Telomere shortening may be associated with human keloids

Development and validation of novel keloid-derived immortalized fibroblast cell lines

Keloids are a common connective tissue disorder with an ill-understood etiopathogenesis and no effective treatment. This is exacerbated because of the absence of an animal model. Patient-derived primary keloid cells are insufficient as they age through passaging and have a limited supply. Therefore, there is an unmet need for development of a cellular model that can consistently and faithfully represent keloid's pathognomic features. In view of this, we developed keloid-derived immortalized fibroblast (KDIF) cell lines from primary keloid fibroblasts (PKF) by transfecting the human telomerase reverse transcriptase (hTERT) gene. The TERT gene encodes the catalytic subunit of the telomerase enzyme, which is responsible for maintaining the cellular replicative potential (cellular immortalization). Primary fibroblasts from keloid-specific lesional (peripheral, middle, and top) as well as extralesional sites were isolated and evaluated for cell line development and comparative cellular characteristics by employing qRT-PCR and immunofluorescence staining. Moreover, the immortalized behavior of KDIF cell lines was evaluated by comparing with cutaneous fibrosarcoma and dermatofibrosarcoma protuberans cell lines. Stable KDIF cell lines with elevated expression of hTERT exhibited the cellular characteristics of site-specific keloid fibroblasts. Histochemical staining for β-galactosidase revealed a significantly lower number of β-gal-positive cells in all three KDIF cell lines compared with that in PKFs. The cell growth curve pattern was studied over 10 passages for all three KDIF cell lines and was compared with the control groups. The results showed that all three KDIF cell lines grew significantly faster and obtained a fast growing characteristic as compared to primary keloid and normal fibroblasts. Phenotypic behavior in growth potential is an indication of hTERT-mediated immortalized transformation. Cell migration analysis revealed that the top and middle KDIF cell lines exhibited similar migration trend as site-specific PKFs. Notably, peripheral KDIF cell line showed significantly enhanced cell migration in comparison to the primary peripheral fibroblasts. All KDIF cell lines expressed Collagen I protein as a keloid-associated fibrotic marker. Functional testing with triamcinolone inhibited cell migration in KDIF. ATCC short tandem repeat profiling validated the KDIF as keloid representative cell line. In summary, we provide the first novel KDIF cell lines. These cell lines overcome the limitations related to primary cell passaging and tissue supply due to immortalized features and present an accessible and consistent experimental model for keloid research.

GLUT-1 Enhances Glycolysis, Oxidative Stress, and Fibroblast Proliferation in Keloid

A keloid is a fibroproliferative skin tumor. Proliferating keloid fibroblasts (KFs) demand active metabolic utilization. The contributing roles of glycolysis and glucose metabolism in keloid fibroproliferation remain unclear. This study aims to determine the regulation of glycolysis and glucose metabolism by glucose transporter-1 (GLUT-1), an essential protein to initiate cellular glucose uptake, in keloids and in KFs. Tissues of keloids and healthy skin were explanted for KFs and normal fibroblasts (NFs), respectively. GLUT-1 expression was measured by immunofluorescence, RT-PCR, and immunoblotting. The oxygen consumption rate (OCR) and extracellular acidification rate (ECAR) were measured with or without WZB117, a GLUT-1 inhibitor. Reactive oxygen species (ROS) were assayed by MitoSOX immunostaining. The result showed that glycolysis (ECAR) was enhanced in KFs, whereas OCR was not. GLUT-1 expression was selectively increased in KFs. Consistently, GLUT-1 expression was increased in keloid tissue. Treatment with WZB117 abolished the enhanced ECAR, including glycolysis and glycolytic capacity, in KFs. ROS levels were increased in KFs compared to those in NFs. GLUT-1 inhibition suppressed not only the ROS levels but also the cell proliferation in KFs. In summary, the GLUT-1-dependent glycolysis and ROS production mediated fibroblast proliferation in keloids. GLUT1 might be a potential target for metabolic reprogramming to treat keloids.

PAX5 activates telomerase activity and proliferation in keloid fibroblasts by transcriptional regulation of SND1, thus promoting keloid growth in burn-injured skin

OBJECTIVE

Staphylococcal nuclease domain-containing 1 (SND1) that functioned as an oncogene in a variety of tumors was upregulated in burn-injured skin tissues, and this study aims to investigate the effect of SND1 on keloid and elucidate the underlying mechanism.

METHODS

Keloid fibroblasts (KFs) and normal skin fibroblasts (NFs) were isolated from the keloid tissues and adjacent normal skin tissues of keloid patients. The SND1 expression was assessed in keloid tissues and KFs with Western blot assay. Gain- and loss-of-function experiments were performed to investigate the role of SND1 in proliferation, colony formation, telomerase activity, expression of fibrogenic genes and production of pro-inflammatory factors in KFs. Chromatin immunoprecipitation (CHIP) and Dual-luciferase reporter gene assays were used to verify the interaction of Paired-box gene 5 (PAX5) on SND1 promoter. Then, a series of rescue experiments were performed to verify the effects of SND1 overexpression on PAX5 knockdown-mediated KF functions. Finally, the role of SND1 in keloid formation in vivo was validated in mice with keloid implantation.

RESULTS

SND1 was upregulated in keloid tissues and KFs. SND1 positively regulated proliferation, colony formation, telomerase activity, production of pro-inflammatory factors and expression of fibrogenic genes. PAX5 directly bound to the SND1 promoter to transcriptionally regulate SND1 expression and positively regulated SND1-mediated KF functions via the ERK/JNK pathway. In vivo assay further demonstrated that SND1 displayed a positive effect on keloid formation.

CONCLUSION

SND1 transcriptionally regulated by PAX5 promotes keloid formation through activating telomerase activity via the ERK/JNK signaling pathways, which provides a promising therapeutic target for clinical treatment of burned skin keloid.

Telomerized fibroblasts as a candidate 3d in vitro model of pathological hypertrophic scars

The search for the optimal cell model for studying the pathogenesis of pathological scars is a pressing challenge. This study aimed at evaluating the feasibility of using telomerized fibroblasts for the in vitro 3D modeling of pathological hypertrophic scars. NF and Fb-hTERT cells were cultured as monolayers and spheroids in the absence and in the presence of TGFβ1. The metabolic activity of the cultured cells was assessed using the MTT assay. Cell migration was estimated using the scratch assay. The expression of genes associated with fibrous scar tissue growth was measured by qRT-PCR. Fb-hTERT cells were more metabolically active than NF cells in the presence of TGFβ1 (for 1 ng/ml: 179 ± 12% vs. 135 ± 13% respectively; p < 0,05). Spheroids grown from Fb-hTERT cells were significantly larger than those derived from NF cells. In the presence of TGFβ1, the expression of proteins associated with extracellular matrix production (COL1A1, COL3A1, FN1) was lower in Fb-hTERT cells than in NF cells (more than 25, 20 and 2-fold, respectively; p < 0.05). Intact NF cells were more active in closing the scratch than Fb-hTERT cells: on day 2, the gap closure rate was 2.28 times higher in NF cells (p < 0.05). Exposure to TGFβ1 stimulated Fb-hTERT, unlike NF cells, to close the gap 2 times faster on day 2 (p < 0.05). Thus, telomerized fibroblasts have a few phenotypic traits observed in keloid fibroblasts; still there are some limitations that should be accounted for when using Fb-hTERT cells for the modeling of pathological hypertrophic 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.

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.

Major trauma and acceleration of the ageing process

It is well established that numerous factors can affect the rate at which we age biologically. Diet, physical activity, lifestyle and our genes all play a major role in influencing the ageing trajectory and longevity. Major trauma affects millions globally, is the major cause of death in young adults and could influence ageing processes but has largely been ignored by biogenterologists. The long-term health consequences of physical trauma are well known in the medical community, how trauma effects the ageing process at a molecular level is not. It has long been difficult to assess ageing trajectories due to the absence of a biomarker of biological rather than chronological age. Recent advances in epigenetics have helped by identifying specific DNA methylation sites as good indicators of biological age. Recent investigations into the impact of psychological trauma and the associated physical stress on accelerating ageing as measured by epigenetic drift are promising. The physical and metabolic stress which is synonymous with physical trauma may also accelerate the ageing process. We suggest that long term epigenetic profiling is required to understand to what degree the ageing trajectory is altered by trauma, which will in turn add support for the development of novel therapies to improve health outcomes for survivors of traumatic injury.

Relative telomere length and oxidative DNA damage in hypertrophic ligamentum flavum of lumbar spinal stenosis

Background

Lumbar spinal stenosis (LSS) is a common cause of low back pain with degenerative spinal change in older adults. Telomeres are repetitive nucleoprotein DNA sequences of TTAGGG at the ends of chromosomes. Oxidative stress originates from an imbalance in pro-oxidant and antioxidant homeostasis that results in the production of reactive oxygen species (ROS). The purpose of this study was to investigate relative telomere length (RTL) and oxidative DNA damage in ligamentum flavum (LF) tissue from LSS patients.

Methods

Forty-eight patients with LSS participated in this study. Genomic DNA from non-hypertrophic and hypertrophic LF tissue were analyzed by real-time polymerase chain reaction for relative telomere length (RTL). 8-hydroxy 2'-deoxygaunosine (8-OHdG) levels were determined by using enzyme-linked immunosorbent assay. We cultivated LF fibroblast cells from patients in different ages (61, 66, and 77 years). After each cultivation cycle, we examined RTL and senescence-associated β-galactosidase (SA-β-gal) expression.

Results

The hypertrophic LF had significantly lower RTL than non-hypertrophic LF (P = 0.04). The levels of 8-OHdG were significantly higher in hypertrophic LF compared to non-hypertrophic LF (P = 0.02). With advancing cell culture passage, the number of cells in each passage was significantly lower in hypertrophic LF fibroblast cells than non-hypertrophic LF fibroblast cells. When evaluated with SA-β-gal staining, all senescent LF fibroblast cells were observed at earlier passages in hypertrophic LF compared with non-hypertrophic LF fibroblast cells.

Discussion

Our results showed that patients with LSS displayed an accelerated RTL shortening and high oxidative stress in hypertrophic LF. These findings implied that telomere shortening and oxidative stress may play roles in the pathogenesis of hypertrophic LF in lumbar spinal stenosis.

Ingenol mebutate treatment in keloids

BACKGROUND

Ingenol-mebutate has been used for the treatment of actinic keratosis. It has been shown that ingenol-mebutate inhibits the growth of cancer cells or induces tumor cell death through pro-apoptotic effects. Keloids are benign skin tumours and are the effect of a deregulated wound-healing process in genetically predisposed patients. Increased cell proliferation, which accounts for the progressive and hypertrophic nature of keloids, correlates with the failure of apoptosis and plays a role in the process of pathological scarring. Keloid cells show a mutated p53 gene resulting in functionally inactive p53 protein which cannot control genomic integrity. They tend to escape from apoptosis which leads to keloid development by means of accumulation of continuously proliferating cells. Currently, the treatment of keloids remains a challenge for high recurrence rates. However, the design and the development of pro-apoptotic therapeutic strategies would be beneficial to keloids treatment.

CASE PRESENTATION

A 55-year-old caucasian woman presented recurrent keloids on a presternal scar. Standard surgical intervention was used to treat the scar. However, this was unsuccessful and a year later the patient sought treatment again, but only by alternative means as the patient refused further surgical intervention. Consequently, based on past research and experience, the authors attempted to treat these lesions with ingenol mebutate gel, due to the pro-apoptotic effects.

CONCLUSION

After 1 month, there was a clinical resolution of lesions, with a slightly squamous, post-inflammatory erythema. A cutaneous biopsy proved the absence of residual keloids and deregulated expression of molecular markers. The last follow-up of the patient, 1 year after treatment, showed that the patient was still free of keloids recurrence.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

NADPH oxidase enzymes in skin fibrosis: molecular targets and therapeutic agents

Fibrosis is characterized by the excessive deposition of extracellular matrix components eventually resulting in organ dysfunction and failure. In dermatology, fibrosis is the hallmark component of many skin diseases, including systemic sclerosis, graft-versus-host disease, hypertrophic scars, keloids, nephrogenic systemic fibrosis, porphyria cutanea tarda, restrictive dermopathy and other conditions. Fibrotic skin disorders may be debilitating and impair quality of life. There are few FDA-approved anti-fibrotic drugs; thus, research in this area is crucial in addressing this deficiency. Recent investigations elucidating the pathogenesis of skin fibrosis have implicated endogenous reactive oxygen species produced by the multicomponent nicotinamide adenine dinucleotide phosphate (NADPH) oxidase (Nox) enzyme complex. In this review, we discuss Nox enzymes and their role in skin fibrosis. An overview of the Nox enzyme family is presented and their role in the pathogenesis of skin fibrosis is discussed. The mechanisms by which Nox enzymes influence specific fibrotic skin disorders are also reviewed. Finally, we describe the therapeutic approaches to ameliorate skin fibrosis by directly targeting Nox enzymes with the use of statins, p47phox subunit modulators, or GKT137831, a competitive inhibitor of Nox enzymes. Nox enzymes can also be targeted indirectly via scavenging ROS with antioxidants. We believe that Nox modulators are worthy of further investigation and have the potential to transform the management of skin fibrosis by dermatologists.

Proteomic profiling reveals upregulated protein expression of hsp70 in keloids

Background. The biochemical characteristics of keloid-derived fibroblasts differ from those of adjacent normal fibroblasts, and these differences are thought to be the cause of abnormal fibrosis. Therefore, we investigated the characteristic proteins that are differentially expressed in keloid-derived fibroblasts using proteomics tools. Objective. We attempted to investigate the novel proteins that play important roles in the pathophysiology of keloids. Methods. Proteomics analysis was performed to identify differentially expressed proteins in keloid-derived fibroblasts. Keloid-derived fibroblasts and adjacent normal fibroblasts were analyzed with 2-DAGE. We validated these proteins with immunoblot analysis, real-time RT-PCR, and immunohistochemistry. Results. Sixteen differentially expressed protein spots were identified in keloid-derived fibroblasts. Among them, heat shock protein 70 (Hsp70) was specifically upregulated in keloid-derived fibroblasts. Also, immunohistochemistry and western blot analysis revealed increased Hsp70, TGF-β, and PCNA expressions in keloids compared to normal tissue. Conclusion. Hsp70 is overexpressed in keloid fibroblasts and tissue. The overexpression of Hsp70 may be involved in the pathogenesis of keloids, and the inhibition of Hsp70 could be a new therapeutic tool for the treatment of keloids.

A combination of nonoperative treatment modalities used for treatment of keloids

Keloid is one abnormal wound healing that occurs commonly in predisposed individuals. Many treatment modalities have been tried, either alone or in variety, including surgical removal, laser therapy, radiation therapy, silicone cream or gel application, cryosurgery, and intralesional injection of various agents. These treatment options have been practiced with largely transient and limited success. In the present study, the present authors prospectively assessed the efficacy of combination methods of the treatment of recalcitrant keloid. One hundred fifty-one sites of keloids in 122 patients were chosen, age of patients varied between 15 and 60 years, size of scar more than 2 cm(2) with pain, itch, or other discomfort, and duration of more than 2 years. Keloids were treated with combination methods of lasers and (32) P radiation on originating scars. One hundred eleven of 151 evaluated sites scored "excellence" and 40 belonged to "effectiveness". These patients demonstrated local control and have remained free of local recurrence for more than 2 years. In addition, there were only 21 and 32 sites with pigmentation and depigmentation, respectively. Over the past 5 years, we established a treatment protocol combining laser with (32) P-patch contact brachyradiotherapy, which represents a safe and effective option in the treatment of keloids.

Sirtuins in dermatology: applications for future research and therapeutics

Sirtuins are a family of seven proteins in humans (SIRT1-SIRT7) that are involved in multiple cellular processes relevant to dermatology. The role of sirtuins in other organ systems is established. However, the importance of these proteins in dermatology is less defined. Recently, sirtuins gained international attention because of their role as "longevity proteins" that may extend and enhance human life. Sirtuins function in the cell via histone deacetylase and/or adenosine diphosphate ribosyltransferase enzymatic activity that target histone and non-histone substrates, including transcription regulators, tumor suppressors, structural proteins, DNA repair proteins, cell signaling proteins, transport proteins, and enzymes. Sirtuins are involved in cellular pathways related to skin structure and function, including aging, ultraviolet-induced photoaging, inflammation, epigenetics, cancer, and a variety of cellular functions including cell cycle, DNA repair and proliferation. This review highlights sirtuin-related cellular pathways, therapeutics and pharmacological targets in atopic dermatitis, bullous dermatoses, collagen vascular disorders, psoriasis, systemic lupus erythematosus, hypertrophic and keloid scars, cutaneous infections, and non-melanoma and melanoma skin cancer. Also discussed is the role of sirtuins in the following genodermatoses: ataxia telangiectasia, Cowden's syndrome, dyskeratosis congenita, Rubenstein-Taybi, Werner syndrome, and xeroderma pigmentosum. The pathophysiology of these inherited diseases is not well understood, and sirtuin-related processes represent potential therapeutic targets for diseases lacking suitable alternative treatments. The goal of this review is to bring attention to the dermatology community, physicians, and scientists, the importance of sirtuins in dermatology and provide a foundation and impetus for future discussion, research and pharmacologic discovery.

Telomerase: structure, functions, and activity regulation

Telomerase is the enzyme responsible for maintenance of the length of telomeres by addition of guanine-rich repetitive sequences. Telomerase activity is exhibited in gametes and stem and tumor cells. In human somatic cells proliferation potential is strictly limited and senescence follows approximately 50-70 cell divisions. In most tumor cells, on the contrary, replication potential is unlimited. The key role in this process of the system of the telomere length maintenance with involvement of telomerase is still poorly studied. No doubt, DNA polymerase is not capable to completely copy DNA at the very ends of chromosomes; therefore, approximately 50 nucleotides are lost during each cell cycle, which results in gradual telomere length shortening. Critically short telomeres cause senescence, following crisis, and cell death. However, in tumor cells the system of telomere length maintenance is activated. Besides catalytic telomere elongation, independent telomerase functions can be also involved in cell cycle regulation. Inhibition of the telomerase catalytic function and resulting cessation of telomere length maintenance will help in restriction of tumor cell replication potential. On the other hand, formation of temporarily active enzyme via its intracellular activation or due to stimulation of expression of telomerase components will result in telomerase activation and telomere elongation that can be used for correction of degenerative changes. Data on telomerase structure and function are summarized in this review, and they are compared for evolutionarily remote organisms. Problems of telomerase activity measurement and modulation by enzyme inhibitors or activators are considered as well.

Telomere dynamics in keloids

OBJECTIVE

Little is known about telomere dynamics in keloids. As keloid formation is dependent on cell replication, in theory telomeres should be shorter in keloids than in normal skin. We examined this concept in the present study.

METHODS

We measured by Southern blot analysis telomere length in keloids and in adjacent normal skin of 16 individuals. When available, we also measured telomere length in blood (leukocytes) and subcutaneous fat.

RESULTS

Telomere length was highly variable among individuals but highly correlated among tissues (cells) within the individual. The mean telomere length in the keloids was longer than that in the adjacent normal skin and displayed a length gradient, with the mean length of telomeres shorter just below the epidermis and longer at the base of the keloids. No apparent telomerase activity was detected in the keloids.

CONCLUSIONS

Our findings suggest a transient activation of telomerase, the reverse transcriptase that prevents telomere shortening, probably during the early phase of keloid formation. The activation of telomerase serves to maintain (or even elongate) telomere length in the keloid. However, telomerase activity is repressed in the fully developed keloid.

Giant keloid of left buttock treated with post-excisional radiotherapy

Keloids are defined as excessive scar tissue formation extending beyond the area of the original skin injury and occurring in predisposed individuals. While no single treatment has proven widely effective, several series report excellent outcomes for keloids with post-surgery radiation therapy as described in the literature. We present a patient with recurrent giant keloid of left buttock after several surgical removals, that at physical examination shows the size of 40×22×10 cm in the largest dimension. Patient underwent a surgical excision of gluteal lesion and postoperative radiotherapy using photons at 8 MV of linear accelerator: the total dose delivered was 22 Gy in 11 days, with a daily fraction of 2 Gy. No relapse was showed at 36 months post-therapy. Several methods seem unsatisfactory for preventing keloid recurrence. The combination of surgery and adjuvant radiotherapy seems an excellent strategy to prevent recurrent disease.