Functional significance of periostin in excisional skin repair: Is the devil in the detail?

In the past year, three papers have been published exploring the role of the matricellular protein periostin in excisional skin repair. These papers all show a delay in wound closure and the kinetics of this delay are strikingly similar across the three reports. The similarities between these papers end, however, when each investigates the mechanism through which periostin influences skin repair. Three proposed mechanisms have been identified: (1) myofibroblast differentiation, (2) keratinocyte proliferation and (3) fibroblast proliferation and migration. The aim of this commentary is to compare and contrast the three studies performed to date in an attempt to decipher the role of periostin in the repair of full-thickness skin wounds.     

Periostin localizes to cells in normal skin, but is associated with the extracellular matrix during wound repair

Epidermal tissue repair represents a complex series of temporal and dynamic events resulting in wound closure. Matricellular proteins, not normally expressed in quiescent adult tissues, play a pivotal role in wound repair and associated extracellular matrix remodeling by modulating the adhesion, migration, intracellular signaling, and gene expression of inflammatory cells, pericytes, fibroblasts and keratinocytes. Several matricellular proteins show temporal expression during dermal wound repair, but the expression pattern of the recently identified matricellular protein, periostin, has not yet been characterized. The primary aim of this study was to assess whether periostin protein is present in healthy human skin or in pathological remodeling (Nevus). The second aim was to determine if periostin is expressed during dermal wound repair. Using immunohistochemistry, periostin reactivity was detected in the keratinocytes, basal lamina, and dermal fibroblasts in healthy human skin. In pathological nevus samples, periostin was present in the extracellular matrix. In excisional wounds in mice, periostin protein was first detected in the granulation tissue at day 3, with levels peaking at day 7. Periostin protein co-localized with α-smooth muscle actin-positive cells and keratinocytes, but not CD68 positive inflammatory cells. We conclude that periostin is normally expressed at the cellular level in human and murine skin, but additionally becomes extracellular during tissue remodeling. Periostin may represent a new therapeutic target for modulating the wound repair process.     

Functional role of periostin in development and wound repair: implications for connective tissue disease

Integrity of the extracellular matrix (ECM) is essential for maintaining the normal structure and function of connective tissues. ECM is secreted locally by cells and organized into a complex meshwork providing physical support to cells, tissues, and organs. Initially thought to act only as a scaffold, the ECM is now known to provide a myriad of signals to cells regulating all aspects of their phenotype from morphology to differentiation. Matricellular proteins are a class of ECM related molecules defined through their ability to modulate cell-matrix interactions. Matricellular proteins are expressed at high levels during development, but typically only appear in postnatal tissue in wound repair or disease, where their levels increase substantially. Members of the CCN family, tenascin-C, osteopontin, secreted protein acidic rich in cysteine (SPARC), bone sialoprotein, thrombospondins, and galectins have all been classed as matricellular proteins. Periostin, a 90 kDa secreted homophilic cell adhesion protein, was recently added to matricellular class of proteins based on its expression pattern and function during development as well as in wound repair. Periostin is expressed in connective tissues including the periodontal ligament, tendons, skin and bone, and is also prominent in neoplastic tissues, cardiovascular disease, as well as in connective tissue wound repair. This review will focus on the functional role of periostin in tissue physiology. Fundamentally, it appears that periostin influences cell behaviour as well as collagen fibrillogenesis, and therefore exerts control over the structural and functional properties of connective tissues in both health and disease. Periostin is a novel matricellular protein with close homology to Drosophila fasciclin 1. In this review, the functional role of periostin is discussed in the context of connective tissue physiology, in development, disease, and wound repair.     

Spatiotemporal expression of periostin during skin development and incisional wound healing: lessons for human fibrotic scar formation

Differentiation of fibroblasts to myofibroblasts and collagen fibrillogenesis are two processes essential for normal cutaneous development and repair, but their misregulation also underlies skin-associated fibrosis. Periostin is a matricellular protein normally expressed in adult skin, but its role in skin organogenesis, incisional wound healing and skin pathology has yet to be investigated in any depth. Using C57/BL6 mouse skin as model, we first investigated periostin protein and mRNA spatiotemporal expression and distribution during development and after incisional wounding. Secondarily we assessed whether periostin is expressed in human skin pathologies, including keloid and hypertrophic scars, psoriasis and atopic dermatitis. During development, periostin is expressed in the dermis, basement membrane and hair follicles from embryonic through neonatal stages and in the dermis and hair follicle only in adult. In situ hybridization demonstrated that dermal fibroblasts and basal keratinocytes express periostin mRNA. After incisional wounding, periostin becomes re-expressed in the basement membrane within the dermal-epidermal junction at the wound edge re-establishing the embryonic deposition pattern present in the adult. Analysis of periostin expression in human pathologies demonstrated that it is over-expressed in keloid and hypertrophic scars, atopic dermatitis, but is largely absent from sites of inflammation and inflammatory conditions such as psoriasis. Furthermore, in vitro we demonstrated that periostin is a transforming growth factor beta 1 inducible gene in human dermal fibroblasts. We conclude that periostin is an important ECM component during development, in wound healing and is strongly associated with pathological skin remodeling.     

Inflammatory microenvironment and tumor necrosis factor alpha as modulators of periostin and CCN2 expression in human non-healing skin wounds and dermal fibroblasts

Non-healing skin wounds remain a significant clinical burden, and in recent years, the regulatory role of matricellular proteins in skin healing has received significant attention. Periostin and CCN2 are both upregulated at day 3 post-wounding in murine skin, where they regulate aspects of the proliferative phase of repair including mesenchymal cell infiltration and myofibroblast differentiation. In this study, we examined 1) the wound phenotype and expression patterns of periostin and CCN2 in non-healing skin wounds in humans and 2) the regulation of their expression in wound fibroblasts by tumor necrosis factor α (TNFα) and transforming growth factor-β1 (TGF-β1). Chronic skin wounds had a pro-inflammatory phenotype, characterized by macrophage infiltration, TNFα immunoreactivity, and neutrophil infiltration. Periostin, but not CCN2, was significantly suppressed in non-healing wound edge tissue at the mRNA and protein level compared with non-involved skin. In vitro, human wound edge fibroblasts populations were still able to proliferate and contract collagen gels. Compared to cells from non-involved skin, periostin and α-SMA mRNA levels increased significantly in the presence of TGF-β1 in wound cells and were significantly decreased by TNFα, but not those of Col1A2 or CCN2. In the presence of both TGF-β1 and TNFα, periostin and α-SMA mRNA levels were significantly reduced compared to TGF-β1 treated wound cells. Effects of TGF-β1 and TNFα on gene expression were also more pronounced in wound edge cells compared to non-involved fibroblasts. We conclude that variations in the expression of periostin and CCN2, are related to an inflammatory microenvironment and the presence of TNFα in human chronic wounds.     

Periostin 蛋白与成骨相关性的研究进展

Peiostin又称为成骨细胞特异因子2(OSF-2),是一种具有多种功能的细胞外基质蛋白,其在物种形成过程中高度保守,已知其在骨、肿瘤、心血管、呼吸系统以及组织修复中均有作用。研究表明,periostin的表达受多种生长因子和环境因子的调控,通过与整合素受体αvβ3或者Notch 1蛋白的结合,激活FAK和Akt/PKB或者c-Fos等相关信号通路,进而调控多种细胞(成纤维细胞、内皮细胞、上皮细胞、成骨细胞和平滑肌细胞)的分化、粘附、迁移和存活。在既往的研究中,学者们主要探讨了Periostin在肿瘤发生和转移中的作用。尽管其最先发现于骨,但是periostin与骨相关的研究相对较少。近几年,部分研究分析了periostin在骨生物学中的作用,并指出periostin可能参与了骨的形成。本文就已有的periostin在成骨中的研究作一综述。     

Periostin Accelerates Bone Healing Mediated by Human Mesenchymal Stem Cell-Embedded Hydroxyapatite/Tricalcium Phosphate Scaffold

Background

Periostin, an extracellular matrix protein, is expressed in bone, more specifically, the periosteum and periodontal ligaments, and plays a key role in formation and metabolism of bone tissues. Human adipose tissue-derived mesenchymal stem cells (hASCs) have been reported to differentiate into osteoblasts and stimulate bone repair. However, the role of periostin in hASC-mediated bone healing has not been clarified. In the current study, we examined the effect of periostin on bone healing capacity of hASCs in a critical size calvarial defect model.

Methods and Results

Recombinant periostin protein stimulated migration, adhesion, and proliferation of hASCs in vitro. Implantation of either hASCs or periostin resulted in slight, but not significant, stimulation of bone healing, whereas co-implantation of hASCs together with periostin further potentiated bone healing. In addition, the number of Ki67-positive proliferating cells was significantly increased in calvarial defects by co-implantation of both hASCs and periostin. Consistently, proliferation of administered hASCs was stimulated by co-implantation with periostin in vivo. In addition, co-delivery of hASCs with periostin resulted in markedly increased numbers of CD31-positive endothelial cells and α-SMA-positive arterioles in calvarial defects.

Conclusions

These results suggest that recombinant periostin potentiates hASC-mediated bone healing by stimulating proliferation of transplanted hASCs and angiogenesis in calvarial defects.     

Induction of Periostin-like Factor and Periostin in Forearm Muscle, Tendon, and Nerve in an Animal Model of Work-related Musculoskeletal Disorder

Work-related musculoskeletal disorders (WMSDs), also known as repetitive strain injuries of the upper extremity, frequently cause disability and impairment of the upper extremities. Histopathological changes including excess collagen deposition around myofibers, cell necrosis, inflammatory cell infiltration, and increased cytokine expression result from eccentric exercise, forced lengthening, exertion-induced injury, and repetitive strain–induced injury of muscles. Repetitive tasks have also been shown to result in tendon and neural injuries, with subsequent chronic inflammatory responses, followed by residual fibrosis. To identify mechanisms that regulate tissue repair in WMSDs, we investigated the induction of periostin-like factor (PLF) and periostin, proteins induced in other pathologies but not expressed in normal adult tissue. In this study, we examined the level of PLF and periostin in muscle, tendon, and nerve using immunohistochemistry and Western blot analysis. PLF increased with continued task performance, whereas periostin was constitutively expressed. PLF was located in satellite cells and/or myoblasts, which increased in number with continued task performance, supporting our hypothesis that PLF plays a role in muscle repair or regeneration. Periostin, on the other hand, was not present in satellite cells and/or myoblasts. (J Histochem Cytochem 57:1061–1073, 2009)     

Periostin regulates collagen fibrillogenesis and the biomechanical properties of connective tissues

Periostin is predominantly expressed in collagen-rich fibrous connective tissues that are subjected to constant mechanical stresses including: heart valves, tendons, perichondrium, cornea, and the periodontal ligament (PDL). Based on these data we hypothesize that periostin can regulate collagen I fibrillogenesis and thereby affect the biomechanical properties of connective tissues. Immunoprecipitation and immunogold transmission electron microscopy experiments demonstrate that periostin is capable of directly interacting with collagen I. To analyze the potential role of periostin in collagen I fibrillogenesis, gene targeted mice were generated. Transmission electron microscopy and morphometric analyses demonstrated reduced collagen fibril diameters in skin dermis of periostin knockout mice, an indication of aberrant collagen I fibrillogenesis. In addition, differential scanning calorimetry (DSC) demonstrated a lower collagen denaturing temperature in periostin knockout mice, reflecting a reduced level of collagen cross-linking. Functional biomechanical properties of periostin null skin specimens and atrioventricular (AV) valve explant experiments provided direct evidence of the role that periostin plays in regulating the viscoelastic properties of connective tissues. Collectively, these data demonstrate for the first time that periostin can regulate collagen I fibrillogenesis and thereby serves as an important mediator of the biomechanical properties of fibrous connective tissues.     

Ageing related periostin expression increase from cardiac fibroblasts promotes cardiomyocytes senescent

Periostin, as an extracellular matrix (ECM) protein, plays a critical role in myocardial fibrosis and also might be involved in the heart inflammatory process since it is a downstream molecule of IL4 and IL13. Considering the possible important role of periostin in heart aging, this study explored periostin expression pattern in both rat and human, the effect of periostin expression on cardiomyocyte senescent and expression of three cytokines (IL13, IL4 and IL6) in different age groups of human. This study found heart aging is associated with increased expression of periostin from cardiac fibroblasts and serum inflammatory cytokines (IL13 and IL6). Excessive periostin expression contributed to cardiomyocyte senescent, which could be alleviated through blocking the Ang-II-TGF β1-MAPK/ERK pathway. Thus, periostin might play an important role in a vicious circle (aging-fibrosis-inflammation-aging) of heart through promoting myocardial fibrosis and cardiomyocyte senescent simultaneously. It is a potential aging marker that could be directly measured in serum.     

Therapeutic angiogenesis in a murine model of limb ischemia by recombinant periostin and its fasciclin I domain

Periostin, an extracellular matrix protein, is expressed in injured tissues, such as the heart with myocardial infarction, and promotes angiogenesis and tissue repair. However, the molecular mechanism associated with periostin-stimulated angiogenesis and tissue repair is still unclear. In order to clarify the role of periostin in neovascularization, we examined the effect of periostin in angiogenic potentials of human endothelial colony forming cells (ECFCs) in vitro and in an ischemic limb animal model. Recombinant periostin protein stimulated the migration and tube formation of ECFCs. To identify the functional domains of periostin implicated in angiogenesis, five fragments of periostin, including four repeating FAS-1 domains and a carboxyl terminal domain, were expressed in Escherichia coli and purified to homogeneity. Of the five different domains, the first FAS-1 domain stimulated the migration and tube formation of human ECFCs as potent as the whole periostin. Chemotactic migration of ECFCs induced by the full length and the first FAS-1 domain of periostin was abrogated by blocking antibodies against β3 and β5 integrins. Intramuscular injection of the full length and the first FAS-1 domain of periostin into the ischemic hindlimb of mice attenuated severe limb loss and promoted blood perfusion and homing of intravenously administered ECFCs to the ischemic limb. These results suggest that the first FAS-1 domain is responsible for periostin-induced migration and angiogenesis and it can be used as a therapeutic tool for treatment of peripheral artery occlusive disease by stimulating homing of ECFCs.     

Increased Levels of Keratin 16 Alter Epithelialization Potential of Mouse Skin Keratinocytes In Vivo and Ex Vivo

The process of wound repair in adult skin is complex, involving dermal contraction and epithelial migration to repair the lesion and restore the skin's barrier properties. At the wound edge, keratinocytes undergo many changes that engender an epithelialization behavior. The type II keratin 6 and type I keratins 16 and 17 are induced well before cell migration begins, but the role of these proteins is not understood. Forced expression of human K16 in skin epithelia of transgenic mice has been shown to cause dose-dependent skin lesions concomitant with alterations in keratin filament organization and in cell adhesion. Here we show, with the use of a quantitative assay, that these transgenic mice show a delay in the closure of full-thickness skin wounds in situ compared with wild-type and low-expressing K16 transgenic mice. We adapted and validated an ex vivo skin explant culture system to better assess epithelialization in a wound-like environment. Transgenic K16 explants exhibit a significant reduction of keratinocyte outgrowth in this setting. This delay is transgene dose-dependent, and is more severe when K16 is expressed in mitotic compared with post-mitotic keratinocytes. Various lines of evidence suggest that the mechanism(s) involved is complex and not strictly cell autonomous. These findings have important implications for the function of K16 in vivo.     

Periostin is expressed by cells of the human and sand rat intervertebral discs

Abstract

Periostin, a matricellular protein in the fasciclin family, is expressed in tissues subjected to constant mechanical stress. Periostin modulates cell-to-extracellular matrix interactions and can bind to collagen, fibronectin, tenascin-C and several integrins. Our objective was to evaluate whether periostin is expressed in the human intervertebral disc. Immunohistochemical localization of periostin was carried out in tissue of human lumbar discs and lumbar discs of the sand rat (Psammomys obesus). Human discs also were examined for periostin gene expression. Immunohistochemical localization demonstrated periostin in the cytoplasm of annulus and nucleus cells, and occasionally in the surrounding pericellular and interterritorial extracellular matrix. Periostin distribution in the human disc was distinctive. Outer annulus contained the highest proportion of periostin-positive cells (88.8%), whereas inner annulus contained only 61.4%. The nucleus pulposus contained the fewest periostin-positive cells (18.5%). There was a significant negative correlation between the percentage of cells positive for periostin in the inner annulus and subject age. Periostin gene expression in the human disc also was confirmed using molecular microarray analysis. Because work by others has shown that periostin plays an important role in the biomechanical properties of other connective tissues (skin, tendon, heart valves), future research is needed to elucidate the role of periostin in disc, loading, aging and degeneration.     

Periostin: its role in asthma and its potential as a diagnostic or therapeutic target

Accumulating evidence shows that periostin, a matricellular protein, is involved in many fundamental biological processes such as cell proliferation, cell invasion, and angiogenesis. Changes in periostin expression are commonly detected in various cancers and pre-cancerous conditions, and periostin may be involved in regulating a diverse set of cancer cell activities that contribute to tumorigenesis, cancer progression, and metastasis. Periostin has also been shown to be involved in many aspects of allergic inflammation, such as eosinophil recruitment, airway remodeling, development of a Th2 phenotype, and increased expression of inflammatory mediators. In an in vivo model, bronchoalveolar lavage (BAL) fluid obtained from ovalbumin-challenged mice was found to contain significantly higher levels of periostin compared to BAL samples from control mice. To date, the molecular mechanisms involving periostin in relation to asthma in humans have not been fully elucidated. This review will focus on what is known about periostin and its role in the pathophysiological mechanisms that mediate asthma in order to evaluate the potential for periostin to serve as a biomarker and therapeutic target for the detection and treatment of asthma, respectively.     

Application of periostin peptide-decorated self-assembled protein cage nanoparticles for therapeutic angiogenesis

Peptides are gaining substantial attention as therapeutics for human diseases. However, they have limitations such as low bioavailability and poor pharmacokinetics. Periostin, a matricellular protein, can stimulate the repair of ischemic tissues by promoting angiogenesis. We have previously reported that a novel angiogenic peptide (amino acids 142-151) is responsible for the pro-angiogenic activity of periostin. To improve the in vivo delivery efficiency of periostin peptide (PP), we used proteins self-assembled into a hollow cage-like structure as a drug delivery nanoplatform in the present study. The periostin peptide was genetically inserted into lumazine synthase (isolated from Aquifex aeolicus) consisting of 60 identical subunits with an icosahedral capsid architecture. The periostin peptide-bearing lumazine synthase protein cage nanoparticle with 60 periostin peptides multivalently displayed was expressed in Escherichia coli and purified to homogeneity. Next, we examined angiogenic activities of this periostin peptide-bearing lumazine synthase protein cage nanoparticle. AaLS-periostin peptide (AaLS-PP), but not AaLS, promoted migration, proliferation, and tube formation of human endothelial colony-forming cells in vitro. Intramuscular injection of PP and AaLS-PP increased blood perfusion and attenuated severe limb loss in the ischemic hindlimb. However, AaLS did not increase blood perfusion or alleviate tissue necrosis. Moreover, in vivo administration of AaLS-PP, but not AaLS, stimulated angiogenesis in the ischemic hindlimb. These results suggest that AaLS is a highly useful nanoplatform for delivering pro-angiogenic peptides such as PP.     

Periostin promotes atrioventricular mesenchyme matrix invasion and remodeling mediated by integrin signaling through Rho/PI 3-kinase

Recent evidence suggests that extracellular matrix components may play a signaling role in embryonic valve development. We have previously identified the spatiotemporal expression patterns of periostin in developing valves, but its function during this process is largely unknown. To evaluate the functional role periostin plays during valvulogenesis, two separate three-dimensional culture assay systems, which model chick atrioventricular cushion development, were employed. These assays demonstrated that cushion mesenchymal cells adhered and spread on purified periostin in a dose-responsive manner, similar to collagen I and fibronectin via alpha(v)beta(3) and beta(1) integrin pairs. Periostin overexpression resulted in enhanced mesenchyme invasion through 3D collagen gels and increased matrix compaction. This invasion was dependent on alpha(v)beta(3) more than beta(1) integrin signaling, and was mediated differentially by Rho kinase and PI 3-kinase. Both matrix invasion and compaction were associated with a colocalization of periostin and beta(1) integrin expression to migratory cell phenotype in both surface and deep cells. The Rho/PI 3-kinase pathway also differentially mediated matrix compaction. Both Rho and PI 3-kinase were involved in normal cushion mesenchyme matrix compaction, but only PI 3-kinase was required for the enhanced matrix compaction due to periostin. Taken together, these results highlight periostin as a mediator of matrix remodeling by cushion mesenchyme towards a mature valve structure.     

Periostin down‐regulation attenuates the pro‐fibrogenic response of hepatic stellate cells induced by TGF‐β1

Liver fibrosis is characterized by an exacerbated accumulation of deposition of the extracellular matrix (ECM), and the activation of hepatic stellate cells (HSC) plays a pivotal role in the development of liver fibrosis. Periostin has been shown to regulate cell adhesion, proliferation, migration and apoptosis; however, the involvement of periostin and its role in transforming growth factor (TGF)‐β1‐induced HSC activation remains unclear. We used RT‐PCR and Western blot to evaluate the expression level of periostin in hepatic fibrosis tissues and HSCs, respectively. Cell proliferation was determined using the Cell Proliferation ELISA BrdU kit, cell cycle was analysed by flow cytometry. The expression of α‐smooth muscle actin (α‐SMA), collagen I, TGF‐β1, p‐Smad2 and p‐Smad3 were determined by western blot. Our study found that periostin was up‐regulated in liver fibrotic tissues and activated HSCs. In addition, siRNA‐periostin suppressed TGF‐β1‐induced HSC proliferation. The HSC transfected with siRNA‐periostin significantly inhibited TGF‐β1‐induced expression levels of α‐SMA and collagen I. Furthermore, TGF‐β1 stimulated the expression of periostin, and siRNA‐periostin attenuated TGF‐β1‐induced Smad2/3 activation in HSCs. These results suggest that periostin may function as a novel regulator to modulate HSC activation, potentially by promoting the TGF‐β1/Smad signalling pathway, and propose a strategy to target periostin for the treatment of liver fibrosis.     

beta-Adrenergic receptor antagonists accelerate skin wound healing: evidence for a catecholamine synthesis network in the epidermis

The skin is our primary defense against noxious environmental agents. Upon injury, keratinocytes migrate directionally into the wound bed to initiate re-epithelialization, essential for wound repair and restoration of barrier integrity. Keratinocytes express a high level of beta2-adrenergic receptors (beta2-ARs) that appear to play a role in cutaneous homeostasis as aberrations in either keratinocyte beta2-AR function or density are associated with various skin diseases. Here we report the novel finding that beta-AR antagonists promote wound re-epithelialization in a "chronic" human skin wound-healing model. beta-AR antagonists increase ERK phosphorylation, the rate of keratinocyte migration, electric field-directed migration, and ultimately accelerate human skin wound re-epithelialization. We demonstrate that keratinocytes express two key enzymes required for catecholamine (beta-AR agonist) synthesis, tyrosine hydroxylase and phenylethanolamine-N-methyl transferase, both localized within keratinocyte cytoplasmic vesicles. Finally, we confirm the synthesis of epinephrine by measuring the endogenously synthesized catecholamine in keratinocyte extracts. Previously, we have demonstrated that beta-AR agonists delay wound re-epithelialization. Here we report that the mechanism for the beta-AR antagonist-mediated augmentation of wound repair is due to beta2-AR blockade, preventing the binding of endogenously synthesized epinephrine. Our work describes an endogenous beta-AR mediator network in the skin that can temporally regulate skin wound repair. Further investigation of this network will improve our understanding of both the skin repair process and the multiple modes of action of one of the most frequently prescribed class of drugs, hopefully resulting in a new treatment for chronic wounds.