Coordinate upregulation of tenascin C expression with degree of photodamage in human skin

Mannose-6-phosphate complex and improvement in biomechanical properties of the skin

BACKGROUND

The dermis is composed of a tangle of macromolecules that provides the skin its biomechanical properties. During chronological aging, fibroblasts lose their ability to synthesize collagen and an accumulation of matrix metalloproteinases leads to an increase in collagen degradation. As a result, there is a decline in the biomechanical properties of the skin. Skin aging is accelerated by external factors such as UV radiation and pollution, which induce accumulation of oxidants, and so of oxidized proteins in the skin.

AIMS

Atomic force microscopy (AFM) has emerged as an alternative method for studying the biomechanical properties of skin cells and tissues.

METHODS/RESULTS

Thus, we identified mannose-6-phosphate complex as a new powerful molecule capable of reversing the visible signs of aging by reorganizing the collagen network of the dermis and by improving the skin biomechanical properties. This effect was correlated with clinical studies that showed a marked antiaging effect through a reduction in the number of crow's feet and in the depth and size of neck wrinkles.

CONCLUSION

Mannose-6-phosphate complex appeared to be able to protect proteins in the dermis scaffold against oxidation and degradation, allowing an improvement in the skin biomechanical properties.

Insights into the key roles of epigenetics in matrix macromolecules-associated wound healing

Extracellular matrix (ECM) is a dynamic network of macromolecules, playing a regulatory role in cell functions, tissue regeneration and remodeling. Wound healing is a tissue repair process necessary for the maintenance of the functionality of tissues and organs. This highly orchestrated process is divided into four temporally overlapping phases, including hemostasis, inflammation, proliferation and tissue remodeling. The dynamic interplay between ECM and resident cells exerts its critical role in many aspects of wound healing, including cell proliferation, migration, differentiation, survival, matrix degradation and biosynthesis. Several epigenetic regulatory factors, such as the endogenous non-coding microRNAs (miRNAs), are the drivers of the wound healing response. microRNAs have pivotal roles in regulating ECM composition during wound healing and dermal regeneration. Their expression is associated with the distinct phases of wound healing and they serve as target biomarkers and targets for systematic regulation of wound repair. In this article we critically present the importance of epigenetics with particular emphasis on miRNAs regulating ECM components (i.e. glycoproteins, proteoglycans and matrix proteases) that are key players in wound healing. The clinical relevance of miRNA targeting as well as the delivery strategies designed for clinical applications are also presented and discussed.

Extracellular matrix contribution to skin wound re-epithelialization

The ability of skin to act as a barrier is primarily determined by cells that maintain the continuity and integrity of skin and restore it after injury. Cutaneous wound healing in adult mammals is a complex multi-step process that involves overlapping stages of blood clot formation, inflammation, re-epithelialization, granulation tissue formation, neovascularization, and remodeling. Under favorable conditions, epidermal regeneration begins within hours after injury and takes several days until the epithelial surface is intact due to reorganization of the basement membrane. Regeneration relies on numerous signaling cues and on multiple cellular processes that take place both within the epidermis and in other participating tissues. A variety of modulators are involved, including growth factors, cytokines, matrix metalloproteinases, cellular receptors, and extracellular matrix components. Here we focus on the involvement of the extracellular matrix proteins that impact epidermal regeneration during wound healing.

Extracellular Matrix and Dermal Fibroblast Function in the Healing Wound

Significance: Fibroblasts play a critical role in normal wound healing. Various extracellular matrix (ECM) components, including collagens, fibrin, fibronectin, proteoglycans, glycosaminoglycans, and matricellular proteins, can be considered potent protagonists of fibroblast survival, migration, and metabolism. Recent Advances: Advances in tissue culture, tissue engineering, and ex vivo models have made the examination and precise measurements of ECM components in wound healing possible. Likewise, the development of specific transgenic animal models has created the opportunity to characterize the role of various ECM molecules in healing wounds. In addition, the recent characterization of new ECM molecules, including matricellular proteins, dermatopontin, and FACIT collagens (Fibril-Associated Collagens with Interrupted Triple helices), further demonstrates our cursory knowledge of the ECM in coordinated wound healing. Critical Issues: The manipulation and augmentation of ECM components in the healing wound is emerging in patient care, as demonstrated by the use of acellular dermal matrices, tissue scaffolds, and wound dressings or topical products bearing ECM proteins such as collagen, hyaluronan (HA), or elastin. Once thought of as neutral structural proteins, these molecules are now known to directly influence many aspects of cellular wound healing. Future Directions: The role that ECM molecules, such as CCN2, osteopontin, and secreted protein, acidic and rich in cysteine, play in signaling homing of fibroblast progenitor cells to sites of injury invites future research as we continue investigating the heterotopic origin of certain populations of fibroblasts in a healing wound. Likewise, research into differently sized fragments of the same polymeric ECM molecule is warranted as we learn that fragments of molecules such as HA and tenascin-C can have opposing effects on dermal fibroblasts.

Healed porcine incisions previously treated with a surgical incision management system: mechanical, histomorphometric, and gene expression properties

BACKGROUND

Computer and bench models have shown previously that surgical incision management with negative pressure (SIM) immediately decreases lateral tissue tension and increases incisional apposition. Better apposition is known to improve healing. Thus, SIM was hypothesized to improve the quality of incisional healing. This study evaluated the impact that 5 days of SIM had on mechanical properties and associated changes in the histology/histomorphometry and gene expression of healed porcine incisions.

METHODS

One incision in each of the 4 pairs of contralateral, sutured, full-thickness incisions in each of 6 Yucatan swine were treated with either SIM (Prevena™ Incision Management System; n = 24 incisions/treatment group) or standard of care (SOC; sterile absorbent abdominal pads; n = 24/group) for 5 days, after which both groups received SOC for an additional 5 days. Biopsies for gene-expression analyses were collected on days 5 (n = 6 pairs/group), 20 (n = 6 pairs/group), and 40 (n = 12 pairs/group). On day 40, the animals were killed, after which healed incisions were harvested for mechanical testing (n = 12/group) and histologic/histomorphometric evaluation (n = 12/group).

RESULTS

Compared with SOC-treated incisions, SIM-treated incisions had significantly improved (p < 0.05) mechanical properties (strain energy density, peak strain) and a narrower scar/healed area in the deep dermis on day 40. Differences in gene expression between SOC- and SIM-treated specimens were observed primarily on day 5. The SIM-treated specimens had significantly fewer genes, which were differentially expressed and showed reduced upregulation of genes associated with inflammation, hypoxia, retardation of reepithelialization, impaired wound healing, and scarring.

CONCLUSION

Early application of SIM improved the quality of healed porcine incisions in terms of mechanical, histomorphometric, and gene-expression properties.

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Tenascin-C is increased in atherothrombotic stroke patients and has an anti-inflammatory effect in the human carotid artery

Tenascin-C (Tn-C) is an endogenous ligand of toll-like receptor-4 (TLR-4); a key signalling molecule associated with chronic inflammatory conditions. Both Tn-C and TLR-4 are increased in unstable human atheroma, but their effects on local inflammatory conditions have not been investigated. The aim of the present study was to investigate the association and functional implications of Tn-C/TLR-4 signalling in large artery atherosclerotic stroke. Plasma Tn-C was measured by ELISA and found to be higher in recent stroke patients (n = 336; median 12.77 µg/mL, inter-quartile range 10.23-15.74 µg/mL) than in controls (n = 321; median 11.31 µg/mL, inter-quartile range 8.89-13.90 µg/mL), P < 0.001. Plasma Tn-C was also independently positively associated with stroke (odds ratio for highest Tn-C quartile 2.27, 95% confidence interval 1.37-3.76). Assessment of Tn-C associated chronic cytokine secretion was performed in vitro using paired, human, macroscopically disease matched, carotid atheroma tissue biopsies obtained from five patients undergoing carotid endarterectomy. A 4-day incubation with specific Tn-C blocking antibodies (Abs) increased secretion of TLR-4-associated cytokines, interleukin (IL)-8, IL-1β, tumour necrosis factor and C-C motif chemokine (CCL)3 and expression of TLR-4 in the tissue. These results suggest with Tn-C blockade another endogenous TLR-4 ligand upregulates TLR-4 expression and subsequent cytokine secretion. Titration of the Tn-C Abs also dose dependently increased secretion of IL-6, IL-8, IL-1β, and CCL3 in mixed, healthy, primary vascular cell culture. In summary, circulating concentrations of Tn-C are higher in patients with a recent history of atherosclerotic stroke and may play an anti-inflammatory role by reducing pro-inflammatory cytokine release from atheroma.

The newcomer in the integrin family: integrin α9 in biology and cancer

Integrins are heterodimeric transmembrane receptors regulating cell-cell and cell-extracellular matrix interactions. Of the 24 integrin heterodimers identified in humans, α9β1 integrin is one of the least studied. α9, together with α4, comprise a more recent evolutionary sub-family of integrins that is only found in vertebrates. Since α9 was thought to have similar functions as α4, due to many shared ligands, it was a rather overlooked integrin until recently, when its importance for survival after birth was highlighted upon investigation of the α9 knockout mouse. α9β1 is expressed on a wide variety of cell types, interacts with many ligands for example fibronectin, tenascin-C and ADAM12, and has been shown to have important functions in processes such as cell adhesion and migration, lung development, lymphatic and venous valve development, and in wound healing. This has sparked an interest to investigate α9β1-mediated signaling and its regulation. This review gives an overview of the recent progress in α9β1-mediated biological and pathological processes, and discusses its potential as a target for cancer diagnosis and therapy.

The role of tenascin-C in tissue injury and tumorigenesis

The extracellular matrix molecule tenascin-C is highly expressed during embryonic development, tissue repair and in pathological situations such as chronic inflammation and cancer. Tenascin-C interacts with several other extracellular matrix molecules and cell-surface receptors, thus affecting tissue architecture, tissue resilience and cell responses. Tenascin-C modulates cell migration, proliferation and cellular signaling through induction of pro-inflammatory cytokines and oncogenic signaling molecules amongst other mechanisms. Given the causal role of inflammation in cancer progression, common mechanisms might be controlled by tenascin-C during both events. Drugs targeting the expression or function of tenascin-C or the tenascin-C protein itself are currently being developed and some drugs have already reached advanced clinical trials. This generates hope that increased knowledge about tenascin-C will further improve management of diseases with high tenascin-C expression such as chronic inflammation, heart failure, artheriosclerosis and cancer.

The role of tenascin-C in tissue injury and tumorigenesis

The extracellular matrix molecule tenascin-C is highly expressed during embryonic development, tissue repair and in pathological situations such as chronic inflammation and cancer. Tenascin-C interacts with several other extracellular matrix molecules and cell-surface receptors, thus affecting tissue architecture, tissue resilience and cell responses. Tenascin-C modulates cell migration, proliferation and cellular signaling through induction of pro-inflammatory cytokines and oncogenic signaling molecules amongst other mechanisms. Given the causal role of inflammation in cancer progression, common mechanisms might be controlled by tenascin-C during both events. Drugs targeting the expression or function of tenascin-C or the tenascin-C protein itself are currently being developed and some drugs have already reached advanced clinical trials. This generates hope that increased knowledge about tenascin-C will further improve management of diseases with high tenascin-C expression such as chronic inflammation, heart failure, artheriosclerosis and cancer.

Analysis of collagen-interacting proteins in patients with incisional hernias

BACKGROUND

In recent years a disorder of the collagen metabolism has been suggested for the pathogenesis of abdominal wall hernias. Previous investigations of skin specimens revealed a reduction in the collagen I/III ratio and alterations in matrix metalloproteinases in patients with incisional hernias. We investigated known collagen-interacting proteins to further characterize connective tissue in these patients.

PATIENTS AND METHODS

Skin scars from patients with either primary or recurrent incisional and recurrent inguinal hernias, as a subgroup of incisional hernias, were analyzed for overall collagen content and for the distribution of collagen types I and III by crosspolarization microscopy. The expression of collagen type V, collagen receptor discoidin domain receptor 2, matrix metalloproteinase 1, connective tissue-like growth factor, and tenascin was determined by immunohistochemistry. Mature abdominal skin scars from patients without evident hernia served as controls.

RESULTS

Patients with recurrent incisional hernia showed lowest ratios of collagen types I to III. Contents of overall collagen and of collagen type V did not differ between the groups. In patients with either primary or recurrent incisional hernias the proportion of collagen receptor discoidin domain receptor 2 positive cells was increased. Matrix metalloproteinase 1 expression was more pronounced in patients with recurrent incisional or inguinal hernias than in controls. Connective tissue-like growth factor was significantly increased in recurrent inguinal hernia patients. The expression of tenascin was notably decreased in all hernia groups.

CONCLUSIONS

The observed alterations in the expression of collagen-interacting proteins again indicate the possibility of a fundamental connective tissue disease as the causal factor in the pathogenesis of (recurrent) incisional hernias.

Molecular mechanisms of skin ageing

Cutaneous ageing is a complex biological phenomenon consisting of two components; intrinsic ageing, which is largely genetically determined and extrinsic ageing caused by environmental exposure, primarily UV light. In sun-exposed areas, these two processes are superimposed. The process of intrinsic skin ageing resembles that seen in most internal organs and is thought to involve decreased proliferative capacity leading to cellular senescence, and altered biosynthetic activity of skin derived cells. Extrinsic ageing, more commonly termed photoageing, also involves changes in cellular biosynthetic activity but leads to gross disorganisation of the dermal matrix. The molecular mechanisms underlying some of these changes are now beginning to be unravelled and are discussed. As these mechanisms are identified, further insights into the underlying processes of skin ageing should emerge and better strategies to prevent the undesirable effects of age on skin appearance should follow.

Accumulation of matrilysin (MMP-7) and macrophage metalloelastase (MMP-12) in actinic damage

Photodamage is characterized by degradation of collagen and accumulation of abnormal elastin in the superficial dermis and several matrix metalloproteinases have previously been implicated in this process. Using immunohistochemistry and in situ hybridization, we have studied the localization of two elastolytic matrix metalloproteinases, matrilysin (matrix metalloproteinase-7) and human macrophage metalloelastase (matrix metalloproteinase-12) in solar damage. Human macrophage metalloelastase protein was detected in the superficial dermis in areas of elastotic material. Matrix metalloproteinase-7 was seen in the mid-dermis in regions with less damaged elastic fibers and morphologically better preserved collagen as well as in a band-like pattern below basal keratinocytes in eight of 18 solar elastosis. In samples taken from healthy volunteers 3 d after repeated ultraviolet A or ultraviolet B photoprovocation, occasional immunopositive cells for human macrophage metalloelastase (stromal) or matrix metalloproteinase-7 (sweat gland epithelium) were detected. In samples taken 1 d after ultraviolet B exposure, however, basal keratinocytes were matrix metalloproteinase-7 immunopositive, explaining the linear immunostaining below basal keratinocytes noted particularly in ultraviolet B treated 3 d specimens. Upregulation of metalloelastase was also demonstrated in the skin of hairless mice after repeated ultraviolet exposure. In normal skin, no staining for human macrophage metalloelastase or matrix metalloproteinase-7 was observed in association with elastin. The amount of immunoreactivity for the substrates of matrix metalloproteinase-7, versican, and tenascin, was clearly increased in solar elastosis and photoprovocated skin; versican but not tenascin was detected in the same areas as matrix metalloproteinase-7. Our results suggest that both matrix metalloproteinase-7 and -12 may contribute to remodeling of elastotic areas in sun-damaged skin.