periostin null mice exhibit dwarfism, incisor enamel defects, and an early-onset periodontal disease-like phenotype

Identification of Postn+ periosteal progenitor cells with bone regenerative potential

Bone contains multiple pools of skeletal stem/progenitor cells (SSPCs), and SSPCs in periosteal compartments are known to exhibit higher regenerative potential than those in BM and endosteal compartments. However, the in vivo identity and hierarchical relationships of periosteal SSPCs (P-SSPCs) remain unclear due to a lack of reliable markers to distinguish BM SSPCs and P-SSPCs. Here, we found that periosteal mesenchymal progenitor cells (P-MPs) in periosteum can be identified based on Postn-CreERT2 expression. Postn-expressing periosteal subpopulation produces osteolineage descendants that fuel bones to maintain homeostasis and support regeneration. Notably, Postn+ P-MPs are likely derived from Gli1+ skeletal stem cells (SSCs). Ablation of Postn+ cells results in impairments in homeostatic cortical bone architecture and defects in fracture repair. Genetic deletion of Igf1r in Postn+ cells dampens bone fracture healing. In summary, our study provides a mechanistic understanding of bone regeneration through the regulation of region-specific Postn+ P-MPs.

Mechanisms of mechanical force in periodontal homeostasis: a review

Mechanical forces affect periodontal health through multiple mechanisms. Normally, mechanical forces can boost soft and hard tissue metabolism. However, excessive forces may damage the periodontium or result in irreversible inflammation, whereas absence of occlusion forces also leads to tissue atrophy and bone resorption. We systemically searched the PubMed and Web of Science databases and found certain mechanisms of mechanical forces on immune defence, extracellular matrix (ECM) metabolism, specific proteins, bone metabolism, characteristic periodontal ligament stem cells (PDLSCs) and non-coding RNAs (ncRNAs) as these factors contribute to periodontal homeostasis. The immune defence functions change under forces; genes, signalling pathways and proteinases are altered under forces to regulate ECM metabolism; several specific proteins are separately discussed due to their important functions in mechanotransduction and tissue metabolism. Functions of osteocytes, osteoblasts, and osteoclasts are activated to maintain bone homeostasis. Additionally, ncRNAs have the potential to influence gene expression and thereby, modify tissue metabolism. This review summarizes all these mechanisms of mechanical forces on periodontal homeostasis. Identifying the underlying causes, this review provides a new perspective of the mechanisms of force on periodontal health and guides for some new research directions of periodontal homeostasis.

Sclerostin antibody corrects periodontal disease in type 2 diabetic mice

Type 2 diabetes (T2D) is on the rise worldwide and is associated with various complications in the oral cavity. Using an adult-onset diabetes preclinical model, we demonstrated profound periodontal alterations in T2D mice, including inflamed gingiva, disintegrated periodontal ligaments (PDLs), marked alveolar bone loss, and unbalanced bone remodeling due to decreased formation and increased resorption. Notably, we observed elevated levels of the Wnt signaling inhibitor sclerostin in the alveolar bone of T2D mice. Motivated by these findings, we investigated whether a sclerostin-neutralizing antibody (Scl-Ab) could rescue the compromised periodontium in T2D mice. Administering Scl-Ab subcutaneously once a week for 4 weeks, starting 4 weeks after T2D induction, led to substantial increases in bone mass. This effect was attributed to the inhibition of osteoclasts and promotion of osteoblasts in both control and T2D mice, effectively reversing the bone loss caused by T2D. Furthermore, Scl-Ab stimulated PDL cell proliferation, partially restored the PDL fibers, and mitigated inflammation in the periodontium. Our study thus established a T2D-induced periodontitis mouse model characterized by inflammation and tissue degeneration. Scl-Ab emerged as a promising intervention to counteract the detrimental effects of T2D on the periodontium, exhibiting limited side effects on other craniofacial hard tissues.

Development of a top-down MS assay for specific identification of human periostin isoforms

Periostin is a matricellular protein encoded by the POSTN gene that is alternatively spliced to produce ten different periostin isoforms with molecular weights ranging from 78 to 91 kDa. It is known to promote fibrillogenesis, organize the extracellular matrix, and bind integrin-receptors to induce cell signaling. As well as being a key component of the wound healing process, it is also known to participate in the pathogenesis of different diseases including atopic dermatitis, asthma, and cancer. In both health and disease, the functions of the different periostin isoforms are largely unknown. The ability to precisely determine the isoform profile of a given human sample is fundamental for characterizing their functional significance. Identification of periostin isoforms is most often carried out at the transcriptional level using RT-PCR based approaches, but due to high sequence homogeneity, identification on the protein level has always been challenging. Top-down proteomics, where whole proteins are measured by mass spectrometry, offers a fast and reliable method for isoform identification. Here we present a fully developed top-down mass spectrometry assay for the characterization of periostin splice isoforms at the protein level.

Periostin in the relation between periodontal disease and atherosclerotic coronary artery disease: A pilot randomized clinical study

OBJECTIVE

The aim of this study was to analyze the effects of periodontal treatment on markers of atherosclerotic coronary artery disease and circulating levels of periostin.

BACKGROUND

Periostin is necessary for periodontal stability, but it is highly present in atherosclerotic plaques. Treatment of periodontal disease, with low levels of local periostin, is thought to reduce systemic levels of periostin. Thus, this may contribute to cardiovascular health.

METHODS

A pilot randomized controlled clinical trial was designed to include patients with severe periodontal disease and history of atherosclerotic coronary artery disease. Samples of gingival crevicular fluid (GCF) and serum were collected before and after periodontal treatment by periodontal surgery or non-surgical therapy. The levels of several markers of inflammation and cardiovascular damage were evaluated including CRP, IFN-γ, IL-1ß, IL-10, MIP-1α, periostin, and TNF-α in GCF and CRP, Fibrinogen, IFN-γ, IL-1ß, IL-6, IL-10, L-Selectin, MIP-1α, Periostin, TNF-α, and vWF in serum.

RESULTS

A total of 22 patients with an average of 56 years old were recruited for participating in this study. Twenty of them were male. Most of them (82%) had suffered an acute myocardial event and underwent surgery for placing 1, 2, or 3 stents in the coronary arteries more than 6 months ago but less than 1 year. The treatment of periodontal disease resulted in an overall improvement of all periodontal parameters. Regarding the evaluation of GCF and serum, a significant increase of periostin in the GCF was observed after periodontal surgery. In contrast, although other markers in GCF and serum improved, no significant correlations were found.

CONCLUSION

Treatment of periodontal disease through periodontal surgery induces a local and transient increase in the levels of periostin in the gingival crevicular fluid. The effects on systemic markers of inflammation and cardiovascular function have not been confirmed.

Temporal and spatial expression analysis of periostin in mice periodontitis model

OBJECTIVES

This study aimed to investigate the temporal and spatial changes in the expression of periostin during periodontal inflammation in mice.

METHODS

A periodontitis model was constructed using silk thread ligation. Mice were randomly divided into five groups including control group, 4-day ligation group, 7-day ligation group, 14-day ligation group, and self-healing group (thread removal for 14 days after 14-day ligation). Micro-CT and histological staining were performed to characterize the dynamic changes in the mouse periodontal tissue in each group. RNAscope and immunohistochemical staining were used to analyze the pattern of changes in periostin at various stages of periodontitis. The cell experiment was divided into three groups: control group, lipopolysaccharide (LPS) stimulation group (treated with LPS for 12 h), and LPS stimulation removal group (treated with LPS for 3 h followed by incubation with medium for 9 h). Quantitative real-time polymerase chain reaction (qRT-PCR) was used to detect the expression of periostin, transforming growth factor-β1 (TGF-β1), and matrix metalloproteinase 2 (MMP2).

RESULTS

Significant alveolar bone resorption was observed 7 days after ligation. With increasing duration of ligation, the damage to the mouse periodontal tissue was aggravated, which manifested as increased osteoclasts, widening of the periodontal membrane space, and decreased alveolar bone height. Some degree of periodontal tissue repair was observed in the self-healing group. Periostin expression decreased at 4 and 7 days compared with the control group and increased at 14 days compared with 4 and 7 days. A significant recovery was found in the self-healing group. The qRT-PCR results showed that the expression of periostin and TGF-β1 in the LPS stimulation group decreased compared with that in the control group but significantly recovered in the LPS removal group.

CONCLUSIONS

Periostin expression in the PDL of mice showed a downward and upward trend with inflammation progression. The significant recovery of periostin expression after removing inflammatory stimuli may be related to TGF-β1, which is crucial to maintain the integrity of the PDL.

Periostin-integrin interaction regulates force-induced TGF-β1 and α-SMA expression by hPDLSCs

OBJECTIVE

Periostin (PN), a major matricellular periodontal ligament (PDL) protein, modulates the remodeling of the PDL and bone, especially under mechanical stress. This study investigated the requirement of PN-integrin signaling in force-induced expression of transforming growth factor-beta 1 (TGF-β1) and alpha-smooth muscle actin (α-SMA) in human PDL stem cells (hPDLSCs).

METHODS

Cells were stimulated with intermittent compressive force (ICF) using computerized controlled apparatus. Cell migration was examined using in vitro scratch assay. The mRNA expression was examined using real-time polymerase chain reaction. The protein expression was determined using immunofluorescent staining and western blot analysis.

RESULTS

Stimulation with ICF for 24 h increased the expression of PN, TGF-β1, and α-SMA, along with increased SMAD2/3 phosphorylation. Knockdown of POSTN (PN gene) decreased the protein levels of TGF-β1 and pSMAD2/3 upon force stimulation. POSTN knockdown of hPDLSCs resulted in delayed cell migration, as determined by a scratch assay. However, migration improved after seeding these knockdown cells on pre-PN-coated surfaces. Further, the knockdown of αVβ5 significantly attenuated the force-induced TGF-β1 expression.

CONCLUSION

Our findings indicate the importance of PN-αVβ5 interactions in ICF-induced TGF-β1 signaling and the expression of α-SMA. Findings support the critical role of PN in maintaining the PDL's tissue integrity and homeostasis.

Simultaneous Expression of CD70 and POSTN in Cancer-Associated Fibroblasts Predicts Worse Survival of Colorectal Cancer Patients

Colorectal cancer (CRC) is one of the most common gastrointestinal cancers worldwide, with high morbidity and mortality rates. The evidence for the tumor-supporting capacities of cancer-associated fibroblasts (CAFs) that modulate cancer cell proliferation, invasion, metastasis, and tumor immunity, including in CRC, has been attracting attention. The present study examined the expression status of CD70 and POSTN in CRC and analyzed their association with clinicopathological features and clinical outcomes. In the present study, in total 15% (40/269) and 44% (119/269) of cases exhibited CD70 and POSTN expression on CAFs, respectively. Co-expression of CD70 and POSTN was detected in 8% (21/269) of patients. Fluorescent immunohistochemistry identified the co-expression of CD70 and POSTN with FAP and PDPN, respectively. ACTA2 was not co-expressed with CD70 or POSTN in CRC CAFs. CRC with CD70+/POSTN+ status in CAFs was significantly associated with distant organ metastasis (p = 0.0020) or incomplete resection status (p = 0.0011). CD70+/POSTN+ status tended to associate with advanced pT stage (p = 0.032) or peritoneal metastasis (p = 0.0059). Multivariate Cox hazards regression analysis identified CD70+/POSTN+ status in CAFs [hazard ratio (HR) = 3.78] as a potential independent risk factor. In vitro experiments revealed the activated phenotypes of colonic fibroblasts induced by CD70 and POSTN, while migration and invasion assays identified enhanced migration and invasion of CRC cells co-cultured with CD70- and POSTN-expressing colonic fibroblasts. On the basis of our observations, CD70 and POSTN immunohistochemistry can be used in the prognostication of CRC patients. CRC CAFs may be a promising target in the treatment of CRC patients.

Bone Scaffold Materials in Periodontal and Tooth-supporting Tissue Regeneration: A Review

BACKGROUND AND OBJECTIVES

Periodontium is an important tooth-supporting tissue composed of both hard (alveolar bone and cementum) and soft (gingival and periodontal ligament) sections. Due to the multi-tissue architecture of periodontium, reconstruction of each part can be influenced by others. This review focuses on the bone section of the periodontium and presents the materials used in tissue engineering scaffolds for its reconstruction.

MATERIALS AND METHODS

The following databases (2015 to 2021) were electronically searched: ProQuest, EMBASE, SciFinder, MRS Online Proceedings Library, Medline, and Compendex. The search was limited to English-language publications and in vivo studies.

RESULTS

Eighty-three articles were found in primary searching. After applying the inclusion criteria, seventeen articles were incorporated into this study.

CONCLUSION

In complex periodontal defects, various types of scaffolds, including multilayered ones, have been used for the functional reconstruction of different parts of periodontium. While there are some multilayered scaffolds designed to regenerate alveolar bone/periodontal ligament/cementum tissues of periodontium in a hierarchically organized construct, no scaffold could so far consider all four tissues involved in a complete periodontal defect. The progress and material considerations in the regeneration of the bony part of periodontium are presented in this work to help investigators develop tissue engineering scaffolds suitable for complete periodontal regeneration.

The effect of light compressive and tensile mechanical forces on SOST and POSTN expressions in human periodontal ligament cells: an in vitro study

Periodontal ligament (PDL) cells play an important role in mechanosensing and secretion of signaling molecules during bone remodeling. However, the regulatory mechanism is unknown. The aim of the present study is to investigate the expression pattern of periostin and sclerostin in response to orthodontic forces in periodontal ligament cells in vitro. PDL cells were isolated from extracted teeth and treated with compressive forces of 25 gr/cm2 or equiaxial tension forces at frequency 1 Hz for 0, 24, 48, and 72 h. qRT-PCR was applied to evaluate the gene expressions. The secretion of sclerostin and periostin was assessed using ELISA. DAPI staining was used to evaluate apoptosis. The expression of sclerostin elevated significantly at protein and gene levels under compression forces after 24 h, while the application of tensile forces induced the expression of periostin and its upstream regulator RUNX2 (p < 0.05). Gene expression up-regulation was significant for POSTN and RUNX2 after 48 and 72 h tensile forces. Also, the gene expression of sclerostin reduced in a time-dependent manner after application of tensile force. The compression forces enhanced apoptosis to 7.5 ± 3.5% and induced gene expression of apoptotic markers of CASP9, and BCL2 within 72 h of exposure. Periostin and sclerostin play an important role in orthodontic loads and their expressions are affected oppositely by compressive and tensile forces that might be suggested as a biomarker for assessment of bone remodeling during orthodontic treatment.

Mechanisms of tissue degeneration mediated by periostin in spinal degenerative diseases and their implications for pathology and diagnosis: a review

Periostin (POSTN) serves a dual role as both a matricellular protein and an extracellular matrix (ECM) protein and is widely expressed in various tissues and cells. As an ECM protein, POSTN binds to integrin receptors, transduces signals to cells, enabling cell activation. POSTN has been linked with various diseases, including atopic dermatitis, asthma, and the progression of multiple cancers. Recently, its association with orthopedic diseases, such as osteoporosis, osteoarthritis resulting from cartilage destruction, degenerative diseases of the intervertebral disks, and ligament degenerative diseases, has also become apparent. Furthermore, POSTN has been shown to be a valuable biomarker for understanding the pathophysiology of orthopedic diseases. In addition to serum POSTN, synovial fluid POSTN in joints has been reported to be useful as a biomarker. Risk factors for spinal degenerative diseases include aging, mechanical stress, trauma, genetic predisposition, obesity, and metabolic syndrome, but the cause of spinal degenerative diseases (SDDs) remains unclear. Studies on the pathophysiological effects of POSTN may significantly contribute toward the diagnosis and treatment of spinal degenerative diseases. Therefore, in this review, we aim to examine the mechanisms of tissue degeneration caused by mechanical and inflammatory stresses in the bones, cartilage, intervertebral disks, and ligaments, which are crucial components of the spine, with a focus on POSTN.

Alteration of extracellular matrix proteins in atrophic periodontal ligament of hypofunctional rat molars

OBJECTIVES

The aim of this study was to investigate the effect of mechanical force on possible dynamic changes of the matrix proteins deposition in the PDL upon in vitro mechanical and in vivo occlusal forces in a rat model with hypofunctional conditions.

MATERIALS AND METHODS

Intermittent compressive force (ICF) and shear force (SF) were applied to human periodontal ligament stem cells (PDLSCs). Protein expression of collagen I and POSTN was analyzed by western blot technique. To establish an in vivo model, rat maxillary molars were extracted to facilitate hypofunction of the periodontal ligament (PDL) tissue of the opposing mandibular molar. The mandibles were collected after 4-, 8-, and 12-weeks post-extraction and used for micro-CT and immunohistochemical analysis.

RESULTS

ICF and SF increased the synthesis of POSTN by human PDLSCs. Histological changes in the hypofunctional teeth revealed a narrowing of the PDL space, along with a decreased amount of collagen I, POSTN, and laminin in perivascular structures compared to the functional contralateral molars.

CONCLUSION

Our results revealed that loss of occlusal force disrupts deposition of some major matrix proteins in the PDL, underscoring the relevance of mechanical forces in maintaining periodontal tissue homeostasis by modulating ECM composition.

Periostin in Osteoporosis and Cardiovascular Disease

Context

Osteoporosis (OP) and cardiovascular disease (CVD), prevalent disorders worldwide, often coexist and share common risk factors. The identification of common biomarkers could significantly improve patients' preventive care.

Objectives

The objectives are 1, to review periostin (Postn) involvement in osteoporosis and in CVD, and 2, identify if Postn could be a common biomarker.

Design

This is a scoping review on Postn in OP and CVD.

Methods

Databases were searched, in vitro and in vivo, for publications in English on Postn, bone, and the cardiovascular system, with no limit regarding publication date.

Results

Postn appears as a key factor in OP and CVD. Its role as a potential biomarker in both pathologies is described in recent studies, but a number of limitations have been identified.

Conclusions

Current evidence provides fragmented views on Postn in OP and CVD and does not encapsulate Postn as a common pivotal thread linking these comorbidities. A number of gaps impede highlighting Postn as a common biomarker. There is room for future basic and clinical research with Postn as a marker and a target to provide new therapeutic options for aging patients with concomitant OP and CVD.

Periostin plays a key role in maintaining the osteogenic abilities of dental follicle stem cells in the inflammatory microenvironment

OBJECTIVE

This study aimed to explore the effect of periostin in the osteogenic abilities of dental follicle stem cells (DFSCs) and DFSC sheets in the inflammatory microenvironment.

DESIGN

DFSCs were isolated from dental follicles and identified. A lentiviral vector was used to knock down periostin in DFSCs. 250 ng/ml lipopolysaccharide from Porphyromonas gingivalis (P.g-LPS) was used to construct the inflammatory microenvironment. Osteogenic differentiation was evaluated by alizarin red staining, quantitative real-time polymerase chain reaction (qRT-PCR), and western blot. The formation of extracellular matrix was assessed by qRT-PCR and immunofluorescence. The expressions of receptor activator of nuclear factor kappa-B ligand (RANKL) and osteoprotegerin (OPG) were measured by western blot.

RESULTS

Knockdown of periostin inhibited osteogenic differentiation and promoted adipogenic differentiation of DFSCs. In an inflammatory microenvironment, knockdown of periostin attenuated the proliferation and osteogenic differentiation of DFSCs. Knockdown of periostin inhibited the formation of extracellular matrix collagen I (COL-I), fibronectin, and laminin in DFSC sheets, but did not affect the expression of osteogenesis-related markers alkaline phosphatase (ALP) and osteocalcin (OCN). In the inflammatory microenvironment, knocking down periostin inhibited the expression of OCN and OPG in DFSC sheets, and promoted the expression of RANKL.

CONCLUSION

Periostin played a key role in maintaining the osteogenic abilities of DFSCs and DFSC sheets in the inflammatory microenvironment and might be an important molecule in the process of DFSCs coping with inflammatory microenvironment and promoting periodontal tissues regeneration.

Enhanced Proliferative and Osteogenic Potential of Periodontal Ligament Stromal Cells

Cell-based therapies using periodontal ligament stromal cells (PDLSC) for periodontal regeneration may represent an alternative source for mesenchymal stromal cells (MSC) to MSC derived from bone marrow (MSC(M)) and adipose tissue (MSC(AT)). We aimed to characterize the osteogenic/periodontal potential of PDLSC in comparison to MSC(M) and MSC(AT). PDLSC were obtained from surgically extracted healthy human third molars, while MSC(M) and MSC(AT) were obtained from a previously established cell bank. Flow cytometry, immunocytochemistry, and cell proliferation analyses provided cellular characteristics from each group. Cells from the three groups presented MSC-like morphology, MSC-related marker expression, and multilineage differentiation capacity (adipogenic, chondrogenic, and osteogenic). In this study, PDLSC expressed osteopontin, osteocalcin, and asporin, while MSC(M) and MSC(AT) did not. Of note, only PDLSC expressed CD146, a marker previously applied to identify PDLSC, and presented higher proliferative potential compared to MSC(M) and MSC(AT). Upon osteogenic induction, PDLSC exhibited higher calcium content and enhanced upregulation of osteogenic/periodontal genes compared to MSC(M) and MSC(AT), such as Runx2, Col1A1 and CEMP-1. However, the alkaline phosphatase activity of PDLSC did not increase. Our findings suggest that PDLSC might be a promising cell source for periodontal regeneration, presenting enhanced proliferative and osteogenic potential compared to MSC(M) and MSC(AT).

Periosteal Bone Formation Varies with Age in Periostin Null Mice

Periostin, also known as osteoblast-specific factor 2, is a matricellular protein predominantly expressed at the periosteum of bone. During growth and development, periostin contributes to periosteal expansion by facilitating osteoblast differentiation and mineralization. Later in life, periosteal expansion provides an adaptive strategy to increase tissue strength without requiring substantial increase in bone mass. However, the function of periostin past skeletal maturity and during advanced aging is relatively unknown. The objective of this study was to examine the function of periostin in maintaining bone mass and tissue strength across different ages. In periostin null mice (Postn-/-), periosteal bone formation was significantly reduced in young (3 months) and adult mice (9 months). The lack of bone formation resulted in reduced bone mass and ultimate strength. Conversely, periosteal bone formation increased at advanced ages in 18-month-old Postn-/- mice. The increase in periosteal mineralization at advanced ages coincides with increased expression of vitronectin and osteopontin. Periosteal progenitors from Postn-/- mice displayed an increased capacity to mineralize when cultured on vitronectin, but not type-1 collagen. Altogether, these findings demonstrate the unique role of periostin in regulating periosteal bone formation at different ages and the potential for vitronectin to compensate in the absence of periostin.

Dental Follicle Stem Cells Promote Periodontal Regeneration through Periostin-Mediated Macrophage Infiltration and Reprogramming in an Inflammatory Microenvironment

Dental follicle stem cells (DFSCs) have been verified to promote periodontal regeneration in an inflammatory microenvironment. When coping with inflammatory stimulation, DFSCs highly express periostin, a bioactive molecule closely related to periodontal homeostasis. It is worth exploring whether and how periostin plays a role in the promotion of periodontal regeneration by DFSCs. By tracking the fate of DFSCs, it was found that DFSCs significantly contributed to periodontal regeneration in rat periodontal defects while they had a low survival rate. They highly expressed periostin and improved the immune microenvironment in the defect area, especially via the recruitment and reprogramming of macrophages. Silencing periostin attenuated the effects of DFSCs in promoting periodontal regeneration and regulating macrophages. Recombinant human periostin (rhPeriostin) could not only directly promote macrophage reprogramming through the integrin αM/phosphorylated extracellular signal-regulated kinase (p-Erk)/Erk signaling pathway, but it also exhibited the potential to promote periodontal regeneration in rats when loaded in a collagen matrix. These results indicated that periostin is actively involved in the process by which DFSCs promote periodontal regeneration through the regulation of macrophages and is a promising molecular agent to promote periodontal regeneration. This study provides new insight into the mechanism by which DFSCs promote periodontal regeneration and suggests a new approach for periodontal regeneration therapy.

Periostin splice variants affect craniofacial growth by influencing chondrocyte hypertrophy

INTRODUCTION

Periostin, an extracellular matrix protein, plays an important role in osteogenesis and is also known to activate several signals that contribute to chondrogenesis. The absence of periostin in periostin knockout mice leads to several disorders such as craniosynostosis and periostitis. There are several splice variants with different roles in heart disease and myocardial infarction. However, little is known about each variant's role in chondrogenesis, followed by bone formation. Therefore, the aim of this study is to investigate the role of several variants in chondrogenesis differentiation and bone formation in the craniofacial region. Periostin splice variants included a full-length variant (Control), a variant lacking exon 17 (ΔEx17), a variant lacking exon 21 (ΔEx21), and another variant lacking both exon 17 and 21 ***(ΔEx17&21).

MATERIALS AND METHODS

We used C56BL6/N mice (n = 6) for the wild type (Control)*** and the three variant type mice (n = 6 each) to identify the effect of each variant morphologically and histologically. Micro-computed tomography demonstrated a smaller craniofacial skeleton in ΔEx17s, ΔEx21s, and ΔEx17&21s compared to Controls, especially the mandibular bone. We, thus, focused on the mandibular condyle.

RESULTS

The most distinctive histological observation was that each defected mouse appeared to have more hypertrophic chondrocytes than Controls. Real-time PCR demonstrated the differences among the group. Moreover, the lack of exon 17 or exon 21 in periostin leads to inadequate chondrocyte differentiation and presents in a diminutive craniofacial skeleton.

DISCUSSION

Therefore, these findings suggested that each variant has a significant role in chondrocyte hypertrophy, leading to suppression of bone formation.

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.

Stromal POSTN Enhances Motility of Both Cancer and Stromal Cells and Predicts Poor Survival in Colorectal Cancer

Evidence for the tumor-supporting capacities of cancer-associated fibroblasts (CAFs) has rapidly been accumulating. To uncover clinicopathological importance of periostin (POSTN) expression in colorectal cancer (CRC), the present study immunohistochemically examined its expression status. Furthermore, to reveal its mechanisms involved, molecular experiments were performed. In CRC tissues, 44% of the cases (119/269) exhibited POSTN expression in the CAFs. In contrast, CRC cells expressed POSTN at almost undetectable levels. Survival analyses identified that patients with POSTN-positive CRC had a significantly worse 5-year survival rate (63.2% vs. 81.2%; p = 0.011). Univariate analyses revealed that POSTN positivity was associated with peritoneal (p = 0.0031) and distant organ metastasis (p < 0.001). Furthermore, immunohistochemical analyses identified a significant association between POSTN and p53 complete loss status in CRC cells. Decorin and fibroblast activation protein expression in CAFs was also associated with POSTN. POSTN significantly enhanced the migration of both CRC cells and fibroblasts with FAK and AKT or STAT3 activation, and co-culture assays demonstrated the communication between CRC cells and fibroblasts, which enhanced STAT3 activation in fibroblasts. On the basis of our results, we speculated that stromal POSTN accelerated metastasis via stromal remodeling capacity and activated the migration of both tumor and stromal cells.

Single-cell transcriptome reveals core cell populations and androgen-RXFP2 axis involved in deer antler full regeneration

Deer antlers constitute a unique mammalian model for the study of both organ formation in postnatal life and annual full regeneration. Previous studies revealed that these events are achieved through the proliferation and differentiation of antlerogenic periosteum (AP) cells and pedicle periosteum (PP) cells, respectively. As the cells resident in the AP and the PP possess stem cell attributes, both antler generation and regeneration are stem cell-based processes. However, the cell composition of each tissue type and molecular events underlying antler development remain poorly characterized. Here, we took the approach of single-cell RNA sequencing (scRNA-Seq) and identified eight cell types (mainly THY1⁺ cells, progenitor cells, and osteochondroblasts) and three core subclusters of the THY1⁺ cells (SC2, SC3, and SC4). Endothelial and mural cells each are heterogeneous at transcriptional level. It was the proliferation of progenitor, mural, and endothelial cells in the activated antler-lineage-specific tissues that drove the rapid formation of the antler. We detected the differences in the initial differentiation process between antler generation and regeneration using pseudotime trajectory analysis. These may be due to the difference in the degree of stemness of the AP-THY1⁺ and PP-THY1⁺ cells. We further found that androgen-RXFP2 axis may be involved in triggering initial antler full regeneration. Fully deciphering the cell composition for these antler tissue types will open up new avenues for elucidating the mechanism underlying antler full renewal in specific and regenerative medicine in general.

Periostin: an emerging activator of multiple signaling pathways

Matricellular proteins are responsible for regulating the microenvironment, the behaviors of surrounding cells, and the homeostasis of tissues. Periostin (POSTN), a non-structural matricellular protein, can bind to many extracellular matrix proteins through its different domains. POSTN usually presents at low levels in most adult tissues but is highly expressed in pathological sites such as in tumors and inflamed organs. POSTN can bind to diverse integrins to interact with multiple signaling pathways within cells, which is one of its core biological functions. Increasing evidence shows that POSTN can activate the TGF-β, the PI3K/Akt, the Wnt, the RhoA/ROCK, the NF-κB, the MAPK and the JAK pathways to promote the occurrence and development of many diseases, especially cancer and inflammatory diseases. Furthermore, POSTN can interact with some pathways in an upstream and downstream relationship, forming complicated crosstalk. This article focuses on the interactions between POSTN and different signaling pathways in diverse diseases, attempting to explain the mechanisms of interaction and provide novel guidelines for the development of targeted therapies.

Periosteal stem cells control growth plate stem cells during postnatal skeletal growth

The ontogeny and fate of stem cells have been extensively investigated by lineage-tracing approaches. At distinct anatomical sites, bone tissue harbors multiple types of skeletal stem cells, which may independently supply osteogenic cells in a site-specific manner. Periosteal stem cells (PSCs) and growth plate resting zone stem cells (RZSCs) critically contribute to intramembranous and endochondral bone formation, respectively. However, it remains unclear whether there is functional crosstalk between these two types of skeletal stem cells. Here we show PSCs are not only required for intramembranous bone formation, but also for the growth plate maintenance and prolonged longitudinal bone growth. Mice deficient in PSCs display progressive defects in intramembranous and endochondral bone formation, the latter of which is caused by a deficiency in PSC-derived Indian hedgehog (Ihh). PSC-specific deletion of Ihh impairs the maintenance of the RZSCs, leading to a severe defect in endochondral bone formation in postnatal life. Thus, crosstalk between periosteal and growth plate stem cells is essential for post-developmental skeletal growth.

Intramembranous and endochondral bone formation have been considered to be independent processes mediated by independent stem cells. Here the authors show that periosteal stem cells participate in both types of bone formation, supporting endochondral formation by producing Ihh.

The pathophysiology of osteoporosis in obesity and type 2 diabetes in aging women and men: The mechanisms and roles of increased bone marrow adiposity

Osteoporosis is defined as a systemic skeletal disease characterized by decreased bone mass and micro-architectural deterioration leading to increased fracture risk. Osteoporosis incidence increases with age in both post-menopausal women and aging men. Among other important contributing factors to bone fragility observed in osteoporosis, that also affect the elderly population, are metabolic disturbances observed in obesity and Type 2 Diabetes (T2D). These metabolic complications are associated with impaired bone homeostasis and a higher fracture risk. Expansion of the Bone Marrow Adipose Tissue (BMAT), at the expense of decreased bone formation, is thought to be one of the key pathogenic mechanisms underlying osteoporosis and bone fragility in obesity and T2D. Our review provides a summary of mechanisms behind increased Bone Marrow Adiposity (BMA) during aging and highlights the pre-clinical and clinical studies connecting obesity and T2D, to BMA and bone fragility in aging osteoporotic women and men.

Orthodontic tooth movement alters cementocyte ultrastructure and cellular cementum proteome signature

Cementum is a mineralized tissue that covers tooth roots and functions in the periodontal attachment complex. Cementocytes, resident cells of cellular cementum, share many characteristics with osteocytes, are mechanoresponsive cells that direct bone remodeling based on changes in loading. We hypothesized that cementocytes play a key role during orthodontic tooth movement (OTM). To test this hypothesis, we used 8-week-old male Wistar rats in a model of OTM for 2, 7, or 14 days (0.5 N), whereas unloaded contralateral teeth served as controls. Tissue and cell responses were analyzed by high-resolution micro-computed tomography, histology, tartrate-resistant acid phosphatase staining for odontoclasts/osteoclasts, and transmission electron microscopy. In addition, laser capture microdissection was used to collect cellular cementum, and extracted proteins were identified by liquid chromatography coupled to tandem mass spectrometry. The OTM model successfully moved first molars mesially more than 250 μm by 14 days introducing apoptosis in a small number of cementocytes and areas of root resorption on mesial and distal aspects. Cementocytes showed increased nuclear size and proportion of euchromatin suggesting cellular activity. Proteomic analysis identified 168 proteins in cellular cementum with 21 proteins found only in OTM sites and 54 proteins only present in control samples. OTM-down-regulated several extracellular matrix proteins, including decorin, biglycan, asporin, and periostin, localized to cementum and PDL by immunostaining. Furthermore, type IV collagen (COL14A1) was the protein most down-regulated (-45-fold) by OTM and immunolocalized to cells at the cementum-dentin junction. Eleven keratins were significantly increased by OTM, and a pan-keratin antibody indicated keratin localization primarily in epithelial remnants of Hertwig's epithelial root sheath. These experiments provide new insights into biological responses of cementocytes and cellular cementum to OTM.

Periostin gene expression in neu-positive breast cancer cells is regulated by a FGFR signaling cross talk with TGFβ/PI3K/AKT pathways

BACKGROUND

Breast cancer is a highly heterogeneous disease with multiple drivers and complex regulatory networks. Periostin (Postn) is a matricellular protein involved in a plethora of cancer types and other diseases. Postn has been shown to be involved in various processes of tumor development, such as angiogenesis, invasion, cell survival and metastasis. The expression of Postn in breast cancer cells has been correlated with a more aggressive phenotype. Despite extensive research, it remains unclear how epithelial cancer cells regulate Postn expression.

METHODS

Using murine tumor models and human TMAs, we have assessed the proportion of tumor samples that have acquired Postn expression in tumor cells. Using biochemical approaches and tumor cell lines derived from Neu+ murine primary tumors, we have identified major regulators of Postn gene expression in breast cancer cell lines.

RESULTS

Here, we show that, while the stromal compartment typically always expresses Postn, about 50% of breast tumors acquire Postn expression in the epithelial tumor cells. Furthermore, using an in vitro model, we show a cross-regulation between FGFR, TGFβ and PI3K/AKT pathways to regulate Postn expression. In HER2-positive murine breast cancer cells, we found that basic FGF can repress Postn expression through a PKC-dependent pathway, while TGFβ can induce Postn expression in a SMAD-independent manner. Postn induction following the removal of the FGF-suppressive signal is dependent on PI3K/AKT signaling.

CONCLUSION

Overall, these results reveal a novel regulatory mechanism and shed light on how breast tumor cells acquire Postn expression. This complex regulation is likely to be cell type and cancer specific as well as have important therapeutic implications.

TGF-Beta Receptor II Is Critical for Osteogenic Progenitor Cell Proliferation and Differentiation During Postnatal Alveolar Bone Formation

Transforming growth factor beta (TGFβ) signaling plays an important role during osteogenesis. However, most research in this area focuses on cortical and trabecular bone, whereas alveolar bone is largely overlooked. To address the role of TGFβR2 (the key receptor for TGFβ signaling) during postnatal alveolar bone development, we conditionally deleted Tgfβr2 in early mesenchymal progenitors by crossing Gli1-Cre ^ERT2; Tgfβr2 ^flox/flox ; R26R ^tdTomato mice (named early cKO) or in osteoblasts by crossing 3.2kb Col1-Cre ^ERT2 ; Tgfβr2 ^flox/flox ; R26R ^tdTomato mice (named late cKO). Both cKO lines were induced at postnatal day 5 (P5) and mice were harvested at P28. Compared to the control littermates, early cKO mice exhibited significant reduction in alveolar bone mass and bone mineral density, with drastic defects in the periodontal ligament (PDL); conversely, the late cKO mice displayed very minor changes in alveolar bone. Mechanism studies showed a significant reduction in PCNA+ PDL cell numbers and OSX+ alveolar bone cell numbers, as well as disorganized PDL fibers with a great reduction in periostin (the most abundant extracellular matrix protein) on both mRNA and protein levels. We also showed a drastic reduction in β-catenin in the early cKO PDL and a great increase in SOST (a potent inhibitor of Wnt signaling). Based on these findings, we conclude that TGFβ signaling plays critical roles during early alveolar bone formation via the promotion of PDL mesenchymal progenitor proliferation and differentiation mechanisms.

Effects of periostin deficiency on kidney aging and lipid metabolism

Periostin plays a crucial role in fibrosis, which is involved in kidney aging. A few studies have shown that lipid metabolism is involved in kidney aging. We investigated the role of periostin in lipid metabolism during kidney aging. Renal function, fibrosis, and inflammatory markers were studied using urine, blood, and tissue samples from wild-type (WT) C57BL/6 mice and Postn-null mice of 2 and 24 months of age. Lipids were quantitatively profiled using liquid chromatography-tandem mass spectrometry in the multiple reaction monitoring mode. Renal function was worse and tubular atrophy/interstitial fibrosis, periostin expression, and inflammatory and fibrotic markers were more severe in aged WT mice than in young WT mice. In aged Postn-null mice, these changes were mitigated. Thirty-five differentially regulated lipids were identified. Phosphatidylcholines, cholesteryl ester, cholesterol, ceramide-1-phosphate, and CCL5 expression were significantly higher in aged WT mice than in aged Postn-null mice. Particularly, linoleic acid, linolenic acid, arachidonic acid, and docosahexaenoic acid differed strongly between the two groups. Lysophosphatidylcholine acyltransferase 2, which converts lysophosphatidylcholine to phosphatidylcholine, was significantly higher in aged WT mice than in aged Postn-null mice. Periostin expression in the kidneys increased with age, and periostin ablation delayed aging. Changes in lipids and their metabolism were found in Postn-null mice. Further research on the precise mechanisms of and relationships between lipid expression and metabolism, kidney aging, and periostin expression is warranted.

Periostin: An Emerging Molecule With a Potential Role in Spinal Degenerative Diseases

Periostin, an extracellular matrix protein, is widely expressed in a variety of tissues and cells. It has many biological functions and is related to many diseases: for example, it promotes cell proliferation and differentiation in osteoblasts, which are closely related to osteoporosis, and mediates cell senescence and apoptosis in chondrocytes, which are involved in osteoarthritis. Furthermore, it also plays an important role in mediating inflammation and reconstruction during bronchial asthma, as well as in promoting bone development, reconstruction, repair, and strength. Therefore, periostin has been explored as a potential biomarker for various diseases. Recently, periostin has also been found to be expressed in intervertebral disc cells as a component of the intervertebral extracellular matrix, and to play a crucial role in the maintenance and degeneration of intervertebral discs. This article reviews the biological role of periostin in bone marrow-derived mesenchymal stem cells, osteoblasts, osteoclasts, chondrocytes, and annulus fibrosus and nucleus pulposus cells, which are closely related to spinal degenerative diseases. The study of its pathophysiological effects is of great significance for the diagnosis and treatment of spinal degeneration, although additional studies are needed.

Vitamin K-Dependent Proteins in Skeletal Development and Disease

Vitamin K and Vitamin K-dependent proteins (VKDPs) are best known for their pivotal role in blood coagulation. Of the 14 VKPDs identified in humans to date, 6 play also important roles in skeletal biology and disease. Thus, osteocalcin, also termed bone Gla-protein, is the most abundant non-collagenous protein in bone. Matrix Gla protein and Ucma/GRP on the other hand are highly abundant in cartilage. Furthermore, periostin, protein S, and growth arrest specific 6 protein (GAS 6) are expressed in skeletal tissues. The roles for these VKDPs are diverse but include the control of calcification and turnover of bone and cartilage. Vitamin K plays an important role in osteoporosis and serum osteocalcin levels are recognized as a promising marker for osteoporosis. On the other hand, matrix Gla protein and Ucma/GRP are associated with osteoarthritis. This review focuses on the roles of these three VKDPs, osteocalcin, matrix Gla protein and Ucma/GRP, in skeletal development and disease but will also summarize the roles the other skeletal VKDPs (periostin, protein S and GAS6) in skeletal biology.

Xenoextracellular matrix-rosiglitazone complex-mediated immune evasion promotes xenogenic bioengineered root regeneration by altering M1/M2 macrophage polarization

Xenogenic extracellular matrix (xECM)-based organ transplantation will be a promising approach to address the problem of donor shortage for allotransplantation, which has achieved great success in organ regeneration. However, current approaches to utilize xECM-based organ have limited capacity to yield the host a biofriendly microenvironment for long-term immunity homeostasis, compromising the application of these xenografts for repairing and replacing damaged tissues. As the key innate immune cells, macrophages directly determine the prognosis of xenografts in long term. However, it has not been fully elucidated that how to modulate their biological behavior for microenvironment homeostasis in tissue reconstruction. In this study, we report a robust strategy to impart an immunosuppressive surface to naturally sponge-like porous xECM scaffolds by loading rosiglitazone (RSG) to activate peroxisome proliferators receptors-γ (PPAR-γ). The resultant xECM-RSG complex, enabling RSG to be delivered sequentially and continuously to cells without obvious systemic side effects, is recognized as "self" to escape immune monitoring in local immunoregulation by downregulating the expression of proinflammatory NOS2+ M1 macrophages and oxygen species (ROS) through suppressing NF-κB expression, greatly facilitating the regeneration of enthesis anchoring between the transplanted xenograft and host in both heterotopic and orthotopic models. The newly formed bio-root is morphologically and biomechanically equivalent to native tooth root with a significant expression of odontogenic differentiation-related critical proteins. Therefore, the PPAR-γ-NF-κB axis activated by the xECM-RSG complex enables the xenografts to converse towards M2 macrophages with a modest immunosuppressive capacity for facilitating in xECM-based tissue or organ regeneration.

RANKL-Induced Increase in Cathepsin K Levels Restricts Cortical Expansion in a Periostin-Dependent Fashion: A Potential New Mechanism of Bone Fragility

Receptor activator of nuclear factor-κΒ ligand (RANKL) is necessary and sufficient to promote osteoclastogenesis and a key pathogenic factor in osteoporosis. Failure of periosteal apposition to compensate for bone loss due to endosteal resorption further contributes to bone fragility. Whether these two processes are biologically related, however, remains unknown. Using high-resolution peripheral quantitative computed tomography (HR-pQCT), we first examined cortical bone parameters at distal radius and tibia in postmenopausal women (PMW) as well as in cadaveric human adult humeri. Increases in medullary area were negatively correlated with cortical bone volume but positively with total bone volume, and this relationship was stronger in the dominant arm, suggesting a mechanically driven process. To investigate the role of RANKL in this dual process, we used mice overexpressing huRANKL (huRANKLTg⁺ ). Trabecular and cortical bone volume (Ct.BV) are reduced in these mice, whereas cortical total volume (Ct.TV) is increased. In these bones, Sost mRNA levels are downregulated and periostin (Postn) mRNA levels upregulated, hence providing a positive message for periosteal bone formation. In turn, genetic deletion of Postn in huRANKLTg⁺  mice prevented the increase in Ct.TV and aggravated bone fragility. In contrast, cathepsin K (Ctsk) ablation improved Ct.TV in both huRANKLTg⁺  and wild-type (WT) mice and stimulated periosteal bone formation, while augmenting Postn protein levels. Therefore, bone strength in huRANKLTg⁺ /Ctsk^-/- mice was restored to WT levels. These findings suggest that high levels of RANKL not only induce endosteal bone loss but may somewhat restrict periosteal bone formation by triggering periostin degradation through cathepsin K, hence providing a biological mechanism for the observed limited increase in cortical area in postmenopausal women. © 2021 American Society for Bone and Mineral Research (ASBMR).

Functions of Matricellular Proteins in Dental Tissues and Their Emerging Roles in Orofacial Tissue Development, Maintenance, and Disease

Matricellular proteins (MCPs) are defined as extracellular matrix (ECM) associated proteins that are important regulators and integrators of microenvironmental signals, contributing to the dynamic nature of ECM signalling. There is a growing understanding of the role of matricellular proteins in cellular processes governing tissue development as well as in disease pathogenesis. In this review, the expression and functions of different MP family members (periostin, CCNs, TSPs, SIBLINGs and others) are presented, specifically in relation to craniofacial development and the maintenance of orofacial tissues, including bone, gingiva, oral mucosa, palate and the dental pulp. As will be discussed, each MP family member has been shown to have non-redundant roles in development, tissue homeostasis, wound healing, pathology and tumorigenesis of orofacial and dental tissues.

MicroRNA-489-3p promotes adipogenesis by targeting the Postn gene in 3T3-L1 preadipocytes

AIMS

Accumulating evidence indicates that a number of microRNAs (miRNAs) serve as essential regulators during adipogenesis and adipolysis in humans and animals and play critical roles in the development of fat tissue. In this study, we aimed to determine the functional role and underlying regulatory mechanism of microRNA-489-3p (miR-489) in adipocytes.

MATERIALS AND METHODS

The expression patterns of miR-489 in mice were measured by qRT-PCR. Overexpression and knockdown of miR-489 by mimic and inhibitor transfections in 3T3-L1 preadipocytes revealed the regulatory effect of miR-489 on cellular proliferation and differentiation and energy turnover. Furthermore, RNA-seq, bioinformatics prediction, and dual luciferase reporter assays were used to identify the direct target of miR-489.

KEY FINDINGS

The results showed that miR-489 was highly expressed in the visceral fat tissue of adult mice, and obese mice exhibited higher levels of miR-489 than normal mice. Overexpression of miR-489 suppressed proliferation but promoted adipogenic differentiation and lipid accumulation in the cells. Mitochondrial oxidation also fluctuated in the cells due to the high expression of miR-489. Notably, knockdown of miR-489 did not have a strong opposing effect on the cells. Periostin (Postn) was identified as a direct target gene for miR-489, and silencing the Postn gene similarly stimulated adipogenesis and differentiation of adipocytes.

SIGNIFICANCE

miR-489 provides a strong driving force for adipogenesis metabolism and adipocyte differentiation by targeting the Postn gene. This result may contribute to the treatment of obesity.

Regulation of Ribosome Function by RNA Modifications in Hematopoietic Development and Leukemia: It Is Not Only a Matter of m6A

Growth and maturation of hematopoietic stem cells (HSCs) are largely controlled at both transcriptional and post-transcriptional levels. In particular, hematopoietic development requires a tight control of protein synthesis. Furthermore, translational deregulation strongly contributes to hematopoietic malignancies. Researchers have recently identified a new layer of gene expression regulation that consists of chemical modification of RNA species, which led to the birth of the epitranscriptomics field. RNA modifications provide an additional level of control in hematopoietic development by acting as post-transcriptional regulators of lineage-specific genetic programs. Other reviews have already described the important role of the N⁶-methylation of adenosine (m⁶A) within mRNA species in regulating hematopoietic differentiation and diseases. The aim of this review is to summarize the current status of the role of RNA modifications in the regulation of ribosome function, beyond m⁶A. In particular, we discuss the importance of RNA modifications in tRNA and rRNA molecules. By balancing translational rate and fidelity, they play an important role in regulating normal and malignant hematopoietic development.

Collagen Assembly at the Cell Surface: Dogmas Revisited

With the increased awareness about the importance of the composition, organization, and stiffness of the extracellular matrix (ECM) for tissue homeostasis, there is a renewed need to understand the details of how cells recognize, assemble and remodel the ECM during dynamic tissue reorganization events. Fibronectin (FN) and fibrillar collagens are major proteins in the ECM of interstitial matrices. Whereas FN is abundant in cell culture studies, it is often only transiently expressed in the acute phase of wound healing and tissue regeneration, by contrast fibrillar collagens form a persistent robust scaffold in healing and regenerating tissues. Historically fibrillar collagens in interstitial matrices were seen merely as structural building blocks. Cell anchorage to the collagen matrix was thought to be indirect and occurring via proteins like FN and cell surface-mediated collagen fibrillogenesis was believed to require a FN matrix. The isolation of four collagen-binding integrins have challenged this dogma, and we now know that cells anchor directly to monomeric forms of fibrillar collagens via the α1β1, α2β1, α10β1 and α11β1 integrins. The binding of these integrins to the mature fibrous collagen matrices is more controversial and depends on availability of integrin-binding sites. With increased awareness about the importance of characterizing the total integrin repertoire on cells, including the integrin collagen receptors, the idea of an absolute dependence on FN for cell-mediated collagen fibrillogenesis needs to be re-evaluated. We will summarize data suggesting that collagen-binding integrins in vitro and in vivo are perfectly well suited for nucleating and supporting collagen fibrillogenesis, independent of FN.

Periostin-expressing Schwann cells and endoneurial cardiac fibroblasts contribute to sympathetic nerve fasciculation after birth

BACKGROUND

The intracardiac nervous system (ICNS) is composed of neurons, in association with Schwann cells (SC) and endoneurial cardiac fibroblasts (ECF). Besides heart rhythm control, recent studies have implicated cardiac nerves in postnatal cardiac regeneration and cardiomyocyte size regulation, but cardiac SC and ECF remain understudied. During the postnatal period, the ICNS undergoes intense remodeling with nerve fasciculation and elongation throughout the myocardium, partially guided by the extracellular matrix (ECM). Here we report the origins, heterogeneity, and functions of SC and ECF that develop in proximity to neurons during postnatal ICNS maturation.

METHODS AND RESULTS

Periostin lineage (Postn+) cells include cardiac Remak SC and ECF during the postnatal period in mice. The developmental origins of cardiac SC and ECF were examined using Rosa26^eGFP reporter mice bred with Wnt1Cre, expressed in Neural crest (NC)-derived lineages, or tamoxifen-inducible Tcf21MerCreMer, expressed predominantly in epicardial-derived fibroblast lineages. ICNS components are NC-derived with the exceptions of the myelinating Plp1+ SC and the Tcf21+ lineage-derived intramural ventricular ECF. In addition, Postn+ lineage GFAP- Remak SC and ECF are present around the fasciculating cardiac nerves. Whole mount studies of the NC-derived cells confirmed postnatal maturation of the complex ICNS network from P0 to P30. Sympathetic, parasympathetic, and sensory neurons fasciculate from P0 to P7 indicated by co-staining with PSA-NCAM. Ablation of Postn+ cells from P0 to P6 or loss of Periostin leads to reduced fasciculation of cardiac sympathetic nerves. In addition, collagen remodeling surrounding maturing nerves of the postnatal heart is reduced in Postn-null mice.

CONCLUSIONS

Postn+ cells include cardiac SC and ECF during postnatal nerve maturation, and these cells have different embryonic origins. At P7, the Postn+ cells associated with cardiac nerves are mainly Remak SC and ECF. Ablation of the Postn+ cells from P0 to P6 and also loss of Postn in Postn-null mice leads to reduced fasciculation of cardiac nerves at P7.

Mechanically Driven Counter-Regulation of Cortical Bone Formation in Response to Sclerostin-Neutralizing Antibodies

Sclerostin (Scl) antibodies (Scl-Ab) potently stimulate bone formation, but these effects are transient. Whether the rapid inhibition of Scl-Ab anabolic effects is due to a loss of bone cells' capacity to form new bone or to a mechanostatic downregulation of Wnt signaling once bone strength exceeds stress remains unclear. We hypothesized that bone formation under Scl-Ab could be reactivated by increasing the dose of Scl-Ab and/or by adding mechanical stimuli, and investigated the molecular mechanisms involved in this response, in particular the role of periostin (Postn), a co-activator of the Wnt pathway in bone. For this purpose, C57Bl/6, Postn^-/- and Postn^+/+ mice were treated with vehicle or Scl-Ab (50 to 100 mg/kg/wk) for various durations and subsequently subjected to tibia axial compressive loading. In wild-type (WT) mice, Scl-Ab anabolic effects peaked between 2 and 4 weeks and declined thereafter, with no further increase in bone volume and strength between 7 and 10 weeks. Doubling the dose of Scl-Ab did not rescue the decline in bone formation. In contrast, mechanical stimulation was able to restore cortical bone formation concomitantly to Scl-Ab treatment at both doses. Several Wnt inhibitors, including Dkk1, Sost, and Twist1, were upregulated, whereas Postn was markedly downregulated by 2 to 4 weeks of Scl-Ab. Mechanical loading specifically upregulated Postn gene expression. In turn, Scl-Ab effects on cortical bone were more rapidly downregulated in Postn^-/- mice. These results indicate that bone formation is not exhausted by Scl-Ab but inhibited by a mechanically driven downregulation of Wnt signaling. Hence, increasing mechanical loads restores bone formation on cortical surfaces, in parallel with Postn upregulation. © 2020 American Society for Bone and Mineral Research (ASBMR).

Pivotal Role of Tenascin-W (-N) in Postnatal Incisor Growth and Periodontal Ligament Remodeling

The continuously growing mouse incisor provides a fascinating model for studying stem cell regulation and organ renewal. In the incisor, epithelial and mesenchymal stem cells assure lifelong tooth growth. The epithelial stem cells reside in a niche known as the cervical loop. Mesenchymal stem cells are located in the nearby apical neurovascular bundle and in the neural plexus. So far, little is known about extracellular cues that are controlling incisor stem cell renewal and guidance. The extracellular matrix protein tenascin-W, also known as tenascin-N (TNN), is expressed in the mesenchyme of the pulp and of the periodontal ligament of the incisor, and is closely associated with collagen 3 fibers. Here, we report for the first time the phenotype of tenascin-W/TNN deficient mice, which in a C57BL/6N background exhibit a reduced body weight and lifespan. We found major defects in the alveolar bone and periodontal ligament of the growing rodent incisors, whereas molars were not affected. The alveolar bone around the incisor was replaced by a dense scar-like connective tissue, enriched with newly formed nerve fibers likely leading to periodontal pain, less food intake and reduced body weight. Using soft food to reduce mechanical load on the incisor partially rescued the phenotype. In situ hybridization and Gli1 reporter mouse experiments revealed decreased hedgehog signaling in the incisor mesenchymal stem cell compartment, which coordinates the development of mesenchymal stem cell niche. These results indicate that TNN deficiency in mice affects periodontal remodeling and increases nerve fiber branching. Through periodontal pain the food intake is reduced and the incisor renewal and the neurovascular sonic hedgehog secretion rate are reduced. In conclusion, tenascin-W/TNN seems to have a primary function in rapid periodontal tissue remodeling and a secondary function in mechanosensation.

Bearing My Heart: The Role of Extracellular Matrix on Cardiac Development, Homeostasis, and Injury Response

The extracellular matrix (ECM) is an essential component of the heart that imparts fundamental cellular processes during organ development and homeostasis. Most cardiovascular diseases involve severe remodeling of the ECM, culminating in the formation of fibrotic tissue that is deleterious to organ function. Treatment schemes effective at managing fibrosis and promoting physiological ECM repair are not yet in reach. Of note, the composition of the cardiac ECM changes significantly in a short period after birth, concurrent with the loss of the regenerative capacity of the heart. This highlights the importance of understanding ECM composition and function headed for the development of more efficient therapies. In this review, we explore the impact of ECM alterations, throughout heart ontogeny and disease, on cardiac cells and debate available approaches to deeper insights on cell–ECM interactions, toward the design of new regenerative therapies.

Matrix Control of Periodontal Ligament Cell Activity Via Synthetic Hydrogel Scaffolds

Rebuilding the tooth-supporting tissues (periodontium) destroyed by periodontitis remains a clinical challenge. Periodontal ligament cells (PDLCs), multipotent cells within the periodontal ligament (PDL), differentiate and form new PDL and mineralized tissues (cementum and bone) during native tissue repair in response to specific extracellular matrix (ECM) cues. Thus, harnessing ECM cues to control PDLC activity ex vivo, and ultimately, to design a PDLC delivery vehicle for tissue regeneration is an important goal. In this study, poly(ethylene glycol) hydrogels were used as a synthetic PDL ECM to interrogate the roles of cell-matrix interactions and cell-mediated matrix remodeling in controlling PDLC activity. Results showed that PDLCs within matrix metalloproteinase (MMP)-degradable hydrogels expressed key PDL matrix genes and showed a six to eightfold increase in alkaline phosphatase (ALP) activity compared with PDLCs in nondegradable hydrogel controls. The increase in ALP activity, commonly considered an early marker of cementogenic/osteogenic differentiation, occurred independent of the presentation of the cell-binding ligand RGD or soluble media cues and remained elevated when inhibiting PDLC-matrix binding and intracellular tension. ALP activity was further increased in softer hydrogels regardless of degradability and was accompanied by an increase in PDLC volume. However, scaffolds that fostered PDLC ALP activity did not necessarily promote hydrogel ECM mineralization. Rather, matrix mineralization was greatest in stiffer, MMP-degradable hydrogels and required the presence of soluble media cues. These divergent outcomes illustrate the complexity of the PDLC response to ECM cues and the limitations of current scaffold materials. Nevertheless, key biomaterial design principles for controlling PDLC activity were identified for incorporation into scaffolds for periodontal tissue regeneration. Impact statement Engineered scaffolds are an attractive approach for delivering periodontal ligament cells (PDLCs) to rebuild the tooth-supporting tissues. Replicating key extracellular matrix (ECM) cues within tissue engineered scaffolds may maximize PDLC potential. However, the identity of important ECM cues and how they can be harnessed to control PDLC activity is still unknown. In this study, matrix degradability, cell-matrix binding, and stiffness were varied using synthetic poly(ethylene glycol) hydrogels for three-dimensional PDLC culture. PDLCs exhibited dramatic and divergent responses to these cues, supporting further investigation of ECM-replicating scaffolds for control of PDLC behavior and periodontal tissue regeneration.

FAM20C directly binds to and phosphorylates Periostin

It is widely accepted that FAM20C functions as a Golgi casein kinase and has large numbers of kinase substrates within the secretory pathway. It has been previously reported that FAM20C is required for maintenance of healthy periodontal tissues. However, there has been no report that any extracellular matrix molecules expressed in periodontal tissues are indeed substrates of FAM20C. In this study, we sought to identify the binding partner(s) of FAM20C. FAM20C wild-type (WT) and its kinase inactive form D478A proteins were generated. These proteins were electrophoresed and the Coomassie Brilliant Blue (CBB)-positive bands were analyzed to identify FAM20C-binding protein(s) by Mass Spectrometry (MS) analysis. Periostin was found by the analysis and the binding between FAM20C and Periostin was investigated in cell cultures and in vitro. We further determined the binding region(s) within Periostin responsible for FAM20C-binding. Immunolocalization of FAM20C and Periostin was examined using mouse periodontium tissues by immunohistochemical analysis. In vitro kinase assay was performed using Periostin and FAM20C proteins to see whether FAM20C phosphorylates Periostin in vitro. We identified Periostin as one of FAM20C-binding proteins by MS analysis. Periostin interacted with FAM20C in a kinase-activity independent manner and the binding was direct in vitro. We further identified the binding domain of FAM20C in Periostin, which was mapped within Fasciclin (Fas) I domain 1-4 of Periostin. Immunolocalization of FAM20C was observed in periodontal ligament (PDL) extracellular matrix where that of Periostin was also immunostained in murine periodontal tissues. FAM20C WT, but not D478A, phosphorylated Periostin in vitro. Consistent with the overlapped expression pattern of FAM20C and Periostin, our data demonstrate for the first time that Periostin is a direct FAM20C-binding partner and that FAM20C phosphorylates Periostin in vitro.

Periostin and matrix stiffness combine to regulate myofibroblast differentiation and fibronectin synthesis during palatal healing

Although the matricellular protein periostin is prominently upregulated in skin and gingival healing, it plays contrasting roles in myofibroblast differentiation and matrix synthesis respectively. Palatal healing is associated with scarring that can alter or restrict maxilla growth, but the expression pattern and contribution of periostin in palatal healing is unknown. Using periostin-knockout (Postn^-/-) and wild-type (WT) mice, the contribution of periostin to palatal healing was investigated through 1.5 mm full-thickness excisional wounds in the hard palate. In WT mice, periostin was upregulated 6 days post-wounding, with mRNA levels peaking at day 12. Genetic deletion of periostin significantly reduced wound closure rates compared to WT mice. Absence of periostin reduced mRNA levels of pivotal genes in wound repair, including α-SMA/acta2, fibronectin and βigh3. Recruitment of fibroblasts and inflammatory cells, as visualized by immunofluorescent staining for fibroblast specific factor-1, vimentin, and macrophages markers Arginase-1 and iNOS was also impaired in Postn^-/-, but not WT mice. Palatal fibroblasts isolated from the hard palate of mice were cultured on collagen gels and prefabricated silicon substrates with varying stiffness. Postn^-/- fibroblasts showed a significantly reduced ability to contract a collagen gel, which was rescued by the exogenous addition of recombinant periostin. As the stiffness increased, Postn^-/- fibroblasts increasingly differentiated into myofibroblasts, but not to the same degree as the WT. Pharmacological inhibition of Rac rescued the deficient myofibroblastic phenotype of Postn^-/- cells. Low stiffness substrates (0.2 kPa) resulted in upregulation of fibronectin in WT cells, an effect which was significantly reduced in Postn^-/- cells. Quantification of immunostaining for vinculin and integrinβ1 adhesions revealed that Periostin is required for the formation of focal and fibrillar adhesions in mPFBs. Our results suggest that periostin modulates myofibroblast differentiation and contraction via integrinβ1/RhoA pathway, and fibronectin synthesis in an ECM stiffness dependent manner in palatal healing.

Wound healing and fibrosis: a contrasting role for periostin in skin and the oral mucosa

Both skin and oral mucosa are characterized by the presence of keratinized epithelium in direct apposition to an underlying collagen-dense connective tissue. Despite significant overlap in structure and physiological function, skin and the oral mucosa exhibit significantly different healing profiles in response to injury. The oral mucosa has a propensity for rapid restoration of barrier function with minimal underlying fibrosis, but in contrast, skin is associated with slower healing and scar formation. Modulators of cell function, matricellular proteins have been shown to play significant roles in cutaneous healing, but their role in restoration of the oral mucosa is poorly defined. As will be discussed in this review, over the last 12 years our research group has been actively investigating the role of the profibrotic matricellular protein periostin in tissue homeostasis and fibrosis, as well as healing, in both skin and gingiva. In the skin, periostin is highly expressed in fibrotic scars and is upregulated during cutaneous wound repair, where it facilitates myofibroblast differentiation. In contrast, in gingival healing, periostin regulates extracellular matrix synthesis but does not appear to be associated with the transition of mesenchymal cells to a contractile phenotype. The significance of these findings will be discussed, with a focus on periostin as a potential therapeutic to augment healing of soft tissues or suppress fibrosis.

Periostin Mediates Oestrogen-Induced Osteogenic Differentiation of Bone Marrow Stromal Cells in Ovariectomised Rats

Osteoporosis is a metabolic disease that results in the progressive loss of bone mass, which, in postmenopausal women, is related to oestrogen deficiency. Periostin (POSTN) plays a key role in the early stages of bone formation. However, whether POSTN participates in oestradiol regulation of osteogenic differentiation of bone marrow stromal cells (BMSCs) from ovariectomised (OVX) rats remains unclear. In vivo, using microcomputed tomography (micro-CT), immunohistochemistry, and dynamic analysis of femurs, we found that 17β-E2 promotes bone formation and POSTN expression at the endosteal surface. In vitro, 17β-E2 upregulated POSTN expression in OVX-BMSCs. POSTN overexpression activated the Wnt/β-catenin signalling pathway and enhanced osteogenic differentiation of OVX-BMSCs. Furthermore, knockdown of Postn blocks the involvement of 17β-E2 in the osteogenic differentiation of OVX-BMSCs. Collectively, our study indicated the role of POSTN in the osteogenesis and stemness of OVX-BMSCs and proves that 17β-E2 reduces osteoporosis and promotes osteogenesis through the POSTN-Wnt/β-catenin pathway. POSTN could, therefore, be a novel target gene for anti-osteoporosis therapies.

Age- and Strain-Related Differences in Bone Microstructure and Body Composition During Development in Inbred Male Mouse Strains

We explored age- and strain-related differences in bone microstructure and body composition in male C57BL/6J, DBA/2JRj and C3H/J mice. Bone microstructure of the femur, tibia and L4 was assessed by μCT at the age of 8, 16 and 24 weeks. The weight of several muscles and fat depots were measured at the same time points. At all timepoints, C3H/J mice had the thickest cortices followed by DBA/2JRj and C57BL/6J mice. Nevertheless, C57BL/6J mice had higher Tb.BV/TV and Tb.N, and lower Tb.Sp than DBA/2JRj and C3H/J mice at least at 24 weeks of age. Skeletal development patterns differed among strains. C57BL/6J and DBA/2JRj mice, but not C3H/J mice, experienced significant increases in the sum of the masses of 6 individual muscles by 24 weeks of age. In C57BL/6J and DBA/2JRj mice, the mass of selected fat depots reached highest values at 24 weeks, whist, in C3H/J mice, the highest values of fat depots masses were achieved at 16 weeks. Early strain differences in muscle and fat masses were largely diminished by 24 weeks of age. C3H/J and C57BL/6J mice displayed the most favorable cortical and trabecular bone parameters, respectively. Strain differences in body composition were less overt than strain specificity in bone microstructure, however, they possibly influenced aspects of skeletal development.

Extracellular Matrix Remodeling During Palate Development

The morphogenesis of the mammalian secondary plate is a series of highly dynamic developmental process, including the palate shelves vertical outgrowth, elevation to the horizontal plane and complete fusion in the midline. Extracellular matrix (ECM) proteins not only form the basic infrastructure for palatal mesenchymal cells to adhere via integrins but also interact with cells to regulate their functions such as proliferation and differentiation. ECM remodeling is essential for palatal outgrowth, expansion, elevation, and fusion. Multiple signaling pathways important for palatogenesis such as FGF, TGF β, BMP, and SHH remodels ECM dynamics. Dysregulation of ECM such as HA synthesis or ECM breakdown enzymes MMPs or ADAMTS causes cleft palate in mouse models. A better understanding of ECM remodeling will contribute to revealing the pathogenesis of cleft palate.

The Matrix Revolution: Matricellular Proteins and Restructuring of the Cancer Microenvironment

The extracellular matrix (ECM) surrounding cells is indispensable for regulating their behavior. The dynamics of ECM signaling are tightly controlled throughout growth and development. During tissue remodeling, matricellular proteins (MCP) are secreted into the ECM. These factors do not serve classical structural roles, but rather regulate matrix proteins and cell-matrix interactions to influence normal cellular functions. In the tumor microenvironment, it is becoming increasingly clear that aberrantly expressed MCPs can support multiple hallmarks of carcinogenesis by interacting with various cellular components that are coupled to an array of downstream signals. Moreover, MCPs also reorganize the biomechanical properties of the ECM to accommodate metastasis and tumor colonization. This realization is stimulating new research on MCPs as reliable and accessible biomarkers in cancer, as well as effective and selective therapeutic targets.

Comparative Evaluation of Serum and Gingival Crevicular Fluid Periostin Levels in Periodontal Health and Disease: A Biochemical Study

Introduction

Periostin, a secreted adhesion molecule, is a matricellular protein secreted most in periodontal ligament and periosteum. This periostin is needed for integrity and maturation of periodontal tissue. The present study was conducted to estimate and compare the gingival crevicular fluid and serum periostin levels in subjects having chronic periodontitis, gingivitis and healthy periodontium.

Methods

Ninety patients belonging to both sexes were categorized into three groups, 30 patients each as healthy periodontium (Group I), chronic gingivitis (Group II) and generalised chronic periodontitis (Group III). The clinical parameters included assessment of plaque index (PI), gingival index (GI), probing pocket depth (PPD) and clinical attachment level (CAL). Gingival crevicular fluid (GCF) and serum samples were collected and the enzyme-linked immunosorbent assay was used to estimate periostin levels.

Results

Periostin levels in GCF were comparatively low in the chronic periodontitis than in the gingivitis and healthy periodontium groups and the difference was statistically significant. No statistical difference was found for serum periostin levels among Group I, Group II and Group III. On comparison of clinical parameters, significant difference was noticed among the three groups. GCF periostin levels were correlated inversely with the clinical parameters in chronic periodontitis patients.

Conclusion

GCF periostin levels were gradually reduced with the increase in severity of periodontal disease. This novel biomarker has role in maintaining normal periodontal tissue function and may be used as a potential marker in periodontal disease activity evaluation.