Aging differentially modulates the expression of collagen and collagenase in dermal fibroblasts

Engineered multi-functional, pro-angiogenic collagen-based scaffolds loaded with endothelial cells promote large deep burn wound healing

The lack of vascularization associated with deep burns delays the construction of wound beds, increases the risks of infection, and leads to the formation of hypertrophic scars or disfigurement. To address this challenge, we have fabricated a multi-functional pro-angiogenic molecule by grafting integrin αvβ3 ligand LXW7 and collagen-binding peptide (SILY) to a dermatan sulfate (DS) glycosaminoglycan backbone, named LXW7-DS-SILY (LDS), and further employed this to functionalize collagen-based Integra scaffolds. Using a large deep burn wound model in C57/BLK6 mice (8-10 weeks old, 26-32g, n = 39), we demonstrated that LDS-modified collagen-based Integra scaffolds loaded with endothelial cells (ECs) accelerate wound healing rate, re-epithelialization, vascularization, and collagen deposition. Specifically, a 2 cm × 3 cm full-thickness skin burn wound was created 48 h after the burn, and then wounds were treated with four groups of different dressing scaffolds, including Integra + ECs, Integra + LDS, and Integra + LDS + ECs with Integra-only as the control. Digital photos were taken for wound healing measurement on post-treatment days 1, 7, 14, 21, 28, and 35. Post-treatment photos revealed that treatment with the Intgera + LDS + ECs scaffold exhibited a higher wound healing rate in the proliferation phase. Histology results showed significantly increased re-epithelialization, increased collagen deposition, increased thin and mixed collagen fiber content, increased angiogenesis, and shorter wound length within the Integra + LDS + ECs group at Day 35. On Day 14, the Integra + LDS + ECs group showed the same trend. The relative proportions of collagen changed from Day 14 to Day 35 in the Integra + LDS + ECs and Integra + ECs groups demonstrated decreased thick collagen fiber deposition and greater thin and mixed collagen fiber deposition. LDS-modified Integra scaffolds represent a promising novel treatment to accelerate deep burn wound healing, thereby potentially reducing the morbidity associated with open burn wounds. These scaffolds can also potentially reduce the need for autografting and morbidity in patients with already limited areas of harvestable skin.

A Systematic Review of Randomized Controlled Trials of Antibiotic Use in Diabetic Foot Ulcer Infections: Focus on Clinical Cure

BACKGROUND

The use of antibiotics in diabetic foot ulcer infections (DFUI) is essential in reducing morbidity. Optimal administration of antibiotics can improve clinical outcomes and reduce the risk of antibiotic resistance. This study aims to review the efficacy, in terms of clinical cure, of various regimens and the duration of antibiotic administration in DFUI patients, based on Preferred Reporting Items for Systematic Reviews and Meta-Analysis guidelines. The efficacy based on microbiological response is also reviewed as the secondary outcome.

MATERIALS AND METHODS

We used three databases, namely PubMed, Scopus, and ScienceDirect, to search for randomized controlled trials (RCTs) in patients with DFUI who required antibiotics.

RESULTS

A total of 16 studies were included in the systematic review. The study locations and bacterial patterns varied, with the most common pathogen being Staphylococcus aureus. Most studies did not demonstrate a significant difference in clinical cure and pathogen eradication, either in the comparison between systemic and topical antibiotics or in the duration of administration. Some studies had similar characteristics and were analyzed to conclude. These studies showed that ertapenem had comparable efficacy to piperacillin/tazobactam. Similar results were also conducted from studies of piperacillin-tazobactam+amoxicillin-clavulanic acid vs. moxifloxacin.

CONCLUSION

Most studies have heterogeneous characteristics, possibly due to differences in research location. Therefore, there is no strong evidence to recommend a specific antibiotic with the highest efficacy. However, since all included studies are RCTs, this review provides a good summary in considering antibiotic choices when treating DFUI patients.

Employing Extracellular Matrix-Based Tissue Engineering Strategies for Age-Dependent Tissue Degenerations

Tissues and organs are not composed of solely cellular components; instead, they converge with an extracellular matrix (ECM). The composition and function of the ECM differ depending on tissue types. The ECM provides a microenvironment that is essential for cellular functionality and regulation. However, during aging, the ECM undergoes significant changes along with the cellular components. The ECM constituents are over- or down-expressed, degraded, and deformed in senescence cells. ECM aging contributes to tissue dysfunction and failure of stem cell maintenance. Aging is the primary risk factor for prevalent diseases, and ECM aging is directly or indirectly correlated to it. Hence, rejuvenation strategies are necessitated to treat various age-associated symptoms. Recent rejuvenation strategies focus on the ECM as the basic biomaterial for regenerative therapies, such as tissue engineering. Modified and decellularized ECMs can be used to substitute aged ECMs and cell niches for culturing engineered tissues. Various tissue engineering approaches, including three-dimensional bioprinting, enable cell delivery and the fabrication of transplantable engineered tissues by employing ECM-based biomaterials.

Secondary metabolites changes in germinated barley and its relationship to anti-wrinkle activity

The purpose of this research was to identify metabolite change during barley (Hordeum vulgare) germination and reveal active principles for the anti-wrinkle activity. Barley was germinated with deionized water (DW) and mineral-rich water (MRW) for the comparison of the effect of mineral contents on the metabolites changes during germination. The effects of germinated barley extracts (GBEs) on collagen production and collagenase inhibition were evaluated in vitro using human dermal fibroblasts (HDFs). A pronounced anti-wrinkle activity was observed in the test group treated with the MRW-GBEs. In order to find out the active components related to the anti-wrinkle activity, an orthogonal projection to latent structure-discriminant analysis (OPLS-DA) was performed, using the data from secondary metabolites profiling conducted by UPLC–PDA–ESI–MS. The anti-wrinkle activity of MRW-GBEs was revealed to be associated with the increase of oligomeric compounds of procyanidin and prodelphinidin, indicating that it can be used as an active ingredient for anti-wrinkle agents.

In vitro modulation of extracellular matrix genes by stingless bee honey in cellular aging of human dermal fibroblast cells

This study determined the antiaging effect of stingless bee honey on the expression of extracellular matrix genes. MTS (3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium, inner salt) assay was performed for determination of optimum concentration and incubation time of stingless bee honey. Gene expression of matrix metalloproteinase-1 (MMP-1) and collagen type Ⅰ (COL1A1) were analyzed using real time reverse transcriptase polymerase chain reaction technique. Incubation with stingless bee honey at concentration of 0.02% for 72 hr showed significant increase in the viability of human fibroblast cells. Stingless bee honey significantly downregulates metalloproteinase-1 gene expression in both pre-senescence and senescence fibroblast cells and upregulates collagen type Ⅰ gene expression in senescence fibroblast cells. In conclusion, stingless bee honey potentially delayed skin aging through modulation of extracellular matrix genes. PRACTICAL APPLICATIONS: Changes of the extracellular matrix regulation promote skin aging. Stingless bee honey is a good source of natural antioxidant which potentially delays skin aging. This study demonstrated that stingless bee honey beneficially increases collagen type Ⅰ expression and decreases MMP-1 expression during cellular aging of human dermal fibroblast cells.

Proteomic Analysis Reveals Anti-Fibrotic Effects of Blue Light Photobiomodulation on Fibroblasts

BACKGROUND AND OBJECTIVES

This study was aimed at determining the effects of blue light photobiomodulation on primary adult mouse dermal fibroblasts (AMDFs) and the associated signaling pathways.

STUDY DESIGN/MATERIALS AND METHODS

Cultured AMDFs from adult C57BL/6 mice were irradiated by blue light from a light-emitting diode (wavelength = 463 ± 50 nm; irradiance = 5 mW/cm² ; energy density = 4-8 J/cm² ). The cells were analyzed using mass spectrometry for proteomics/phosphoproteomics, AlamarBlue assay for mitochondrial activity, time-lapse video for cell migration, quantitative polymerase chain reaction for gene expression, and immunofluorescence for protein expression.

RESULTS

Proteomic/phosphoproteomic analysis showed inhibition of extracellular signal-regulated kinases/mammalian target of rapamycin and casein kinase 2 pathways, cell motility-related networks, and multiple metabolic processes, including carbon metabolism, biosynthesis of amino acid, glycolysis/gluconeogenesis, and the pentose phosphate pathway. Functional analysis demonstrated inhibition of mitochondrial activities, cell migration, and mitosis. Expression of growth promoting insulin-like growth factor 1 and fibrosis-related genes, including transforming growth factor β1 (TGFβ1) and collagen type 1 ɑ2 chain diminished. Protein expression of α-smooth muscle actin, an important regulator of myofibroblast functions, was also suppressed.

CONCLUSIONS

Low-level blue light exerted suppressive effects on AMDFs, including suppression of mitochondrial activity, metabolism, cell motility, proliferation, TGFβ1 levels, and collagen I production. Low-level blue light can be a potential treatment for the prevention and reduction of tissue fibrosis, such as hypertrophic scar and keloids. Lasers Surg. Med. © 2019 Wiley Periodicals, Inc.

Extracellular matrix alterations in senescent cells and their significance in tissue homeostasis

Normal cells after a defined number of successive divisions or after exposure to genotoxic stresses are becoming senescent, characterized by a permanent growth arrest. In addition, they secrete increased levels of pro-inflammatory and catabolic mediators, collectively termed "senescence-associated secretory phenotype". Furthermore, senescent cells exhibit an altered expression and organization of many extracellular matrix components, leading to specific remodeling of their microenvironment. In this review we present the current knowledge on extracellular matrix alterations associated with cellular senescence and critically discuss certain characteristic examples, highlighting the ambiguous role of senescent cells in the homeostasis of various tissues under both normal and pathologic conditions.

Gene Therapy: A Lipofection Approach for Gene Transfer into Primary Endothelial Cells

Despite the great potential of gene therapy to become a new treatment modality in future medicine, there are still many limitations to overcome before this gene approach can pass to the stage of human trial. The foremost obstacle is the development of a safe, efficient, and efficacious vector system for in vivo gene application. This study evaluated the efficacy of lipofection as a gene delivery vehicle into primary endothelial cells. Transfection efficiency of several lipid-based reagents (Effectene, Fugene 6, DOTAP) was examined at experimental temperatures of 37°C, 24°C, and 6°C. Human umbilical vein endothelial cells (HUVECs) were transfected with the enhanced green fluorescent protein (EGFP) using precise amounts of DNA (Effectene, 0.2 μg; Fugene 6, 0.5 μg; DOTAP, 2.5 μg) and lipids (Effectene, 10 μl; Fugene 6, 6 μl; DOTAP, 15 μl) optimized in our laboratory. Duration of incubation in the DNA/lipid transfection mixture varied for each lipid transfectant as follows: 5 h for both Fugene 6 and DOTAP and 3 h for Effectene. Efficiency of transfection was quantified by microscopic evaluation of EFGP expression in a minimum of 100 cells per group. Transfection efficiencies achieved with these lipofection agents were 34 ± 1.3% (mean ± SEM), 33 ± 1.4%, and 18 ± 1.5% for Effectene, Fugene 6, and DOTAP, respectively, at 37°C. Transfection results were lower at 24°C with mean efficiencies of 26 ± 2.4% for Effectene, 14 ± 2.9% for Fugene 6, and 15 ± 3.2% for DOTAP. Furthermore, mean efficiencies at 6°C were 6 ± 0.5%, 8 ± 1.5%, and 6 ± 0.0% for Effectene, Fugene 6, and DOTAP, respectively. Efficiency of transfection appeared to be temperature dependent (ANOVA; p < 0.0001). In spite of a significant decrease (37°C vs. 24°C: p < 0.0001; 37°C vs. 6°C: p < 0.0001; 24°C vs. 6°C: p < 0.0115) in transfection efficiency at low temperatures, the successful in vitro gene manipulation renders lipofection a potential gene delivery strategy for in vivo gene therapy.

Lactoferrin and the lactoferrin-sophorolipids-assembly can be internalized by dermal fibroblasts and regulate gene expression

Lactoferrin (Lf) is an iron-binding multifunctional protein, mainly present in external secretions. Lf is known to penetrate skin and may thus exert its multiple functions in skin. Sophorolipids (SLs) are glycolipid biosurfactants, which have been shown to enhance absorption of commercial bovine Lf (CbLf) in model skin via forming an assembly with CbLf. In this study, uptake and post-internalization localization of bovine Lf (bLf), CbLf, and human Lf (hLf) with or without forming assemblies with SLs in human dermal fibroblasts (HDFn) were determined using ¹²⁵I-labeled Lfs and confocal microscopy, respectively. Our results show that all 3 Lfs were internalized by HDFn; although SLs did not significantly affect the uptake of Lfs, it changed Lf localization by accumulating Lfs in the perinuclear region. Furthermore, microarrays were used to investigate transcriptional profiling in HDFn in response to CbLf, SLs, or CbLf-SLs-assembly treatments. Transcriptome profiling indicates that CbLf may play roles in the protection of skin from oxidative stress, immunomodulatory activities, and enhancement of wound healing. The assembly had similar effects but dramatically modulated the transcription of some genes. SLs alone modified signaling pathways related to lipid metabolism, as well as synthesis of sex hormones and vitamins. Thus, CbLf may exert beneficial effects on skin, and these effects may be modulated by SLs.

Differential Matrix Metalloprotease (MMP) Expression Profiles Found in Aged Gingiva

The periodontium undergoes age-related cellular and clinical changes, but the involved genes are not yet known. Here, we investigated age-related genetic changes in gingiva at the transcriptomic level. Genes that were differentially expressed between young and old human gingiva were identified by RNA sequencing and verified by real-time PCR. A total of 1939 mRNA transcripts showed significantly differential expression between young and old gingival tissues. Matrix metalloprotease (MMP) regulation was the top pathway involved in gingival aging. MMP3, MMP9, MMP12, and MMP13 were upregulated in old gingival tissues, concomitantly with interleukin-1 beta (IL1B) expression. In vitro experiments using human gingival fibroblasts (hGFs) showed that MMP12 was upregulated in old hGFs compared to young hGFs. Moreover, the MMP3, MMP9 and IL1B levels were more highly stimulated by infection with the oral bacterium, Fusobacterium nucleatum, in old hGFs compared to young hGFs. Collectively, these findings suggest that, in gingiva, the upregulation of MMP12 may be a molecular hallmark of natural aging, while the upregulations of MMP3, MMM9, and IL1B may indicate externally (e.g., infection)-induced aging. These findings contribute to our understanding of the molecular targets involved in gingival aging.

The natural phytochemical dehydroabietic acid is an anti-aging reagent that mediates the direct activation of SIRT1

Dehydroabietic acid (DAA) is a naturally occurring diterpene resin acid of confers, such as pinus species (P. densiflora, P. sylvestris) and grand fir (Abies grandis), and it induces various biological actions including antimicrobial, antiulcer, and cardiovascular activities. The cellular targets that mediate these actions are largely unknown yet. In this report, we suggest that DAA is an anti-aging reagent. DAA has lifespan extension effects in Caenorhabditis elegans, prevents lipofuscin accumulation, and prevents collagen secretion in human dermal fibroblasts. We found that these anti-aging effects are primarily mediated by SIRT1 activation. Lifespan extension effects by DAA were ameliorated in sir-2.1 mutants and SIRT1 protein expression was increased, resulting in the deacetylation of SIRT1 target protein PGC-1α. Moreover, DAA binds directly to the SIRT1 protein independent of the SIRT1 substrate NAD(+) levels. Through a molecular docking study, we also propose a binding model for DAA-SIRT1. Taken together, our results demonstrate that the anti-aging effects are the first identified biological property of DAA and that the direct activation of SIRT1 enzymatic activity suggests the potential use of this natural diterpene, or related compounds, in age-related diseases or as a preventive reagent against the aging process.

miR-526b targets 3' UTR of MMP1 mRNA

Regulation of matrix metalloproteinases (MMPs) is important for many physiological processes involving cancers, inflammation, tissue remodeling and skin aging. Here, we report the novel finding that the expression of MMP1 mRNA is downregulated by the overexpression of miR-526b which is a member of chromosome 19 microRNA cluster (C19MC). Our analysis using reporter constructs containing the 3' untranslated region (3' UTR) of MMP1 and its mutant form showed that the region from 377-383 in the 3' UTR of MMP1 is critical for targeting by miR-526b. In addition, the expression pattern of miR-526b and MMP1 mRNA showed reverse relation between adult dermal and neonatal fibroblasts. We show for the first time that miR-526b, an miRNA belonging to C19MC, can target the 377-383 region of the MMP1 3' UTR.

Ultraviolet irradiation represses TGF-β type II receptor transcription through a 38-bp sequence in the proximal promoter in human skin fibroblasts

Transforming growth factor-β (TGF-β) is a major regulator of collagen gene expression in human skin fibroblasts. Cellular responses to TGF-β are mediated primarily through its cell surface type I (TβRI) and type II (TβRII) receptors. Ultraviolet (UV) irradiation impairs TGF-β signalling largely due to reduced TβRII gene expression, thereby decreasing type I procollagen synthesis, in human skin fibroblasts. UV irradiation does not alter either TβRII mRNA or protein stability, indicating that UV reduction in TβRII expression likely results from transcriptional or translational repression. To understand how UV irradiation regulates TβRII transcription, we used a series of TβRII promoter-luciferase 5'-deletion constructs (covering 2 kb of the TβRII proximal promoter) to determine transcriptional rate in response to UV irradiation. We identified a 137-bp region upstream of the transcriptional start site that exhibited high promoter activity and was repressed 60% by UV irradiation, whereas all other TβRII promoter reporter constructs exhibited either low promoter activities or no regulation by UV irradiation. Mutation of potential transcription factor binding sites within the promoter region revealed that an inverted CCAAT box (-81 bp from transcription start site) is required for promoter activity. Mutation of the CCAAT box completely abolished UV irradiation regulation of the TβRII promoter. Protein-binding assay, as determined by electrophoretic mobility-shift assays (EMSAs) using the inverted CCAAT box as probe (-100/-62), demonstrated significantly enhanced protein binding in response to UV irradiation. Super shift experiments indicated that nuclear factor Y (NFY) is able to binding to this sequence, but NFY binding was not altered in response to UV irradiation, indicating additional protein(s) are capable of binding this sequence in response to UV irradiation. Taken together, these data indicate that UV irradiation reduces TβRII expression, at least partially, through transcriptional repression. This repression is mediated by a 38-bp sequence in TβRII promoter, in human skin fibroblasts.

Continuous irradiation with a 633-nm light-emitting diode exerts an anti-aging effect on human skin cells

Accumulating evidence has indicated that the light source emitted from light‑emitting diode (LED) has a potential anti-aging effect on human skin. Studies using single and interval LED irradiation have documented such effects; however, to the best of our knowledge, the anti-aging effects of continuous LED irradiation have not yet been investigated. In the present study, we demonstrated that continuous irradiation with a 633±3-nm LED exerted anti-aging effects in both in vitro and ex vivo experiments. More specifically, irradiation with a 633-nm LED for 2 days increased the synthesis of type 1 procollagen and decreased the expression of matrix metalloproteinase (MMP)1 and MMP2 in skin fibroblasts. In addition, irradiation with a 633-nm LED decreased the expression levels of inflammatory genes, such has cyclooxygenase-2 (COX-2), and interleukin-1-α (IL-1α) in keratinocytes. Furthermore, a 14-day LED irradiation moderately increased keratinocyte proliferation. Using human skin explants, we confirmed the safety of this 633-nm LED irradiation, which resulted in unaltered morphology and allergy-free potential in human tissue. Overall, these data provide insight into the anti-aging effects of continuous LED irradiation on human skin.

Paracrine anti-fibrotic effects of neonatal cells and living cell constructs on young and senescent human dermal fibroblasts

Senescent cells observed in the area of chronic wounds have been proposed to affect wound healing. Therapeutic approaches against chronic wounds include, among others, the local application of living cell constructs (LCCs), containing fibroblasts and/or keratinocytes. Accordingly, the aim of the present work was to examine the effects of factors secreted by early passage neonatal fibroblasts and LCCs--in the form of a conditioned medium (CM)--on senescent adult dermal fibroblasts regarding functions related to the healing process, i.e., cell proliferation, alpha-smooth muscle actin and metalloproteinase expression, and collagen synthesis. Target cells were fibroblasts senescent either due to subsequent divisions (replicative senescence) or due to an exogenous stress (stress-induced premature senescence). No effect on the proliferation of senescent fibroblasts was observed, as expected. All CMs were found to inhibit overall collagen synthesis both in early passage and in senescent fibroblasts. The LCC-derived CM was found to be more potent than fibroblast-derived CMs and, furthermore, to inhibit alpha-smooth muscle actin expression. In conclusion, these results may indicate anti-contractile and anti-fibrotic activities of factor(s) secreted by neonatal skin fibroblasts, and more intensely by LCCs on adult donor-derived fibroblasts. These activities seem to persist during senescence of the target cells.

Deep tissue injury in development of pressure ulcers: a decrease of inflammasome activation and changes in human skin morphology in response to aging and mechanical load

Molecular mechanisms leading to pressure ulcer development are scarce in spite of high mortality of patients. Development of pressure ulcers that is initially observed as deep tissue injury is multifactorial. We postulate that biomechanical forces and inflammasome activation, together with ischemia and aging, may play a role in pressure ulcer development. To test this we used a newly-developed bio-mechanical model in which ischemic young and aged human skin was subjected to a constant physiological compressive stress (load) of 300 kPa (determined by pressure plate analyses of a person in a reclining position) for 0.5–4 hours. Collagen orientation was assessed using polarized light, whereas inflammasome proteins were quantified by immunoblotting. Loaded skin showed marked changes in morphology and NLRP3 inflammasome protein expression. Sub-epidermal separations and altered orientation of collagen fibers were observed in aged skin at earlier time points. Aged skin showed significant decreases in the levels of NLRP3 inflammasome proteins. Loading did not alter NLRP3 inflammasome proteins expression in aged skin, whereas it significantly increased their levels in young skin. We conclude that aging contributes to rapid morphological changes and decrease in inflammasome proteins in response to tissue damage, suggesting that a decline in the innate inflammatory response in elderly skin could contribute to pressure ulcer pathogenesis. Observed morphological changes suggest that tissue damage upon loading may not be entirely preventable. Furthermore, newly developed model described here may be very useful in understanding the mechanisms of deep tissue injury that may lead towards development of pressure ulcers.

Processed Panax ginseng, Sun Ginseng Increases Type I Collagen by Regulating MMP-1 and TIMP-1 Expression in Human Dermal Fibroblasts

In the present study, effects of sun ginseng (SG) on the collagen synthesis and the proliferation of dermal fibroblast were investigated. Collagen synthesis was measured by assaying procollagen type I C-peptide production. In addition, the level of matrix metalloproteinase (MMP)-1 was assessed by western blot analysis. SG suppressed the MMP-1 protein level in a dose-dependent manner. In contrast, SG dose-dependently increased tissue inhibitors of MMP (TIMP)-1 production in fibroblasts. SG increased type I collagen production directly and/or indirectly by reducing MMP-1 and stimulating TIMP-1 production in human dermal fibroblasts. SG dose-dependently induced fibroblast proliferation and this, in turn, can trigger more collagen production. These results suggest that SG may be a potential pharmacological agent with anti-aging properties in cultured human skin fibroblast.

Serum insulin-like growth factor 1 and facial ageing: high levels associate with reduced skin wrinkling in a cross-sectional study

BACKGROUND

Insulin-like growth factor (IGF)-1 is a growth factor that can influence fibroblast functioning, with effects including the inhibition of collagenases and the induction of collagen expression.

OBJECTIVES

To assess whether serum IGF-1, IGF-binding protein (IGFBP)3 and the ratio between IGF-1 and IGFBP3, as a measure of IGF-1 bioavailability, are associated with facial ageing and skin wrinkling.

METHODS

From a random sample comprising 617 subjects from the Leiden Longevity Study, perceived age and skin wrinkling were assessed from facial photographs, and IGF-1 and IGFBP3 were measured in serum. The associations were assessed using linear regression models, adjusted for chronological age, sex, body mass index, smoking and sun exposure.

RESULTS

Across tertiles of the ratio of IGF-1 to IGFBP3, and after adjusting for all potential confounding factors, the mean perceived age decreased from 60·6 years in the lowest tertile to 59·5 years in the highest (P = 0·045). Similarly, the mean skin wrinkling grade decreased from 4·8 in the lowest tertile to 4·5 in the highest (P = 0·011). Adding skin wrinkling as a covariate in the analysis between IGF-1 and perceived age diminished this association.

CONCLUSIONS

This study demonstrates that a higher ratio of IGF-1 to IGFBP3 associates with a lower perceived age, via its association with reduced skin wrinkling. Whether high IGF-1 levels actually delay the accumulation of skin wrinkling now needs investigating.

Cysteine-rich protein 61 (CCN1) mediates replicative senescence-associated aberrant collagen homeostasis in human skin fibroblasts

Dermal fibroblasts produce a collagen-rich extracellular matrix, which confers mechanical strength and resiliency to human skin. During aging, collagen production is reduced and collagen fragmentation is increased, which is initiated by matrix metalloproteinase-1 (MMP-1). This aberrant collagen homeostasis results in net collagen deficiency, which impairs the structural integrity and function of skin. Cysteine-rich protein 61 (CCN1), a member of the CCN family, negatively regulates collagen homeostasis, in primary human skin dermal fibroblasts. As replicative senescence is a form of cellular aging, we have utilized replicative senescent dermal fibroblasts to further investigate the connection between elevated CCN1 and aberrant collagen homeostasis. CCN1 mRNA and protein levels were significantly elevated in replicative senescent dermal fibroblasts. Replicative senescent dermal fibroblasts also expressed significantly reduced levels of type I procollagen and increased levels of MMP-1. Knockdown of elevated CCN1 in senescent dermal fibroblasts partially normalized both type I procollagen and MMP-1 expression. These data further support a key role of CCN1 in regulation of collagen homeostasis. Elevated expression of CCN1 substantially increased collagen lattice contraction and fragmentation caused by replicative senescent dermal fibroblasts. Atomic force microscopy (AFM) further revealed collagen fibril fragmentation and disorganization were largely prevented by knockdown of CCN1 in replicative senescent dermal fibroblasts, suggesting CCN1 mediates MMP-1-induced alterations of collagen fibrils by replicative senescent dermal fibroblasts. Given the ability of CCN1 to regulate both production and degradation of type I collagen, it is likely that elevated-CCN1 functions as an important mediator of collagen loss, which is observed in aged human skin.

A review of fetal scarless healing

Wound healing is a complex process involving a number of processes. Fetal regeneration has been shown to have a number of differences compared to scar-forming healing. This review discusses the number of differences identified in fetal regeneration. Understanding these differences may result in new therapeutic targets which may reduce or even prevent scarring in adult healing.

Collagen-binding peptidoglycans inhibit MMP mediated collagen degradation and reduce dermal scarring

Scarring of the skin is a large unmet clinical problem that is of high patient concern and impact. Wound healing is complex and involves numerous pathways that are highly orchestrated, leaving the skin sealed, but with abnormal organization and composition of tissue components, namely collagen and proteoglycans, that are then remodeled over time. To improve healing and reduce or eliminate scarring, more rapid restoration of healthy tissue composition and organization offers a unique approach for development of new therapeutics. A synthetic collagen-binding peptidoglycan has been developed that inhibits matrix metalloproteinase-1 and 13 (MMP-1 and MMP-13) mediated collagen degradation. We investigated the synthetic peptidoglycan in a rat incisional model in which a single dose was delivered in a hyaluronic acid (HA) vehicle at the time of surgery prior to wound closure. The peptidoglycan treatment resulted in a significant reduction in scar tissue at 21 days as measured by histology and visual analysis. Improved collagen architecture of the treated wounds was demonstrated by increased tensile strength and transmission electron microscopy (TEM) analysis of collagen fibril diameters compared to untreated and HA controls. The peptidoglycan's mechanism of action includes masking existing collagen and inhibiting MMP-mediated collagen degradation while modulating collagen organization. The peptidoglycan can be synthesized at low cost with unique design control, and together with demonstrated preclinical efficacy in reducing scarring, warrants further investigation for dermal wound healing.

SIRT1 modulates expression of matrix metalloproteinases in human dermal fibroblasts

BACKGROUND

SIRT1, an NAD(+) -dependent histone/protein deacetylase, controls a broad range of cellular functions.

OBJECTIVES

We examined if SIRT1 is involved in the regulation of matrix metalloproteinase (MMP) expression in human dermal fibroblasts.

METHODS

We studied the effect of inhibition of SIRT1 by specific inhibitor and small interfering RNA (siRNA) on MMP-1 and MMP-3 expression in human dermal fibroblasts.

RESULTS

Treatment with a potent and selective inhibitor of SIRT1, EX-527, increased the basal expression levels of MMP-1 and MMP-3 proteins. Knockdown of endogenous SIRT1 by siRNA led to increased expression of MMP-1 and MMP-3 at both mRNA and protein levels. SIRT1 knockdown also upregulated MMP protein induction caused by an inflammatory cytokine, interleukin (IL)-1β. Moreover, treatment with a SIRT1 activator, resveratrol, significantly suppressed IL-1β-mediated induction of MMP-1, which was attenuated by pretreatment with EX-527. Finally, MMP-1 promoter activity was increased by EX-527 in cells treated with or without IL-1β.

CONCLUSIONS

Our findings suggest that SIRT1 exerts a negative regulatory role in the production of MMP-1 and MMP-3 in human dermal fibroblasts.

Beneficial regulation of matrix metalloproteinases for skin health

Matrix metalloproteinases (MMPs) are essential to the remodeling of the extracellular matrix. While their upregulation facilitates aging and cancer, they are essential to epidermal differentiation and the prevention of wound scars. The pharmaceutical industry is active in identifying products that inhibit MMPs to prevent or treat aging and cancer and products that stimulate MMPs to prevent epidermal hyperproliferative diseases and wound scars.

Differential surface antigen expression and 1α,25-dihydroxyvitamin D3 responsiveness distinguish human dermal fibroblasts with age-dependent osteogenic differentiation potential from marrow-derived stromal cells in vitro

BACKGROUND AIMS

Recent studies have demonstrated that cells committed to a fibroblastic lineage, including dermal fibroblasts, may undergo osteoblastic differentiation when treated with steroid hormones. However, stem cells have also been isolated from the dermis, making it unclear whether osteoinduction of dermal fibroblasts is the result of transdifferentiation of committed fibroblasts or differentiation of resident multipotent stromal cells, which are morphologically indistinguishable.

METHODS

Flow cytometry was used to characterize the expression of CD26, CD90 and CD105 on neonatal and adult human dermal fibroblasts and adult human bone marrow-derived stromal cells. These cells were then cultured with the steroid hormones 1α,25-dihydroxyvitamin D(3) and dexamethasone, and evaluated for protein expression and mineral deposition typical of an osteoblastic phenotype.

RESULTS

The surface peptidase, dipeptidyl peptidase IV (CD26), was differentially expressed between human neonatal (98.22 ± 1.47%) and adult (90.73 ± 7.97%) dermal fibroblasts and adult bone marrow-derived stromal cells (6.84 ± 5.07%). In addition, neonatal dermal fibroblasts treated with vitamin D(3) expressed alkaline phosphatase, osteocalcin and bone sialoprotein, and deposited mineral, which is consistent with an osteoblastic phenotype. Such differentiation was not observed in adult dermal fibroblasts. In contrast, marrow-derived stromal cells required dexamethasone in order to undergo osteoblastic differentiation.

CONCLUSIONS

Taken together, the differential surface antigen expression and disparate response to steroid hormones suggest that committed neonatal dermal fibroblasts are distinct from mesenchymal stromal cells and possess osteogenic differentiation potential.

Resveratrol oligomers from Vatica albiramis

Five new stilbenoids, vatalbinosides A-E (1-5), and 13 known compounds (6-18) were isolated from the stem of Vatica albiramis. The effects of these new compounds on interleukin-1β-induced production of matrix metalloproteinase-1 (MMP-1) in human dermal fibroblasts were examined. Three resveratrol tetramers, (-)-hopeaphenol (6), vaticanol C (13), and stenophyllol C (14), were identified as strong inhibitors of MMP-1 production.

Beneficial regulation of matrixmetalloproteinases and their inhibitors, fibrillar collagens and transforming growth factor-beta by Polypodium leucotomos, directly or in dermal fibroblasts, ultraviolet radiated fibroblasts, and melanoma cells

The extracellular matrix (ECM) that gives tissue its structural integrity is remodeled in skin aging/photoaging and cancer via the increased expression/activities of matrixmetalloproteinases (MMP), inhibition of the tissue inhibitors of matrix metalloproteinases (TIMP), or inhibition of collagen synthesis. Transforming growth factor-beta (TGF-beta), a predominant regulator of the ECM, is inhibited in aging/photoaging and stimulated in carcinogenesis. P. leucotomos (fern) extract has potential to counteract these alterations via its antioxidant, anti-inflammatory and photoprotective properties. The goal of this research was to determine the efficacy of P. leucotomos to (a) directly inhibit MMP-1, 2, 3, and 9 activities, (b) inhibit MMP-2, and stimulate TIMPs, fibrillar collagens and TGF-beta in non-irradiated or ultraviolet (UV) radiated fibroblasts, and (c) inhibit MMPs and TGF-beta, and stimulate TIMPs in melanoma cells. To this purpose, we examined the direct effect of P. leucotomos (0-1%) on MMPs' activities, and its effects on the expression (protein and/or transcription levels) of (1) MMPs and TIMPs in dermal fibroblasts, and melanoma cells, (2) TGF-beta in non-irradiated, UVA (2.5 J/cm2) or UVB (2.5 mJ/cm2) irradiated fibroblasts, and melanoma cells, and (3) types I, III, and V collagen in non-irradiated or UV irradiated fibroblasts. P. leucotomos directly inhibited the activities of MMPs as well as the expression of MMPs in fibroblasts, and melanoma cells while stimulating the expression of TIMPs in these cells. P. leucotomos stimulated types I, III, and V collagen in non-irradiated fibroblasts, and types I and V collagen in UV radiated fibroblasts. P. leucotomos had predominant stimulatory effects on TGF-beta expression in non-irradiated or UV radiated fibroblasts, and inhibited TGF-beta expression in melanoma cells. The effects of P. leucotomos were largely similar to that of ascorbic acid. P. leucotomos demonstrated dual protective effects on the ECM via its inhibition of the ECM proteolytic enzymes and the stimulation of the structural ECM collagens. The effects of P. leucotomos on fibroblasts and melanoma cells may be partly via its cell-specific regulation of TGF-beta expression and partly via its antioxidant property. The intake or topical application of P. leucotomos may be beneficial to skin health, in aging and cancer prevention or treatment.

Development, optimization and characterization of a full-thickness tissue engineered human oral mucosal model for biological assessment of dental biomaterials

Restorative dental materials and oral health care products come into direct contact with oral mucosa and can cause adverse reactions. In order to obtain an accurate risk assessment, the in vitro test model must reflect the clinical situation as closely as possible. The aim of this study was to develop and optimize a three-dimensional full-thickness engineered human oral mucosal model, which can be used for biological assessment of dental materials. In this study human oral fibroblasts and keratinocytes were isolated from patients and seeded onto a number of collagen-based and synthetic scaffolds using a variety of cell seeding techniques and grown at the air/liquid interface to construct human oral mucosa equivalents. Suitability of 10 different scaffolds for engineering human oral mucosa was evaluated in terms of biocompatibility, biostability, porosity, and the ability to mimic normal human oral mucosa morphology. Finally an optimized full-thickness engineered human oral mucosa was developed and characterized using transmission electron microscopy and immunostaining. The oral mucosa reconstruct resembled native human oral mucosa and it has the potential to be used as an accurate and reproducible test model in mucotoxicity and biocompatibility evaluation of dental materials.

Dermal fibroblasts derived from fetal and postnatal humans exhibit distinct responses to insulin like growth factors

Background

It has been well established that human fetuses will heal cutaneous wounds with perfect regeneration. Insulin-like growth factors are pro-fibrotic fibroblast mitogens that have important roles in both adult wound healing and during development, although their relative contribution towards fetal wound healing is currently unknown. We have compared responses to IGF-I and -II in human dermal fibroblast strains derived from early gestational age fetal (<14 weeks) and developmentally mature postnatal skin to identify any differences that might relate to their respective wound healing responses of regeneration or fibrosis.

Results

We have established that the mitogenic response of fetal cells to both IGF-I and -II is much lower than that seen in postnatal dermal fibroblasts. Further, unlike postnatal cells, fetal cells fail to synthesise collagen in response to IGF-I, whereas they do increase synthesis in response to IGF-II. This apparent developmentally regulated difference in response to these related growth factors is also reflected in changes in the tyrosine phosphorylation pattern of a number of proteins. Postnatal cells exhibit a significant increase in phosphorylation of ERK 1 (p44) in response to IGF-I and conversely the p46 isoform of Shc on IGF-II stimulation. Fetal cells however only show a significant increase in an unidentified 100 kDa tyrosine-phosphorylated protein on stimulation with IGF-II.

Conclusion

Dermal fibroblasts exhibit different responses to the two forms of IGF depending on their developmental maturity. This may relate to the developmental transition in cutaneous wound healing from regeneration to fibrosis.

Macrophage migration inhibitory factor (MIF) promotes fibroblast migration in scratch-wounded monolayers in vitro

MIF was recently redefined as an inflammatory cytokine, which functions as a critical mediator of diseases such as septic shock, rheumatoid arthritis, atherosclerosis, and cancer. MIF also regulates wound healing processes. Given that fibroblast migration is a central event in wound healing and that MIF was recently demonstrated to promote leukocyte migration through an interaction with G-protein-coupled receptors, we investigated the effect of MIF on fibroblast migration in wounded monolayers in vitro. Transient but not permanent exposure of primary mouse or human fibroblasts with MIF significantly promoted wound closure, a response that encompassed both a proliferative and a pro-migratory component. Importantly, MIF-induced fibroblast activation was accompanied by an induction of calcium signalling, whereas chronic exposure with MIF down-regulated the calcium transient, suggesting receptor desensitization as the underlying mechanism.

Gene expression profiling by DNA microarray technology

Methods in molecular and genetic biology have provided important clues to elucidate the complex mechanisms of oral and craniofacial development and pathogenesis of diseases. It has become increasingly clear that a biological phenotype is a result of multiple factors involving a large number of regulatory genes, while a single nucleotide mutation can cause various degrees of oral and craniofacial abnormalities. These oral and craniofacial problems often present a challenge to the molecular screening process. Recent advances in microarray-based technologies allow for large-scale gene expression analysis in a single experiment, which have been applied to genome-wide assays, mutational analysis, drug discovery, developmental biology, and molecular analysis of various diseases. This review introduces the basic principle and some modifications of techniques and materials used in microarray technology, as well as currently available microarray data analysis strategies. Microarray technology can be applied to the soon-to-be-available human genome database and will be a powerful research tool for those inquiring into specific problems associated with oral and craniofacial biology.

A cell culture model using rat coronary artery adventitial fibroblasts to measure collagen production

Background

We have developed a rat cell model for studying collagen type I production in coronary artery adventitial fibroblasts. Increased deposition of adventitial collagen type I leads to stiffening of the blood vessel, increased blood pressure, arteriosclerosis and coronary heart disease. Although the source and mechanism of collagen deposition is yet unknown, the adventitia appears to play a significant role. To demonstrate the application of our cell model, cultured adventitial fibroblasts were treated with sex hormones and the effect on collagen production measured.

Methods

Hearts (10–12 weeks) were harvested and the left anterior descending coronary artery (LAD) was isolated and removed. Tissue explants were cultured and cells (passages 2–4) were confirmed as fibroblasts using immunohistochemistry. Optimal conditions were determined for cell tissue harvest, timing, proliferation and culture conditions. Fibroblasts were exposed to 10^-7 M testosterone or 10^-7 M estrogen for 24 hours and either immunostained for collagen type I or subjected to ELISA.

Results

Results showed increased collagen staining in fibroblasts treated with testosterone compared to control and decreased staining with estrogen. ELISA results showed that testosterone increased collagen I by 20% whereas estrogen decreased collagen I by 15%.

Conclusion

Data demonstrates the usefulness of our cell model in studying the specific role of the adventitia apart from other blood vessel tissue in rat coronary arteries. Results suggest opposite effects of testosterone and estrogen on collagen synthesis in the rat coronary artery adventitial fibroblasts.

Prior Chronic in Vivo Glucocorticoid Excess Leads to an Anabolic Phenotype and an Extension of Cellular Life Span of Skin Fibroblasts in Vitro

Intense stress can be detrimental for tissue homeostasis and accelerates aging. On the other hand, repeated mild stresses can have beneficial and even life-prolonging effects. Hypersecretion of glucocorticoids (GCs) represents the major hormonal response to stress. However, besides its life-sustaining role, GC excess can promote a "catabolic" phenotype. Accordingly, we have studied the effect of long-lasting exposure to high GC levels in vivo on several parameters of tissue homeostasis, as well as cellular senescence, in cells removed from the high-GC milieu in vivo and then cultured in vitro. To this end, we have used human skin fibroblasts from (a) Cushing's syndrome patients that are characterized by chronic endogenous GC excess and (b) patients treated with exogenous GC administration. Interestingly, when Cushing's syndrome fibroblasts were cultured in vitro under standard conditions they express an "anabolic" phenotype, i.e., they restore their ability for collagen synthesis, secrete reduced levels of metalloproteases, and have an increased proliferative capacity and contractility. Furthermore, these cells exhibit a significant extension of their proliferative life span, while they respond better to exogenous stress by producing significantly higher levels of heat-shock protein-70 (HSP70). In addition, preliminary results with fibroblasts from patients subjected to chronic exogenous GC administration indicate that they express a similar behavior in vitro, at least with regard to the restoration of collagen expression. These data suggest that prior exposure to elevated GC concentrations is not associated with persisting adverse effects on fibroblasts and may also have a beneficial outcome in some aspects of cell physiology, including longevity in vitro.

Tissue-engineered oral mucosa: a review of the scientific literature

Tissue-engineered oral mucosal equivalents have been developed for clinical applications and also for in vitro studies of biocompatibility, mucosal irritation, disease, and other basic oral biology phenomena. This paper reviews different tissue-engineering strategies used for the production of human oral mucosal equivalents, their relative advantages and drawbacks, and their applications. Techniques used for skin tissue engineering that may possibly be used for in vitro reconstruction of human oral mucosa are also discussed.

Protein oxidation and degradation during aging: role in skin aging and neurodegeneration

During aging, the products of oxidative processes accumulate and might disturb cellular metabolism. Among them are oxidized proteins and protein aggregates. On the other hand, in a functioning metabolic system oxidized proteins are degraded, mainly by the proteasome. During aging, however, proteasome activity declines. Therefore, the ability to degrade oxidized proteins is attenuated. The following review summarises the accumulation of oxidized proteins and the decline of the proteasomal system during skin and brain aging including some age-related neurodegenerative processes. The role of protein aggregates will be discussed as a potential reason for the accelerated dysfunction of tissue during aging.

Imbalance of Matrix Metalloproteinase-1 and Tissue Inhibitor of Metalloproteinases: A Novel Approach for Explaining the Parenchymal Liquefaction of the Septic Spleen?

OBJECTIVE

The causal pathophysiological mechanisms involved in the parenchymal liquefaction of the septic spleen are still far from clear. The balance between matrix metalloproteinases (MMPs) and their inhibitors, the tissue inhibitors of metalloproteinases (TIMPs), is largely responsible for the remodelling of tissues. Deregulation of this balance is a characteristic of extensive tissue degradation in certain chronic inflammatory diseases.

METHODS

This study focuses on a search for alterations in the balance between MMP-1 (interstitial collagenase) and TIMP-1 by means of immunostaining, by immunoblotting, and by gel zymography.

RESULTS

We found a deregulation of the balance between MMP-1 and TIMP-1 in the septic spleen in favor of the active form of MMP-1.

CONCLUSION

Our findings suggest that active MMP-1 is involved in collagenolytic extracellular matrix breakdown in the septic spleen.

Serum-dependent effects on adult and fetal tendon fibroblast migration and collagen expression

Cell migration and extracellular matrix synthesis play an important role in the wound-healing response to injury. Several studies have described differences in migratory behavior and collagen biosynthetic activity in adult vs. fetal skin fibroblasts. The objective of this study was to examine the serum- and age-dependent effects on cell migration and collagen expression in tendon fibroblasts. Medial tendon fibroblasts were isolated from pregnant ewes and their fetuses, and cultured with and without serum for up to 7 days. Cell migration was determined by quantitative image analysis, and collagen expression was assessed by reverse transcription-polymerase chain reaction and immunohistochemical staining. In serum-containing medium, tendon fibroblasts migrated significantly faster than cells in serum-free medium. Additionally, fetal tendon fibroblasts migrated significantly faster than adult tendon fibroblasts under both culture conditions. The expression of types I and III collagen mRNA was significantly up-regulated in tendon cell populations in serum-free medium compared with those in serum-containing medium. Quantitative assessment of collagen staining indicated that fetal tenocytes produced more type I collagen than adult tenocytes under both culture conditions. These findings suggest that there is an inherent difference between adult and fetal tendon fibroblasts, which may have implications in the wound-healing response in tendons.

Influence of serum on adult and fetal dermal fibroblast migration, adhesion, and collagen expression

The wound healing response to injury can be affected by many factors such as cell migration and extracellular matrix elaboration. The objective of this study was to examine the serum- and age-dependent effects on cell migration, adhesion, and collagen expression by skin fibroblasts. Dermal fibroblasts were isolated and plated with and without serum for up to 7 d. Cell migration was determined by quantitative image analysis, adhesion was quantified using a centrifugation assay, and collagen expression was assessed by PCR and immunohistochemical staining. Both adult and fetal fibroblasts migrated significantly faster in serum-containing medium compared to serum-free medium. There was no significant difference in migration between the two cell types in either serum-containing or serum-free medium. There was no significant difference in adhesion in the presence of serum, although there was a greater fraction of adherent fetal skin fibroblasts than adult fibroblasts in serum-free medium. Moreover, the adherent fraction of fetal fibroblasts in serum-free medium was not significantly different from that in serum-containing medium, suggesting that fetal skin fibroblasts possess serum-independent adhesion properties. Collagen mRNA expression was significantly up-regulated in serum-free compared to serum-containing medium for both cell types. With respect to collagen immunohistochemistry, both dermal fibroblast populations exhibited greater type I collagen compared to type III collagen staining. Quantitative assessment of collagen staining indicated significantly enhanced type I collagen secretion in the presence of serum by fetal skin fibroblasts. These findings suggest that intrinsic cellular characteristics may govern the observed differences in adult and fetal wound healing.

Ageing effects on the expression of cell defence genes after UVA irradiation in human male cutaneous fibroblasts using cDNA arrays

Ageing is a multifactorial process in which reactive oxygen species (ROS) are thought to be implicated. ROS cause oxidative alterations on cell constituents, and damage accumulation can lead to mutations in DNA. Modulation of gene expression during ageing is now quite documented but results are often controversial and/or incomplete. As ultraviolet A is one of the exogenous factors involved in skin ageing, by the production of ROS, we further document the modifications in gene expression during ageing process and response to an oxidative stress. For this purpose, we used a cDNA macroarray containing 82 genes related to cell defence, essentially represented by antioxidant and DNA repair proteins. Ageing-associated gene expression was assessed in normal skin human fibroblasts from three age groups: children (n=4), adults (n=4) and olders (n=3), at the basal state and after a 5J/cm2 UVA irradiation. Analysis revealed that 22 genes were never detected, whereas certain were always expressed such as those related to antioxidant defence, extracellular matrix (ECM) regulator and XPC. Transcripts related to ECM, MMP1 and MMP3 were increased with age and after UVA irradiation, independently of age. It appeared that transcripts involved in the redox status control (TXN and APEX) decreased as a function of age, at the basal state and after irradiation, respectively. Most of transcripts involved in DNA repair were not detected but repression of POLD1 in the adult group and induction of XRCC5 and LIG4 were observed after UVA irradiation, as a function of age. In the basal state, the transcript of GAS1, regulator of cell cycle arrest in G1 phase was found to be decreased with age. HMOX1 increased after UVA irradiation. In conclusion, the decrease in expression of some antioxidant system, cell cycle control gene and extracellular matrix enzymes, particularly after UV exposure can explain the occurrence of photoaging.

Age-related changes in focal adhesions lead to altered cell behavior in tendon fibroblasts

During aging the increase in collagen cross-linking and total amount of collagen in tendon leads to a decline in both its flexibility and its ability to heal after injury. Fibroblasts are responsible for the synthesis of the macromolecules that constitute tendonous tissue. The ability of fibroblasts to maintain tissue homeostasis is compromised with increasing age underlying many of the age-related pathologies of the musculoskeletal system. This leads to a slowdown in connective tissue healing. Whether these deficits are due to changes in connective tissue, structure or to changes in tendon fibroblast function is unknown. We show that tendon fibroblasts from old mice have an altered morphology, reduced level of function, and exhibit changes in protein transport, compared to fibroblasts from young mice. The fibroblasts from old mice are not senescent, they are distinct phenotypes. Achilles tendon fibroblasts from old mice have low motility and proliferation, a poorly organised actin cytoskeleton and a different localisation of key focal adhesion proteins compared to the same cells from young mice. Additionally we found more of the protein misfolding indicator protein, GADD 153, in fibroblasts from old tendon. These results indicate that changes in tendon fibroblast function may well explain the age-related decline in tendon healing.

The unexpected anabolic phenotype and extended longevity of skin fibroblasts after chronic glucocorticoid excess

Intense stress can challenge tissue homeostasis and accelerate the ageing process. However, several lines of evidence indicate that repeated mild stresses can have beneficial and even life-prolonging effects. Hypersecretion of glucocorticoids (GC) represents the major hormonal response to stress. Besides its life-sustaining role, GC excess, usually due to several side-effects that promote a "catabolic" phenotype, can be detrimental for several tissues. Cushing's syndrome patients are characterized by chronic endogenous GC excess and consequently at the time of diagnosis they have an atrophic elderly-like skin. Interestingly, when Cushing's syndrome fibroblasts were removed from the high-GC milieu in vivo and cultured in vitro under standard conditions they express an "anabolic" phenotype, i.e. they restore their ability for collagen synthesis, they secrete reduced levels of metalloproteases (MMP-1 and MMP-2) and have an increased proliferative capacity and contractility. Furthermore, these cells exhibit a significant extension of their proliferative lifespan, while they respond better to exogenous stress by producing significantly higher levels of heat-shock protein-70 (HSP70). These results imply that long-term hypercortisolism in vivo can have beneficial consequences on fibroblast physiology in vitro.