Ultraviolet irradiation induces the accumulation of chondroitin sulfate, but not other glycosaminoglycans, in human skin

The hyaluronan metabolism in the UV-irradiated human epidermis and the relevance of in vitro epidermal models

Exposure to the sun affects the skin and may eventually result in UV-induced skin damage. It is generally known that hyaluronan (HA) is one of the main structural and functional components of the skin. However, UV-related changes in the HA metabolism in the skin have not yet been elucidated. Using qRT-PCR, confocal microscopy and LC-MS/MS we compared the naturally sun-exposed (SE), sun-protected, experimentally repeatedly UVA + UVB-exposed and acutely (once) UVA + UVB irradiated skin of Caucasian women. The epidermis was harvested by means of suction blistering 24 h after the acute irradiation. In addition, the epidermis was compared with a UV-irradiated in vitro reconstituted 3D epidermis (EpiDerm) and an in vitro 2D culture of normal human keratinocytes (NHEK). The amount of HA was found to be statistically significantly enhanced in the acutely irradiated epidermis. The acute UV evinced the upregulation of HA synthases (HAS2 and HAS3), hyaluronidases (HYAL2 and HYAL3), Cluster of differentiation 44 (CD44), and Cell Migration Inducing Proteins (CEMIP and CEMIP2), while only certain changes were recapitulated in the 3D epidermis. For the first time, we demonstrated the enhanced gene and protein expression of CEMIP and CEMIP2 following UV irradiation in the human epidermis. The data suggest that the HA metabolism is affected by UV in the irradiated epidermis and that the response can be modulated by the underlying dermis.

Hyaluronan: A key player or just a bystander in skin photoaging?

Photoaged skin exhibits signs of inflammation, DNA damage and changes in morphology that are visible at the macroscopic and microscopic levels. Photoaging also affects the extracellular matrix (ECM) including hyaluronan (HA), the main polysaccharide component thereof. HA is a structurally simple but biologically complex molecule that serves as a water-retaining component and provides both a scaffold for a number of the proteins of the ECM and the ligand for cellular receptors. The study provides an overview of the literature concerning the changes in HA amount, size and metabolism, and the potential role of HA in photoaging. We also suggest novel HA contributions to photoaging based on our knowledge of the role of HA in other pathological processes, including the senescence and inflammation-triggered ECM reorganization. Moreover, we discuss potential direct or indirect intervention to mitigate photoaging that targets the hyaluronan metabolism, as well as supplementation.

Glycosaminoglycans: Sweet as Sugar Targets for Topical Skin Anti-Aging

Glycosaminoglycans (GAGs) are long, linear polysaccharides comprised of repeating disaccharide units with pleiotropic biological functions, with the non-sulfated GAG hyaluronic acid (HA), and sulfated GAGs dermatan sulfate, chondroitin sulfate, heparan sulfate, keratan sulfate, and to a lesser extent heparin all being expressed in skin. Their ability to regulate keratinocyte proliferation and differentiation, inflammatory processes and extracellular matrix composition and quality demonstrates their critical role in regulating skin physiology. Similarly, the water-binding properties of GAGs and structural qualities, particularly for HA, are crucial for maintaining proper skin form and hydration. The biological importance of GAGs, as well as extensive evidence that their properties and functions are altered in both chronological and extrinsic skin aging, makes them highly promising targets to improve cosmetic skin quality. Within the present review, we examine the cutaneous biological activity of GAGs alongside the protein complexes they form called proteoglycans and summarize the age-related changes of these molecules in skin. We also examine current topical interventional approaches to modulate GAGs for improved skin quality such as direct exogenous administration of GAGs, with a particular interest in strategies targeted at potentiating GAG levels in skin through either attenuating GAG degradation or increasing GAG production.

A role for estrogen in skin ageing and dermal biomechanics

The skin is the body's primary defence against the external environment, preventing infection and desiccation. Therefore, alterations to skin homeostasis, for example with skin ageing, increase susceptibility to skin disease and injury. Skin biological ageing is uniquely influenced by a combination of intrinsic and extrinsic (primarily photoageing) factors, with differential effects on skin structure and function. Interestingly, skin architecture rapidly changes following the menopause, as a direct result of reduced circulating 17β-estradiol. The traditional clinical benefit of estrogens are supported by recent experimental data, where 17β-estradiol supplementation prevents age-related decline in the skin's structural and mechanical properties. However, the off-target effects of 17β-estradiol continue to challenge therapeutic application. Here we discuss how ageing alters the physiological and structural properties of the dermal extracellular matrix, and explore how estrogen receptor-targeted therapies may restore the mechanical defects associated with skin ageing.

Platelet α-granule cargo packaging and release are affected by the luminal proteoglycan, serglycin

BACKGROUND

Serglycin (SRGN) is an intragranular, sulfated proteoglycan in hematopoietic cells that affects granule composition and function.

OBJECTIVE

To understand how SRGN affects platelet granule packaging, cargo release, and extra-platelet microenvironments.

METHODS

Platelets and megakaryocytes from SRGN-/- mice were assayed for secretion kinetics, cargo levels, granule morphology upon activation, and receptor shedding.

RESULTS

Metabolic, 35 SO4 labeling identified SRGN as a major sulfated macromolecule in megakaryocytes. SRGN colocalized with α-granule markers (platelet factor 4 [PF4], von Willebrand factor [VWF], and P-selectin), but its deletion did not affect α-granule morphology or number. Platelet α-granule composition was altered, with a reduction in basic proteins (pI ≥8; e.g., PF4, SDF-1, angiogenin) and constitutive release of PF4 from SRGN-/- megakaryocytes. P-Selectin, VWF, and fibrinogen were unaffected. Serotonin (5-HT) uptake and β-hexosaminidase (HEXB) were slightly elevated. Thrombin-induced exocytosis of PF4 from platelets was defective; however, release of RANTES/CCL5 was normal and osteopontin secretion was more rapid. Release of 5-HT and HEXB (from dense granules and lysosomes, respectively) were unaffected. Ultrastructural studies showed distinct morphologies in activated platelets. The α-granule lumen of SRGN-/- platelet had a grainy staining pattern, whereas that of wild-type granules had only fibrous material remaining. α-Granule swelling and decondensation were reduced in SRGN-/- platelets. Upon stimulation of platelets, a SRGN/PF4 complex was released in a time- and agonist-dependent manner. Shedding of GPVI from SRGN-/- platelets was modestly enhanced. Shedding of GP1b was unaffected.

CONCLUSION

The polyanionic proteoglycan SRGN influences α-granule packaging, cargo release, and shedding of platelet membrane proteins.

Functions of, and replenishment strategies for, chondroitin sulfate in the human body

Chondroitin sulfate (CS) belongs to a class of molecules called glycosaminoglycans (GAGs). These are long, linear chains of polysaccharides comprising alternating amino sugars and hexuronic acid. Similar to other GAGs, CS is important in a multitude of biological activities. Alteration of CS levels has been implicated in several pathological conditions, including osteoarthritis (OA) and other inflammatory diseases, as well as physiological conditions, such as aging. Therefore, devising replenishment strategies for this molecule is an important area of research. In this review, we discuss the nature of CS, its function in different organs, and its implications in health and disease. We also describe different methods for the exogenous administration of CS.

Transcriptome Profile of Human Fibroblasts in an Ex Vivo Culture

Implantation of autologous fibroblasts is a method used to correct age-related changes in facial skin. The aim of this study was to establish the optimal population of cultured human fibroblasts according to the organization of the extracellular matrix in the dermis. Transcriptome profile analysis of cells derived from three consecutive passages indicated that fibroblasts after the second passage were the population with the greatest number of upregulated genes encoding the critical biological processes responsible for skin regeneration, such as extracellular matrix organization, collagen fibril organization, and cell adhesion. Furthermore, genes encoding proteinases responsible for the degradation of dermal extracellular matrix proteins were noticeably downregulated at this stage of culture. Autologous fibroblasts seem to be an optimal and safe biological filler for the renewal of all skin structures.

Serglycin as part of IL-1β induced inflammation in human chondrocytes

Serglycin (SRGN) is an intracellular proteoglycan produced and secreted by several cell types. The increased expression of SRGN was associated with greater aggressiveness in cancer and inflammation. In this study, we demonstrated that SRGN is increased in human chondrocytes after IL-β stimulation. Furthermore, we found that secreted SRGN was able to bind the CD44 receptor thus participating in the extension of the inflammatory response. Using SRGN knockdown cells we observed a significantly decrease in specific inflammatory markers and NF-kB activation. Similar results were observed by blocking the CD44 receptor. These data provide further evidences for a direct involvement of SRGN in the mechanisms regulating the non-infectious chondrocytes damage, and the consequent joint inflammation and cartilage destruction in arthritis.

Tumorigenic functions of serglycin: Regulatory roles in epithelial to mesenchymal transition and oncogenic signaling

Numerous studies point out serglycin as an important regulator of tumorigenesis in a variety of malignancies. Serglycin expression correlates with the aggressive phenotype of tumor cells and serves as a poor prognostic indicator for disease progression. Although serglycin is considered as an intracellular proteoglycan, it is also secreted in the extracellular matrix by tumor cells affecting cell properties, oncogenic signaling and exosomes cargo. Serglycin directly interacts with CD44 and possibly other cell surface receptors including integrins, evoking cell adhesion and signaling. Serglycin also creates a pro-inflammatory and pro-angiogenic tumor microenvironment by regulating the secretion of proteolytic enzymes, IL-8, TGFβ2, CCL2, VEGF and HGF. Hence, serglycin activates multiple signaling cascades that drive angiogenesis, tumor cell growth, epithelial to mesenchymal transition, cancer cell stemness and metastasis. The interference with the tumorigenic functions of serglycin emerges as an attractive prospect to target malignancies.

Global periorbital skin rejuvenation by a topical eye cream containing low molecular weight heparan sulfate (LMW-HS) and a blend of naturally derived extracts

Background

Maintaining a youthful appearance is a priority for many people. Global eye rejuvenation is sought more frequently and at a younger age than other treatments. Major concerns around the eye area are periorbital hyperpigmentation, puffiness, and lines and wrinkles. Glycosaminoglycans (GAGs) are complex carbohydrates that modulate skin health, repair and renew skin's appearance. Heparan sulfate (HS) is the most biologically active GAG, although it is too large and polar to penetrate the skin. Low Molecular Weight Heparan Sulfate (LMW‐HS) is a smaller version of HS designed for skin penetration while preserving its activity. In this study, we investigated the effects of a topical eye cream containing LMW‐HS and a blend of naturally derived extracts to address global periorbital rejuvenation.

Method

A single‐center, open‐label study including female and male subjects (n = 15) was conducted to evaluate the efficacy and tolerability of an eye cream containing LMW‐HS and a blend of naturally derived extracts applied twice daily for 12 weeks.

Results

Improvements in the appearance of periorbital hyperpigmentation and fine and coarse wrinkles were observed as early as week 2 with continuous improvement up to 12 weeks. Decrease in puffiness (73%) and dark circles (93%) were reported by subjects. The test product was highly rated by subjects on performance and attributes and was well tolerated by all the subjects in this study.

Conclusion

Results demonstrated that an eye cream containing LMW‐HS and a blend of naturally derived extracts achieved global skin rejuvenation by improving appearance of periorbital hyperpigmentation, puffiness, and fine and coarse wrinkles.

Serglycin is involved in inflammatory response in articular mouse chondrocytes

Serglycin is expressed by a variety of cell types and mediates different functions in both normal and pathological conditions by interacting with different biological molecules, such as the CD44 receptor. Many studies suggest that serglycin has a crucial role in inflammatory response, but there are limited data on the functions of this proteoglycan in chondrocytes. In this study we investigated the effect of serglycin knockdown induced by a specific serglycin small interfering RNA (SRGN siRNA) in normal mouse chondrocytes stimulated with lipopolysaccharide (LPS). LPS administration in normal chondrocytes increased the expression of serglycin mRNA and related protein and the production of the pro-inflammatory mediators TNF-alpha, IL-1beta, IL-6, iNOS and MMP-9, through NF-kB activation. In addition, a marked increased expression of CD44 after LPS stimulation was observed. Notably, the CD44 expression and the inflammatory response were significantly reduced by SRGN siRNA treatment in LPS treated chondrocytes. Similar results were obtained in normal mouse chondrocytes exposed to LPS, using a specific blocking antibody against CD44. These results indicate that serglycin produced in LPS-induced inflammation in normal mouse chondrocytes is able to modulate inflammation by interacting with CD44 receptor, suggesting a possible key role in the cartilage inflammation.

Evaluation of the UVB-screening capacity and restorative effects exerted by farnesol gel on UVB-caused sunburn

Farnesol, a natural 15-carbon organic compound, has various microbiological and cellular activities. It has been found to exert apoptosis-inducing effects against carcinoma cells as well as antiallergic and anti-inflammatory effects in vivo. In the current study, a series of formulations composed of various concentrations of hydroxypropyl methylcellulose (HPMC) with the addition of hyaluronan (HA) and xanthan gum (XG) was designed to evaluate the UVB-screening and H₂ O₂ -eliminating effects of farnesol in normal fibroblasts. Farnesol at 0.005, 0.0075, and 0.01% exhibited significant capacity for H₂ O₂ scavenging; at 0.0025%, it showed insignificant effects. Under 120-min UVB exposure, screening with plural gel composed of 0.0025% farnesol, 0.5% HA, and 0.5% XG containing 1.5% or 2% HPMC retained normal fibroblast viability. After 60-min exposure to UVB, screening with plural gel composed of farnesol, HA, XG, and 0.5%, 1.0%, 1.5%, or 2% HPMC decreased the ratio of the G1 phase and increased ratio of the S phase in comparison with the accumulated cell cycle of the normal fibroblasts without screening. The gel with 2% HPMC displayed the strongest cell cycle-reversal ability. In vivo histopathological results showed that the prepared plural gels with 0.5% or 2% HPMC and farnesol, HA, and XG had greater antiphotoaging and reparative effects against UVB-induced changes and damage in the skin. In conclusion, the current in vitro and in vivo results demonstrated that the prepared plural composed of 0.0025% farnesol, 0.5% HA, 0.5% XG, and 2% HPMC possessed the greatest UVB-screening capacity and the strongest restorative effects on UVB-induced sunburned skin.

Soybean-fragmented proteoglycans against skin aging

OBJECTIVE

The majority of age-dependent skin changes happen in the dermis layer inducing changes in skin collagen and in the proteoglycans. The main aim of this work is to study the efficacy of a Proteum serum, containing soybean-fragmented proteoglycans, against skin aging.

MATERIALS AND METHODS

In vitro tests were performed to evaluate the Proteum serum ability on activating the production of collagen and proteoglycans. An in vivo long-term study was performed to determine the efficacy of the Proteum serum when applied on skin. Protection of healthy skin against detergent-induced dermatitis and the antioxidant properties of the applied Proteum serum were also studied.

RESULTS AND DISCUSSION

The in vitro tests demonstrated that the Proteum serum was able to elevate the production of molecules which are essential for supporting the dermal extracellular matrix organization. These results were correlated by the in vivo measurements where a clear trend on improving the measured skin parameters due to the Proteum serum application was found.

CONCLUSIONS

A beneficial effect of the Proteum serum was demonstrated with an improvement in the skin roughness and a reinforcement of the skin barrier function. Moreover, a significant protector effect on human stratum corneum against lipids peroxides (LPO) was demonstrated.

Serglycin in Quiescent and Proliferating Primary Endothelial Cells

Proteoglycans are fundamental components of the endothelial barrier, but the functions of the proteoglycan serglycin in endothelium are less described. Our aim was to describe the roles of serglycin in processes relevant for endothelial dysfunction. Primary human umbilical vein endothelial cells (HUVEC) were cultured in vitro and the expression of proteoglycans was investigated. Dense cell cultures representing the quiescent endothelium coating the vasculature was compared to sparse activated cell cultures, relevant for diabetes, cancer and cardiovascular disease. Secretion of 35S- proteoglycans increased in sparse cultures, and we showed that serglycin is a major component of the cell-density sensitive proteoglycan population. In contrast to the other proteoglycans, serglycin expression and secretion was higher in proliferating compared to quiescent HUVEC. RNAi silencing of serglycin inhibited proliferation and wound healing, and serglycin expression and secretion was augmented by hypoxia, mechanical strain and IL-1β induced inflammation. Notably, the secretion of the angiogenic chemokine CCL2 resulting from IL-1β activation, was increased in serglycin knockdown cells, while angiopoietin was not affected. Both serglycin and CCL2 were secreted predominantly to the apical side of polarized HUVEC, and serglycin and CCL2 co-localized both in perinuclear areas and in vesicles. These results suggest functions for serglycin in endothelial cells trough interactions with partner molecules, in biological processes with relevance for diabetic complications, cardiovascular disease and cancer development.

Proteoglycans in Normal and Healing Skin

Significance: Proteoglycans have a distinct spatial localization in normal skin and are essential for the correct structural development, organization, hydration, and functional properties of this tissue. The extracellular matrix (ECM) is no longer considered to be just an inert supportive material but is a source of directive, spatial and temporal, contextual information to the cells via components such as the proteoglycans. There is a pressing need to improve our understanding of how these important molecules functionally interact with other matrix structures, cells and cellular mediators in normal skin and during wound healing. Recent Advances: New antibodies to glycosaminoglycan side chain components of skin proteoglycans have facilitated the elucidation of detailed localization patterns within skin. Other studies have revealed important proliferative activities of proteinase-generated fragments of proteoglycans and other ECM components (matricryptins). Knockout mice have further established the functional importance of skin proteoglycans in the assembly and homeostasis of the normal skin ECM. Critical Issues: Our comprehension of the molecular and structural complexity of skin as a complex, dynamic, constantly renewing, layered connective tissue is incomplete. The impact of changes in proteoglycans on skin pathology and the wound healing process is recognized as an important area of pathobiology and is an area of intense investigation. Future Directions: Advanced technology is allowing the development of new artificial skins. Recent knowledge on skin proteoglycans can be used to incorporate these molecules into useful adjunct therapies for wound healing and for maintenance of optimal tissue homeostasis in aging skin.

Hyaluronan synthase 2 protects skin fibroblasts against apoptosis induced by environmental stress

A balanced turnover of dermal fibroblasts is crucial for structural integrity and normal function of the skin. During recovery from environmental injury (such as UV exposure and physical wounding), apoptosis is an important mechanism regulating fibroblast turnover. We are interested in the role that hyaluronan (HA), an extracellular matrix molecule synthesized by HA synthase enzymes (Has), plays in regulating apoptosis in fibroblasts. We previously reported that Has1 and Has3 double knock-out (Has1/3 null) mice show accelerated wound closure and increased numbers of fibroblasts in the dermis. In the present study, we report that HA levels and Has2 mRNA expression are higher in cultured Has1/3 null primary skin fibroblasts than in wild type (WT) cells. Apoptosis induced by two different environmental stressors, UV exposure and serum starvation (SS), was reduced in the Has1/3 null cells. Hyaluronidase, added to cultures to remove extracellular HA, surprisingly had no effect upon apoptotic susceptibility to UVB or SS. However, cells treated with 4-methylumbelliferone to inhibit HA synthesis were sensitized to apoptosis induced by SS or UVB. When fibroblasts were transfected with Has2-specific siRNA that lowered Has2 mRNA and HA levels by 90%, both Has1/3 null and WT cells became significantly more sensitive to apoptosis. The exogenous addition of high molecular weight HA failed to reverse this effect. We conclude that Has1/3 null skin fibroblasts (which have higher levels of Has2 gene expression) are resistant to stress-induced apoptosis.

Age-dependent alterations of decorin glycosaminoglycans in human skin

Proteoglycans, a family of glycosaminoglycan (GAG) conjugated proteins, are important constituents of human skin connective tissue (dermis) and are essential for maintaining mechanical strength of the skin. Age-related alterations of dermal proteoglycans have not been fully elucidated. We quantified transcripts of 20 known interstitial proteoglycans in human skin and found that decorin was the most highly expressed. Decorin was predominantly produced by dermal fibroblasts. Decorin was localized in dermal extracellular matrix with GAG bound to type I collagen fibrils. Analysis of decorin extracted from young (21–30 years) and aged (>80 years) sun-protected human buttock skin revealed that decorin molecular size in aged skin is significantly smaller than in young skin. The average size of decorin protein did not alter, indicating size of GAG chain is reduced in aged, compared to young skin. This age-dependent alteration of decorin GAG may contribute to skin fragility of elderly people.

Serglycin: at the crossroad of inflammation and malignancy

Serglycin has been initially characterized as an intracellular proteoglycan expressed by hematopoietic cells. All inflammatory cells highly synthesize serglycin and store it in granules, where it interacts with numerous inflammatory mediators, such as proteases, chemokines, cytokines, and growth factors. Serglycin is implicated in their storage into the granules and their protection since they are secreted as complexes and delivered to their targets after secretion. During the last decade, numerous studies have demonstrated that serglycin is also synthesized by various non-hematopoietic cell types. It has been shown that serglycin is highly expressed by tumor cells and promotes their aggressive phenotype and confers resistance against drugs and complement system attack. Apart from its direct beneficial role to tumor cells, serglycin may promote the inflammatory process in the tumor cell microenvironment thus enhancing tumor development. In the present review, we discuss the role of serglycin in inflammation and tumor progression.

Solar ultraviolet irradiation induces decorin degradation in human skin likely via neutrophil elastase

Exposure of human skin to solar ultraviolet (UV) irradiation induces matrix metalloproteinase-1 (MMP-1) activity, which degrades type I collagen fibrils. Type I collagen is the most abundant protein in skin and constitutes the majority of skin connective tissue (dermis). Degradation of collagen fibrils impairs the structure and function of skin that characterize skin aging. Decorin is the predominant proteoglycan in human dermis. In model systems, decorin binds to and protects type I collagen fibrils from proteolytic degradation by enzymes such as MMP-1. Little is known regarding alterations of decorin in response to UV irradiation. We found that solar-simulated UV irradiation of human skin in vivo stimulated substantial decorin degradation, with kinetics similar to infiltration of polymorphonuclear (PMN) cells. Proteases that were released from isolated PMN cells degraded decorin in vitro. A highly selective inhibitor of neutrophil elastase blocked decorin breakdown by proteases released from PMN cells. Furthermore, purified neutrophil elastase cleaved decorin in vitro and generated fragments with similar molecular weights as those resulting from protease activity released from PMN cells, and as observed in UV-irradiated human skin. Cleavage of decorin by neutrophil elastase significantly augmented fragmentation of type I collagen fibrils by MMP-1. Taken together, these data indicate that PMN cell proteases, especially neutrophil elastase, degrade decorin, and this degradation renders collagen fibrils more susceptible to MMP-1 cleavage. These data identify decorin degradation and neutrophil elastase as potential therapeutic targets for mitigating sun exposure-induced collagen fibril degradation in human skin.

Inflammasome activation of IL-1 family mediators in response to cutaneous photodamage

Although keratinocytes are relatively resistant to ultraviolet radiation (UVR) induced damage, repeated UVR exposure result in accumulated DNA mutations that can lead to epidermal malignancies. Keratinocytes play a central role in elaborating innate responses that lead to inflammation and influence the generation of adaptive immune responses in skin. Apart from the minor cellular constituents of the epidermis, specifically Langerhans cells and melanocytes, keratinocytes are the major source of cytokines. UVR exposure stimulates keratinocytes to secrete abundant pro-inflammatory IL-1-family proteins, IL-1α, IL-1β, IL-18, and IL-33. Normal skin contains only low levels of inactive precursor forms of IL-1β and IL-18, which require caspase 1-mediated proteolysis for their maturation and secretion. However, caspase-1 activation is not constitutive, but dependents on the UV-induced formation of an active inflammasome complex. IL-1 family cytokines can induce a secondary cascade of mediators and cytokines from keratinocytes and other cells resulting in wide range of innate processes including infiltration of inflammatory leukocytes, induction of immunosuppression, DNA repair or apoptosis. Thus, the ability of keratinocytes to produce a wide repertoire of proinflammatory cytokines can influence the immune response locally as well as systematically, and alter the host response to photodamaged cells. We will highlight differential roles played by each IL-1 family molecule generated by UV-damaged keratinocytes, and reveal their complementary influences in modulating acute inflammatory and immunological events that follow cutaneous UV exposure.

Acute UV irradiation increases heparan sulfate proteoglycan levels in human skin

Glycosaminoglycans are important structural components in the skin and exist as various proteoglycan forms, except hyaluronic acid. Heparan sulfate (HS), one of the glycosaminoglycans, is composed of repeated disaccharide units, which are glucuronic acids linked to an N-acetyl-glucosamine or its sulfated forms. To investigate acute ultraviolet (UV)-induced changes of HS and HS proteoglycans (HSPGs), changes in levels of HS and several HSPGs in male human buttock skin were examined by immunohistochemistry and real-time quantitative polymerase chain reaction (qPCR) after 2 minimal erythema doses (MED) of UV irradiation (each n = 4-7). HS staining revealed that 2 MED of UV irradiation increased its expression, and staining for perlecan, syndecan-1, syndecan-4, CD44v3, and CD44 showed that UV irradiation increased their protein levels. However, analysis by real-time qPCR showed that UV irradiation did not change mRNA levels of CD44 and agrin, and decreased perlecan and syndecan-4 mRNA levels, while increased syndecan-1 mRNA level. As HS-synthesizing or -degrading enzymes, exostosin-1 and heparanase mRNA levels were increased, but exostosin-2 was decreased by UV irradiation. UV-induced matrix metalloproteinase-1 expression was confirmed for proper experimental conditions. Acute UV irradiation increases HS and HSPG levels in human skin, but their increase may not be mediated through their transcriptional regulation.

Animal models of acute photodamage: comparisons of anatomic, cellular and molecular responses in C57BL/6J, SKH1 and Balb/c mice

Human cutaneous photodamage is a major medical problem that includes premature aging and fragility of the skin. Nonxenografted animal models have not been comparatively evaluated for how well they resemble the changes seen in human skin. Here, we sought to identify a suitable mouse model that recapitulates key anatomic, cellular and molecular responses observed in human skin during acute UV exposure. Adult females from three strains of mice, C57BL/6J, SKH1 and Balb/c were exposed to UVB and then evaluated 3 or 20 h after the last irradiation. Skin from UVB-exposed C57BL/6J mice showed features resembling human photodamage, including epidermal thickening, infiltration of the dermis with inflammatory cells, induction of tumor necrosis factor-α (TNF-α) mRNA, accumulation of glycosaminoglycans, particularly hyaluronan in the epidermis and loss of collagen. Hairless SKH1 mouse skin responded similarly, but without any induction of TNF-α mRNA or chondroitin sulfate. Irradiated Balb/c mice were the least similar to humans. Our results in C57BL/6J mice and to a lesser extent in SKH1 mice, show cutaneous responses to a course of UVB-irradiation that mirror those seen in human skin. Proper choice of model is critical for investigating cellular and molecular mechanisms of photodamage and photoaging.