Age-related changes in the proteoglycans of human skin

Expression, localisation and synthesis of versican by the enamel organ of developing mouse molar tooth germ: an in vivo and in vitro study

OBJECTIVE

Versican is a large, aggregating chondroitin sulphate proteoglycan. In dental tissue, versican expression occurs primarily in mesenchymal tissue but rarely in epithelial tissue. We investigated the expression, localisation and synthesis of versican in the enamel organ of the developing tooth germ.

DESIGN

To elucidate versican localisation in vivo, in situ hybridisation and immunohistochemistry were conducted in foetal ICR mice at E11.5-E18.5. Epithelium and mesenchyme from the lower first molars at E16.0 were enzymatically separated and versican mRNA expression was investigated by semi-quantitative RT-PCR. Organ culture of the separated samples combined with metabolic labelling with [(35)S], followed by gel filtration, was performed to analyse secreted proteoglycans.

RESULTS

Versican mRNA was first expressed in the thickened dental epithelium at E12.0 and continued to be expressed in the enamel organ until the bell stage. Versican immunostaining was detected in the stellate reticulum areas from the bud stage to the apposition stage. The enamel organ at E16.0 expressed versican mRNA at a level comparable to that in dental mesenchyme. Furthermore, when compared to dental mesenchyme, about 1/2-3/4 of the [(35)S]-labelled versican-like large proteoglycan was synthesised and released into tissue explants by the enamel organ.

CONCLUSIONS

The dental epithelium of developing tooth germ is able to synthesise significant amounts of versican.

Glycan profiling of a defect in decorin glycosylation in equine systemic proteoglycan accumulation, a potential model of progeroid form of Ehlers-Danlos syndrome

Defects in glycosylation of decorin can result in systemic hereditary disease. A mutation in the galactosyl transferase I gene is the underlying defect of a progeroid form of Ehlers-Danlos syndrome. We have previously described pathological changes in equine systemic proteoglycan accumulation (ESPA, formerly degenerative suspensory ligament desmitis) as consisting of excessive presence of decorin and other proteoglycans in organs and structures with a high content of connective tissue. Using liquid chromatography/mass spectrometry, and one- and two-dimensional immunoblotting we have determined that decorin from ESPA-tendons had a higher molecular weight than decorin from non-affected control tendons. Glycosaminoglycan structure and monosaccharide composition were determined with HPLC analysis of chondroitinase ABC-digested glycosaminoglycans and gas chromatography/mass spectrometry. This analysis revealed an increase in the total content of sulfated disaccharides, particularly due to enhanced sulfation at 6-position of N-acetyl galactosamine (GalNAc) with a subsequent decrease in the ratio of 4-sulfation to 6-sulfation disaccharides in the ESPA decorin. The ESPA-affected decorin also exhibited altered biological activity resulting in (1) diminished binding of TGFbeta1 (and of anti-decorin antibody) to ESPA decorin, and (2) increased expression of TGFbeta1 in ESPA tissues.

Fibroblasts-a diverse population at the center of it all

The capacity of fibroblasts to produce and organize the extracellular matrix and to communicate with other cells makes them a central component of tissue biology. Even so, fibroblasts remain a somewhat enigmatic population. Our inability to fully comprehend these cells is in large part due to the paucity of unique cellular markers and to their pervasive diversity. Much of our understanding of fibroblast diversity has evolved from studies where subpopulations of these cells have been produced without resorting to cell surface markers. In this regard, cloning and mechanical separation of tissues prior to establishing cultures has provided multiple subpopulations. Nonetheless, in isolated situations, the expression or lack of expression of Thy-1/CD90 has been used to separate fibroblast subsets. The role of fibroblasts in intercellular communication is emerging through the implementation of organotypic studies in which three-dimensional fibroblast culture are combined with other populations of cells. Such studies have revealed critical paracrine loops that are essential for organ development and for wound repair. These studies also provide a backdrop for the emerging field of tissue engineering. The participation of fibroblasts in the regulation of tissue homeostasis and their contribution to the aging process are emerging issues that require better understanding. In short, fibroblasts represent a multifaceted, complex group of cells.

Coenzyme Q10 protects against oxidative stress-induced cell death and enhances the synthesis of basement membrane components in dermal and epidermal cells

Coenzyme Q10 (CoQ10), which has both energizing and anti-oxidative effects, is also reported to have antiaging action, e.g., reducing the area of facial wrinkles. However, the mechanism of its anti-aging activity is not fully established. Here, we examined the effect of CoQ10 on human dermal and epidermal cells. CoQ10 promoted proliferation of fibroblasts but not keratinocytes. It also accelerated production of basement membrane components, i.e., laminin 332 and type IV and VII collagens, in keratinocytes and fibroblasts, respectively; however, it had no effect on type I collagen production in fibroblasts. CoQ10 also showed protective effects against cell death induced by several reactive oxygen species in keratinocytes, but only when its cellular absorption was enhanced by pretreatment of the cells with highly CoQ10-loaded serum. These results suggest that protection of epidermis against oxidative stress and enhancement of production of epidermal basement membrane components may be involved in the antiaging properties of CoQ10 in skin.

Decorin is significantly overexpressed in nephrogenic systemic fibrosis

The role of the proteoglycans in the pathogenesis of nephrogenic systemic fibrosis (NSF) is unclear. We assessed expression of decorin, versican, and transforming growth factor beta1 (TGF-beta1) in skin specimens of 10 patients with biopsy-proven NSF and different control groups. Real-time reverse transcription-polymerase chain reaction studies and immunohistochemical analysis were performed on full-thickness skin specimens. The messenger RNA (mRNA) and protein levels of decorin were significantly higher in the skin lesions of patients with NSF than in skin lesions of patients with systemic sclerosis, patients undergoing hemodialysis, and healthy subjects. The versican mRNA levels in NSF lesions differed significantly only from the levels in healthy subjects. TGF-beta1 mRNA expression was significantly overexpressed in NSF lesions compared with control skin specimens investigated. In NSF specimens, the mRNA expression of TGF-beta1 and decorin were highly correlated (r = 0.92). Our results suggest that decorin and TGF-beta1 may have a fundamental role in the pathogenesis of NSF. Conversely, versican seems less likely to be of pathogenetic significance in NSF.

Cocoa polyphenols and their influence on parameters involved in ex vivo skin restructuring

Polyphenols in general are compounds that are known to promote health and have a preventive effect against various chronic diseases. The influence of cocoa polyphenols on skin, however, has scarcely been studied from a histological point of view. The aim of this study is to assess the influence of cocoa polyphenols on several indicators of skin elasticity and skin tonus, namely, glycosaminoglycans and collagen I, III and IV. This was carried out by using a model of ex vivo human skin explants maintained in survival, on which a cocoa polyphenol extract was applied. After processing by standard histological techniques (fixation, paraffin embedding, sectioning, staining, immunostaining and microscopical observation), the influence of cocoa polyphenols on the evaluated parameters was quantified by image analysis. The results obtained show that cocoa polyphenols exhibit a positive action on the parameters assessed, and the dose at which they improve the most parameters associated with skin tonus and elasticity was determined. Their activity was compared with a commercially available product, and the results obtained show that their efficacy is equivalent. Moreover, an enhancing effect of cocoa butter on activity of cocoa polyphenol was highlighted. Now that the properties of cocoa polyphenols on ex vivo skin restructuring parameters have been assessed, the next step could include their evaluation in vivo.

Deregulation of versican and elastin binding protein in solar elastosis

Several changes in skin appearance including loss of elasticity and wrinkle formation are associated with alterations in the composition of the dermal extracellular matrix. They are induced by intrinsic aging or by environmental factors such as UV light referred to as photoaging. A general characteristic in the histology of photoaged skin is the accumulation of elastotic material suggesting impaired formation and/or massive breakdown of elastic fibres. In order to shed light on some of the underlying mechanisms we tracked two of the major players in elastic fibre formation in different skin conditions: EBP (elastin binding protein), a regulator of elastic fibre assembly and VER (versican), a component of functional elastic fibres as well as non-functional elastotic material. Using quantitative RT-PCR on skin biopsies we found that the expression levels of VER and EBP were unaltered during intrinsic skin aging. Upon acute UV stress however, VER and EBP showed different regulation patterns: VER mRNA increased after 6 h and was further up-regulated until 24 h. The EBP mRNA by contrast was reduced after 6 h but showed massive induction at 24 h after acute UV stress. In chronically sun-exposed skin, VER protein was accumulated similar to elastotic material in the extracellular space, whereas its mRNA level was consistently reduced compared to sun-protected skin. The EBP mRNA by contrast showed slightly increased expression levels in the sun-exposed area compared to its sun-protected counterpart. Based on these data we propose a model which may help to explain parts of the mechanisms leading to the formation of elastotic masses. We further hypothesize that the presence of elastotic material triggers some yet unknown feedback mechanism(s) resulting in altered expression patterns of VER and EBP in chronically sun-exposed skin.

Reconstructed skin modified by glycation of the dermal equivalent as a model for skin aging and its potential use to evaluate anti-glycation molecules

Glycation is a slow chemical reaction which takes place between amino residues in protein and a reducing sugar. In skin this reaction creates new residues or induces the formation of cross-links (advanced glycation end products or AGEs) in the extracellular matrix of the dermis. Formation of such cross-links between macromolecules may be responsible for loss of elasticity or modification of other properties of the dermis observed during aging. We had previously developed a reconstructed skin model which enabled us to study the consequences of matrix alteration by preglycation of the collagen and have reported several modifications of interest induced by glycation in the dermal and epidermal compartments of reconstructed skin as well as at the level of the dermal-epidermal junction. For example we showed that collagen IV and laminin were increased in the basement membrane zone and that alpha6 and beta1 integrins in epidermis were expanded to suprabasal layers. The aim of this new study was to look at the biological effects of glycation inhibitors like aminoguanidine in the skin model. Aminoguanidine was mixed with collagen in the presence of ribose as reducing sugar, and immunostaining was used to visualize its effects on AGE Products and biological markers. After aminoguanidine treatment, we found a low amount of AGE products and a possible return to the normal pattern of distribution of markers in skin constructs as compared to those treated with ribose only. Interestingly similar results were also obtained, although to a lesser extent, with a blueberry extract. In conclusion the glycation inhibitory effect has been functionally demonstrated in the reconstructed skin model and it is shown that this model can be used to assess anti-glycation agents.

The secreted metalloprotease ADAMTS20 is required for melanoblast survival

ADAMTS20 (Adisintegrin-like and metalloprotease domain with thrombospondin type-1 motifs) is a member of a family of secreted metalloproteases that can process a variety of extracellular matrix (ECM) components and secreted molecules. Adamts20 mutations in belted (bt) mice cause white spotting of the dorsal and ventral torso, indicative of defective neural crest (NC)-derived melanoblast development. The expression pattern of Adamts20 in dermal mesenchymal cells adjacent to migrating melanoblasts led us to initially propose that Adamts20 regulated melanoblast migration. However, using a Dct-LacZ transgene to track melanoblast development, we determined that melanoblasts were distributed normally in whole mount E12.5 bt/bt embryos, but were specifically reduced in the trunk of E13.5 bt/bt embryos due to a seven-fold higher rate of apoptosis. The melanoblast defect was exacerbated in newborn skin and embryos from bt/bt animals that were also haploinsufficient for Adamts9, a close homolog of Adamts20, indicating that these metalloproteases functionally overlap in melanoblast development. We identified two potential mechanisms by which Adamts20 may regulate melanoblast survival. First, skin explant cultures demonstrated that Adamts20 was required for melanoblasts to respond to soluble Kit ligand (sKitl). In support of this requirement, bt/bt;Kit(tm1Alf)/+ and bt/bt;Kitl(Sl)/+ mice exhibited synergistically increased spotting. Second, ADAMTS20 cleaved the aggregating proteoglycan versican in vitro and was necessary for versican processing in vivo, raising the possibility that versican can participate in melanoblast development. These findings reveal previously unrecognized roles for Adamts proteases in cell survival and in mediating Kit signaling during melanoblast colonization of the skin. Our results have implications not only for understanding mechanisms of NC-derived melanoblast development but also provide insights on novel biological functions of secreted metalloproteases.

Tobacco smoke causes premature skin aging

Smoking tobacco is the most preventable cause of morbidity and is responsible for more than three million deaths a year worldwide. In addition to a strong association with a number of systemic diseases, smoking is also associated with many dermatological conditions, including poor wound healing, premature skin aging, squamous cell carcinoma, melanoma, oral cancer, acne, psoriasis, and hair loss. This review focuses on the effects of smoking on premature skin aging. It has been long established that smoking has deleterious effects on skin. Epidemiological studies indicate that smoking is an important environmental factor in premature skin aging. In vitro studies indicate that tobacco smoke extract impairs the production of collagen and increases the production of tropoelastin and matrix metalloproteinases (MMP), which degrade matrix proteins, and also causes an abnormal production of elastosis material. Smoking increases MMP levels, which leads to the degradation of collagen, elastic fibers, and proteoglycans, suggesting an imbalance between biosynthesis and degradation in dermal connective tissue metabolism. Reactive oxygen species are also involved in tobacco smoke-induced premature skin aging. Scavengers of reactive oxygen species ameliorate the induction of MMP. Tobacco smoke extract also impacts dermal connective tissue in nude mice. Thus, in vitro and in vivo evidence indicates that smoking tobacco leads to accelerated aging of the skin. These findings might be useful to motivate those patients who are more concerned about their appearance than the potential internal damage associated with smoking to stop smoking.

The extracellular matrix in wound healing: a closer look at therapeutics for chronic wounds

Disappointing results with the use of exogenous recombinant growth factors in chronic wounds have redirected the focus to the extracellular matrix (ECM). Newer research has clearly changed our view on the role of the ECM in tissue repair and dismissed the dogma that the sole function of ECM is a passive physical support for cells. It is now clear that intact or fragmented ECM molecules are capable of transducing signals pivotal for cell processes in wound healing primarily via integrin interactions in concert with growth factor activation. In addition, our knowledge about ECM molecules in minute concentrations with biological activity, but devoid of significant structural influence, is increasing. This article reviews the multifaceted molecular roles of ECM in the normal wound-healing process and some molecular abnormalities in chronic wounds, and touches on potential therapies based on the developments of tissue biology.

Lumican, a small leucine-rich proteoglycan substituted with keratan sulfate chains is expressed and secreted by human melanoma cells and not normal melanocytes

Melanoma is a frequent and therapy-resistant human disease. Malignant melanocytes modulate their microenvironment in order to penetrate the dermal/epidermal junction and eventually invade the dermis. The small leucine-rich proteoglycans (SLRPs) constitute important constituents of the dermis extracellular matrix (ECM), participating in both the structural and the functional organization of the skin. The role of a keratan sulphate SLRP lumican, has recently been investigated in the growth and metastasis of several cancers. In this study, the expression of lumican was studied in two human melanoma cell lines (WM9, M5) as well as in normal neonatal human melanocytes (HEMN) using real time PCR, western blotting with antibodies against the protein core and keratan sulfate, and treatments with specific enzymes. Both human metastatic melanoma cell lines were found to express lumican mRNA and effectively secrete lumican in a proteoglycan form, characterized to be substituted mostly with keratan sulfate chains. Lumican mRNA was not detected in normal melanocytes. This is the first time that the synthesis and secretion of lumican in human melanoma cell lines is reported. The role of this proteoglycan in the development and progression of malignant melanoma has to be further investigated.

Chondroitin sulfate in normal human plasma is modified depending on the age. Its evaluation in patients with pseudoxanthoma elasticum

Plasma chondroitin sulfate (CS) amount and charge density were determined in 45 healthy volunteers (control group), 45 pseudoxanthoma elasticum (PXE)-affected patients and 19 healthy carriers by using fluorophore-assisted carbohydrate electrophoresis (FACE) and HPLC equipped with postcolumn derivatization and fluorescence detection. The mean values of CS amount were 4.9+/-1.21 for volunteers, 4.7+/-1.40 for PXE subjects and 4.4+/-1.44 for the carriers. No significant differences were found for the three human subjects groups. On the contrary, by considering the age of normal volunteers, a significant increase of plasma CS amount was measured. In fact, the volunteers aging from 17 to 40 years (mean 32.1) showed a CS concentration of 4.3+/-1.30 while the group ranging from 50 to 74 years (mean 56.9) had a value of 5.6+/-1.16 with a significant increase of +30.2%. The same significant increase in CS plasma content with increasing age was measured for PXE-affected and healthy carriers group. Extracted plasma CS was evaluated for the main two unsaturated disaccharides, non-sulfated and 4-monosulfated, and the charge density determined. The mean values were 0.54+/-0.13 for volunteers, 0.60+/-0.15 for PXE subjects and 0.50+/-0.15 for the carriers. A significant increase of +11.1% was found between the PXE patients and healthy human group but no differences were calculated between the control group and the carriers. Furthermore, besides a CS amount, the volunteers aging from 17 to 40 years (mean 32.1) showed a charge density of 0.53+/-0.14 while the group ranging from 50 to 74 years (mean 56.9) had a value of 0.58+/-0.17 with a significant increase of +9.4%. The same trend was measured for the healthy carriers group. The CS charge density of PXE-affected subjects was found to increase significantly more than healthy controls depending on the age. In fact, the PXE patients aging from 10 to 40 years (mean 29.3) showed a charge density of 0.56+/-0.14 while the group ranging from 50 to 74 years (mean 58.6) had a value of 0.67+/-0.11 with a significant increase of +19.6%. Furthermore, the group of PXE-affected subjects ranging from 50 to 74 years (mean 58.6) showed a significant increase of 15.5% in comparison with the group matched for age (mean 56.9) of healthy volunteers.

Change in decorin during aging of rat placenta

By immunohistochemistry, with or without chondroitinases, decorin was found to be distributed in the extracellular matrix of chorionic villi and amnia. The strength of staining intensified with increasing gestational age. Decorin was isolated from the placenta of 13- to 20-day-old pregnant rats and identified by Western blotting, using an antidecorin core protein antibody. The molecular weight of decorin is approximately 100 kDa, whereas the respective figures for the core protein treated with chondroitinase (chase) ABC and with chase B are approximately 40 kDa and 43 kDa. The difference in the molecular weight between the core protein with chase ABC and B suggests that the glycosaminoglycan (GAG)- base structure on the core protein was chondroitin sulfate (CS) without dermatan sulfate (DS). The decorin content and the proportion of CS to DS in GAG increased with age. We concluded that the age-related changes in the GAG chain may be related to specific functional properties and may have a crucial role in placental tissue organization.

Structural change in decorin with skin aging

Decorin, the main proteoglycan in skin, has a small size with a core protein of approximately 40kDa and one chondroitin sulfate/dermatan sulfate glycosaminoglycan (GAG) chain. The main function of decorin is to regulate the collagen matrix assembly. Decorin is distributed along collagen fibrils with the core protein and the decorin GAG chain controls the distance between the collagen fibrils. Reducing the length of the decorin GAG chain reduces the distance between the collagen fibrils. Age-related changes in decorin are apparent in the GAG chain in respect to the molecular size and sulfate position but not in the core protein. Structural changes in the decorin GAG chain may be involved in changes in collagen matrix assembly during the aging process.

Expression and localization of versican during postnatal development of rat temporomandibular joint disc

To analyze the growth-related changes in extracellular matrix components in temporomandibular joint (TMJ) discs, the expression and localization of the core protein of a large chondroitin sulphate proteoglycan, versican, in rat TMJ discs during postnatal development (2-32 weeks) were examined using Western blot analysis, real-time quantitative PCR and immunohistochemistry. Western blot analysis showed that rat TMJ discs predominantly expressed one isoform (V1) and the core protein sharply increased after birth, reached a peak at 8 weeks, and then gradually decreased up to 32 weeks. Real-time quantitative PCR with TaqMan probes indicated that mRNA expression of versican was highest at 2 weeks and gradually decreased with growth. An immunohistochemical study showed that staining for versican was weak and evenly distributed in TMJ discs at 2 weeks. Regional differences in staining for versican became prominent after 8 weeks; staining was intense in the anterior and posterior peripheral attachments, and weak in the central part of the discs. These results demonstrate that growth-related changes and regional differences exist in the expression of versican in the TMJ discs of growing rats, and these probably reflect the changes in the biomechanical environment caused by the development of orofacial functions.

Influence of aging on glycosaminoglycans and small leucine-rich proteoglycans production by skin fibroblasts

Skin aging is characterised by a progressive deterioration of its functional properties, linked to alterations of dermal connective tissue. Whereas many studies have been devoted to collagen alterations during aging, the situation is less clear concerning glycosaminoglycans and proteoglycans. Particularly, the alterations of the expression of small leucine-rich proteoglycans (SLRPs), a family of proteoglycans strongly implicated in cell regulation, have never been studied. In the present study we measured glycosaminoglycans and small leucine-rich proteoglycans synthesis by skin fibroblasts from donors of 1 month to 83 years old. [3H]-glucosamine and [35S]-sulfate incorporation did not show significant differences of sulfated GAG synthesis during aging. On the other hand, a significant positive correlation was found between hyaluronan secretion and donor's age. Northern blot analysis of SLRPs mRNAs showed a significant negative correlation of lumican mRNA with donor's age, whereas decorin and biglycan mRNAs were not significantly altered. Immunohistochemical study and quantitative image analysis confirmed a decreased lumican accumulation in aged human skin. Taken together, our results suggest that impairment of glycosaminoglycans and SLRPs synthesis might be involved in the functional alterations of aged skin.

Sulfated glycosaminoglycans of the vagina and perineal skin in pre- and postmenopausal women, according to genital prolapse stage

The aim of this study was to analyze the amount and types of sulfated glycosaminoglycans (GAGs) of the extracellular matrix (ECM) in the posterior vaginal wall and perineal skin in menacme and postmenopausal women, according to genital prolapse stage. Samples of vaginal tissue and perineal skin were obtained from 40 women who underwent vaginal surgery. Sulfated glycosaminoglycans were extracted by extensive tissue maxatase digestion, submitted to electrophoresis on agarose gel, and their concentrations were determined by densitometry. Dermatan sulphate (DS) was the predominant GAG, followed by chondroitin sulfate (CS) and heparan sulfate (HS). In the vagina there was a significant decrease in total GAGs, CS, DS and HS in postmenopausal women with prolapse stage 2 and 3 compared to the premenopausal group, independent of the stage. In stage 2 and 3 postmenopausal patients there was a significant decrease of DS and HS compared to the stage 1 postmenopausal group. In perineal skin there was no significant difference between total GAG amount, DS and HS. However, the amount of CS in premenopausal stage 1 patients was significantly than that in postmenopausal patients stage 1 and stages 2 and 3. In conclusions, there are quantitative and qualitative differences in GAGs of the ECM in vaginal wall and perineal skin between women in menacme and the postmenopause, according to genital prolapse stage.

Structural changes in the glycosaminoglycan chain of rat skin decorin with growth

Decorin controls collagen fibrilogenesis in skin, and its molecular weight changes in wound healing and with age. In this report, the quantitative and structural changes of decorin were investigated with growth in rat skin from the fetus to the young adult. A northern blot analysis showed that the highest level of skin decorin mRNA was at post partus 0.5 days; this level was about 3.7 times the level at embryo 16.5 days. The mRNA level in the rat skin decreased by 1/5 from post partus 0.5 days until 90 days of age. Western blotting showed that the amount of decorin increased with age in protein level. The molecule size of decorin at embryo 18.5 days was about 110 kDa, and that at post partus 90 days was about 70 kDa. There were no changes in molecular size of its core protein, so the reduction in the size of decorin was dependent on the size of the glycosaminoglycan (GAG) as shown by western blot analyses. Electron micrography of the rat skin with cupromeronic blue staining showed that the length of GAG at embryo 18.5 days was about 78.58 +/- 13.94 nm, and that at post partus 90 days was about 54.05 +/- 4.79 nm. The reduction in length of decorin GAG with age shrunk the distance between the collagen fibrils. We suggested that decorin changes the GAG length in order to control skin reconstruction in response to inflammation and injury.

Age-related changes in the proteoglycans of human skin. Specific cleavage of decorin to yield a major catabolic fragment in adult skin

Dramatic changes occur in skin as a function of age, including changes in morphology, physiology, and mechanical properties. Changes in extracellular matrix molecules also occur, and these changes likely contribute to the overall age-related changes in the physical properties of skin. The major proteoglycans detected in extracts of human skin are decorin and versican. In addition, adult human skin contains a truncated form of decorin, whereas fetal skin contains virtually undetectable levels of this truncated decorin. Analysis of this molecule, herein referred to as decorunt, indicates that it is a catabolic fragment of decorin rather than a splice variant. With antibody probes to the core protein, decorunt is found to lack the carboxyl-terminal portion of decorin. Further analysis by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry shows that the carboxyl terminus of decorunt is at Phe(170) of decorin. This result indicates that decorunt represents the amino-terminal 43% of the mature decorin molecule. Such a structure is inconsistent with alternative splicing of decorin and suggests that decorunt is a catabolic fragment of decorin. A neoepitope antiserum, anti-VRKVTF, was generated against the carboxyl terminus of decorunt. This antiserum does not recognize intact decorin in any skin proteoglycan sample tested on immunoblots but recognizes every sample of decorunt tested. The results with anti-VRKVTF confirm the identification of the carboxyl terminus of decorunt. Analysis of collagen binding by surface plasmon resonance indicates that the affinity of decorunt for type I collagen is 100-fold less than that of decorin. This observation correlates with the structural analysis of decorunt, in that it lacks regions of decorin previously shown to be important for interaction with type I collagen. The detection of a catabolic fragment of decorin suggests the existence of a specific catabolic pathway for this proteoglycan. Because of the capacity of decorin to influence collagen fibrillogenesis, catabolism of decorin may have important functional implications with respect to the dermal collagen network.

Estudo histoquímico das proteoglicanas da fáscia transversal e bainha anterior do músculo reto abdominal em homens adultos, portadores de hérnia inguinal tipo II e IIIA de NYHUS

OBJETIVO: Avaliar, de maneira quantitativa, as proteoglicanas na fáscia transversal e na bainha anterior do músculo reto abdominal de pacientes homens, adultos, portadores de hérnia inguinal tipo II e IIIA de NYHUS. MÉTODO: Foram constituídos três grupos de estudo: um grupo controle, composto por dez cadáveres com óbito até 24 horas e de dois grupos, cada um com vinte pacientes, portadores de hérnias tipo II e IIIA de NYHUS. Foram retiradas amostras da fáscia transversal e da bainha anterior do músculo reto abdominal que foram coradas com Alcian Blue, pH 2,5. As lâminas foram analisadas no programa IMAGELAB de avaliação histológica informatizada. RESULTADOS: Observou-se menor quantidade de proteoglicanas nos pacientes com hérnia inguinal, em relação ao grupo controle. Essa diferença foi estatisticamente significante. CONCLUSÃO: A concentração de proteoglicanas na matriz extracelular está diminuída na fáscia transversal e na bainha anterior do músculo reto abdominal de pacientes homens adultos, portadores de hérnia inguinal tipo II e IIIA de NYHUS, em relação ao grupo controle, constituído por cadáveres não portadores de hérnia inguinal.

Mechanobiology of force transduction in dermal tissue

BACKGROUND/AIMS

The influence of mechanical forces on skin has been examined since 1861 when Langer first reported the existence of lines of tension in cadaver skin. Internal tension in the dermis is not only passively transferred to the epidermis but also gives rise to active cell-extracellular matrix and cell-cell mechanical interactions that may be an important part of the homeostatic processes that are involved in normal skin metabolism. The purpose of this review is to analyse how internal and external mechanical loads are applied at the macromolecular and cellular levels in the epidermis and dermis.

METHODS

A review of the literature suggests that internal and external forces applied to dermal cells appear to be involved in mechanochemical transduction processes involving both cell-cell and cell-extra-cellular matrix (ECM) interactions. Internal forces present in dermis are the result of passive tension that is incorporated into the collagen fiber network during development. Active tension generated by fibroblasts involves specific interactions between cell membrane integrins and macromolecules found in the ECM, especially collagen fibrils. Forces appear to be transduced at the cell-ECM interface via re-arrangement of cytoskeletal elements, activation of stretch-induced changes in ion channels, cell contraction at adherens junctions, activation of cell membrane-associated secondary messenger pathways and through growth factor-like activities that influence cellular proliferation and protein synthesis.

CONCLUSIONS

Internal and external mechanical loading appears to affect skin biology through mechanochemical transduction processes. Further studies are needed to understand how mechanical forces, energy storage and conversion of mechanical energy into changes in chemical potential of small and large macromolecules may occur and influence the metabolism of dermal cells.

Modulation of cell-phenotype during in vitro aging. Glycosaminoglycan biosynthesis by skin fibroblasts and corneal keratocytes

The aim of this study was to compare keratocyte and fibroblast phenotypes during in vitro aging by comparing their biosynthesis of glycosaminoglycans using explant and cell cultures. Human skin and corneal explant cultures were realised with Dulbecco Modified Eagle's medium containing 3H glucosamine. Sequential cell cultures were studied at different passages for GAGs biosynthesis by 3H glucosamine incorporation followed by selective degradation with specific hydrolases. Radioactivity was determined and each GAG fraction evaluated. KS and DS are the major components synthesised by corneal explant culture. During in vitro aging, keratocytes synthesised 41% less KS between passages 4-9 with a decrease by 26% of the proportion of DS observed in the same conditions. In skin explant cultures, as expected the major components are CS and hyaluronan (HA). In the first cell passage studied compared with skin organ cultures we could notice a strong decrease of the proportions of DS and KS compensated by an increase of the proportion of HA. During the successive passages of fibroblasts, the proportions of DS and HS decreased (-30 and -62%, respectively) and those of KS increased (+90%). These results indicate that there remain measurable differences between keratocyte and fibroblast phenotypes as far as GAG-synthesis is concerned all though the successive passages, starting from explant cultures and up to the limits of in vitro cell passages.

Age-related changes in human bone proteoglycan structure. Impact of osteogenesis imperfecta

Proteoglycans (PGs) are a family of molecules that undergo extensive post-translational modifications that include addition of glycosaminoglycan (GAG) chains as well as N- and O-linked oligosaccharides to the protein core. PG composition and structure have been reported to alter with age. To test whether the post-translational modifications to PGs can serve as in vitro surrogate end point markers for chronological age, the extent of GAG modifications was determined for PGs derived from normal human bone cells of 14 donors (age range, fetal to 60 years). Isolated cells were steady state radiolabeled with (35)SO(4)(2-) and [(3)H]GlcN. For biglycan and decorin, iduronate content was linearly correlated with age (increased 1.5x between fetal and age 60 years). For the syndecan-like heparan sulfate PG, the N-sulfation of post-natal cells increased over 3.5-fold until reaching a plateau during the 4th decade of life. The amount of O-linked oligosaccharides was also found to decrease as a function of increasing normal donor age, whereas the specific activity of the metabolic precursor pool remained constant regardless of donor age. These age-related changes in post-translational modifications were then used to demonstrate that osteoblasts derived from patients with osteogenesis imperfecta did not exhibit facets of a pre-mature aging, but rather were arrested in a fetal-like phenotypic state. A growth matrix rich in thrombospondin altered PG metabolism in osteoblastic cells, resulting in the production and secretion of the fetal-like (rich in O-linked oligosaccharides) forms of decorin and biglycan. This effect was qualitatively different from the effect of transforming growth factor-beta, which predominantly altered GAGs rather than O-linked oligosaccharides. No other Arg-Gly-Asp protein (fibronectin, vitronectin, type I collagen, osteopontin, and bone sialoprotein) showed any detectable effect on PG metabolism in bone cells. These results indicate that a proper matrix stoichiometry is critical for metabolism of PGs.

Dermatan sulfate: new functions from an old glycosaminoglycan

Glycosaminoglycans constitute a considerable fraction of the glycoconjugates found on cellular membranes and in the extracellular matrix of virtually all mammalian tissues. Their ability to bind and alter protein-protein interactions or enzymatic activity has identified them as important determinants of cellular responsiveness in development, homeostasis, and disease. Although heparan sulfate tends to be emphasized as the most biologically active glycosaminoglycan, dermatan sulfate is a particularly attractive subject for further study because it is expressed in many mammalian tissues and it is the predominant glycan present in skin. Dermatan and dermatan sulfate proteoglycans have also been implicated in cardiovascular disease, tumorigenesis, infection, wound repair, and fibrosis. Growing evidence suggests that this glycosaminoglycan, like the better studied heparin and heparan sulfate, is an important cofactor in a variety of cell behaviors.

The cellular proliferative phase of the wound repair process

The proliferative--or new-tissue formation--phase of wound healing is complex. This article examines the changes that occur to cells during this stage and the effect on the extracellular matrix environment.

Structural varieties of small proteoglycans in human spinal ligament

Three types of small proteoglycan were purified from human spinal ligaments by ultracentrifugation, ion-exchange chromatography, gel-chromatography, and hydrophobic chromatography. Two of them were identified as decorin and biglycan, and the other was thought to be a decorin-subtype. Molecular sizes of decorin and decorin-subtype were both 85 kDa, and that of biglycan was 200 kDa. N-Terminal amino acid sequence of decorin-subtype corresponded with that of decorin, although it was different from decorin in terms of composition of amino acids and glycosaminoglycan chains, and reactivity with anti-human decorin antibody. The ratios of chondroitin sulfate to dermatan sulfate contained in the three proteoglycans were different, and the location of that in glycosaminoglycan chains was also thought to be different. It was demonstrated that three types of proteoglycan which are structurally different are present in extracellular matrix.

Nervous system-derived chondroitin sulfate proteoglycans regulate growth cone morphology and inhibit neurite outgrowth: a light, epifluorescence, and electron microscopy study

Proteoglycans influence aging and plasticity in the nervous system. Particularly prominent are the chondroitin sulfate proteoglycans (CSPGs), which are generally inhibitory to neurite outgrowth. During development, CSPGs facilitate normal guidance, but following nervous system injury and in diseases of aging (e.g., Alzheimer's disease), they block successful regeneration, and are associated with axon devoid regions and degenerating nerve cells. Whereas previous studies used non-nervous system sources of CSPGs, this study analyzed the morphology and behavior of sensory (dorsal root ganglia) neurons, and a human nerve cell model (SH-SY5Y neuroblastoma cells) as they contacted nervous system-derived CSPGs, using a variety of microscopy techniques. The results of these qualitative analyses show that growth cones of both nerve cell types contact CSPGs via actin-based filopodia, sample the CSPGs repeatedly without collapse, and alter their trajectory to avoid nervous system-derived CSPGs. Turning and branching are correlated with increased filopodial sampling, and are common to both neurons and Schwann cells. We show that CSPG expression by rat CNS astrocytes in culture is correlated with sensory neuron avoidance. Further, we show for the first time the ultrastructure of sensory growth cones at a CSPG-laminin border and reveal details of growth cone and neurite organization at this choice point. This type of detailed analysis of the response of growth cones to nervous system-derived CSPGs may lead to an understanding of CSPG function following injury and in diseases of aging, where CSPGs are likely to contribute to aberrant neurite outgrowth, failed or reduced synaptic connectivity, and/or ineffective plasticity.

Gros1, a potential growth suppressor on chromosome 1: its identity to basement membrane-associated proteoglycan, leprecan

By immunoscreening with an antibody raised against a plasma membrane protein, we have cloned a growth suppressor gene, Gros1 and assigned it to short arm of human chromosome 1. Two alternatively spliced forms of the gene encoding 84- and 41-kDa (carboxy-terminus truncated) proteins were cloned. The two transcripts, 4.4 and 2.7 kb, were expressed weakly in most of the human tissues, with a high expression of the smaller transcript in placenta, ovary and testis. Normal human fibroblasts in culture showed two transcripts, with a higher level of expression of the 4.4 kb transcript. Transformed cells on the other hand showed predominant expression of the 2.7 kb transcript. Two Gros1 transcripts were also detected in most of the mouse tissues. Stable transfection of the mouse cDNA encoding the 85-kDa protein into NIH3T3 cells resulted in their slow growth and reduced colony-forming efficiency. Stable clones expressing antisense RNA on the other hand exhibited higher colony forming efficiency. While our data implied that Gros1 is a novel growth suppressor gene on human chromosome 1, an independent study has recently characterized its rat-homolog as a leucine proline-enriched novel basement membrane-associated proteoglycan leprecan. We describe here cloning, expression and biological activity analysis implying that this novel proteoglycan is a potential growth suppressor on chromosome 1p31, frequently altered in many malignancies.