Periostin activates distinct modules of inflammation and itching downstream of the type 2 inflammation pathway.

Atopic dermatitis (AD) is a chronic relapsing skin disease accompanied by recurrent itching. Although type 2 inflammation is dominant in allergic skin inflammation, it is not fully understood how non-type 2 inflammation co-exists with type 2 inflammation or how type 2 inflammation causes itching. We have recently established the FADS mouse, a mouse model of AD. In FADS mice, either genetic disruption or pharmacological inhibition of periostin, a downstream molecule of type 2 inflammation, inhibits NF-κB activation in keratinocytes, leading to downregulating eczema, epidermal hyperplasia, and infiltration of neutrophils, without regulating the enhanced type 2 inflammation. Moreover, inhibition of periostin blocks spontaneous firing of superficial dorsal horn neurons followed by a decrease in scratching behaviors due to itching. Taken together, periostin links NF-κB-mediated inflammation with type 2 inflammation and promotes itching in allergic skin inflammation, suggesting that periostin is a promising therapeutic target for AD.

A Positive Loop Formed by SOX11 and Periostin Upregulates TGF-ß Signals Leading to Skin Fibrosis.

Systemic sclerosis (SSc) is a chronic, heterogeneous disease of connective tissue characterized by organ fibrosis together with vascular injury and autoimmunity. TGF-ß plays a central role in generating fibrosis, including SSc. Periostin is a matricellular protein playing a key role in the generation of fibrosis by amplifying the TGF-ß signals. SOX11 is a transcription factor playing several important roles in organ development in embryos. We have previously shown that SOX11 induces periostin expression. However, the roles of the interactions among the TGF-ß signals, periostin, and SOX11 remain unknown in the pathogenesis of SSc. In this study, we found that most clones of dermal fibroblasts derived from patients with SSc showed constitutive, high expression of SOX11, which is significantly induced by TGF-ß1. SOX11 forms a positive loop with periostin to activate the TGF-ß signals in SSc dermal fibroblasts. Genetic deletion of Sox11 in Postn-expressing fibroblasts impairs dermal fibrosis by bleomycin. Moreover, using the DNA microarray method, we identified several fibrotic factors dependent on the TGF-ß/SOX11/periostin pathway in SSc dermal fibroblasts. Our findings, taken together, show that a positive loop formed by SOX11 and periostin in fibroblasts upregulates the TGF-ß signals, leading to skin fibrosis.

Establishment of a novel ELISA system for measuring periostin independently of formation of the IgA complex.

BACKGROUND: Periostin, a matricellular protein that modulates cell functions having various pathophysiological roles, has the potential to be a useful biomarker for various diseases. We recently found that periostin forms a complex with IgA in human serum, which may affect the periostin measurement. METHODS: We investigated (1) whether the formation of the periostin-IgA complex affects the original periostin ELISA system, decreasing the values of serum periostin? (2) bow each domain of periostin affects periostin measurement by the original periostin ELISA system? (3) whether we can establish a novel ELISA system that is not affected by formation of the IgA complex? RESULTS: The periostin value at the reducing condition was significantly higher than that of the non-reducing condition, demonstrating that formation of the IgA complex affects periostin measurement. The monoclonal antibodies (mAbs) for periostin recognizing the EMI and R1 domains immunoprecipitated serum periostin in the reducing condition more than in the non-reducing condition, whereas the mAbs recognizing the R2 or R3 domain immunoprecipitated comparable amounts of serum periostin in the reducing and non-reducing conditions, suggesting the EMI and R1 domains contribute to formation of the complex with IgA. Using SS16A recognizing the R3 domain combined with SS17B recognizing the R4 domain, we established an ELISA system that was able to measure periostin independently of the IgA complex. CONCLUSIONS: We have established a novel ELISA system that measures periostin independently of the IgA complex. This system is promising in identifying periostin as a biomarker for various diseases.

The FADS mouse: A novel mouse model of atopic keratoconjunctivitis.

BACKGROUND: Atopic keratoconjunctivitis (AKC) is a chronic allergic conjunctival disease. However, a mouse model of AKC to investigate the underlying mechanism of the therapeutic agents and estimate their efficacy has not been established. We recently generated mice in which Ikk2 is specifically deleted in facial skin fibroblasts and found that these mice spontaneously develop atopic dermatitis (AD)-like facial skin inflammation and scratching behaviors; thus, we named them facial AD with scratching (FADS) mice. OBJECTIVE: We sought to evaluate whether the ocular lesions that FADS mice spontaneously develop are similar to those of patients with AKC and to estimate the efficacy of topical treatments with tacrolimus and betamethasone for FADS mice by using tear periostin, a novel biomarker for allergic conjunctival disease. METHODS: FADS mice, in which Ikk2 is deleted in dermal fibroblasts, were generated by crossing female Ikk2Flox/Flox mice to male Nestincre; Ikk2Flox/+ mice. We conducted histologic analysis of the ocular lesions in FADS mice. Furthermore, we measured periostin in the tears collected from FADS mice untreated or treated with tacrolimus or betamethasone. RESULTS: The FADS mice exhibited severe blepharitis and scratch behaviors for their faces. In these mice, corneal epithelium and stroma showed hyperplasia and infiltration of eosinophils, mast cells, and TH2/TC2 cells. Periostin was significantly expressed in the lesions and tear periostin was upregulated. Betamethasone showed more suppressive effects than did tacrolimus on severe corneal lesions and increased tear periostin level. CONCLUSIONS: The FADS mouse is a novel mouse model of AKC and is useful to examine the therapeutic effects of anti-AKC agents.

Epithelial SOX11 regulates eyelid closure during embryonic eye development.

Fibroblast growth factor (FGF10)-mediated signals are essential for embryonic eyelid closure in mammals. Systemic SOX11-deficient mice are born with unclosed eyelids, suggesting a possible role of SOX11 in eyelid closure. However, the underlying mechanisms of this process remain unclear. In this study, we show that epithelial deficiency of SOX11 causes a defect in the extension of the leading edge of the eyelid, leading to failure of embryonic eyelid closure. c-Jun in the eyelid is a transcription factor downstream of FGF10 required for the extension of the leading edge of the eyelid, and c-Jun level was decreased in epithelial SOX11-deficient embryos. These results suggest that epithelial SOX11 plays an important role in embryonic eyelid closure.

Periostin plays a critical role in the cell cycle in lung fibroblasts.

BACKGROUND: Idiopathic pulmonary fibrosis (IPF) is a devastating disease with a median survival of only three to 5 years. Fibroblast proliferation is a hallmark of IPF as is secretion of extracellular matrix proteins from fibroblasts. However, it is still uncertain how IPF fibroblasts acquire the ability to progressively proliferate. Periostin is a matricellular protein highly expressed in the lung tissues of IPF patients, playing a critical role in the pathogenesis of pulmonary fibrosis. However, it remains undetermined whether periostin affects lung fibroblast proliferation. METHODS: In this study, we first aimed at identifying periostin-dependently expressed genes in lung fibroblasts using DNA microarrays. We then examined whether expression of cyclins and CDKs controlling cell cycle progression occur in a periostin-dependent manner. We next examined whether downregulation of cell proliferation-promoting genes by knockdown of periostin or integrin, a periostin receptor, using siRNA, is reflected in the cell proliferation of lung fibroblasts. We then looked at whether lung fibroblasts derived from IPF patients also require periostin for maximum proliferation. We finally investigated whether CP4715, a potent inhibitor against integrin αVß3 (a periostin receptor), which we have recently found blocks TGF-ß signaling, followed by reduced BLM-induced pulmonary fibrosis in mice, can block proliferation of lung fibroblasts derived from IPF patients. RESULTS: Many cell-cycle-related genes are involved in the upregulated or downregulated genes by periostin knockdown. We confirmed that in lung fibroblasts, periostin silencing downregulates expression of several cell-cycle-related molecules, including the cyclin, CDK, and, E2F families, as well as transcription factors such as B-MYB and FOXM1. Periostin or integrin silencing slowed proliferation of lung fibroblasts and periostin silencing increased the distribution of the G0/G1 phase, whereas the distribution of the G2/M phase was decreased. Lung fibroblasts derived from IPF patients also required periostin for maximum proliferation. Moreover, CP4715 downregulated proliferation along with expression of cell-cycle-related genes in IPF lung fibroblasts as well as in normal lung fibroblasts. CONCLUSIONS: Periostin plays a critical role in the proliferation of lung fibroblasts and the present results provide us a solid basis for considering inhibitors of the periostin/integrin αVß3 interaction for the treatment of IPF patients.

Cross-Talk between Transforming Growth Factor-ß and Periostin Can Be Targeted for Pulmonary Fibrosis.

Idiopathic pulmonary fibrosis (IPF) is a devastating disease characterized as progressive and irreversible fibrosis in the interstitium of lung tissues. There is still an unmet need to develop a novel therapeutic drug for IPF. We have previously demonstrated that periostin, a matricellular protein, plays an important role in the pathogenesis of pulmonary fibrosis. However, the underlying mechanism of how periostin causes pulmonary fibrosis remains unclear. In this study, we sought to learn whether the cross-talk between TGF-ß (transforming growth factor-ß), a central mediator in pulmonary fibrosis, and periostin in lung fibroblasts leads to generation of pulmonary fibrosis and whether inhibitors for integrin αVß3, a periostin receptor, can block pulmonary fibrosis in model mice and the TGF-ß signals in fibroblasts from patients with IPF. We found that cross-talk exists between TGF-ß and periostin signals via αVß3/ß5 converging into Smad3. This cross-talk is necessary for the expression of TGF-ß downstream effector molecules important for pulmonary fibrosis. Moreover, we identified several potent integrin low-molecular-weight inhibitors capable of blocking cross-talk with TGF-ß signaling. One of the compounds, CP4715, attenuated bleomycin-induced pulmonary fibrosis in vivo in mice and the TGF-ß signals in vitro in fibroblasts from patients with IPF. These results suggest that the cross-talk between TGF-ß and periostin can be targeted for pulmonary fibrosis and that CP4715 can be a potential therapeutic agent to block this cross-talk.

Periostin forms a functional complex with IgA in human serum.

BACKGROUND: Periostin is a matricellular protein belonging to the fasciclin family, playing a role for the pathogenesis of allergic diseases by binding to integrins on cell surfaces. Serum periostin is elevated in various allergic diseases reflecting type 2 inflammation and tissue remodeling so that for allergic diseases, periostin is expected to be a novel biomarker for diagnosis, assessing severity or prognosis, and predicting responsiveness to treatments. We have previously shown that most serum periostin exists in the oligomeric form by intermolecular disulfide bonds. METHODS: In this study, we examined how periostin forms a complex in serum, whether the periostin complex in serum is functional, and whether the complex formation interferes with reactivity to anti-periostin Abs. RESULTS: We found that periostin formed a complex with IgA1 at a 1:1 ratio. The periostin in the serum complex contained at least five different isoforms. However, IgA was not essential for the oligomeric formation of periostin in mouse serum or in IgA-lacking serum. The periostin-IgA complex in human serum was functional, sustaining the ability to bind to αVß3 integrin on cell surfaces. Moreover, periostin formed the complex with IgA broadly, which interferes the binding of the Abs recognizing all of the domains except the R4 domain to periostin. CONCLUSIONS: Periostin is a novel member of the IgA-associated molecules. These results are of great potential use to understand the pathological roles of periostin in allergic diseases and, from a practical standpoint, to develop diagnostics or therapeutic agents against periostin.