid scars were DPP4^lowTGFβ1^high compared with DPP4^highTGFβ1^low fibroblasts in normal skin tissue, which facilitated extracellular CXCL12 accumulation in fibroblasts in keloid scars. Furthermore, we found that most circulating leukocytes in peripheral blood and tissue-infiltrated inflammatory cells in keloid scars expressed the C-X-C motif chemokine receptor 4 (CXCR4) instead of CXCR7, indicating that the chemotaxis driven by CXCL12 is likely to be mediated mainly by CXCR4.

Conclusion

Our study indicated that the TGF-β/DPP4/CXCL12 axis may contribute to chronic inflammation in keloid scars by recruiting inflammatory cells through the CXCR4 receptor.

Fibronectin in development and wound healing

Fibronectin structure and composition regulate contextual cell signaling. Recent advances have been made in understanding fibronectin and its role in tissue organization and repair. This review outlines fibronectin splice variants and their functions, evaluates potential therapeutic strategies targeting or utilizing fibronectin, and concludes by discussing potential future directions to modulate fibronectin function in development and wound healing.

Glucocorticoid counteracts cellular mechanoresponses by LINC01569-dependent glucocorticoid receptor-mediated mRNA decay

Mechanical stimuli on cells and mechanotransduction are essential in many biological and pathological processes. Glucocorticoid is an important hormone, roles, and mechanisms of which in cellular mechanotransduction remain unknown. Here, we report that glucocorticoid counteracted cellular mechanoresponses dependently on a novel long noncoding RNA (lncRNA), LINC01569 Further, LINC01569 mediated glucocorticoid effects on mechanotransduction by destabilizing messenger RNA (mRNA) of mechanosensors including early growth response protein 1 (EGR1), Cbp/P300-interacting transactivator 2 (CITED2), and bone morphogenic protein 7 (BMP7) in glucocorticoid receptor-mediated mRNA decay (GMD) manner. Mechanistically, LINC01569 directly bound to the GMD factor Y-box-binding protein 1 (YBX1). Then, the LINC01569-YBX1 complex was guided to the mRNAs of EGR1, CITED2, and BMP7 through specific LINC01569-mRNA interaction, thereby contributing to the successful assembly of GMD complex and triggering GMD. Our results uncovered roles of glucocorticoid in cellular mechanotransduction and novel lncRNA-dependent GMD machinery and provided potential strategy for early intervention in mechanical disorder-associated diseases.

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

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

The Roles of Inflammation in Keloid and Hypertrophic Scars

The underlying mechanisms of wound healing are complex but inflammation is one of the determining factors. Besides its traditional role in combating against infection upon injury, the characteristics and magnitude of inflammation have dramatic impacts on the pathogenesis of scar. Keloids and hypertrophic scars are pathological scars that result from aberrant wound healing. They are characterized by continuous local inflammation and excessive collagen deposition. In this review, we aim at discussing how dysregulated inflammation contributes to the pathogenesis of scar formation. Immune cells, soluble inflammatory mediators, and the related intracellular signal transduction pathways are our three subtopics encompassing the events occurring in inflammation associated with scar formation. In the end, we enumerate the current and potential medicines and therapeutics for suppressing inflammation and limiting progression to scar. Understanding the initiation, progression, and resolution of inflammation will provide insights into the mechanisms of scar formation and is useful for developing effective treatments.

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.

Combination Therapy Composed of Surgery, Postoperative Radiotherapy, and Wound Self-management for Umbilical Keloids

A universally accepted therapeutic strategy for umbilical keloids has not been determined. Our team has had considerable success with combination therapy composed of surgical excision followed by postoperative radiotherapy and steroid plaster/injection.

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

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

A New Animal Model for Pathological Subcutaneous Fibrosis: Surgical Technique and in vitro Analysis

Fibrosis is a condition that affects the connective tissue in an organ or tissue in the restorative or responsive phase as a result of injury. The consequences of excessive fibrotic tissue growth may lead to various physiological complications of deformity and impairment due to hypertrophic scars, keloids, and tendon adhesion without understating the psychological impact on the patient. However, no method accurately quantifies the rate and pattern of subcutaneous induced hypertrophic fibrosis. We, therefore, devised a rodent excisional model to evaluate the extent of fibrosis with talc. Tissue specimens were set on formalin, and paraffin sections for histological, immunohistochemical, and molecular analysis talc was used to induce the fibroproliferative mechanism typical of hypertrophic scars. This pathway is relevant to the activation of inflammatory and fibrotic agents to stimulate human hypertrophic scarring. This model reproduces morpho-functional features of human hypertrophic scars to investigate scar formation and assess potential anti-scarring therapies.

Adipose-Derived Stromal Cells Seeded on Integra® Dermal Regeneration Template Improve Post-Burn Wound Reconstruction

Fibrosis of burn-related wounds remains an unresolved clinical issue that leads to patient disability. The aim of this study was to assess the efficacy of the transplantation of adipose-derived stromal cells seeded onto a collagen-based matrix in the reconstruction of burn-related scars. Here, we characterized an in vitro interaction between adipose-derived stromal cells and a collagen-based matrix, Integra^®DRT. Our results show that transcription of pro-angiogenic, remodeling, and immunomodulatory factors was more significant in adipose-derived stromal cells than in fibroblasts. Transcription of metalloproteinases 2 and 9 is positively correlated with the collagenolytic activity of the adipose-derived stromal cells seeded onto Integra^®DRT. The increase in the enzymatic activity corresponds to the decrease in the elasticity of the whole construct. Finally, we validated the treatment of a post-excision wound using adipose-derived stromal cells and an Integra^®DRT construct in a 25-year-old woman suffering from burn-related scars. Scarless healing was observed in the area treated by adipose-derived stromal cells and the Integra^®DRT construct but not in the reference area where Integra^®DRT was applied without cells. This clinical observation may be explained by in vitro findings: Enhanced transcription of the vascular endothelial growth factor as well as remodeling of the collagen-based matrix decreased mechanical stress. Our experimental treatment demonstrated that the adipose-derived stromal cells seeded onto Integra^®DRT exhibit valuable properties that may improve post-excision wound healing and facilitate skin regeneration without scars.

The Keloid Disorder: Heterogeneity, Histopathology, Mechanisms and Models

Keloids constitute an abnormal fibroproliferative wound healing response in which raised scar tissue grows excessively and invasively beyond the original wound borders. This review provides a comprehensive overview of several important themes in keloid research: namely keloid histopathology, heterogeneity, pathogenesis, and model systems. Although keloidal collagen versus nodules and α-SMA-immunoreactivity have been considered pathognomonic for keloids versus hypertrophic scars, conflicting results have been reported which will be discussed together with other histopathological keloid characteristics. Importantly, histopathological keloid abnormalities are also present in the keloid epidermis. Heterogeneity between and within keloids exists which is often not considered when interpreting results and may explain discrepancies between studies. At least two distinct keloid phenotypes exist, the superficial-spreading/flat keloids and the bulging/raised keloids. Within keloids, the periphery is often seen as the actively growing margin compared to the more quiescent center, although the opposite has also been reported. Interestingly, the normal skin directly surrounding keloids also shows partial keloid characteristics. Keloids are most likely to occur after an inciting stimulus such as (minor and disproportionate) dermal injury or an inflammatory process (environmental factors) at a keloid-prone anatomical site (topological factors) in a genetically predisposed individual (patient-related factors). The specific cellular abnormalities these various patient, topological and environmental factors generate to ultimately result in keloid scar formation are discussed. Existing keloid models can largely be divided into in vivo and in vitro systems including a number of subdivisions: human/animal, explant/culture, homotypic/heterotypic culture, direct/indirect co-culture, and 3D/monolayer culture. As skin physiology, immunology and wound healing is markedly different in animals and since keloids are exclusive to humans, there is a need for relevant human in vitro models. Of these, the direct co-culture systems that generate full thickness keloid equivalents appear the most promising and will be key to further advance keloid research on its pathogenesis and thereby ultimately advance keloid treatment. Finally, the recent change in keloid nomenclature will be discussed, which has moved away from identifying keloids solely as abnormal scars with a purely cosmetic association toward understanding keloids for the fibroproliferative disorder that they are.

Effects of Electrical Stimulation on Stem Cells

Recent interest in developing new regenerative medicine- and tissue engineering-based treatments has motivated researchers to develop strategies for manipulating stem cells to optimize outcomes in these potentially, game-changing treatments. Cells communicate with each other, and with their surrounding tissues and organs via electrochemical signals. These signals originate from ions passing back and forth through cell membranes and play a key role in regulating cell function during embryonic development, healing, and regeneration. To study the effects of electrical signals on cell function, investigators have exposed cells to exogenous electrical stimulation and have been able to increase, decrease and entirely block cell proliferation, differentiation, migration, alignment, and adherence to scaffold materials. In this review, we discuss research focused on the use of electrical stimulation to manipulate stem cell function with a focus on its incorporation in tissue engineering-based treatments.

Z-plasty and Postoperative Radiotherapy for Upper-arm Keloids: An Analysis of 38 Patients

Therapies for upper arm keloids include surgical excision followed by postoperative radiotherapy, silicone tape stabilization, and steroid plaster. However, a universally accepted therapeutic strategy for upper-arm keloids is lacking.