Distinct expression pattern of periostin splice variants in chondrocytes and ligament progenitor cells

Mapping the Periostin splice isoforms in atopic dermatitis and an in vitro asthma model - A multi-platform analysis using mass spectrometry and RT-qPCR

Periostin is a matricellular protein known to be alternatively spliced to produce ten isoforms with a molecular weight of 78-91 kDa. Within the extracellular matrix, periostin attaches to cell surfaces to induce signaling via integrin-binding and actively participates in fibrillogenesis, orchestrating the arrangement of collagen in the extracellular environment. In atopic diseases such as atopic dermatitis (AD) and asthma, periostin is known to participate in driving the disease-causing type 2 inflammation. The periostin isoforms expressed in these diseases and the implication of the alternative splicing events are unknown. Here, we present two universal assays to map the expression of periostin isoforms at the mRNA (RT-qPCR) and protein (PRM-based mass spectrometry) levels. We use these assays to study the splicing profile of periostin in AD lesions as well as in in vitro models of AD and asthma. In these conditions, periostin displayed overexpression with isoforms 3 and 5 standing out as highly overexpressed. Notably, isoforms 9 and 10 exhibited a divergent pattern relative to the remaining isoforms. Isoforms 9 and 10 are often overlooked in periostin research and this paper presents the first evidence of their expression at the protein level. This underlines the necessity to include isoforms 9 and 10 in future research addressing periostin splice isoforms. The assays presented in this paper hold the potential to improve our insight into the splicing profile of periostin in tissues and diseases of interest. The application of these assays to AD lesions and in vitro models demonstrated their potential for identifying isoforms of particular significance, warranting a further in-depth investigation.

Loss of periostin function impairs ligament fibroblast activity and facilitates ROS-mediated cellular senescence

Anterior cruciate ligament (ACL) injuries pose a significant challenge due to their limited healing potential, often resulting in premature arthritis. The factors and mechanisms contributing to this inadequate healing process remain elusive. During the acute phase of injury, ACL tissues express elevated periostin levels that decline over time. The functional significance of periostin in ligament biology remains understudied. In this study, we investigated the functional and mechanistic implications of periostin deficiency in ACL biology, utilizing ligament fibroblasts derived from patients and a murine model of ACL rupture. Our investigations unveiled that periostin knockdown compromised fibroblast growth characteristics, hindered the egress of progenitor cells from explants, and arrested cell-cycle progression, resulting in the accumulation of cells in the G0/G1 phase and moderate apoptosis. Concurrently, a significant reduction in the expression of cell-cycle and matrix-related genes was observed. Moreover, periostin deficiency triggered apoptosis through STAT3Y705/p38MAPK signaling and induced cellular senescence through increased production of reactive oxygen species (ROS). Mechanistically, inhibition of ROS production mitigated cell senescence in these cells. Notably, in vivo data revealed that ACL in Postn-/- mice exhibited a higher tearing frequency than wild-type mice under equivalent loading conditions. Furthermore, injured ACL with silenced periostin expression, achieved through nanoparticle-siRNA complex delivery, displayed an elevated propensity for apoptosis and senescence compared to intact ACL in C57BL/6 mice. Together, our findings underscore the pivotal role of periostin in ACL health, injury, and potential for healing.

Get Spliced: Uniting Alternative Splicing and Arthritis

Immune responses demand the rapid and precise regulation of gene protein expression. Splicing is a crucial step in this process; ~95% of protein-coding gene transcripts are spliced during mRNA maturation. Alternative splicing allows for distinct functional regulation, as it can affect transcript degradation and can lead to alternative functional protein isoforms. There is increasing evidence that splicing can directly regulate immune responses. For several genes, immune cells display dramatic changes in isoform-level transcript expression patterns upon activation. Recent advances in long-read RNA sequencing assays have enabled an unbiased and complete description of transcript isoform expression patterns. With an increasing amount of cell types and conditions that have been analyzed with such assays, thousands of novel transcript isoforms have been identified. Alternative splicing has been associated with autoimmune diseases, including arthritis. Here, GWASs revealed that SNPs associated with arthritis are enriched in splice sites. In this review, we will discuss how alternative splicing is involved in immune responses and how the dysregulation of alternative splicing can contribute to arthritis pathogenesis. In addition, we will discuss the therapeutic potential of modulating alternative splicing, which includes examples of spliceform-based biomarkers for disease severity or disease subtype, splicing manipulation using antisense oligonucleotides, and the targeting of specific immune-related spliceforms using antibodies.

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.

Targeted Antisense Oligonucleotide-Mediated Skipping of Murine Postn Exon 17 Partially Addresses Fibrosis in D2.mdx Mice

Periostin, a multifunctional 90 kDa protein, plays a pivotal role in the pathogenesis of fibrosis across various tissues, including skeletal muscle. It operates within the transforming growth factor beta 1 (Tgf-β1) signalling pathway and is upregulated in fibrotic tissue. Alternative splicing of Periostin's C-terminal region leads to six protein-coding isoforms. This study aimed to elucidate the contribution of the isoforms containing the amino acids encoded by exon 17 (e17+ Periostin) to skeletal muscle fibrosis and investigate the therapeutic potential of manipulating exon 17 splicing. We identified distinct structural differences between e17+ Periostin isoforms, affecting their interaction with key fibrotic proteins, including Tgf-β1 and integrin alpha V. In vitro mouse fibroblast experimentation confirmed the TGF-β1-induced upregulation of e17+ Periostin mRNA, mitigated by an antisense approach that induces the skipping of exon 17 of the Postn gene. Subsequent in vivo studies in the D2.mdx mouse model of Duchenne muscular dystrophy (DMD) demonstrated that our antisense treatment effectively reduced e17+ Periostin mRNA expression, which coincided with reduced full-length Periostin protein expression and collagen accumulation. The grip strength of the treated mice was rescued to the wild-type level. These results suggest a pivotal role of e17+ Periostin isoforms in the fibrotic pathology of skeletal muscle and highlight the potential of targeted exon skipping strategies as a promising therapeutic approach for mitigating fibrosis-associated complications.

RNA-binding proteins potentially regulate the alternative splicing of apoptotic genes during knee osteoarthritis progression

BACKGROUND

Alternative splicing (AS) is a principal mode of genetic regulation and one of the most widely used mechanisms to generate structurally and functionally distinct mRNA and protein variants. Dysregulation of AS may result in aberrant transcription and protein products, leading to the emergence of human diseases. Although considered important for regulating gene expression, genome-wide AS dysregulation, underlying mechanisms, and clinical relevance in knee osteoarthritis (OA) remain unelucidated. Therefore, in this study, we elucidated and validated AS events and their regulatory mechanisms during OA progression.

RESULTS

In this study, we identified differentially expressed genes between human OA and healthy meniscus samples. Among them, the OA-associated genes were primarily enriched in biological pathways such as extracellular matrix organization and ossification. The predominant OA-associated regulated AS (RAS) events were found to be involved in apoptosis during OA development. The expression of the apoptosis-related gene BCL2L13, XAF1, and NF2 were significantly different between OA and healthy meniscus samples. The construction of a covariation network of RNA-binding proteins (RBPs) and RAS genes revealed that differentially expressed RBP genes LAMA2 and CUL4B may regulate the apoptotic genes XAF1 and BCL2L13 to undergo AS events during OA progression. Finally, RT-qPCR revealed that CUL4B expression was significantly higher in OA meniscus samples than in normal controls and that the AS ratio of XAF1 was significantly different between control and OA samples; these findings were consistent with their expected expression and regulatory relationships.

CONCLUSIONS

Differentially expressed RBPs may regulate the AS of apoptotic genes during knee OA progression. XAF1 and its regulator, CUL4B, may serve as novel biomarkers and potential therapeutic targets for this disease.

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.

Periostin C-Terminal Is Intrinsically Disordered and Interacts with 143 Proteins in an In Vitro Epidermal Model of Atopic Dermatitis

Human periostin is a 78-91 kDa matricellular protein implicated in extracellular matrix remodeling, tumor development, metastasis, and inflammatory diseases like atopic dermatitis, psoriasis, and asthma. The protein consists of six domains, including an N-terminal Cys-rich CROPT domain, four fasciclin-1 domains, and a C-terminal domain. The exons encoding the C-terminal domain may be alternatively spliced by shuffling four exons, generating ten variants of unknown function. Here, we investigate the structure and interactome of the full-length variant of the C-terminal domain with no exons spliced out. The structural analysis showed that the C-terminal domain lacked a tertiary structure and was intrinsically disordered. In addition, we show that the motif responsible for heparin-binding is in the conserved very C-terminal part of periostin. Pull-down confirmed three known interaction partners and identified an additional 140 proteins, among which nine previously have been implicated in atopic dermatitis. Based on our findings, we suggest that the C-terminal domain of periostin facilitates interactions between connective tissue components in concert with the four fasciclin domains.

Anatomical Tissue Engineering of the Anterior Cruciate Ligament Entheses

The firm integration of anterior cruciate ligament (ACL) grafts into bones remains the most demanding challenge in ACL reconstruction, since graft loosening means graft failure. For a functional-tissue-engineered ACL substitute to be realized in future, robust bone attachment sites (entheses) have to be re-established. The latter comprise four tissue compartments (ligament, non-calcified and calcified fibrocartilage, separated by the tidemark, bone) forming a histological and biomechanical gradient at the attachment interface between the ACL and bone. The ACL enthesis is surrounded by the synovium and exposed to the intra-articular micromilieu. This review will picture and explain the peculiarities of these synovioentheseal complexes at the femoral and tibial attachment sites based on published data. Using this, emerging tissue engineering (TE) strategies addressing them will be discussed. Several material composites (e.g., polycaprolactone and silk fibroin) and manufacturing techniques (e.g., three-dimensional-/bio-printing, electrospinning, braiding and embroidering) have been applied to create zonal cell carriers (bi- or triphasic scaffolds) mimicking the ACL enthesis tissue gradients with appropriate topological parameters for zones. Functionalized or bioactive materials (e.g., collagen, tricalcium phosphate, hydroxyapatite and bioactive glass (BG)) or growth factors (e.g., bone morphogenetic proteins [BMP]-2) have been integrated to achieve the zone-dependent differentiation of precursor cells. However, the ACL entheses comprise individual (loading history) asymmetric and polar histoarchitectures. They result from the unique biomechanical microenvironment of overlapping tensile, compressive and shear forces involved in enthesis formation, maturation and maintenance. This review should provide a road map of key parameters to be considered in future in ACL interface TE approaches.

Long-term platinum-based drug accumulation in cancer-associated fibroblasts promotes colorectal cancer progression and resistance to therapy

A substantial proportion of cancer patients do not benefit from platinum-based chemotherapy (CT) due to the emergence of drug resistance. Here, we apply elemental imaging to the mapping of CT biodistribution after therapy in residual colorectal cancer and achieve a comprehensive analysis of the genetic program induced by oxaliplatin-based CT in the tumor microenvironment. We show that oxaliplatin is largely retained by cancer-associated fibroblasts (CAFs) long time after the treatment ceased. We determine that CT accumulation in CAFs intensifies TGF-beta activity, leading to the production of multiple factors enhancing cancer aggressiveness. We establish periostin as a stromal marker of chemotherapeutic activity intrinsically upregulated in consensus molecular subtype 4 (CMS4) tumors and highly expressed before and/or after treatment in patients unresponsive to therapy. Collectively, our study underscores the ability of CT-retaining CAFs to support cancer progression and resistance to treatment.

Elucidating the Focal Immunomodulatory Clues Influencing Mesenchymal Stem Cells in the Milieu of Intervertebral Disc Degeneration

The intervertebral discs (IVDs) are a relatively mobile joint that interconnects vertebrae of the spine. Intervertebral disc degeneration (IVDD) is one of the leading causes of low back pain, which is most often related to patient morbidity as well as high medical costs. Patients with chronic IVDD often need surgery that may sometimes lead to biomechanical complications as well as augmented degeneration of the adjacent segments. Moreover, treatment modalities like rigid intervertebral fusion, dynamic instrumentation, as well as other surgical interventions are still controversial. Mesenchymal stem cells (MSCs) have exhibited to have immunomodulatory functions and the ability to differentiate into cartilage, making these cells possibly an epitome for IVD regeneration. Transplanted MSCs were able to repair IVDD back to the normal disc milieu via the activation of the generation of extracellular matrix (ECM) proteins such as aggrecan, proteoglycans and collagen types I and II. IVD milieu clues like, periostin, cluster of differentiation, tumor necrosis factor alpha, interleukins, chemokines, transforming growth factor beta, reactive oxygen species, toll-like receptors, tyrosine protein kinase receptor and disialoganglioside, exosomes are capable of influencing the MSCs during treatment of IVDD. ECM microenvironment clues above have potentials as biomarkers as well as accurate molecular targets for therapeutic intervention in IVDD.

The Multiple Roles of Periostin in Non-Neoplastic Disease

Periostin, identified as a matricellular protein and an ECM protein, plays a central role in non-neoplastic diseases. Periostin and its variants have been considered to be normally involved in the progression of most non-neoplastic diseases, including brain injury, ocular diseases, chronic rhinosinusitis, allergic rhinitis, dental diseases, atopic dermatitis, scleroderma, eosinophilic esophagitis, asthma, cardiovascular diseases, lung diseases, liver diseases, chronic kidney diseases, inflammatory bowel disease, and osteoarthrosis. Periostin interacts with protein receptors and transduces signals primarily through the PI3K/Akt and FAK two channels as well as other pathways to elicit tissue remodeling, fibrosis, inflammation, wound healing, repair, angiogenesis, tissue regeneration, bone formation, barrier, and vascular calcification. This review comprehensively integrates the multiple roles of periostin and its variants in non-neoplastic diseases, proposes the utility of periostin as a biological biomarker, and provides potential drug-developing strategies for targeting periostin.

RNA-Seq analysis reveals sex-dependent transcriptomic profiles of human subacromial bursa stratified by tear etiology

Rotator cuff tendinopathy, a major cause of shoulder disability, occurs due to trauma or degeneration. Our molecular understanding of traumatic and degenerative tears remains elusive. Here, we probed transcript level differences between traumatic and degenerative tears. Subacromial bursa tissues were collected from patients with traumatic or degenerative tears during arthroscopy (N = 32). Transcripts differentially expressed by tear etiology were detected by RNA-seq. RNA-seq results were validated by real-time quantitative polymerase chain reaction. We identified 334 protein-coding transcripts differentially expressed between traumatic and degenerative tears in females and 167 in males at a fold-change greater than 2. In females, XIRP2, MYL1, MYBPC1, TNNT1, and LMOD2, were highly expressed in traumatic tears whereas TPSD1, CDSN, RCVRN, LTBP4, and PTGS1 were elevated in degen tears. Transcripts elevated in traumatic tears represented muscle cell differentiation and development, and muscle contraction whereas those elevated in degenerative tears represented cell activation and immune response. In males, AZGP1, CNTFR, COL9A1, ZNF98, and EREG were highly elevated in traumatic tears whereas MYL2, HOXD11, SLC6A7, CADM1, and MMP17 were highly expressed in degenerative tears. Transcripts elevated in traumatic tears represented metabolic/catabolic processes, and transmembrane protein transport while processes related to cell cycle were mainly enriched in degenerative tears. Numerous long noncoding RNAs were differentially expressed between traumatic and degenerative tears in both sexes. In summary, this study provides insights into molecular biology of bursa in patients with rotator cuff tendon disease based on tear acuity and novel sex-based transcript differences that could inform clinical decision making in treating patients with traumatic or degenerative shoulder injuries.

RNA binding proteins in osteoarthritis

Osteoarthritis (OA) is a common chronic degenerative joint disease worldwide. The pathological features of OA are the erosion of articular cartilage, subchondral bone sclerosis, synovitis, and metabolic disorder. Its progression is characterized by aberrant expression of genes involved in inflammation, proliferation, and metabolism of chondrocytes. Effective therapeutic strategies are limited, as mechanisms underlying OA pathophysiology remain unclear. Significant research efforts are ongoing to elucidate the complex molecular mechanisms underlying OA focused on gene transcription. However, posttranscriptional alterations also play significant function in inflammation and metabolic changes related diseases. RNA binding proteins (RBPs) have been recognized as important regulators in posttranscriptional regulation. RBPs regulate RNA subcellular localization, stability, and translational efficiency by binding to their target mRNAs, thereby controlling their protein expression. However, their role in OA is less clear. Identifying RBPs in OA is of great importance to better understand OA pathophysiology and to figure out potential targets for OA treatment. Hence, in this manuscript, we summarize the recent knowledge on the role of dysregulated RBPs in OA and hope it will provide new insight for OA study and targeted treatment.

Reduced dynamic loads due to hip dislocation induce acetabular cartilage degeneration by IL-6 and MMP3 via the STAT3/periostin/NF-κB axis

Developmental dysplasia of the hip (DDH) is characterized by anatomical abnormalities of the hip joint, ranging from mild acetabular dysplasia to hip subluxation and eventually dislocation. The mechanism underlying the cartilage degeneration of the hip joints exposed to reduced dynamic loads due to hip dislocation remains unknown. We established a rodent hip dislocation (disarticulation; DA) model of DDH (DA-DDH rats and mice) by swaddling. Expression levels of periostin (Postn) and catabolic factors, such as interleukin-6 (IL-6) and matrix metalloproteinase 3 (Mmp3), increased and those of chondrogenic markers decreased in the acetabular cartilage of the DA-DDH models. Postn induced IL-6 and Mmp3 expression in chondrocytes through integrin αVβ3, focal adhesion kinase, Src, and nuclear factor-κB (NF-κB) signaling. The microgravity environment created by a random positioning machine induced Postn expression in chondrocytes through signal transducer and activator of transcription 3 (STAT3) signaling. IL-6 stimulated Postn expression via STAT3 signaling. Furthermore, cartilage degeneration was suppressed in the acetabulum of Postn^−/− DA-DDH mice compared with that in the acetabulum of wild type DA-DDH mice. In summary, reduced dynamic loads due to hip dislocation induced acetabular cartilage degeneration via IL-6 and MMP3 through STAT3/periostin/NF-κB signaling in the rodent DA-DDH models.

Periostin promotes nucleus pulposus cells apoptosis by activating the Wnt/β-catenin signaling pathway

Intervertebral disc (IVD) degeneration (IVDD) is closely linked to degenerative spinal disease, resulting in disability, poor quality of life, and financial burden. Apoptosis of nucleus pulposus (NP) cells (NPCs) is a key pathological basis of IVDD. Periostin (POSTN), an extracellular matrix protein, is expressed in many tissues, whereas its abnormal expression is associated with IVDD. The conventional Wnt/β-catenin pathway is also involved in IVDD and contributes to NPCs apoptosis. However, research on the mechanisms of POSTN in IVDD is lacking. This study investigated the relationship between POSTN and β-catenin expression in degenerated IVDs. We detected the expression of POSTN, β-catenin, and cleaved-caspase-3 (C-caspase3) in degenerated and non-degenerated IVD tissues of different grades (n = 8) using RT-qPCR, immunohistochemical staining, and western blotting analysis. Next, we explored the effects of recombinant periostin (rPOSTN) and isoquercitrin (Iso), an inhibitor of the Wnt/β-catenin pathway, on NPCs apoptosis. Finally, we inhibited the expression of POSTN in degenerated NPCs in vivo and investigated the anti-apoptotic effect. The expression of β-catenin, POSTN, and C-caspase3 in severe degenerative IVDs was significantly higher than that in mild degenerative IVDs. These findings were confirmed in rat and cell-based degenerative models. When treated with rPOSTN, the Wnt/β-catenin pathway activity and cell apoptosis were time- and dose-dependent. However, rPOSTN-induced NPCs apoptosis decreased after iso-induced inhibition of the Wnt/β-catenin pathway. POSTN inhibition reduced apoptosis but was restored by rPOSTN re-addition. Lastly, POSTN inhibition ameliorated puncture-induced IVDD in vivo. Overall, our study demonstrated that POSTN promotes NPCs apoptosis and aggravates degeneration by activating the Wnt/β-catenin pathway.

Mechano Growth Factor Accelerates ACL Repair and Improves Cell Mobility of Mechanically Injured Human ACL Fibroblasts by Targeting Rac1-PAK1/2 and RhoA-ROCK1 Pathways

Exceeded mechanical stress leads to a sublethal injury to anterior cruciate ligament (ACL) fibroblasts, and it will hinder cell mobility and ACL regeneration, and even induce osteoarthritis. The mechano growth factor (MGF) could be responsible for mechanical stress and weakening its negative effects on cell physiological behaviors. In this study, effects of MGF on cell mobility and relevant molecules expression in injured ACL fibroblasts were detected. After an injurious mechanical stretch, the analysis carried out, at 0 and 24 h, respectively, showed that the cell area, roundness, migration, and adhesion of ACL fibroblasts were reduced. MGF (10, 100 ng/mL) treatment could improve cell area, roundness and promote cell migration and adhesion capacity compared with the injured group without MGF. Further study indicated that cell mobility-relevant molecules (PAK1/2, Cdc42, Rac1, RhoA, and ROCK1) expression in ACL fibroblasts was down-regulated at 0 or 24 h after injurious stretch (except Rac1 and RhoA at 0 h). Similarly, MGF improved cell mobility-relevant molecule expression, especially the ROCK1 expression level in ACL fibroblasts at 0 or 24 h after injurious stretch. Protein expression of ROCK1 in injured ACL fibroblasts was also reduced and could be recovered by MGF treatment. In a rabbit partial ACL transection (ACLT) model, ACL exhibited poor regenerative capacity in collagen and extracellular matrix (ECM) synthesis after partial ACLT for 2 or 4 weeks, and MGF remarkably accelerated ACL regeneration and restored its mechanical loading capacity after partial ACLT for four weeks. Our findings suggest that MGF weakens the effects of pathological stress on cell mobility of ACL fibroblasts and accelerates ACL repair, and might be applied as a future treatment approach to ACL rupture in the clinic.

KIF26B Silencing Prevents Osseous Transdifferentiation of Progenitor/Stem Cells and Attenuates Ectopic Calcification in a Murine Model

Ectopic calcification is an osteogenic process that leads to the formation of inappropriate bone within intra-articular soft tissues, often in response to injury or surgery. The molecular mechanisms governing this phenotype have yet to be determined. Using a population genetics approach, we identified an association of the kinesin superfamily member 26b (Kif26b) with injury-induced ectopic calcification through quantitative trait locus analysis of recombinant inbred mouse strains, consistent with a genomewide association study that identified KIF26B as a severity locus for ectopic calcification in patients with hip osteoarthritis. Despite these associations of KIF26B with ectopic calcification, its mechanistic role and functional implications have not yet been fully elucidated. Here, we aim to decipher the functional role of KIF26B in osseous and chondrogenic transdifferentiation of human and murine progenitor/stem cells and in a murine model of non-invasive injury-induced intra-articular ectopic calcification. We found that KIF26B ablation via lentivirus-mediated shRNA significantly arrested osteogenesis of progenitor/stem cells and suppressed the expression of typical osteogenic marker genes. Conversely, KIF26B loss-of-function increased chondrogenesis as demonstrated by enhanced Safranin-O staining and by the elevated expression of chondrogenic marker genes. Furthermore, cell function analysis revealed that KIF26B knockdown significantly decreased cell viability and proliferation and induced cellular apoptosis. Mechanistically, loss of osteogenesis was reverted by the addition of a Wnt agonist, SKL2001, demonstrating a role of KIF26B in canonical Wnt/β-catenin signaling. Finally, intra-articular delivery of Kif26b shRNA in B6-129SF2/J mice significantly hampered the development of intra-articular ectopic calcification at 8 weeks after injury compared with mice treated with non-target scrambled shRNA. In summary, these observations highlight that KIF26B plays a crucial role in ectopic bone formation by repressing osteogenesis, but not chondrogenesis, potentially via modulating Wnt/β-catenin signaling. These findings establish KIF26B as a critical determinant of the osteogenic process in pathologic endochondral bone formation and an actionable target for pharmacotherapy to mitigate ectopic calcification (and heterotopic ossification). © 2021 American Society for Bone and Mineral Research (ASBMR).

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.

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.

Intra-articular silencing of periostin via nanoparticle-based siRNA ameliorates post-traumatic osteoarthritis in mice

OBJECTIVE

Recent evidence delineates an emerging role of Periostin (Postn) in osteoarthritis (OA) as its expression subsequent to knee injury is detrimental to the articular cartilage. We hypothesize that intra-articular knockdown of Postn in a murine model of post-traumatic OA would ameliorate OA.

METHODS

Post-traumatic OA was induced in 10-week-old male C57BL/6J mice (n=24) by destabilization of the medial meniscus (DMM) and analyzed 8-week post-surgery. Intra-articular Postn was inhibited by siRNA using a novel peptide-nucleotide polyplex. Cartilage degeneration (OARSI score) and synovitis were assessed histologically. Bone changes were measured by μCT. The effect and mechanism of Postn silencing were investigated in human chondrocytes treated with IL-1β with or without IKK2 inhibitor, SC-514.

RESULTS

Peptide-siRNA nanoplatform significantly abolished Postn expression. OARSI score was significantly less in mice receiving Postn siRNA (10.94±0.66) compared to both untreated (22.38±1.30,P=0.002) and scrambled siRNA (22.69±0.87,P=0.002) treatment. No differences were observed in synovitis. Subchondral bone sclerosis, BV/TV, vBMD, and heterotopic ossification were significantly low in Postn siRNA treatment. Immunostaining of cartilage revealed that Postn knockdown reduced the DMM-induced MMP-13 intensity, phosphorylation of p65, and immunoreactivity of aggrecan neoepitope, DIPEN. Postn knockdown also suppressed IL-1β-induced MMP-13 and ADAMTS-4 in chondrocytes. Mechanistically, Postn-induced MMP-13 was abrogated by SC-514 demonstrating a link between Postn and NF-κB.

CONCLUSION

Intra-articular delivery of Postn siRNA nanocomplex represents a promising clinical approach to mitigate the severity of joint degeneration and provides an unequivocal scientific rationale for longitudinal studies. Employing a cartilage-specific gene knockout strategy will further illuminate the functional role of Postn in OA.

Periostin loss-of-function protects mice from post-traumatic and age-related osteoarthritis

Background

Elevated levels of periostin (Postn) in the cartilage and bone are associated with osteoarthritis (OA). However, it remains unknown whether Postn loss-of-function can delay or prevent the development of OA. In this study, we sought to better understand the role of Postn in OA development and assessed the functional impact of Postn deficiency on post-traumatic and age-related OA in mice.

Methods

The effects of Postn deficiency were studied in two murine experimental OA models using Postn^−/− (n = 32) and littermate wild-type (wt) mice (n = 36). Post-traumatic OA was induced by destabilization of the medial meniscus (DMM) in 10-week-old mice (n = 20); age-related OA was analyzed in 24-month-old mice (n = 13). Cartilage degeneration was assessed histologically using the OARSI scoring system, and synovitis was evaluated by measuring the synovial lining cell layer and the cells density in the synovial stroma. Bone changes were measured by μCT analysis. Serum levels of Postn were determined by ELISA. Expression of Postn and collagenase-3 (MMP-13) was measured by immunostaining. RNA-seq was performed on chondrocytes isolated from 21-day old Postn^−/− (n = 3) and wt mice (n = 3) to discover genes and pathways altered by Postn knockout.

Results

Postn^−/− mice exhibited significantly reduced cartilage degeneration and OARSI score relative to wt mice in post-traumatic OA after 8 weeks (maximum: 2.37 ± 0.74 vs. 4.00 ± 1.20, P = 0.011; summed: 9.31 ± 2.52 vs. 21.44 ± 6.01, P = 0.0002) and spontaneous OA (maximum: 1.93 ± 0.45 vs. 3.58 ± 1.16, P = 0.014; summed: 6.14 ± 1.57 vs. 11.50 ± 3.02, P = 0.003). Synovitis was significantly lower in Postn^−/− mice than wt only in the DMM model (1.88 ± 1.01 vs. 3.17 ± 0.63; P = 0.039). Postn^−/− mice also showed lower trabecular bone parameters such as BV/TV, vBMD, Tb.Th, and Tb.N and high Tb. Sp in both models. Postn^−/− mice had negligible levels of serum Postn compared with wt. Immunofluorescent studies of cartilage indicated that Postn^−/− mice expressed lower MMP-13 levels than wt mice. RNA-seq revealed that cell-cell-adhesion and cell-differentiation processes were enriched in Postn^−/− mice, while those related to cell-cycle and DNA-repair were enriched in wt mice.

Conclusions

Postn deficiency protects against DMM-induced post-traumatic and age-related spontaneous OA. RNA-seq findings warrant further investigations to better understand the mechanistic role of Postn and its potential as a therapeutic target in OA.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13075-021-02477-z.

Expression profile of the matricellular protein periostin in paediatric inflammatory bowel disease

The precise role of periostin, an extra-cellular matrix protein, in inflammatory bowel disease (IBD) is unclear. Here, we investigated periostin in paediatric IBD including its relationship with disease activity, clinical outcomes, genomic variation and expression in the colonic tissue. Plasma periostin was analysed using ELISA in 144 paediatric patients and 38 controls. Plasma levels were assessed against validated disease activity indices in IBD and clinical outcomes. An immuno-fluorescence for periostin and detailed isoform-expression analysis in the colonic tissue was performed in 23 individuals. We integrated a whole-gene based burden metric ‘GenePy’ to assess the impact of variation in POSTN and 23 other genes functionally connected to periostin. We found that plasma periostin levels were significantly increased during remission compared to active Crohn’s disease. The immuno-fluorescence analysis demonstrated enhanced peri-cryptal ring patterns in patients compared to controls, present throughout inflamed, as well as macroscopically non-inflamed colonic tissue. Interestingly, the pattern of isoforms remained unchanged during bowel inflammation compared to healthy controls. In addition to its role during the inflammatory processes in IBD, periostin may have an additional prominent role in mucosal repair. Additional studies will be necessary to understand its role in the pathogenesis, repair and fibrosis in IBD.

Identification of Diagnostic Biomarkers of Osteoarthritis Based on Multi-Chip Integrated Analysis and Machine Learning

The pathogenesis of osteoarthritis (OA) is still unclear. It is therefore important to identify relevant diagnostic marker genes for OA. We performed an integrated analysis with multiple microarray data cohorts to identify potential transcriptome markers of OA development. Further, to identify OA diagnostic markers, we established gene regulatory networks based on the protein-protein interaction network involved in these differentially expressed genes (DEGs). Using support vector machine (SVM) pattern recognition, a diagnostic model for OA prediction and prevention was established. Kyoto Encyclopedia of Genes and Genomes pathway analysis revealed that 190 DEGs were mainly enriched in pathways like the tumor necrosis factor signaling pathway, interleukin-17 signaling pathway, mitogen-activated protein kinase signaling pathway, nuclear factor kappa-light-chain-enhancer of activated B cells signaling pathway, and osteoclast differentiation. Eight hub genes (POSTN, MMP2, CTSG, ELANE, COL3A1, MPO, COL1A1, and COL1A2) were considered potential diagnostic biomarkers for OA, the area under curve (AUC) was >0.95, which showed high accuracy. The sensitivity and specificity of the SVM model of OA based on these eight genes reached 100% in multiple external verification cohorts. Our research provides a theoretical basis for OA diagnosis for clinicians.

TAT-Beclin-1 induces severe synovial hyperplasia and does not protect from injury-induced osteoarthritis in mice

OBJECT

Autophagy maintains cartilage homeostasis and is compromised during osteoarthritis (OA), contributing to cartilage degeneration. We sought to determine if D-isomer TAT-Beclin-1, a potent inducer of autophagy, could attenuate post-traumatic OA in mice.

METHODS

10-week-old mice underwent destabilization of the medial meniscus (DMM) surgery to induce post-traumatic OA, or sham surgery (control), and injected intra-articularly with D-isomer TAT-Beclin-1 (0.5-2 mg/kg) or PBS 1 week post-surgery for up to 9 weeks. Mice were sacrificed at 2 or 10 weeks post-surgery. Knee joint sections were evaluated by histopathology for cartilage degeneration and synovitis, and immunostaining for key markers of autophagy (LC3B), cell proliferation (nuclear Ki67), activated fibroblasts (αSMA), and cells of hematopoietic origin (CD45).

RESULTS

All D-isomer TAT-Beclin-1-treated DMM mice had no difference in the degree of cartilage degeneration compared to PBS-injected DMM mice. Surprisingly, all D-isomer TAT-Beclin-1-treated mice exhibited substantial synovial hyperplasia, with increased cellularity and ECM deposition (fibrosis-like phenotype), as compared to PBS-injected mice. Synovial effects of D-isomer TAT-Beclin-1 were dose- and injection frequency-dependent. An increased percentage of cells positive for LC3B and nuclear Ki67 were found in the synovial intima early after injection, which persisted after frequent injections.

CONCLUSIONS

D-isomer TAT-Beclin-1 did not attenuate cartilage degeneration, but rather induced synovial hyperplasia associated with increased expression of key markers of autophagy and cell proliferation and a fibrosis-like phenotype, independent of markers of fibroblast activation or persistent hematopoietic-origin cell infiltration. These data suggest that, if not tissue-targeted, caution should be taken using autophagy activators due to diverse cellular responses in the joint.

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 interaction with discoidin domain receptor-1 (DDR1) promotes cartilage degeneration

Osteoarthritis (OA) is characterized by progressive loss of articular cartilage accompanied by the new bone formation and, often, a synovial proliferation that culminates in pain, loss of joint function, and disability. However, the cellular and molecular mechanisms of OA progression and the relative contributions of cartilage, bone, and synovium remain unclear. We recently found that the extracellular matrix (ECM) protein periostin (Postn, or osteoblast-specific factor, OSF-2) is expressed at high levels in human OA cartilage. Multiple groups have also reported elevated expression of Postn in several rodent models of OA. We have previously reported that in vitro Postn promotes collagen and proteoglycan degradation in human chondrocytes through AKT/β-catenin signaling and downstream activation of MMP-13 and ADAMTS4 expression. Here we show that Postn induces collagen and proteoglycan degradation in cartilage by signaling through discoidin domain receptor-1 (DDR1), a receptor tyrosine kinase. The genetic deficiency or pharmacological inhibition of DDR1 in mouse chondrocytes blocks Postn-induced MMP-13 expression. These data show that Postn is signaling though DDR1 is mechanistically involved in OA pathophysiology. Specific inhibitors of DDR1 may provide therapeutic opportunities to treat OA.

Proteomic analysis of synovial fluid identifies periostin as a biomarker for anterior cruciate ligament injury

OBJECTIVE

Emerging evidence suggests that injury to the anterior cruciate ligament (ACL) typically initiates biological changes that contribute to the development of osteoarthritis (OA). The molecular biomarkers or mediators of these biological events remain unknown. The goal of this exploratory study was to identify novel synovial fluid biomarkers associated with early biological changes following ACL injury distinct from findings in end-stage OA.

METHODS

Synovial fluid was aspirated from patients with acute (≤30 days) and subacute (31-90 days) ACL tears and from patients with advanced OA and probed via tandem mass spectrometry for biomarkers to distinguish OA from ACL injury. Periostin (POSTN) was identified as a potential candidate. Further analyses of POSTN were performed in synovial fluid, OA cartilage, torn ACL remnants, and cultured cells and media by Western blot, PCR, immunostaining and ELISA.

RESULTS

Synovial fluid analysis revealed that POSTN exhibited higher expression in subacute ACL injury than OA. POSTN expression was relatively low in cartilage/chondrocytes suggesting it is also produced by other intra-articular tissues. Conversely, high and time-dependent expression of POSTN in ACL tear remnants and isolated cells was consistent with the synovial fluid results.

CONCLUSIONS

Elevated POSTN may provide a synovial fluid biomarker of subacute ACL injury setting separate from OA. Increased expression of POSTN in ACL suggests that the injured ACL may play a pivotal role in POSTN production, which is sensitive to time from injury. Previous studies have shown potential catabolic effects of POSTN, raising the possibility that POSTN contributes to the initiation of joint degeneration and may offer a window of opportunity to intervene in the early stages of post-traumatic OA.