Novel Insights on Understanding of Keloid Scar: Article Review

HIF-1α promotes the keloid development through the activation of TGF-β/Smad and TLR4/MyD88/NF-κB pathways

A keloid is defined as an overgrowth of the dense fibrous tissues that form around a wound. Since they destroy the vascular network, keloid tissues often exhibit anoxic conditions. Hypoxia-inducible factor-1α (HIF-1α) is a core factor that mediates hypoxia stress responses and regulates the hypoxic cellular and biological behaviors. In this study, we found that the expression level of HIF-1α in keloid tissue was significantly higher than that in the normal skin tissue. Hypoxia-induced HIF-1α expression significantly inhibited cellular apoptosis and promoted cellular proliferation in keloid fibroblasts but not in normal fibroblasts. Specifically, HIF-1α activated the TGF-β/Smad and TLR4/MyD88/NF-κB pathways, and the interaction of these two pathways may promote the development of keloids. Moreover, in vivo experiments showed that the inhibition of HIF-1α significantly reduced the growth of keloids.

CUDC‑907 reverses pathological phenotype of keloid fibroblasts in vitro and in vivo via dual inhibition of PI3K/Akt/mTOR signaling and HDAC2

Keloids are benign skin tumors with a high recurrence rate following surgical excision. Abnormal intracellular signaling is one of the key mechanisms involved in its pathogenesis. Over-activated phosphoinositide 3-kinase/RAC-alpha serine/threonine-protein kinase/mammalian target of rapamycin (PI3K/Akt/mTOR) signaling pathway and overproduction of histone deacetylases 2 (HDAC2) have also been observed in keloid fibroblasts (KFs). The present study aimed to explore the possibility of reversing the KF pathological phenotype using CUDC-907, a dual inhibitor of PI3K/Akt/mTOR pathway and HDACs. KFs and keloid xenografts were treated with CUDC-907 to examine its inhibitory effects on the pathological activities of KFs in vitro and in vivo. CUDC-907 inhibited cell proliferation, migration, invasion and extracellular matrix deposition of in vitro cultured KFs and also suppressed collagen accumulation and disrupted the capillaries of keloid explants ex vivo and in vivo. A mechanistic study of CUDC-907 revealed the initiation of cell cycle arrest at G2/M phase along with the enhanced expression of cyclin-dependent kinase inhibitor 1 and decreased expression of cyclin B in cells treated with CUDC-907. CUDC-907 not only inhibited AKT and mTOR phosphorylation and promoted the acetylation of histone H3, but also significantly inhibited the phosphorylation levels of Smad2/3 and Erk. These preclinical data demonstrating its anti-keloid effects suggest that CUDC-907 may represent a candidate drug for systemic keloid therapy.

Advances in diagnostic methods for keloids and biomarker-targeted fluorescent probes

A keloid is a type of unusually raised scar. Unlike other raised scars, keloids form larger sizes than the wound site due to overgrowth, generally related to various biological factors. To date, only a few diagnostic and therapeutic methods for keloids have been reported. The high recurrence rates and undesirable side effects of keloids, at the end stage, encourage the invention of novel diagnostic tools, in order to cure keloids at an earlier stage. In this review, we summarize the general information about keloid diagnosis, keloid biomarkers, and recently reported fluorescent probes that can sense the key biomarkers of keloids. The focused description of fluorescent probes for keloid biomarkers and the author's perspective give useful insights in order to design the next-generation diagnostic sensing system for keloids.

Aliskiren Attenuates the Inflammatory Response and Wound Healing Process in Diabetic Mice With Periodontal Disease

The aim of this study was to characterize the role of local RAS (renin–angiotensin system) in the inflammatory response of normal (N) and diabetic (D) mice with periodontal disease (PD). Diabetes Mellitus (DM) was induced by peritoneal injection of streptozotocin in Balb/c mice. PD was induced by ligature around the first molar in both N and D, irrespective of whether they were treated with aliskiren (50 mg/kg, Alisk). Mandibles were harvested for histomorphometric analyses, and gingival tissue (GT) was collected to evaluate gene expression and extracellular matrix components (ECM). Immunohistochemical (IHC) analyses were used to localize RAS in GT. The production of C-reactive protein (CRP), IL-1β, CXCL2, and CCL8 was evaluated by enzyme-linked immunosorbent assay (ELISA). Renin was found to exacerbate the inflammation and periodontal bone loss at 14 days after PD, and Alisk inhibited this process in GT of N and D. PD increased CRP, CXCL2, CCL8, and IL-1β production in both animals. Alisk could inhibit CRP, CXCL2, and CCL8 primarily in D animals. However, only CCL8 was decreased in N animals after Alisk pretreatment. PD enhanced expression and production of AGT, ACE, AT1R, and AT2R in both N and D. AT1R expression was higher in D with PD, and AT2R expression was higher in N with PD. ACE2 and receptor Mas (MasR) expression and production was elevated in the control group of both animals. PD inhibited ACE2 in N but not in D. MasR expression was unaffected in both N and D with PD. Alisk reduced expression and production of all RAS components in GT of both animals, except for ACE2 in N. RAS staining was observed in all layers of epithelium, basal cell layer, and lamina propria and was higher in N with PD. Col1a1, Col1a2, Col3a1, and fibronectin (Fn1) were increased in both animals with PD. Alisk inhibited Col1a1 and Fn in both animals, Col1a2 was decreased only in D, while levels of Col3a1 remained unchanged in all animal groups. In conclusion, these data demonstrated the presence and functional role of local RAS in GT, exacerbating the inflammatory response, periodontal bone loss, and wound healing processes in both N and D animal groups. In addition, Alisk was able to significantly reduce gingival inflammation, excessive wound healing processes, and periodontal bone loss.

Toward understanding scarless skin wound healing and pathological scarring

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

Role of Hypoxia Inducible Factor-1 Alpha (HIF-1α) in Cytoglobin Expression and Fibroblast Proliferation of Keloids

BACKGROUND

Keloids are characterized by an overabundance of collagen deposition due to elevated activity and proliferation of fibroblasts, which lead to hypoxic conditions. Adaptation to these conditions is regulated by the transcription factor hypoxia inducible factor-1α (HIF-1α). Cytoglobin (Cygb), a reactive oxygen species scavenger, is a target gene of HIF-1α. In our previous study, we showed that Cygb expression in keloid tissue was correlated with HIF-1α expression. However, whether HIF-1α regulates Cygb expression and the proliferation of keloid fibroblasts remained unclear. Therefore, this study aimed to determine the role of HIF-1α in Cygb expression and fibroblast proliferation of keloids.

METHODS

This was an in vitro study using a primary culture of keloid fibroblasts in which ibuprofen was used to inhibit HIF-1α expression. The expression of HIF-1α and Cygb mRNA were analyzed using quantitative reverse transcriptase polymerase chain reaction (qRT-PCR) methods, and their protein levels were analyzed using an enzyme-linked immunosorbent assay (ELISA). Fibroblast proliferation was analyzed using a Trypan blue exclusion assay.

RESULTS

Inhibition of HIF-1α by ibuprofen decreased Cygb mRNA expression but not in all the samples, followed by a decrease in the protein level of Cygb. There was a positive correlation between the HIF-1α protein and Cygb mRNA, probably due to the regulation of Cygb by HIF-1α at the mRNA level, but not the protein level. The proliferation of keloid fibroblasts was significantly decreased and positively correlated with the HIF-1α protein.

CONCLUSION

HIF-1α regulates Cygb expression and fibroblast proliferation in keloids.

Analysis of Keloid Response to 5-Fluorouracil Treatment and Long-Term Prevention of Keloid Recurrence

Keloids are benign fibroproliferative skin tumors that can cause disfigurement and disability. Although they frequently recur after excision or medical management and can affect 6 to 16 percent of African Americans, there is no gold standard therapy. Keloids are challenging to study because there are no animal or in vitro models of this disorder. This makes it very difficult to validate data from treated tissue samples or cells and develop targeted therapies for this disease. In this study, the authors demonstrate that intralesional 5-fluorouracil injection after keloid excision prevents recurrence for 2 years, with no reported adverse events. The authors analyze the expression of treated and untreated biopsy specimens of the same keloids in their native context to capture insights that may be missed by in vitro cell culture models and correct for intrakeloid variability. Random forest analysis of the microarray data dramatically increased the statistical power of the authors' results, permitting hypothesis-free creation of a gene expression profile of 5-fluorouracil-treated keloids. Through this analysis, the authors found a set of genes, including YAP1 and CCL-2, whose expression changes predict 5-fluorouracil therapy status and include genes that have not previously been associated with keloid biology and are of unknown function. The authors further describe keloid heterogeneity for the first time using multidimensional analysis of their microarray results. The methods and tools the authors developed in this research may overcome some of the challenges in studying keloids and developing effective treatments for this disease. CLINICAL QUESTION/LEVEL OF EVIDENCE:: Therapeutic, V.

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

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

Keloid Formation due to Repetitive Mammographies

A keloid is the result of an abnormal wound healing response to a variety of skin injuries, characterized by a well-circumscribed, firm, irregular, mildly tender, and pink to purple hyperpigmented lump with a glossy surface. The present case reports on excessive formation of keloid due to repetitive mammographies causing symptomatic, cosmetically disturbing symptoms.

Comparison of Fractional CO2 Laser, Verapamil, and Triamcinolone for the Treatment of Keloid

Objective: Scar biology is a territory less understood. The search for ideal treatment of keloid continues. The aim of this study was to compare the role of CO₂ laser, triamcinolone (TAC), and verapamil in the treatment of keloid. Approach: A randomized parallel-group study was conducted in which 60 patients were randomly allocated to three groups from May 2017 to April 2018. First group received fractional CO₂ laser therapy, second group received triamcinolone, and third group received intralesional verapamil. Outcomes were evaluated using Vancouver scar scale score at 3 weekly intervals for 6 months. Results: There was a reduction in scar height, vascularity, and pliability in all the three groups. However, pigmentation was not completely resolved by any of the three modalities. The response was fastest in case of triamcinolone followed by verapamil and laser, which was statistically significant. There was reduction in pain and pruritus in all the three groups and lesser injection site pain with verapamil. There was some amount of charring with CO₂ laser. Innovation: Our study provides evidence that TAC has the fastest response in treating keloids when compared to other modalities. Scar pigmentation is the parameter that is not completely resolved by TAC, verapamil, or CO₂ laser. Conclusion: The study revealed that fractional CO₂ laser and verapamil are as efficient as triamcinolone acetonide (TAC) for treating keloids, except it takes longer for laser and verapamil to act compared to TAC. Verapamil can be used as an alternative treatment modality that is cost-effective with minimal adverse effects.

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

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

Detection of Angiotensin II and AT1 Receptor Concentrations in Keloid and Hypertrophic Scar

Background: Keloid and hypertrophic scars (HTS) are formed by excessive collagen formation. Angiotensin II, through the AT₁ receptor, plays an important role in extracellular matrix production. However, less is known about angiotensin II and AT₁ receptor concentrations in HTS and keloid tissues. Objective: The purpose of this study was to determine the angiotensin II and AT₁ receptor concentrations in keloid, HTS, and normal skin tissues. Methods: Skin biopsy samples from patients with HTS (n=26), keloid (n=20), and normal (n=30) skin tissues were evaluated for angiotensin II and AT₁ receptor concentrations by use of the enzyme-linked immunosorbent assay technique. Results: The angiotensin II concentration in patients with HTS was higher than that in the normal (P<0.0067) and keloid (P>0.9553) groups, while the AT₁ receptor concentration in patients with keloid was higher than that in the HTS (P<0.0001) and normal (P<0.0048) groups. Conclusion: Angiotensin II and AT₁ receptor concentrations could stimulate the formation of HTS and keloid. Angiotensin II receptor blockers and angiotensin-converting enzyme inhibitors may be suitable compounds for the treatment of scar tissue.

Probing endogenous collagen by laser-induced autofluorescence in burn wound biopsies: A pilot study

The focus of the current study was to interrogate the predictive potential of laser-induced autofluorescence (LIAF) by objectively assessing collagen synthesis in burn wound granulation tissues ex vivo. Prior grafting, granulation tissues (20 samples) following burn injury were collected from 17 subjects of age range 18 to 60 years with patient/donor consent and the corresponding autofluorescence spectra were recorded at 325 nm He-Cd laser (≈2 mW) excitations. The resulting endogenous collagen intensity from the above tissue samples was computed by normalizing the nicotinamide adenine dinucleotide levels. In addition, the hydroxyproline content was also estimated biochemically from the same granulation tissues. A comparative assessment of both LIAF and biochemical estimations for endogenous collagen by hydroxyproline resulted in strong positive correlation among them. The above relevant observations suggest that LIAF is equally informative as that of biochemical estimations, in evaluating endogenous collagen content in wound granulation tissues. Thus, it can be concluded that LIAF has the predictive potential, as a noninvasive objective tool to measure the endogenous collagen levels in wound biopsy tissues and provide complementary data conducive for making clinical decisions.

Growth hormone-releasing peptide 6 prevents cutaneous hypertrophic scarring: early mechanistic data from a proteome study

Hypertrophic scars (HTS) and keloids are forms of aberrant cutaneous healing with excessive extracellular matrix (ECM) deposition. Current therapies still fall short and cause undesired effects. We aimed to thoroughly evaluate the ability of growth hormone releasing peptide 6 (GHRP6) to both prevent and reverse cutaneous fibrosis and to acquire the earliest proteome data supporting GHRP6's acute impact on aesthetic wound healing. Two independent sets of experiments addressing prevention and reversion effects were conducted on the classic HTS model in rabbits. In the prevention approach, the wounds were assigned to topically receive GHRP6, triamcinolone acetonide (TA), or vehicle (1% sodium carboxy methylcellulose [CMC]) from day 1 to day 30 post-wounding. The reversion scheme was based on the infiltration of either GHRP6 or sterile saline in mature HTS for 4 consecutive weeks. The incidence and appearance of HTS were systematically monitored. The sub-epidermal fibrotic core area of HTS was ultrasonographically determined, and the scar elevation index was calculated on haematoxylin/eosin-stained, microscopic digitised images. Tissue samples were collected for proteomics after 1 hour of HTS induction and treatment with either GHRP6 or vehicle. GHRP6 prevented the onset of HTS without the untoward reactions induced by the first-line treatment triamcinolone acetonide (TA); however, it failed to significantly reverse mature HTS. The preliminary proteomic study suggests that the anti-fibrotic preventing effect exerted by GHRP6 depends on different pathways involved in lipid metabolism, cytoskeleton arrangements, epidermal cells' differentiation, and ECM dynamics. These results enlighten the potential success of GHRP6 as one of the incoming alternatives for HTS prevention.

Linking Race, Cancer Outcomes, and Tissue Repair

The burden of cancer in the United States is unevenly spread across its different populations, with stark differences in both disease prevalence and outcome on the basis of race and ethnicity. Although a large portion of these differences can be explained by a variety of sociobehavioral and socioeconomic factors, even after these exposures are taken into consideration, considerable disparities persist. In this review, we explore a conceptual framework of biological theories and unifying concepts, based on an evolutionary perspective, that may help better define common guiding principles for exploration of underlying causes of cancer health disparities. The ultimate goal of this conceptual perspective is to outline approaches that may aid in establishing integrated pathway and processes analyses to provide useful insights to guide the development of future interventions. These interventions will improve outcome, increase prevention, and ultimately eliminate all disparities.

Cesarean-Section Scar Endometrioma: A Case Report and Review of the Literature

Endometriomas can occur after any surgery where there is endometrial manipulation, and there are a number of reports of endometriomas developing in the abdominal wall at the site of the Pfannenstiel incision following Cesarean-section. Although this is ultimately a histopathologically-confirmed diagnosis, preoperative imaging including ultrasound, computed tomography, and magnetic resonance imaging may be helpful in the diagnosis and assessment. We report a pathology-confirmed case of Cesarean-section endometrioma with a classic, clinical presentation and imaging findings on computed tomography. A comprehensive literature review and discussion of the multi-modality imaging appearance of Cesarean-section endometrioma is also provided.

Status of M1 and M2 type macrophages in keloid

Macrophages, differentiation from monocytes infiltrated in the wound, have been suggested to be involved and to play an important role in the pathogenesis of wound healing. Nevertheless, no evidence has been established regarding M1 and M2 type macrophages in Keloid. To understand the status of M1 and M2 type macrophages in keloid, immunohistochemistry was performed on 30 cases of Keloid tissues and normal controls, with CD68, typical surface marker for M1 and CD163, well-accepted marker for M2 being immunostained. Meanwhile, the glucocorticoid receptor NR3C1 was also detected. As further confirmation, quantitative real-time PCR was utilized to verify the expression of CD68, CD163 and NR3C1 on mRNA level. It was consistently shown that infiltrated M2 macrophages pronouncedly outnumbered M1 macrophages in the dermis of keloids; and that NR3C1 expression was significantly up-regulated in keloids than that in normal controls. In addition, there was a marked correlation between CD163 and NR3C1 expression. Our results suggest that the number of infiltrated M2 macrophages in the dermis of keloids may be linked to the responsiveness to glucocorticoids in the pathogenesis of keloid.

Intralesional excision with topical intralesional cryotherapy improves the treatment of keloid scarring in a paediatric patient

Recurrent keloid scarring has a significant impact on quality of life. Management is complex, particularly for scars resistant to conventional treatments and in paediatric cases where radiotherapy is not a suitable adjunct to surgical excision. We present the case of a nine-year-old African Caribbean girl with multiple large and recurrent keloid scars on both ears and bilateral sensorineural deafness. Following repeated intralesional excisions, corticosteroid and botulinum toxin injections, she continued to experience rapid recurrence of her keloids, worsening pain and pruritus. She was no longer able to wear her hearing aids because of the large size of the keloids. We employed a novel technique using topical intralesional cryotherapy, applying liquid nitrogen intraoperatively to the inside of the skin flaps immediately post-intralesional keloid excision and before wound closure. At 26-month follow-up a good aesthetic and symptomatic result was achieved, with minimal hypopigmentation, significantly reduced scar volume and significantly slowed recurrence. We discuss this case and review the current literature on the use of topical intralesional cryotherapy for keloid scarring.

Downregulation of microRNA-31 inhibits proliferation and induces apoptosis by targeting HIF1AN in human keloid

microRNAs (miRNAs) play a pivotal role in the regulation of cell proliferation and apoptosis in keloid scarring. Integrative analysis of the previous miRNA microarray revealed miRNA-31 was among the most frequently altered miRNAs in keloid and hypertrophic scar. Using qRT-PCR, we further validated miRNA-31 was increased in keloid tissues and keloid-derived fibroblasts. Moreover, downregulation of miRNA-31 inhibited the cell proliferation, induced the cell apoptosis and disturbed the cell cycle progression by targeting HIF1AN, a negative modulator of hypoxia inducible factor 1. Through the luciferase reporter assay, HIF1AN was confirmed to be a target of miRNA-31. Further studies demonstrated that miRNA-31 regulated proliferation, apoptosis and cell cycle of keloid-derived fibroblasts by mediating HIF1AN/VEGF signaling pathway. Overall, our findings shed new light on miRNA-31 as a promising therapeutic target in keloid scarring.