Culture medium and cell density impact gene expression in normal skin and abnormal scar-derived fibroblasts

LARP6 Regulates Keloid Fibroblast Proliferation, Invasion, and Ability to Synthesize Collagen

Keloid is a skin fibroproliferative disease currently having no uniformly successful treatment. The lesion is composed of actively proliferating and collagen-overproducing fibroblasts. LARP6 is an RNA-binding protein able to regulate collagen synthesis in fibroblasts and to promote proliferation and invasion of tumor cells. To explore LARP6's likely functions in keloid pathogenesis, we performed immunohistochemistry staining on human keloid tissues and discovered markedly upregulated LARP6 expression in lesion fibroblasts compared with that of normal skin and hypertrophic scar tissues. In addition, the keloid tissue‒derived fibroblasts showed constitutive upregulation of LARP6 expression as well as significantly upregulated mRNA and protein expressions of type I collagen and enhanced cell proliferation and invasive behavior in cell culture system. Intriguingly, LARP6 knockdown by targeting with small interfering RNAs significantly inhibited type I collagen expression, proliferation, and invasion capability of keloid tissue‒derived fibroblasts relative to that of normal skin‒ and hypertrophic scar‒derived fibroblasts and control keloid tissue‒derived fibroblasts that were transfected with a scrambled small interfering RNA. In conclusion, the abnormally upregulated expression of LARP6 in fibroblasts may play an important role in the growth and invasive behavior of keloid lesions.

Effect of a DACC-coated dressing on keratinocytes and fibroblasts in wound healing using an in vitro scratch model

Wound dressings that exert an antimicrobial effect in order to prevent and treat wound infections can be harmful to the wound healing process. Dressings with hydrophobic coatings, however, have been suggested to both reduce the microbial load and promote the healing process. Therefore, the potential effects of a dialkylcarbamoyl chloride (DACC)-coated dressing on fibroblasts and keratinocytes in wound healing were studied using mechanical scratch wounding of confluent cell layers as an in vitro model. Additionally, gene expression analysis by qRT-PCR was used to elucidate the longitudinal effects of the DACC-coated dressing on cell responses, specifically inflammation, growth factor induction and collagen synthesis. DACC promoted cell viability, did not stick to the cell layers, and supported normal wound healing progression in vitro. In contrast, cells became attached to the uncoated reference material, which inhibited scratch closure. Moreover, DACC slightly induced KGF, VEGF, and GM-CSF expression in HaCaT cells and NHDF. Physiological COL1A1 and COL3A1 gene expression by NHDF was observed under DACC treatment with no observable effect on S100A7 and RNASE7 levels in HaCaT cells. Overall, the DACC coating was found to be safe and may positively influence the wound healing outcome. Graphical abstract.

Cyclic Adenosine Monophosphate Eliminates Sex Differences in Estradiol-Induced Elastin Production from Engineered Dermal Substitutes

Lack of adult cells' ability to produce sufficient amounts of elastin and assemble functional elastic fibers is an issue for creating skin substitutes that closely match native skin properties. The effects of female sex hormones, primarily estrogen, have been studied due to the known effects on elastin post-menopause, thus have primarily included older mostly female populations. In this study, we examined the effects of female sex hormones on the synthesis of elastin by female and male human dermal fibroblasts in engineered dermal substitutes. Differences between the sexes were observed with 17β-estradiol treatment alone stimulating elastin synthesis in female substitutes but not male. TGF-β levels were significantly higher in male dermal substitutes than female dermal substitutes and the levels did not change with 17β-estradiol treatment. The male dermal substitutes had a 1.5-fold increase in cAMP concentration in the presence of 17β-estradiol compared to no hormone controls, while cAMP concentrations remained constant in the female substitutes. When cAMP was added in addition to 17β-estradiol and progesterone in the culture medium, the sex differences were eliminated, and elastin synthesis was upregulated by 2-fold in both male and female dermal substitutes. These conditions alone did not result in functionally significant amounts of elastin or complete elastic fibers. The findings presented provide insights into differences between male and female cells in response to female sex steroid hormones and the involvement of the cAMP pathway in elastin synthesis. Further explorations into the signaling pathways may identify better targets to promote elastic fiber synthesis in skin substitutes.

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.

Modulation of Extracellular Matrix by Scrophularia striata Extract in Vitro: A Potential Antiscarring Agent

Background: Hypertrophic scars are the consequences of the aberration of normal wound healing. To date, therapeutic strategies for abnormal scarring have been unsuccessful. ‎‏The abnormal extracellular‎ matrix is one of the most important contributing factors to ‎hypertrophic scars. ‏Scrophularia striata has been used in Iranian folk medicine for the treatment of burn wounds. ‏The plant extract accelerates wound healing and attenuates scar formation. Objectives: The study was performed to investigate the effects of Scrophularia striata hydroalcoholic extract (SSE) on MMP1, MMP8, fibronectin, collagen type I, and total collagen produced by human skin fibroblasts in the culture medium. Methods: The effects of SSE on the expression of MMP1, MMP8, fibronectin, and collagen type I in human skin fibroblast (HSF) were evaluated using Q-PCR and Western blotting methods. In addition, the effect of SSE on the total collagen content was measured in cultured HSF using Red Sirius Kit. Results: SSE significantly induced the expression of MMP1 and suppressed the production of fibronectin at the mRNA and protein levels. The total collagen content was significantly lower in SSE-treated cells than in untreated cells. SSE did not have any significant effect on MMP8 and collagen type I expression. Conclusions: The results of this study revealed that SSE could modulate the extracellular matrix turnover and had the potential for the prevention and treatment of 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.

Normal and keloid fibroblasts are differentially influenced by IFN-γ and triamcinolone as well as by their combination

Impaired wound healing as well as imbalanced cell proliferation and extracellular matrix synthesis and degeneration can cause aberrant scarring. The most severe impacts of such scarring on patients' lives are stigmatization and physical restriction. Although, a broad variety of combinatorial approaches with, e.g., glucocorticoids, chemotherapeutics, and immunomodulators are used, there is still a high recurrence rate of keloids. The aim of this study was to investigate which influence interferon γ (IFN-γ, 1.000-10.000 IU/mL) and/or triamcinolone acetonide (TA, 1 μg/mL) have on proliferation, cell viability, collagen type I synthesis, and cytokine secretion in healthy and keloid fibroblasts. It was shown that mono-treatment with IFN-γ or TA for 2 days induced a severe reduction of the proliferative potential in both cell species. The combinatory treatment (IFN-γ plus TA) of keloid fibroblasts enhanced the anti-proliferative effect of the mono-treatments, whereas no additional anti-proliferative effect was observed in normal fibroblasts. Furthermore, we observed that the combinatory treatment regimen reduced the expression of α-smooth muscle actin (α-SMA), an actin isotype contributing to cell-generated mechanical tension, in keloid fibroblasts. In normal fibroblasts, α-SMA was reduced by the mono-treatment with IFN-γ as well as by the combinatory treatment. The analysis of collagen-type I synthesis revealed that TA did not reduce collagen type I synthesis in normal fibroblasts but in keloid fibroblasts. IFN-γ reduced in both cell species the collagen type I synthesis. The combination of TA and IFN-γ intensified the previously observed collagen type I synthesis reduction in keloid fibroblasts. The herein presented data suggest the combinatory application of IFN-γ and TA as a promising therapy concept for keloids.

Characterization of In Vitro Reconstructed Human Normotrophic, Hypertrophic, and Keloid Scar Models

To understand scar pathology, develop new drugs, and provide a platform for personalized medicine, physiologically relevant human scar models are required, which are characteristic of different scar pathologies. Hypertrophic scars and keloids are two types of abnormal scar resulting from unknown abnormalities in the wound healing process. While they display different clinical behavior, differentiation between the two can be difficult-which in turn means that it is difficult to develop optimal therapeutic strategies. The aim of this study was to develop in vitro reconstructed human hypertrophic and keloid scar models and compare these to normotrophic scar and normal skin models to identify distinguishing biomarkers. Keratinocytes and fibroblasts from normal skin and scar types (normotrophic, hypertrophic, keloid) were used to reconstruct skin models. All skin models showed a reconstructed differentiated epidermis on a fibroblast populated collagen-elastin matrix. Both abnormal scar types showed increased contraction, dermal thickness, and myofibroblast staining compared to normal skin and normotrophic scar. Notably, the expression of extracellular matrix associated genes showed distinguishing profiles between all scar types and normal skin (hyaluronan synthase-1, matrix-metalloprotease-3), between keloid and normal skin (collagen type IV), between normal scar and keloid (laminin α1), and between keloid and hypertrophic scar (matrix-metalloprotease-1, integrin α5). Also, inflammatory cytokine and growth factor secretion (CCL5, CXCL1, CXCL8, CCL27, IL-6, HGF) showed differential secretion between scar types. Our results strongly suggest that abnormal scars arise from different pathologies rather than simply being on different ends of the scarring spectrum. Furthermore, such normal skin and scar models together with biomarkers, which distinguish the different scar types, would provide an animal free, physiologically relevant scar diagnostic and drug testing platform for the future.

Photobiomodulation of human dermal fibroblasts in vitro: decisive role of cell culture conditions and treatment protocols on experimental outcome

Photobiomodulation-based (LLLT) therapies show tantalizing promise for treatment of skin diseases. Confidence in this approach is blighted however by lamentable inconsistency in published experimental designs, and so complicates interpretation. Here we interrogate the appropriateness of a range of previously-reported treatment parameters, including light wavelength, irradiance and radiant exposure, as well as cell culture conditions (e.g., serum concentration, cell confluency, medium refreshment, direct/indirect treatment, oxygen concentration, etc.), in primary cultures of normal human dermal fibroblasts exposed to visible and near infra-red (NIR) light. Apart from irradiance, all study parameters impacted significantly on fibroblast metabolic activity. Moreover, when cells were grown at atmospheric O2 levels (i.e. 20%) short wavelength light inhibited cell metabolism, while negligible effects were seen with long visible and NIR wavelength. By contrast, NIR stimulated cells when exposed to dermal tissue oxygen levels (approx. 2%). The impact of culture conditions was further seen when inhibitory effects of short wavelength light were reduced with increasing serum concentration and cell confluency. We conclude that a significant source of problematic interpretations in photobiomodulation reports derives from poor optimization of study design. Further development of this field using in vitro/ex vivo models should embrace significant standardization of study design, ideally within a design-of-experiment setting.

The mighty fibroblast and its utility in scleroderma research

Fibroblasts are the effector cells of fibrosis characteristic of systemic sclerosis (SSc, scleroderma) and other fibrosing conditions. The excess production of extracellular matrix (ECM) proteins is the hallmark of fibrosis in different organs, such as skin and lung. Experiments designed to assess the pro-fibrotic capacity of factors, their signaling pathways, and potential inhibitors of their effects that are conducted in fibroblasts have paved the way for planning clinical trials in SSc. As such, fibroblasts have proven to be valuable tools in the search for effective anti-fibrotic therapies for fibrosis. Herein we highlight the characteristics of fibroblasts, their role in the etiology of fibrosis, utility in experimental assays, and contribution to drug development and clinical trials in SSc.

Soluble Epoxide Hydrolase Inhibition and Epoxyeicosatrienoic Acid Treatment Improve Vascularization of Engineered Skin Substitutes

BACKGROUND

Autologous engineered skin substitutes comprised of keratinocytes, fibroblasts, and biopolymers can serve as an adjunctive treatment for excised burns. However, engineered skin lacks a vascular plexus at the time of grafting, leading to slower vascularization and reduced rates of engraftment compared with autograft. Hypothetically, vascularization of engineered skin grafts can be improved by treatment with proangiogenic agents at the time of grafting. Epoxyeicosatrienoic acids (EETs) are cytochrome P450 metabolites of arachidonic acid that are inactivated by soluble epoxide hydrolase (sEH). EETs have multiple biological activities and have been shown to promote angiogenesis. Inhibitors of sEH (sEHIs) represent attractive therapeutic agents because they increase endogenous EET levels. We investigated sEHI administration, alone or combined with EET treatment, for improved vascularization of engineered skin after grafting to mice.

METHODS

Engineered skin substitutes, prepared using primary human fibroblasts and keratinocytes, were grafted to full-thickness surgical wounds in immunodeficient mice. Mice were treated with the sEHI 1-trifluoromethoxyphenyl-3-(1-propionylpiperidin-4-yl) urea (TPPU), which was administered in drinking water throughout the study period, with or without topical EET treatment, and were compared with vehicle-treated controls. Vascularization was quantified by image analysis of CD31-positive areas in tissue sections.

RESULTS

At 2 weeks after grafting, significantly increased vascularization was observed in the TPPU and TPPU + EET groups compared with controls, with no evidence of toxicity.

CONCLUSIONS

The results suggest that sEH inhibition can increase vascularization of engineered skin grafts after transplantation, which may contribute to enhanced engraftment and improved treatment of full-thickness wounds.

Genetic Predictors of Susceptibility to Dermatophytoses

Countless observational studies conducted over the last century reveal that dermatophytes infect humans of every age, race, gender, and socioeconomic status with strikingly high rates. The curious disparity in dermatophyte infection patterns observed within and between populations has led countless investigators to explore whether genetics underlie a susceptibility to, or confer protection against, dermatophyte infections. This paper examines the data that offer a link between genetics and dermatophytoses and discusses the underlying mechanisms that support these observations.

Cell density-dependent stimulation of PAI-1 and hyaluronan synthesis by TGF-β in orbital fibroblasts

During the course of Graves' orbitopathy (GO), orbital fibroblasts are exposed to factors that lead to proliferation and extracellular matrix (ECM) overproduction. Increased levels of tissue plasminogen activator inhibitor type 1 (PAI-1 (SERPINE1)) might promote the accumulation of ECM components. PAI-1 expression is regulated by cell density and various cytokines and growth factors including transforming growth factorβ(TGF-β). We examined the effects of increasing cell densities and TGF-β on orbital fibroblasts obtained from GO patients and controls. Responses were evaluated by the measurement of proliferation, PAI-1 expression, and ECM production. There was an inverse correlation between cell density and the per cell production of PAI-1. GO orbital, normal orbital, and dermal fibroblasts behaved similarly in this respect. Proliferation rate also declined with increasing cell densities. Hyaluronan (HA) production was constant throughout the cell densities tested in all cell lines. In both GO and normal orbital fibroblasts, but not in dermal fibroblasts, TGF-β stimulated PAI-1 production in a cell density-dependent manner, reaching up to a five-fold increase above baseline. This has been accompanied by increased HA secretion and pericellular HA levels at high cell densities. Increasing cell density is a negative regulator of proliferation and PAI-1 secretion both in normal and GO orbital fibroblasts; these negative regulatory effects are partially reversed in the presence of TGF-β. Cell density-dependent regulation of PAI-1 expression in the orbit, together with the local cytokine environment, may have a regulatory role in the turnover of the orbital ECM and may contribute to the expansion of orbital soft tissue in GO.

Characterization of human vocal fold fibroblasts derived from chronic scar

OBJECTIVES/HYPOTHESIS

In vitro modeling of cell-matrix interactions that occur during human vocal fold scarring is uncommon, as primary human vocal fold scar fibroblast cell lines are difficult to acquire. The purpose of this study was to characterize morphologic features, growth kinetics, contractile properties, α-smooth muscle actin (α-SMA) protein expression and gene expression profile of human vocal fold fibroblasts derived from scar (sVFF) relative to normal vocal fold fibroblasts (nVFF).

STUDY DESIGN

In vitro.

METHODS

We successfully cultured human vocal fold fibroblasts from tissue explants of scarred vocal folds from a 56-year-old female and compared these to normal fibroblasts from a 59-year-old female. Growth and proliferation were assessed by daily cell counts, and morphology was compared at 60% confluence for 5 days. Gel contraction assays were evaluated after seeding cells within a collagen matrix. α-SMA was measured using western blotting and immunocytochemistry (ICC). Quantitative reverse-transcriptase polymerase chain reaction (qRT-PCR) was used to assess differential extracellular matrix gene expression between the two cell types.

RESULTS

sVFF were morphologically indistinguishable from nVFF. sVFF maintained significantly lower proliferation rates relative to nVFF on days 3 to 6 (day 3: P = .0138; days 4, 5, and 6: P < .0001). There were no significant differences in contractile properties between the two cell types at any time point (0 hours: P = .70, 24 hours: P = .79, 48 hours: P = .58). ICC and western blot analyses revealed increased expression of α-SMA in sVFF as compared with nVFF at passages 4 and 5, but not at passage 6 (passage 4: P = .006, passage 5: P = .0015, passage 6: P = .8860). Analysis of 84 extracellular matrix genes using qRT-PCR revealed differential expression of 15 genes (P < .01).

CONCLUSIONS

nVFF and sVFF displayed differences in proliferation rates, α-SMA expression, and gene expression, whereas no differences were observed in contractile properties or morphology. Further investigation with a larger sample size is necessary to confirm these findings.

Genetic predictors of susceptibility to cutaneous fungal infections: a pilot genome wide association study to refine a candidate gene search

BACKGROUND

Trichophyton tonsurans is the foremost fungal pathogen of minority children in the U.S. Despite overwhelming infection rates, it does not appear that this fungus infects children in a non-specific manner.

OBJECTIVE

This study was designed to identify genes that may predispose or protect a child from T. tonsurans infection.

METHODS

Children participating in an earlier longitudinal study wherein infection rates could be reliably determined were eligible for inclusion. DNA from a subset (n=40) of these children at the population extremes underwent whole genome genotyping (WGG). Allele frequencies between cases and controls were examined and significant SNPs were used to develop a candidate gene list for which the remainder of the cohort (n=115) were genotyped. Cumulative infection rate was examined by genotype and the ability of selected genotypes to predict the likelihood of infection explored by multivariable analysis.

RESULTS

23 genes with a putative mechanistic role in cutaneous infection were selected for evaluation. Of these, 21 demonstrated significant differences in infection rate between genotypes. A risk index assigned to genotypes in the 21 genes accounted for over 60% of the variability observed in infection rate (adjusted r(2)=0.665, p<0.001). Among these, 8 appeared to account for the majority of variability that was observed (r(2)=0.603, p<0.001). These included genes involved in: leukocyte activation and migration, extracellular matrix integrity and remodeling, epidermal maintenance and wound repair, and cutaneous permeability.

CONCLUSIONS

Applying WGG to individuals at the extremes of phenotype can help to guide the selection of candidate genes in populations of small cohorts where disease etiology is likely polygenic in nature.