Granulin-epithelin precursor binds directly to ADAMTS-7 and ADAMTS-12 and inhibits their degradation of cartilage oligomeric matrix protein

Progranulinopathy: A diverse realm of disorders linked to progranulin imbalances

Progranulin (PGRN), encoded by the GRN gene in humans, was originally isolated as a secreted growth factor that implicates in a multitude of processes ranging from regulation of tumorigenesis, inflammation to neural proliferation. Compelling evidence indicating that GRN mutation can lead to various common neuronal degenerative diseases and rare lysosomal storage diseases. These findings have unveiled a critical role for PGRN as a lysosomal protein in maintaining lysosomal function. The phenotypic spectrum of PGRN imbalance has expanded to encompass a broad spectrum of diseases, including autoimmune diseases, metabolic, musculoskeletal and cardiovascular diseases. These diseases collectively referred to as Progranulinopathy- a term encompasses the wide spectrum of disorders influenced by PGRN imbalance. Unlike its known extracellular function as a growth factor-like molecule associated with multiple membrane receptors, PGRN also serves as an intracellular co-chaperone engaged in the folding and traffic of its associated proteins, particularly the lysosomal hydrolases. This chaperone activity is required for PGRN to exert its diverse functions across a broad range of diseases, encompassing both the central nervous system and peripheral systems. In this comprehensive review, we present an update of the emerging role of PGRN in Progranulinopathy, with special focus on elucidating the intricate interplay between PGRN and a diverse array of proteins at various levels, ranging from extracellular fluids and intracellular components, as well as various pathophysiological processes involved. This review seeks to offer a comprehensive grasp of PGRN's diverse functions, aiming to unveil intricate mechanisms behind Progranulinopathy and open doors for future research endeavors.

Diagnostic value of serum COMP and ADAMTS7 for intervertebral disc degeneration

OBJECTIVE

Intervertebral disc degeneration (IVDD) is a major cause of morbidity and disability. Our study aimed to investigate the potential of cartilage oligomeric matrix protein (COMP) and ADAMTS7 (A disintegrin and metalloproteinases with thrombospondin motifs 7) as biomarkers for IVDD together with their functional relationship.

METHODS

IVD tissues and peripheral blood samples were collected from IVDD rabbit models over 1-4 weeks. Tissues and blood samples were also collected from clinical patients those were stratified into four equal groups according to Pfirrmann IVDD grading (I-V) with baseline data collected for each participant. COMP and ADAMTS7 expression were analyzed and biomarker characteristics were assessed using linear regression and receiver operating curve (ROC) analyses.

RESULTS

COMP and ADAMTS7 expression increased in tissues and serum during IVDD progression. Serum COMP (sCOMP) and serum ADAMTS7 (sADAMTS7) levels increased in a time-dependent manner following IVD damage in the rabbit model while significant positive correlations were detected between sCOMP and sADAMTS7 and Pfirrmann grade in human subjects. ROC analysis showed that combining sCOMP and sADAMTS7 assay results produced an improved diagnostic measure for IVDD compared to individual sCOMP or sADAMTS7 tests. In vitro assays conducted on human cell isolates revealed that COMP prevented extracellular matrix degradation and antagonized ADAMTS7 expression although this protective role was uncoupled under microenvironmental conditions mimicking IVDD.

CONCLUSIONS

Increases in circulating COMP and ADAMTS7 correlate with IVDD progression and may play regulatory roles. Assays for sCOMP and/or sADAMTS7 levels can discriminate between healthy subjects and IVDD patients, warranting further clinical assessment.

Molecular Mechanisms Linking Osteoarthritis and Alzheimer's Disease: Shared Pathways, Mechanisms and Breakthrough Prospects

Alzheimer's disease (AD) is a progressive neurodegenerative disease mostly affecting the elderly population. It is characterized by cognitive decline that occurs due to impaired neurotransmission and neuronal death. Even though deposition of amyloid beta (Aβ) peptides and aggregation of hyperphosphorylated TAU have been established as major pathological hallmarks of the disease, other factors such as the interaction of genetic and environmental factors are believed to contribute to the development and progression of AD. In general, patients initially present mild forgetfulness and difficulty in forming new memories. As it progresses, there are significant impairments in problem solving, social interaction, speech and overall cognitive function of the affected individual. Osteoarthritis (OA) is the most recurrent form of arthritis and widely acknowledged as a whole-joint disease, distinguished by progressive degeneration and erosion of joint cartilage accompanying synovitis and subchondral bone changes that can prompt peripheral inflammatory responses. Also predominantly affecting the elderly, OA frequently embroils weight-bearing joints such as the knees, spine and hips leading to pains, stiffness and diminished joint mobility, which in turn significantly impacts the patient's standard of life. Both infirmities can co-occur in older adults as a result of independent factors, as multiple health conditions are common in old age. Additionally, risk factors such as genetics, lifestyle changes, age and chronic inflammation may contribute to both conditions in some individuals. Besides localized peripheral low-grade inflammation, it is notable that low-grade systemic inflammation prompted by OA can play a role in AD pathogenesis. Studies have explored relationships between systemic inflammatory-associated diseases like obesity, hypertension, dyslipidemia, diabetes mellitus and AD. Given that AD is the most common form of dementia and shares similar risk factors with OA-both being age-related and low-grade inflammatory-associated diseases, OA may indeed serve as a risk factor for AD. This work aims to review literature on molecular mechanisms linking OA and AD pathologies, and explore potential connections between these conditions alongside future prospects and innovative treatments.

The role of inflammatory mediators and matrix metalloproteinases (MMPs) in the progression of osteoarthritis

Osteoarthritis (OA) is a chronic musculoskeletal disorder characterized by an imbalance between (synthesis) and catabolism (degradation) in altered homeostasis of articular cartilage mediated primarily by the innate immune system. OA degenerates the joints resulting in synovial hyperplasia, degradation of articular cartilage with damage of the structural and functional integrity of the cartilage extracellular matrix, subchondral sclerosis, osteophyte formation, and is characterized by chronic pain, stiffness, and loss of function. Inflammation triggered by factors like biomechanical stress is involved in the development of osteoarthritis. In OA apart from catabolic effects, anti-inflammatory anabolic processes also occur continually. There is also an underlying chronic inflammation present, not only in cartilage tissue but also within the synovium, which perpetuates tissue destruction of the OA joint. The consideration of inflammation in OA considers synovitis and/or other cellular and molecular events in the synovium during the progression of OA. In this review, we have presented the progression of joint degradation that results in OA. The critical role of inflammation in the pathogenesis of OA is discussed in detail along with the dysregulation within the cytokine networks composed of inflammatory and anti-inflammatory cytokines that drive catabolic pathways, inhibit matrix synthesis, and promote cellular apoptosis. OA pathogenesis, fluctuation of synovitis, and its clinical impact on disease progression are presented here along with the role of synovial macrophages in promoting inflammatory and destructive responses in OA. The role of interplay between different cytokines, structure, and function of their receptors in the inter-cellular signaling pathway is further explored. The effect of cytokines in the increased synthesis and release of matrix-decomposing proteolytic enzymes, such as matrix metalloproteinase (MMPs) and a disintegrin-like and metalloproteinase with thrombospondin motif (ADAMTS), is elaborated emphasizing the potential impact of MMPs on the chondrocytes, synovial cells, articular and periarticular tissues, and other immune system cells migrating to the site of inflammation. We also shed light on the pathogenesis of OA via oxidative damage particularly due to nitric oxide (NO) via its angiogenic response to inflammation. We concluded by presenting the current knowledge about the tissue inhibitors of metalloproteinases (TIMPs). Synthetic MMP inhibitors include zinc binding group (ZBG), non-ZBG, and mechanism-based inhibitors, all of which have the potential to be therapeutically beneficial in the treatment of osteoarthritis. Improving our understanding of the signaling pathways and molecular mechanisms that regulate the MMP gene expression, may open up new avenues for the creation of therapies that can stop the joint damage associated with OA.

Progranulin and GPNMB: interactions in endo-lysosome function and inflammation in neurodegenerative disease

BACKGROUND

Alterations in progranulin (PGRN) expression are associated with multiple neurodegenerative diseases (NDs), including frontotemporal dementia (FTD), Alzheimer's disease (AD), Parkinson's disease (PD), and lysosomal storage disorders (LSDs). Recently, the loss of PGRN was shown to result in endo-lysosomal system dysfunction and an age-dependent increase in the expression of another protein associated with NDs, glycoprotein non-metastatic B (GPNMB).

MAIN BODY

It is unclear what role GPNMB plays in the context of PGRN insufficiency and how they interact and contribute to the development or progression of NDs. This review focuses on the interplay between these two critical proteins within the context of endo-lysosomal health, immune function, and inflammation in their contribution to NDs.

SHORT CONCLUSION

PGRN and GPNMB are interrelated proteins that regulate disease-relevant processes and may have value as therapeutic targets to delay disease progression or extend therapeutic windows.

Adipokines in Rheumatoid Arthritis: Emerging Biomarkers and Therapeutic Targets

Rheumatoid arthritis (RA) is a chronic inflammatory disease manifested by joint involvement, extra-articular manifestations, and general symptoms. Adipose tissue, previously perceived as an inert energy storage organ, has been recognised as a significant contributor to RA pathophysiology. Adipokines modulate immune responses, inflammation, and metabolic pathways in RA. Although most adipokines have a pro-inflammatory and aggravating effect on RA, some could counteract this pathological process. The coexistence of RA and sarcopenic obesity (SO) has gained attention due to its impact on disease severity and outcomes. Sarcopenic obesity further contributes to the inflammatory milieu and metabolic disturbances. Recent research has highlighted the intricate crosstalk between adipose tissue and skeletal muscle, suggesting potential interactions between these tissues in RA. This review summarizes the roles of adipokines in RA, particularly in inflammation, immune modulation, and joint destruction. In addition, it explores the emerging role of adipomyokines, specifically irisin and myostatin, in the pathogenesis of RA and their potential as therapeutic targets. We discuss the therapeutic implications of targeting adipokines and adipomyokines in RA management and highlight the challenges and future directions for research in this field.

Effects of metalloprotease ADAMTS12 on cervical cancer cell phenotype and its potential mechanism

ADAMTS12 is a gene widely expressed in human tissues. We studied the expression level of ADAMTS12 in cervical cancer tissue and its relationship with clinicopathological features. We also explored the function of ADAMTS12 in cervical cancer cells and its underlying mechanisms. We found the higher expression level of ADAMTS12 in cancer tissues, which was associated with the worse overall survival rate. The immunofluorescence assay showed that the cytoplasm of cervical cancer cells is the main expression site of ADAMTS12. Overexpression of ADAMTS12 in HeLa and CaSki cells prominently promoted the cell proliferation, migration and invasion. We found that 2032 genes were correlated with ADAMTS12, which was mainly related to extracellular matrix, TGF-β signaling pathway. The phosphorylation levels of mTOR and 4E-BP1 were upregulated in ADAMTS12-overexpressing cells. Co-Immunoprecipitation combined with protein mass spectrometry showed that TGF-β signaling pathway-related proteins interacting with ADAMTS12 were screened from HeLa cells with ADAMTS12 overexpression. Therefore, we concluded that ADAMTS12 may affect the mTOR signaling pathway through the interacting with TGF-β1, and then affect the biological function of cervical cancer cells.

Beyond mechanical loading: The metabolic contribution of obesity in osteoarthritis unveils novel therapeutic targets

Osteoarthritis (OA) is a prevalent progressive disease that frequently coexists with obesity. For several decades, OA was thought to be the result of ageing and mechanical stress on cartilage. Researchers' perspective has been greatly transformed when cumulative findings emphasized the role of adipose tissue in the diseases. Nowadays, the metabolic effect of obesity on cartilage tissue has become an integral part of obesity research; hoping to discover a disease-modifying drug for OA. Recently, several adipokines have been reported to be associated with OA. Particularly, metrnl (meteorin-like) and retinol-binding protein 4 (RBP4) have been recognized as emerging adipokines that can mediate OA pathogenesis. Accordingly, in this review, we will summarize the latest findings concerned with the metabolic contribution of obesity in OA pathogenesis, with particular emphasis on dyslipidemia, insulin resistance and adipokines. Additionally, we will discuss the most recent adipokines that have been reported to play a role in this context. Careful consideration of these molecular mechanisms interrelated with obesity and OA will undoubtedly unveil new avenues for OA treatment.

Progranulin inhibits phospholipase sPLA2-IIA to control neuroinflammation

Mutations in the granulin (GRN) gene, resulting in haploinsufficiency of the progranulin (PGRN) protein, are a leading cause of frontotemporal lobar degeneration (FTLD) and PGRN polymorphisms are associated with Alzheimer's disease (AD) and Parkinson's disease (PD). PGRN is a key regulator of microglia-mediated inflammation but the mechanism is still unknown. Here we report that PGRN interacts with sPLA2-IIA, a secreted phospholipase involved in inflammatory responses, to downregulate sPLA2-IIA activities and levels. sPLA2-IIA expression modifies PGRN deficiency phenotypes in mice and sPLA2-IIA inhibition rescues inflammation and lysosomal abnormalities in PGRN deficient mice. Furthermore, FTLD patients with GRN mutations show increased levels of sPLA2-IIA in astrocytes. Our data support sPLA2-IIA as a critical target for PGRN and a novel therapeutic target for FTLD-GRN.

The association between ADAM12 gene polymorphisms and osteoarthritis: an updated meta-analysis

BACKGROUND

Osteoarthritis of the knee is an irreversible disease that causes great pain, and genetic factors play an important role in its occurrence and development. There have been many studies on the correlation between ADAM12 polymorphisms and genetic susceptibility to osteoarthritis, but the results remain inconclusive.

METHODS

Papers from PubMed, Web of Science, EMbase, Springer, SCOPUS, Google Scholar and other databases were systematically retrieved with a cut-off of January 2022. All case-control studies on ADAM12 rs3740199, rs1871054, rs1044122, and rs1278279 polymorphisms and osteoarthritis were searched. Fixed or random effects models were used for pooled analysis with OR values and 95% confidence intervals (CI), and publication bias was assessed. In addition, the false-positive reporting probability test was used to assess the confidence of a statistically significant association.

RESULTS

Eleven articles were included, which included 3332 patients with osteoarthritis and 5108 healthy controls. Meta-analysis showed that the rs1871054 polymorphism of ADAM12 was associated with osteoarthritis in dominant, recessive, allelic, and homozygote genetic models [C vs. T: OR = 1.34 95% CI (1.05, 1.71), P < 0.001]. Our subgroup analysis revealed an association between the ADAM12 polymorphism rs1871054 in Asians and osteoarthritis [C vs. T: OR = 1.61, 95% CI (1.25, 2.08), P < 0.001], albeit this was only for three studies. In addition, the ADAM12 polymorphism rs1871054 is associated with osteoarthritis in patients younger than 60 years of age [C vs. T: OR = 1.39, 95% CI (1.01, 1.92), P = 0.289]; however, the ADAM12 gene rs3740199, rs1044122, and rs1278279 site polymorphisms were not significantly. Furthermore, when assessing the confidence of the positive results, the positive results were found to be credible (except for Age < 60).

CONCLUSION

Polymorphism at the rs1871054 site of ADAM12 is associated with genetic susceptibility to osteoarthritis, but rs3740199, rs1044122, and rs1278279 site polymorphisms are not.

Progranulin is essential for bone homeostasis and immunology

Intercellular communication or crosstalk between immune and skeletal cells is considered a crucial element in bone homeostasis modulation. Progranulin (PGRN) is an autocrine growth factor that is structured as beads-on-a-string and participates in multiple pathophysiological processes, including atherosclerosis, arthritis, neurodegenerative pathologies, cancer, and wound repair. PGRN functions as a competitor that binds to tumor necrosis factor receptor 1 (TNFR1), thereby blocking the TNF-α pathway. PGRN is regarded as an agonist of chondrogenesis and osteogenesis, delaying the progression of inflammation through the TNFR2 pathway. The exploitation of PGRN may bring benefits for inflammatory bone diseases and the stabilization of bone homeostasis. The PGRN-modified analog Atsttrin possesses three TNFR-binding fragments and thereby exerts superior therapeutic effects on multiple preclinical animal models compared to PGRN. In this review, we highlight the emerging roles of PGRN in bone formation, as well as in physiological and TNF-α-mediated inflammatory conditions revealed in recent discoveries. We address potential therapies for the treatment of inflammatory bone conditions, such as periodontitis, by the use of PGRN and its derivative Atsttrin.

The Mechanism and Role of ADAMTS Protein Family in Osteoarthritis

Osteoarthritis (OA) is a principal cause of aches and disability worldwide. It is characterized by the inflammation of the bone leading to degeneration and loss of cartilage function. Factors, including diet, age, and obesity, impact and/or lead to osteoarthritis. In the past few years, OA has received considerable scholarly attention owing to its increasing prevalence, resulting in a cumbersome burden. At present, most of the interventions only relieve short-term symptoms, and some treatments and drugs can aggravate the disease in the long run. There is a pressing need to address the safety problems due to osteoarthritis. A disintegrin-like and metalloprotease domain with thrombospondin type 1 repeats (ADAMTS) metalloproteinase is a kind of secretory zinc endopeptidase, comprising 19 kinds of zinc endopeptidases. ADAMTS has been implicated in several human diseases, including OA. For example, aggrecanases, ADAMTS-4 and ADAMTS-5, participate in the cleavage of aggrecan in the extracellular matrix (ECM); ADAMTS-7 and ADAMTS-12 participate in the fission of Cartilage Oligomeric Matrix Protein (COMP) into COMP lyase, and ADAMTS-2, ADAMTS-3, and ADAMTS-14 promote the formation of collagen fibers. In this article, we principally review the role of ADAMTS metalloproteinases in osteoarthritis. From three different dimensions, we explain how ADAMTS participates in all the following aspects of osteoarthritis: ECM, cartilage degeneration, and synovial inflammation. Thus, ADAMTS may be a potential therapeutic target in osteoarthritis, and this article may render a theoretical basis for the study of new therapeutic methods for osteoarthritis.

ADAM and ADAMTS disintegrin and metalloproteinases as major factors and molecular targets in vascular malfunction and disease

A Disintegrin and Metalloproteinase (ADAM) and A Disintegrin and Metalloproteinase with Thrombospondin Motifs (ADAMTS) are two closely related families of proteolytic enzymes. ADAMs are largely membrane-bound enzymes that act as molecular scissors or sheddases of membrane-bound proteins, growth factors, cytokines, receptors and ligands, whereas ADAMTS are mainly secreted enzymes. ADAMs have a pro-domain, and a metalloproteinase, disintegrin, cysteine-rich and transmembrane domain. Similarly, ADAMTS family members have a pro-domain, and a metalloproteinase, disintegrin, and cysteine-rich domain, but instead of a transmembrane domain they have thrombospondin motifs. Most ADAMs and ADAMTS are activated by pro-protein convertases, and can be regulated by G-protein coupled receptor agonists, Ca²⁺ ionophores and protein kinase C. Activated ADAMs and ADAMTS participate in numerous vascular processes including angiogenesis, vascular smooth muscle cell proliferation and migration, vascular cell apoptosis, cell survival, tissue repair, and wound healing. ADAMs and ADAMTS also play a role in vascular malfunction and cardiovascular diseases such as hypertension, atherosclerosis, coronary artery disease, myocardial infarction, heart failure, peripheral artery disease, and vascular aneurysm. Decreased ADAMTS13 is involved in thrombotic thrombocytopenic purpura and microangiopathies. The activity of ADAMs and ADAMTS can be regulated by endogenous tissue inhibitors of metalloproteinases and other synthetic small molecule inhibitors. ADAMs and ADAMTS can be used as diagnostic biomarkers and molecular targets in cardiovascular disease, and modulators of ADAMs and ADAMTS activity may provide potential new approaches for the management of cardiovascular disorders.

Progranulin as a Potential Therapeutic Target in Immune-Mediated Diseases

Progranulin (PGRN), a secretory glycoprotein consisting of 593 amino acid residues, is a key actor and regulator of multiple system functions such as innate immune response and inflammation, as well as tissue regeneration. Recently, there is emerging evidence that PGRN is protective in the development of a variety of immune-mediated diseases, including rheumatoid arthritis (RA), inflammatory bowel disease (IBD), type 1 diabetes mellitus (T1DM) and multiple sclerosis (MS) by regulating signaling pathways known to be critical for immunology, particularly the tumor necrosis factor alpha/TNF receptor (TNF-α/TNFR) signaling pathway. Whereas, the role of PGRN in psoriasis, systemic lupus erythematosus (SLE) and systemic sclerosis (SSc) is controversial. This review summarizes the immunological functions of PGRN and its role in the pathogenesis of several immune-mediated diseases, in order to provide new ideas for developing therapeutic strategies for these diseases.

14-3-3 epsilon is an intracellular component of TNFR2 receptor complex and its activation protects against osteoarthritis

OBJECTIVES

Osteoarthritis (OA) is the most common joint disease; however, the indeterminate nature of mechanisms by which OA develops has restrained advancement of therapeutic targets. TNF signalling has been implicated in the pathogenesis of OA. TNFR1 primarily mediates inflammation, whereas emerging evidences demonstrate that TNFR2 plays an anti-inflammatory and protective role in several diseases and conditions. This study aims to decipher TNFR2 signalling in chondrocytes and OA.

METHODS

Biochemical copurification and proteomics screen were performed to isolate the intracellular cofactors of TNFR2 complex. Bulk and single cell RNA-seq were employed to determine 14-3-3 epsilon (14-3-3ε) expression in human normal and OA cartilage. Transcription factor activity screen was used to isolate the transcription factors downstream of TNFR2/14-3-3ε. Various cell-based assays and genetically modified mice with naturally occurring and surgically induced OA were performed to examine the importance of this pathway in chondrocytes and OA.

RESULTS

Signalling molecule 14-3-3ε was identified as an intracellular component of TNFR2 complexes in chondrocytes in response to progranulin (PGRN), a growth factor known to protect against OA primarily through activating TNFR2. 14-3-3ε was downregulated in OA and its deficiency deteriorated OA. 14-3-3ε was required for PGRN regulation of chondrocyte metabolism. In addition, both global and chondrocyte-specific deletion of 14-3-3ε largely abolished PGRN's therapeutic effects against OA. Furthermore, PGRN/TNFR2/14-3-3ε signalled through activating extracellular signal-regulated kinase (ERK)-dependent Elk-1 while suppressing nuclear factor kappa B (NF-κB) in chondrocytes.

CONCLUSIONS

This study identifies 14-3-3ε as an inducible component of TNFR2 receptor complex in response to PGRN in chondrocytes and presents a previously unrecognised TNFR2 pathway in the pathogenesis of OA.

Serum progranulin to TNF-α ratio in patients with gonarthrosis

OBJECTIVE

Progranulin (PGRN) is a growth factor that has antiinflammatory, immunosuppressive, and chondroprotective effects. It blocks Tumor Necrosis Factor-α (TNF-α) signal pathway by binding its receptor. Recently, it has been claimed that PGRN may be overexpressed in patients with Osteoarthritis (OA). However, these patients tend to be obese and obesity also may be one of the factors that affect PGRN levels. The aim of this study was to compare the PGRN levels of patients with Knee OA (KOA) with that of healthy controls by eliminating the effect of obesity and to evaluate PGRN-to-Tumor Necrosis Factor-α (TNF-α) ratio in KOA, both of which were investigated first in literature by this study.

METHODS

A total of 80 individuals (40 patients with KOA and 40 healthy controls) were included in this study. The patients and controls were divided into two groups according to their Body Mass Indexes (BMI): nonobese (BMI between 18.5 and 24.9) and obese (BMI of 30 or higher). Each of the groups included 20 subjects and had an equal number of men and women. Blood samples were obtained from all participants, and the serum PGRN and TNF-α levels were measured using commercial ELISA kits.

RESULTS

There was no difference among groups in terms of age (P = 0.416) and gender distribution. There was no statistical difference among study groups with regard to serum PGRN levels. Serum TNF-α levels were significantly higher in obese controls (P < 0.001) and nonobese patients (P = 0.003) compared to that of nonobese healthy controls. Correspondingly, serum PGRN-to-TNF-α ratio was considerably lower in obese controls (P < 0.001) and nonobese patients (P < 0.001) by comparison with that of nonobese healthy controls.

CONCLUSION

We determined that both obesity and KOA increased serum TNF-α levels and concordantly decreased serum PGRNto- TNF-α ratio. The results of the study suggest that the activation of the PGRN pathway and/or the inhibition of the TNFα pathway may be essential in terms of the reestablishment of the disrupted inflammatory balance in patients with KOA.

LEVEL OF EVIDENCE

Level III, Diagnostic study.

ADAMTS-12: Functions and Challenges for a Complex Metalloprotease

Nineteen members of the ADAMTS family of secreted zinc metalloproteinases are present in the human degradome. A wide range of different functions are being attributed to these enzymes and the number of their known substrates is considerably increasing in recent years. ADAMTSs can participate in processes such as fertility, inflammation, arthritis, neuronal and behavioral disorders, as well as cancer. Since its first annotation in 2001, ADAMTS-12 has been described to participate in different processes displayed by members of this family of proteinases. In this sense, ADAMTS-12 performs essential roles in modulation and recovery from inflammatory processes such as colitis, endotoxic sepsis and pancreatitis. ADAMTS-12 has also been involved in cancer development acting either as a tumor suppressor or as a pro-tumoral agent. Furthermore, participation of ADAMTS-12 in arthritis or in neuronal disorders has also been suggested through degradation of components of the extracellular matrix. In addition, ADAMTS-12 proteinase activity can also be modified by interaction with other proteins and thus, can be an alternative way of modulating ADAMTS-12 functions. In this review we revised the most relevant findings about ADAMTS-12 function on the 20th anniversary of its identification.

In Vitro Physical and Functional Interaction Assays to Examine the Binding of Progranulin Derivative Atsttrin to TNFR2 and Its Anti-TNFα Activity

TNFα/TNFR signaling plays a critical role in the pathogenesis of various inflammatory and autoimmune diseases, and anti-TNFα therapies have been accepted as the effective approaches for treating several autoimmune diseases. Progranulin (PGRN), a multi-faced growth factor-like molecule, directly binds to TNFR1 and TNFR2, particularly to the latter with higher affinity than TNFα. PGRN derivative Atsttrin is composed of three TNFR-binding domain of PGRN and exhibits even better therapeutic effects than PGRN in several inflammatory disease models, including collagen-induced arthritis. Herein we describe the detailed methodology of using (1) ELISA-based solid phase protein-protein interaction assay to demonstrate the direct binding of Atsttrin to TNFR2 and its inhibition of TNFα/TNFR2 interaction; and (2) tartrate-resistant acid phosphatase (TRAP) staining of in vitro osteoclastogenesis to reveal the cell-based anti-TNFα activity of Atsttrin. Using the protocol described here, the investigators should be able to reproducibly detect the physical inhibition of TNFα binding to TNFR and the functional inhibition of TNFα activity by Atsttrin and various kinds of TNF inhibitors.

Monitoring Atsttrin-Mediated Inhibition of TNFα/NF-κβ Activation Through In Vivo Bioluminescence Imaging

The NF-κβ transcription factor is a molecular mediator crucial to many biological functions and a central regulator of inflammatory and immune responses. NF-κβ is activated by multiple immunologically relevant stimuli, including members of the tumor necrosis factor (TNF) superfamily, and targeting TNF/NFκβ activity is a therapeutic objective in many inflammatory and autoimmune conditions. Here, we describe the generation of a transgenic reporter mouse model, expressing the human tumor necrosis factor α (TNF-α) transgene (TNF-tg) and carrying the luciferase gene under control of the NFκB-responsive element (NF-κB-Luc). Bioluminescence imaging shows that overexpression of TNF-α effectively activates NF-κB luciferase in vivo. To evaluate this system as a screen for potential therapeutics targeting the TNF/NFκβ signaling pathway, we treated double mutant mice with PGRN-derived Atsttrin, an engineered molecule comprising the minimal progranulin (PGRN):TNFR binding fragments previously demonstrated as therapeutic in multiple models of TNF/NFκβ-driven disease. Administration of Atsttrin could effectively inhibit luciferase activity in TNF-tg:NF-κB-Luc double mutant mice and demonstrates that this transgenic model can be used to non-invasively monitor the in vivo efficacy of modulators of TNF-activated NF-κB signaling pathway.

Are granulins copper sequestering proteins?

Granulins (GRN 1-7) are short (~6 kDa), cysteine-rich proteins that are generated upon the proteolytic processing of progranulin (PGRN). These peptides, along with their precursor, have been implicated in multiple pathophysiological roles, especially in neurodegenerative diseases. Previously we showed that GRN-3 and GRN-5 are fully disordered in the reduced form implicating redox sensitive attributes to the proteins. Redox-based modulations are often carried out by metalloproteins in mitigating oxidative stress and maintaining metal-homeostasis within cells. To probe whether GRNs play a role in metal sequestration, we tested the metal binding propensity of the reduced forms of GRNs -3 and - 5 under neutral and acidic pH mimicking cytosolic and lysosomal conditions, respectively. We found, at neutral pH, both GRNs selectively bind Cu and no other divalent metal cations, with a greater specificity for Cu(I). Binding of Cu did not result in a disorder-to-order structural transition but partly triggered the multimerization of GRNs via uncoordinated cystines at both pH conditions. Overall, the results indicate that GRNs -3 and - 5 have surprisingly strong affinity for Cu in the pM range, comparable to other known copper sequestering proteins. The results also hint at a potential of GRNs to reduce Cu(II) to Cu(I), a process that has significance in mitigating Cu-induced ROS cytotoxicity in cells. Together, this report uncovers metal-coordinating property of GRNs for the first time, which may have profound significance in their structure and pathophysiological functions.

Age-associated changes in the transcriptomes of non-cultured adipose-derived stem cells from young and old mice assessed via single-cell transcriptome analysis

Adipose-derived stem cells (ASCs) exhibit self-renewal and pluripotency. The differentiation potency of ASCs has been reported to deteriorate with aging; however, relevant studies used ASCs that were isolated and subcultured several times. It is still unclear whether subcultured ASCs accurately reflect the in vivo state. To address this question, we used freshly isolated stromal vascular fractions (SVFs) and performed comprehensive single-cell transcriptome analysis. In this study, we identified three cell populations as putative ASC candidates in SVFs and three novel ASC-related genes: Adamts7, Snai2, and Tgfbr1, that are reported to be negative regulators of cell differentiation. Moreover, we identified age-associated high gene expression levels of Adamts7, Egfr, and Igfbp4 in the earliest differentiation stage of ASCs. These results suggest that aging may make it impossible to maintain the stringency of the regulation of the expression of some genes related to ASC differentiation.

ADAMTS7 degrades Comp to fuel BMP2-dependent osteogenic differentiation and ameliorate oncogenic potential in osteosarcomas

Osteosarcoma (OS) is the most common primary malignant bone tumor in children and adolescents, with a high metastatic potential. Despite dramatic changes in OS treatments over the past decades, their efficiency still remains limited, with severe complications and adverse side effects. Key mechanisms underlining tumorigenesis, metastasis and chemotherapy resistance are currently lacking, in turn hindering any progress with respect to developing effective and safe therapeutic strategies against OS. Recently, ADAMTS7, a member of the disintegrin and metalloproteinase with thrombospondin motifs (ADAMTS) family, was shown to be involved in osteogenic differentiation‐related pathological processes. ADAMTS7 promotes vascular calcification via disturbing the balance between osteogenic bone morphogenetic protein (BMP)2 (regulating osteogenic differentiation and bone formation during development) and its natural inhibitor cartilage oligomeric matrix protein (Comp). Hence, in the present study, we aimed to investigate the role of ADAMTS7 in the pathological process of OS. We first revealed that ADAMTS7 was decreased in OS tissues. Lower expression of ADAMTS7 was correlated with poor histological differentiation and an advanced clinical stage of OS. Through loss‐ and gain‐function analysis, we further revealed that ADAMTS7 attenuated cell proliferation, migration and invasion, at the same time as promoting the expression of osteogenic differentiation markers in two OS cell lines: MG63 and SAOS2. Moreover, Comp was responsible for the effects of ADAMTS7 on OS pathogenesis by reinforcing cell osteogenic differentiation mediated by BMP2 in vitro. In conclusion, ADAMTS7‐mediated degradation of Comp may provide a potential therapeutic target for the treatment of OS.

Progranulin modulates cartilage-specific gene expression via sirtuin 1-mediated deacetylation of the transcription factors SOX9 and P65

Progranulin (PGRN) is an autocrine growth factor that exerts crucial roles within cartilage tissue; however, the molecular mechanisms underlying PGRN-mediated cartilage homeostasis remain elusive. In the present study, we investigated the role of PGRN in regulating chondrocyte homeostasis and its therapeutic potential for managing osteoarthritis (OA). We found that PGRN levels are significantly increased in human cartilage in mild OA and that its expression is decreased in the cartilage in severe OA. In vitro, treatment of primary rat chondrocytes with recombinant PGRN significantly enhanced the levels of collagen type II α 1 chain (COL2A1) and aggrecan, and attenuated TNFα-induced up-regulation of matrix metallopeptidase 13 (MMP13) and ADAM metallopeptidase with thrombospondin type 1 motif 5 (ADAMTS5) in chondrocytes. These effects were abrogated in SIRT1^-/- cells, indicating a causative role of SIRT1 in the effects of PGRN on protein expression in chondrocytes. Mechanistically, PGRN increased SIRT1 expression and activity, which reduced the acetylation levels of SRY-box transcription factor (SOX9) and transcription factor P65 (P65) and thereby promoted nuclear translocation of SOX9 and inhibited TNFα-induced P65 nuclear accumulation to maintain chondrocyte homeostasis. In conclusion, our findings reveal a mechanism of action for PGRN that maintains cartilage homeostasis and supports the notion that PGRN up-regulation may be a promising strategy for managing OA.

Serum progranulin/tumor necrosis factor-α ratio as independent predictor of systolic blood pressure in overweight hypertensive patients: a cross-sectional study

Background

Vascular inflammation plays a key role in the progression of hypertension. Progranulin (PGRN), an anti-inflammatory growth factor, mediated inhibition of tumor necrosis factor-α (TNF-α), a pleiotropic cytokine, activity has been well-established. Despite the role of chronic low-grade inflammation in hypertension, serum levels of PGRN and PGRN/TNF-α ratio and, their association with systolic and diastolic blood pressure has not been determined in hypertensive patients till now. This study aims to find and correlate the serum levels of pro-inflammatory cytokine (TNF-α), anti-inflammatory growth factor (PGRN), and PGRN/TNF-α ratio with the blood pressure in systolic-diastolic hypertension (SDH) and isolated systolic hypertension (ISH) patients.

Results

A cross-sectional study was conducted on SDH patients (mean age, 52.95 ± 12.6 years; male/female (M/F) number = 15/10) and ISH patients (mean age, 55.80 ± 9.40 years; M/F number = 12/13) (n = 25 each). Twenty-five age and body mass index (BMI)-matched healthy subjects (mean age, 56.00 ± 8.55 years; male/female number = 11/14) were considered as control. All patients and healthy subjects were overweight (BMI, 25–30 kg/m²). Overnight fasting blood samples of subjects were taken and levels of PGRN and TNF-α were measured using ELISA diagnostic kits. PGRN and TNF-α levels were found significantly high, whereas PGRN/TNF ratio was found very low, in SDH and ISH patients as compared to healthy subjects. Reduced PGRN/TNF-α ratio and pulse pressure were found as independent predictors of SBP both in SDH and ISH patients.

Conclusions

Findings of elevated PGRN levels in response to raised TNF-α levels depict the counter regulation by PGRN to neutralize TNF-α. Findings of reduced PGRN/TNF ratio, and it being an independent predictor of SBP, ascertain the key role of imbalance in pro- and anti-inflammatory environment in hypertension. Thus, it strengthens the cross-link between the concept of immunity–adiposity–inflammation–blood pressure¸ a vicious network. Further, this cross-link of SBP and progranulin must be explored in longitudinal studies. New researches should be focused not only on impact of pro-inflammatory environment rather to find on a balance between pro- and anti-inflammatory status, so that new target sites could be explored for therapeutic management of hypertension.

The Adipokine Network in Rheumatic Joint Diseases

Rheumatic diseases encompass a diverse group of chronic disorders that commonly affect musculoskeletal structures. Osteoarthritis (OA) and rheumatoid arthritis (RA) are the two most common, leading to considerable functional limitations and irreversible disability when patients are unsuccessfully treated. Although the specific causes of many rheumatic conditions remain unknown, it is generally accepted that immune mechanisms and/or uncontrolled inflammatory responses are involved in their etiology and symptomatology. In this regard, the bidirectional communication between neuroendocrine and immune system has been demonstrated to provide a homeostatic network that is involved in several pathological conditions. Adipokines represent a wide variety of bioactive, immune and inflammatory mediators mainly released by adipocytes that act as signal molecules in the neuroendocrine-immune interactions. Adipokines can also be synthesized by synoviocytes, osteoclasts, osteoblasts, chondrocytes and inflammatory cells in the joint microenvironment, showing potent modulatory properties on different effector cells in OA and RA pathogenesis. Effects of adiponectin, leptin, resistin and visfatin on local and systemic inflammation are broadly described. However, more recently, other adipokines, such as progranulin, chemerin, lipocalin-2, vaspin, omentin-1 and nesfatin, have been recognized to display immunomodulatory actions in rheumatic diseases. This review highlights the latest relevant findings on the role of the adipokine network in the pathophysiology of OA and RA.

Progranulin: A conductor of receptors orchestra, a chaperone of lysosomal enzymes and a therapeutic target for multiple diseases

Progranulin (PGRN), a widely expressed glycoprotein with pleiotropic function, has been linked to a host of physiological processes and diverse pathological states. A series of contemporary preclinical disease models and clinical trials have evaluated various therapeutic strategies targeting PGRN, highlighting PGRN as a promising therapeutic target. Herein we summarize available knowledge of PGRN targeting in various kinds of diseases, including common neurological diseases, inflammatory autoimmune diseases, cancer, tissue repair, and rare lysosomal storage diseases, with a focus on the functional domain-oriented drug development strategies. In particular, we emphasize the role of extracellular PGRN as a non-conventional, extracellular matrix bound, growth factor-like conductor orchestrating multiple membrane receptors and intracellular PGRN as a chaperone/co-chaperone that mediates the folding and traffic of its various binding partners.

Upregulation of ADAMTS‑7 and downregulation of COMP are associated with spontaneous abortion

A disintegrin and metalloproteinase with thrombospondin motifs 7 (ADAMTS-7) has been revealed to serve an important role in inflammation-associated diseases. However, the role of ADAMTS-7 in spontaneous abortion (SA) remains unclear. In the present study, human and mouse decidual tissues were used to detect the expression of ADAMTS-7 and cartilage oligomeric matrix protein (COMP) in mice with lipopolysaccharide (LPS)-induced abortion (10 mice/group), and in SA humans and the corresponding control group (21 participants in the SA group and 15 participants in the control group). The results revealed that ADAMTS-7 expression was upregulated and that COMP expression was downregulated in the mouse decidual tissue of the LPS-induced abortion group, when compared with that of the normal control group. The results were further confirmed by western blot analysis and reverse transcription-quantitative polymerase chain reaction (RT-qPCR) analysis, which revealed increased ADAMTS-7 and decreased COMP expression at the protein and mRNA levels in mice treated with LPS. Additionally, the expression of ADAMTS-7 was negatively correlated with the expression of COMP in mice, with a correlation coefficient of −0.936 (P<0.001). In addition, the expression of ADAMTS-7 and COMP exhibited was similar in the decidual tissue of SA patients when compared with the levels observed in the tissues of the normal control participants, as demonstrated by increased ADAMTS-7 expression and decreased COMP expression. Western blotting and RT-qPCR analysis revealed that ADAMTS-7 was increased and COMP was decreased in the decidual tissue of SA subjects. The correlation analysis of ADAMTS-7 and COMP in human decidual tissue also revealed a similar result, with a correlation coefficient of −0.836 (P<0.001). The results of the present study demonstrated that ADAMTS-7 was upregulated and COMP was downregulated in the decidual tissues of humans and mice with SA, and a negative correlation was identified between the expression levels of ADAMTS-7 and COMP, thereby providing novel evidence for a better understanding of the pathogenesis of SA, which may lead to improvements in the clinical pregnancy outcomes of these individuals.

Innate Anti-microbial and Anti-chemotaxis Properties of Progranulin in an Acute Otitis Media Mouse Model

Acute otitis media (AOM) is one of the most common infectious diseases primarily caused by Streptococcus pneumoniae (S.pn) among children. Progranulin (PGRN) is a multifunctional growth factor widely expressed in various tissues and cells. Studies have confirmed that PGRN is involved in the development of a variety of inflammatory diseases. We found that the expression of PGRN increased significantly in the middle ear of wild mice with AOM. However, its physiological functions in AOM still remain unknown. To examine the role of PGRN during AOM, we established an acute otitis media model in both C57BL/6 wild mice and PGRN-deficient (PGRN^−/−) mice via transbullar injection with S.pn clinical strain serotype 19F. Interestingly, we observed dual results: on one hand, macrophage recruitment notably increased in PGRN^−/− mice compared with WT mice; on the other hand, the overall bacterial clearance was surprisingly dampened in PGRN^−/− mice. The enhanced recruitment of macrophages was associated with increased production of chemokine (C-C motif) ligand 2 (CCL2), while the decreased bacterial clearance was associated with impaired endocytosis capacity of macrophages. The scavenging ability of bacteria in PGRN^−/− mice was recovered with administration of recombinant PGRN. These results suggested a novel dual role of PGRN in affecting the activities of macrophages.

Increased serum levels of progranulin (PGRN) in patients with haemophilic arthropathy

Haemophilia A and B are rarely occurring X chromosome-linked congenital coagulation disorders dominated by spontaneous joint bleedings and chronic synovitis, leading to development of haemophilic arthropathy (HA). Progranulin (PGRN) is a growth factor with anti-inflammatory and immunomodulatory properties. PGRN is an important molecule in the pathogenesis of osteoarthritis (OA) and rheumatological disorders. This study was aimed at investigating the potential role of PGRN in the mechanisms underlying the pathogenesis of HA. The serum levels of PGRN were measured by enzyme-linked immunosorbent assay (ELISA) in patients with end-stage knee joint HA (n = 20) and end-stage primary knee joint OA (n = 20) who met the inclusion and exclusion criteria. The clinical and radiological assessment of disease severity was evaluated by the Knee Society Score (KSS) and Kellgren-Lawrence scale. Median PGRN levels in HA patients was 349.1 ng/mL (232.8-415.6 ng/mL) and in OA patients 148.3 ng/mL (112.1-275.3 ng/mL) with statistically significant differences between both groups (P < 0.015). Further analysis revealed no correlation between PGRN levels and any of the patient demographics and clinical parameters. This study demonstrates increased PGRN serum levels in patients with HA and provides new insights into the mechanisms underlying the pathogenesis of HA indicating a new potential target for therapeutic intervention.

Role of ADAMTS-12 in Protecting Against Inflammatory Arthritis in Mice By Interacting With and Inactivating Proinflammatory Connective Tissue Growth Factor

OBJECTIVE

It has been reported that ADAMTS-12 is a susceptibility gene for rheumatoid arthritis (RA) development, and its level is significantly increased in RA patients. In addition, ADAMTS-12 is reported to be required for inflammation in otherwise healthy subjects. This study was undertaken to determine the role of ADAMTS-12 and the underlying mechanisms in the pathogenesis of inflammatory arthritis.

METHODS

The collagen-induced arthritis (CIA) model was established in ADAMTS-12-deficient mice and their control littermates to determine the role of ADAMTS-12 in vivo. Micro-computed tomography scanning was used to demonstrate the destruction of the ankle joint; histologic analysis illustrated synovitis, pannus formation, and bone and cartilage destruction; enzyme-linked immunosorbent assay was performed to measure serum levels of inflammatory cytokines; and protein-protein interaction assays were performed to detect the interactions of ADAMTS-12 and its various deletion mutants with connective tissue growth factor (CTGF).

RESULTS

Deficiency of ADAMTS-12 led to accelerated inflammatory arthritis in the CIA mouse model. Loss of ADAMTS-12 caused enhanced osteoclastogenesis. In vitro and in vivo protein-protein interaction assays demonstrated that ADAMTS-12 bound and processed CTGF, a previously unrecognized substrate of ADAMTS-12. In addition, deletion of ADAMTS-12 enhanced, while overexpression of ADMATS-12 reduced, CTGF-mediated inflammation. Furthermore, ADAMTS-12 regulation of inflammation was largely lost in CTGF-deficient macrophages. Importantly, blocking of CTGF attenuated elevated inflammatory arthritis seen in the ADAMTS-12-deficient CIA mouse model.

CONCLUSION

This study provides evidence that ADAMTS-12 is a critical regulator of inflammatory arthritis and that this is mediated, at least in part, through control of CTGF turnover.

Progranulin Protects Against Osteonecrosis of the Femoral Head by Activating ERK1/2 Pathway

The aim of this study was to investigate progranulin (PGRN) expression and its effect in cartilage degradation and in the pathogenesis of osteonecrosis of the femoral head (ONFH). Cartilage specimens were obtained from ONFH and FNF patients and PGRN expression was analyzed by immunohistochemistry, western blot analysis, and RT-PCR. Peripheral blood PGRN level was detected by ELISA. Additionally, primary chondrocytes were cultured and treated with PGRN. Next, the expression of aggrecan and collagen II and the activation of ERK1/2 were detected. We observed that the expression of PGRN was significantly upregulated in ONFH patients' articular cartilage, and recombinant PGRN could promote expression of aggrecan and collagen II and the activation of ERK1/2. Collectively, PGRN can improve chondrocyte anabolism and perform a therapeutic role in the pathogenesis of ONFH. This study helps to elucidate the pathogenesis of ONFH and presents PGRN as a potential target for the treatment of ONFH.

Progranulin derivative Atsttrin protects against early osteoarthritis in mouse and rat models

BACKGROUND

Atsttrin, an engineered protein composed of three tumor necrosis factor receptor (TNFR)-binding fragments of progranulin (PGRN), shows therapeutic effect in multiple murine models of inflammatory arthritis . Additionally, intra-articular delivery of PGRN protects against osteoarthritis (OA) progression. The purpose of this study is to determine whether Atsttrin also has therapeutic effects in OA and the molecular mechanisms involved.

METHODS

Surgically induced and noninvasive rupture OA models were established in mouse and rat, respectively. Cartilage degradation and OA were evaluated using Safranin O staining, immunohistochemistry, and ELISA. Additionally, expressions of pain-related markers, degenerative factors, and anabolic and catabolic markers known to be involved in OA were analyzed. Furthermore, the anabolic and anti-catabolic effects and underlying mechanisms of Atsttrin were determined using in-vitro assays with primary chondrocytes.

RESULTS

Herein, we found Atsttrin effectively prevented the accelerated OA phenotype associated with PGRN deficiency. Additionally, Atsttrin exhibited a preventative effect in OA by protecting articular cartilage and reducing OA-associated pain in both nonsurgically induced rat and surgically induced murine OA models. Mechanistic studies revealed that Atsttrin stimulated TNFR2-Akt-Erk1/2-dependent chondrocyte anabolism, while inhibiting TNFα/TNFR1-mediated inflammatory catabolism.

CONCLUSIONS

These findings not only provide new insights into the role of PGRN and its derived engineered protein Atsttrin in cartilage homeostasis as well as OA in vivo, but may also lead to new therapeutic alternatives for OA as well as other relative degenerative joint diseases.

MiR-29b-3p promotes chondrocyte apoptosis and facilitates the occurrence and development of osteoarthritis by targeting PGRN

This study was aimed to explore the role of miR-29b-3p and PGRN in chondrocyte apoptosis and the initiation and progress of osteoarthritis (OA). Both miR-29b-3p and PGRN were up-regulated in cartilage tissue from patients with OA. Transfection of miR-29b-3p mimic into rat primary chondrocytes and SW1353 chondrosarcoma cells significantly suppressed PGRN expression and release, induced apoptosis, inhibited proliferation and scratch wound closure. By contrast, transfection of miR-29b-3p inhibitor exhibited the opposite effects. Moreover, the expression and secretion of cartilaginous degeneration-related molecules were also altered by miR-29b-3p. Luciferase reporter gene assay showed rat GRN mRNA is directly targeted and repressed by miR-29b-3p. The fact that recombinant PGRN or shPGRN-mediated PGRN interference abolished miR-29b-3p mimic-induced cell apoptosis and growth inhibition suggested miR-29b-3p affect the cellular functions of chondrocyte through regulating PGRN expression. In vivo, joint cavity injection of miR-29b-3p antagomir prior to surgical induction of OA significantly suppressed the upregulation of miR-29b-3p, whereas further promoted the increased expression of PGRN. Articular chondrocytes apoptosis and cartilage loss in the knee joint of surgically induced OA rats were also ameliorated by the injection of miR-29b-3p antagomir, demonstrated by TUNEL and safranin O-fast green staining. This work showed miR-29b-3p facilitates chondrocyte apoptosis and OA by targeting PGRN, and miR-29b-3p or PGRN may be the potential target for OA treatments.

ADAMTS and ADAM metalloproteinases in osteoarthritis - looking beyond the 'usual suspects'

INTRODUCTION

Matrix metalloproteinases (MMPs) and 'aggrecanase' a disintegrin and metalloproteinase with thrombospondin motifs (ADAMTSs) are well established to play key roles in osteoarthritis (OA) through degradation of extracellular matrix (ECM) type II collagen and aggrecan, and are thus potential targets for development of OA therapies.

OBJECTIVE

This paper aims to provide a comprehensive review of the expression and potential roles of other, lesser-known ADAMTSs and related adamalysins (or a disintegrin and metalloproteinases (ADAMs)) in cartilage, with a view to identifying potentially protective or homeostatic metalloproteinases in the joint and informing consequent selective inhibitor design.

DESIGN

A comprehensive literature search was performed using PubMed terms 'osteoarthritis' and 'ADAMTS' or 'ADAM'.

RESULTS

Several ADAMTSs and ADAMs were identified as having reportedly increased expression in OA. These include enzymes likely to play roles in cartilage matrix anabolism (e.g., the procollagen N-proteinases ADAMTS-2, ADAMTS-3 and ADAMTS-14), chondrocyte differentiation and proliferation (e.g., ADAM9, ADAM10, ADAM12), as well as enzymes contributing to cartilage catabolism (e.g., Cartilage oligomeric protein (COMP)-degrading ADAMTS-7 and ADAMTS-12).

CONCLUSIONS

In addition to the well-characterised MMPs, ADAMTS-4 and ADAMTS-5, many other ADAMTSs and ADAMs are expressed in cartilage and several show significantly altered expression in OA. Studies aimed at elucidating the pathophysiological roles of these enzymes in cartilage will contribute to our understanding of OA pathogenesis and enable design of targeted inhibitors that effectively target metalloproteinase-mediated cartilage degradation while sparing cartilage repair pathways.

Serum and synovial cartilage oligomeric matrix protein levels in early and established rheumatoid arthritis

OBJECTIVE

To assess cartilage oligomeric matrix protein (COMP) levels in serum and synovial fluid in patients with early and established rheumatoid arthritis (RA), and to correlate the levels with clinical, laboratory and radiological characteristics.

PATIENTS AND METHODS

The study included 24 female RA patients. Full medical history was taken, thorough clinical examination and laboratory investigations performed, and body mass index (BMI) recorded. Radiological damage was assessed according to the modified Larsen score. Disease activity score 28 (DAS28) was calculated. The control group comprised 30 age- and gender-matched healthy subjects. Serum and synovial COMP levels were determined by enzyme-linked immunosorbent assay (ELISA).

RESULTS

Mean patient age was 44.04 ± 10.5 years. Of the 24 patients, 12 had early RA and 12 had established disease with joint destruction; 5 of each group had knee effusion. Serum COMP was significantly higher in patients (19.54 ± 5.47 µg/ml) compared to controls (5.93 ± 1.95 µg/ml; p < 0.001) and was also significantly higher in patients with established disease (23.9 ± 3.1 µg/ml) compared to those in early stages (15.1 ± 3.2 µg/ml; p < 0.001). Synovial COMP was also significantly increased in established compared to early-stage RA (31.2 ± 9.8 µg/ml vs. 51.6 ± 10.4 µg/ml; p = 0.013). Serum and synovial COMP significantly correlated with age, disease duration, BMI, DAS28 and modified Larsen score. On performing regression analysis in RA patients, only BMI could predict the serum level of COMP (p = 0.02).

CONCLUSION

COMP is a promising biomarker for disease activity in RA, making it a potential therapeutic target. The obvious correlation with the BMI throws light on the importance of weight control not only in osteoarthritis (OA), but also in RA.

Foxo4- and Stat3-dependent IL-10 production by progranulin in regulatory T cells restrains inflammatory arthritis

Progranulin (PGRN) restrains inflammation and is therapeutic against inflammatory arthritis; however, the underlying immunological mechanism remains unknown. In this study, we demonstrated that anti-inflammatory cytokine IL-10 was a critical mediator for PGRN-mediated anti-inflammation in collagen-induced arthritis by using PGRN and IL-10 genetically modified mouse models. IL-10 green fluorescent protein reporter mice revealed that regulatory T (T_reg) cells were the predominant source of IL-10 in response to PGRN. In addition, PGRN-mediated expansion and activation of T_reg cells, as well as IL-10 production, depends on JNK signaling, but not on known PGRN-activated ERK and PI3K pathways. Furthermore, microarray and chromatin immunoprecipitation sequencing screens led to the discovery of forkhead box protein O4 and signal transducer and activator of transcription 3 as the transcription factors required for PGRN induction of IL-10 in T_reg cells. These findings define a previously unrecognized signaling pathway that underlies IL-10 production by PGRN in T_reg cells and present new insights into the mechanisms by which PGRN resolves inflammation in inflammatory conditions and autoimmune diseases, particularly inflammatory arthritis.-Fu, W., Hu, W., Shi, L., Mundra, J. J. Xiao, G., Dustin, M. L., Liu, C. Foxo4- and Stat3-dependent IL-10 production by progranulin in regulatory T cells restrains inflammatory arthritis.

Progranulin Controls Sepsis via C/EBPα-Regulated Il10 Transcription and Ubiquitin Ligase/Proteasome-Mediated Protein Degradation

Progranulin (PGRN) is a widely expressed, pleiotropic protein that is involved in diverse biological processes, including cellular proliferation, neuron development, and wound healing. However, the role of PGRN in the regulation of pathogen-induced systemic inflammation and the mechanisms involved have not been established. In this study, we show that PGRN-deficient mice display heightened mortality in models of polymicrobial sepsis and endotoxinemia, with increased tissue levels of inflammatory cytokines and reduced IL-10 production. Conversely, administration of rPGRN decreases the susceptibility of PGRN-deficient mice to LPS-induced endotoxemic shock and augments IL-10 production by LPS-activated macrophages in a TNFR-dependent manner. Molecular analysis reveals a direct role of the transcription factor C/EBPα in PGRN-regulated IL-10 expression. C/EBPα-deficient macrophages produce less IL-10 in response to LPS. Furthermore, mice deficient in C/EBPα in hematopoietic cells are highly vulnerable to LPS-induced septic shock. Lastly, the defective IL-10 production by PGRN-deficient cells is primarily due to reduced C/EBPα protein stability via the E3 ubiquitin-conjugating enzyme E6AP and proteasome-mediated degradation. To our knowledge, this study provides the first evidence that PGRN is a nonredundant regulator of systemic inflammation via modulating the levels and activity of C/EBPα, IL-10, and the ubiquitin-proteasome proteolysis pathway. The results bear strong and profound implications for PGRN insufficiency and its mutation-associated systemic and organ-specific inflammatory human diseases.

Progranulin: A key player in autoimmune diseases

Autoimmune disease encompasses an array of conditions with a variety of presentations and the involvement of multiple organs. Though the etiologies of many autoimmune conditions are unclear, uncontrolled inflammatory immune response is believed to be a major cause of disease development and progression. Progranulin (PGRN), an anti-inflammatory molecule with therapeutic effect in inflammatory arthritis, was identified as an endogenous antagonist of TNFα by competitively binding to TNFR. PGRN exerts its anti-inflammatory activity through multiple pathways, including induction of T_reg differentiation and IL-10 expression and inhibition of chemokine release from macrophages. In addition, the protective role of PGRN has also been demonstrated in osteoarthritis, inflammatory bowel disease, and psoriasis. Intriguingly, PGRN was reported to contribute to development of insulin resistance in high-fat diet induced diabetes. Emerging evidences indicate that PGRN may also be associated with various autoimmune diseases, including systemic lupus erythematous, systemic sclerosis, multiple sclerosis and Sjogren's syndrome. This review summarizes recent studies of PGRN as a novel target molecule in the field of autoimmune disease, and provides updated information to inspire future studies.

Extracellular matrix protein 1, a direct targeting molecule of parathyroid hormone-related peptide, negatively regulates chondrogenesis and endochondral ossification via associating with progranulin growth factor

Chondrogenesis and endochondral ossification are precisely controlled by cellular interactions with surrounding matrix proteins and growth factors that mediate cellular signaling pathways. Here, we report that extracellular matrix protein 1 (ECM1) is a previously unrecognized regulator of chondrogenesis. ECM1 is induced in the course of chondrogenesis and its expression in chondrocytes strictly depends on parathyroid hormone-related peptide (PTHrP) signaling pathway. Overexpression of ECM1 suppresses, whereas suppression of ECM1 enhances, chondrocyte differentiation and hypertrophy in vitro and ex vivo In addition, target transgene of ECM1 in chondrocytes or osteoblasts in mice leads to striking defects in cartilage development and endochondral bone formation. Of importance, ECM1 seems to be critical for PTHrP action in chondrogenesis, as blockage of ECM1 nearly abolishes PTHrP regulation of chondrocyte hypertrophy, and overexpression of ECM1 rescues disorganized growth plates of PTHrP-null mice. Furthermore, ECM1 and progranulin chondrogenic growth factor constitute an interaction network and act in concert in the regulation of chondrogenesis.-Kong, L., Zhao, Y.-P., Tian, Q.-Y., Feng, J.-Q., Kobayashi, T., Merregaert, J., Liu, C.-J. Extracellular matrix protein 1, a direct targeting molecule of parathyroid hormone-related peptide, negatively regulates chondrogenesis and endochondral ossification via associating with progranulin growth factor.

The novel adipokine progranulin counteracts IL-1 and TLR4-driven inflammatory response in human and murine chondrocytes via TNFR1

Progranulin (PGRN) is a recently identified adipokine that is supposed to have anti-inflammatory actions. The proinflammatory cytokine interleukin-1β (IL1β) stimulates several mediators of cartilage degradation. Toll like receptor-4 (TLR4) can bind to various damage-associated molecular patterns, leading to inflammatory condition. So far, no data exist of PGRN effects in inflammatory conditions induced by IL1β or lipopolysaccharide (LPS). Here, we investigated the anti-inflammatory potential of PGRN in IL1β- or LPS-induced inflammatory responses of chondrocytes. Human osteoarthritic chondrocytes and ATDC-5 cells were treated with PGRN in presence or not of IL1β or LPS. First, we showed that recombinant PGRN had no effects on cell viability. We present evidence that PGRN expression was increased during the differentiation of ATDC-5 cell line. Moreover, PGRN mRNA and protein expression is increased in cartilage, synovial and infrapatellar fat pad tissue samples from OA patients. PGRN mRNA levels are upregulated under TNFα and IL1β stimulation. Our data showed that PGRN is able to significantly counteract the IL1β-induced expression of NOS2, COX2, MMP13 and VCAM-1. LPS-induced expression of NOS2 is also decreased by PGRN. These effects are mediated, at least in part, through TNFR1. Taken together, our results suggest that PGRN has a clear anti-inflammatory function.

Progranulin deficiency leads to severe inflammation, lung injury and cell death in a mouse model of endotoxic shock

Progranulin (PGRN) is a crucial secreted growth factor involved in various kinds of physiologic and disease processes and often has a protective role in inflammatory diseases. This study was designed to investigate the protective effects of PGRN on endotoxic shock in a mouse model of PGRN deficiency. After lipopolysaccharide (LPS) injection to induce endotoxic shock in mice, PGRN levels were induced in wild‐type (WT) mice at 6 and 24 hrs. Survival rate analysis, haematoxylin and eosin staining, immunohistochemical staining, enzyme‐linked immunosorbent assay and in situ terminal deoxynucleotidyl transferase–mediated uridine triphosphate nick‐end labelling assay were used to reveal the susceptibility, lung injury, inflammatory cell infiltration, production of inflammatory mediators and lung cell death in mice after LPS injection. PGRN‐deficient (Grn^−/−) mice were highly susceptible to LPS‐induced endotoxic shock, with decreased survival, severe lung injury, increased production of pro‐inflammatory mediators, and inflammatory cell infiltration and apoptotic death in the lung. Additionally, recombinant PGRN (rPGRN) administration before LPS stimulation ameliorated the survival of and abnormalities in both WT and Grn^−/− mice. Altogether, these findings indicate that PGRN may be a novel biologic agent with therapeutic potential for endotoxic shock probably by inhibiting LPS‐induced systemic and local inflammation in mice for treating endotoxic shock.

The Function and Roles of ADAMTS-7 in Inflammatory Diseases

The ADAMTS proteinases are a group of multidomain and secreted metalloproteinases containing the thrombospondin motifs. ADAMTS-7 is a member of ADAMTS family and plays a crucial role in the pathogenesis of arthritis. Overexpression of ADAMTS-7 gene promotes the breakdown of cartilage oligomeric matrix protein (COMP) matrix and accelerates the progression of both surgically induced osteoarthritis and collagen-induced arthritis. Moreover, ADAMTS-7 and tumor necrosis factor-α (TNF-α) form a positive feedback loop in osteoarthritis. More significantly, granulin-epithelin precursor, a growth factor has important roles in bone development and bone-associated diseases, disturbs the interaction between ADAMTS-7 and COMP, and prevents COMP degradation. This review is based on our results and provides an overview of current knowledge of ADAMTS-7, including its structure, function, gene regulation, and inflammatory diseases involvement.

Serum progranulin irrelated with Breg cell levels, but elevated in RA patients, reflecting high disease activity

Soluble progranulin (PGRN) is known to directly regulate regulatory T cells; however, whether PGRN levels are elevated in patients with rheumatoid arthritis and affect the regulatory subsets of B cells remain unknown. In this study, a total of 80 RA patients and 60 healthy controls were studied. Serum progranulin levels were determined using enzyme-linked immune-sorbent assay. A receiver operating characteristic (ROC) curve was used to evaluate the feasibility of serum PGRN as a biomarker for distinguishing patients with RA. CD19(+)CD5(+)GrB(+) B cells were analyzed by flow cytometry in peripheral blood mononuclear cells (PBMCs). Serum progranulin levels in RA patients (median, 59.4 ng/mL) and in RA patients DAS28 > 5.1 (median, 71.98 ng/mL) were much higher than those in normal controls (median, 46.3 ng/mL; P < 0.001). The area under the ROC curve for progranulin levels was 0.705 for RA versus normal controls and the area under the ROC curve for progranulin levels in RA patients DAS28 > 5.1 was 0.977 versus normal controls (P < 0.001). Interestingly, serum progranulin and DAS28, CRP, ESR were all positively correlated in RA patients (P < 0.001). The number of CD19(+)CD5(+)GrB(+) B cells was significantly higher in RA patients (P < 0.05); however, the level of Breg cells was not related to PGRN (P > 0.05). Our findings indicated that induction of PGRN expression may play a role in RA immune reaction and PGRN levels could be a useful biomarker in RA inflammatory response, but irrelated with Breg cell levels.

Progranulin Is Associated with Disease Activity in Patients with Rheumatoid Arthritis

OBJECTIVE

Progranulin (PGRN) is implicated in the pathogenesis of rheumatoid arthritis (RA). The aim of this study was to assess the relationship between PGRN and disease activity in RA.

METHODS

PGRN levels were evaluated in patients with RA (n = 47) and OA (n = 42) and healthy controls (n = 41). Immunohistochemical analysis of PGRN in synovial tissues was performed. The association between PGRN and C-reactive protein (CRP), disease activity score (DAS28-CRP), and health assessment questionnaire (HAQ) was studied.

RESULTS

Circulating PGRN was elevated in patients with RA and OA compared to healthy controls (227.1 ± 100.2 and 221.5 ± 102.5 versus 128.1 ± 34.7 ng/mL; P < 0.001). Synovial fluid levels of PGRN were higher in patients with RA compared to OA (384.5 ± 275.3 versus 241.4 ± 165.2 ng/mL; P = 0.002). PGRN expression was significantly upregulated in the synovial tissue of RA patients particularly in the inflammatory infiltrates. Serum PGRN levels correlated with DAS28 (r = 0.327, P = 0.049) and HAQ score (r = 0.323, P = 0.032), while synovial fluid PGRN correlated only with HAQ (r = 0.310, P = 0.043) in patients with RA. PGRN levels were not associated with CRP or autoantibodies.

CONCLUSIONS

This study demonstrates increased PGRN expression at local sites of inflammation and association between PGRN levels, disease activity, and functional impairment in patients with RA.

ADAMTS7 locus confers high cross-race risk for development of coronary atheromatous plaque

Genome-wide association studies of coronary artery disease (CAD) have recently identified a new susceptibility locus, ADAMTS7, in subjects of European ancestry. However, the significance of this locus in Chinese populations has not been identified. Therefore, this study was designed to evaluate the effect of rs3825807, a non-synonymous variant in the prodomain of the ADAMTS7 protease, on CAD risk and atherosclerosis severity in a Chinese population. We performed genetic association analyses in two independent case-control cohorts, which included a total of 8154 participants. Additionally, the association between the ADAMTS7 rs3825807 genotype and the proportion of CAD patients with 3- and 1-vessel disease was tested. We found that ADAMTS7 rs3825807 was associated with susceptibility to CAD in a Chinese population [odds ratio (OR) = 1.15, 95 % confidence interval (CI) = 1.05-1.26, P = 0.002]. The association remained significant after adjusting for clinical covariates (adjusted OR = 1.12, 95 % CI = 1.02-1.24, P = 0.02). Among 3741 angiographically documented CAD patients, the rs3825807 risk allele showed a significant association with disease severity (P = 0.04, trend P = 0.02). Additionally, 3-vessel disease demonstrated a strong and direct association with ADAMTS7 rs3825807 gene dosage (P = 0.02). Overall, our findings indicate that the significant associations observed between this coding variant in ADAMTS7 and the risk of CAD development are cross-ethnic, and the gene dosage is consistent with the degree of coronary atheromatous burden.

Increased serum GP88 (Progranulin) concentrations in rheumatoid arthritis

GP88 (Progranulin; PGRN) is a secreted glycosylated protein with important functions in several processes, including immune response and cancer growth. Recent reports have shown that PGRN is a therapeutic target for rheumatoid arthritis (RA) because of its capability to bind with tumor necrosis factor receptor (TNFR). However, the serum PGRN level in RA patients has not been investigated. We used enzyme-linked immunosorbent assay (ELISA) to quantify the serum levels of PGRN in 417 healthy subjects, 56 patients with RA and 31 patients with osteoarthritis (OA). In RA patients, we also measured the serum TNF-α and sTNFR concentration. Immunohistochemical staining of PGRN was performed using synovectomy tissue of RA patients. The serum PGRN normal range was established as 40.1 ± 8.7 ng/ml. PGRN levels were not influenced by sex or age. A significant increase in serum PGRN levels was observed in RA (50.2 ± 11.1 ng/ml) and OA (45.4 ± 6.6 ng/ml) groups compared to those in age-matched healthy controls (40.4 ± 9.9 ng/ml) (p<0.05, Tukey). Further, PGRN levels in the synovial fluid of RA patients (68.4 ± 3.4 ng/ml) were found to be significantly higher than those in OA patients (35.9 ± 16.8 ng/ml). Immunohistochemical staining of PGRN revealed that the highest positive signal was detected in macrophages. Circulating PGRN in RA patients was weakly associated with TNF-α and sTNFR 2 concentration. Furthermore, PGRN/TNF-α ratio was correlated the stage of the disease in RA patients. The concentrations of serum PGRN in RA were found to be significantly higher than those in age-matched healthy controls, although it remains to be clarified how blood PGRN is related to the pathogenesis of RA. Our results showed that the serum PGRN may be a useful approach to monitor the disease activity in RA patients.

Effect of insulin on the mRNA expression of procollagen N-proteinases in chondrosarcoma OUMS-27 cells

Chondrosarcoma is one of the most common bone tumors, and at present, there is no non-invasive treatment option for this cancer. The chondrosarcoma OUMS-27 cell line produces proteoglycan and type II, IX, and XI collagens, which constitutes cartilage tissue. A disintegrin and metalloproteinase with thrombospondin motifs (ADAMTS) proteases are a group of secreted proteases, which include the procollagen N-proteinases ADAMTS-2, -3 and -14. These procollagen N-proteinases perform a role in the processing of procollagens to collagen and the maturation of type I collagen. The present study aimed to improve the understanding of the causes of metastasis, local invasion and resistance to chemo- and radiotherapy in chondrosarcoma, as well as the effect of insulin on cancer cells. The present study was designed to reveal the effects of insulin on procollagen N-proteinases in chondrosarcoma OUMS-27 cells. The cells were cultured in Dulbecco's modified Eagle's medium (DMEM) alone or in DMEM containing 10 µg/ml insulin. The medium was changed every other day for 11 days. The cells were harvested on days 1, 3, 7 and 11, and total RNA isolation was performed immediately following harvesting. The expression levels of ADAMTS2, ADAMTS3 and ADAMTS14 mRNA were estimated by reverse transcription-quantitative polymerase chain reaction using appropriate primers. ADAMTS2 mRNA expression was found to be decreased on day 7 (P=0.028) and increased at day 11 compared with the control group (P=0.016). The increase in mRNA concentration at day 11 was significantly different compared to the concentrations on days 3 (P=0.047) and 7 (P=0.008). The expression of ADAMTS3 mRNA decreased immediately subsequent to insulin induction on day 1 compared with the control group (P=0.008). The most evident decrease in mRNA concentration was seen at day 7 subsequent to insulin induction (P=0.008). The present results demonstrated that ADAMTS2 and ADAMTS3 may perform a role in the invasion and metastasis of tumors, and may also possess proteolytic activity that results in the breakdown of the extracellular matrix (ECM). Insulin itself can modulate the biosynthesis of ECM macromolecules that are altered in diabetes through various pathways.

The ADAMTS (A Disintegrin and Metalloproteinase with Thrombospondin motifs) family

The ADAMTS (A Disintegrin and Metalloproteinase with Thrombospondin motifs) enzymes are secreted, multi-domain matrix-associated zinc metalloendopeptidases that have diverse roles in tissue morphogenesis and patho-physiological remodeling, in inflammation and in vascular biology. The human family includes 19 members that can be sub-grouped on the basis of their known substrates, namely the aggrecanases or proteoglycanases (ADAMTS1, 4, 5, 8, 9, 15 and 20), the procollagen N-propeptidases (ADAMTS2, 3 and 14), the cartilage oligomeric matrix protein-cleaving enzymes (ADAMTS7 and 12), the von-Willebrand Factor proteinase (ADAMTS13) and a group of orphan enzymes (ADAMTS6, 10, 16, 17, 18 and 19). Control of the structure and function of the extracellular matrix (ECM) is a central theme of the biology of the ADAMTS, as exemplified by the actions of the procollagen-N-propeptidases in collagen fibril assembly and of the aggrecanases in the cleavage or modification of ECM proteoglycans. Defects in certain family members give rise to inherited genetic disorders, while the aberrant expression or function of others is associated with arthritis, cancer and cardiovascular disease. In particular, ADAMTS4 and 5 have emerged as therapeutic targets in arthritis. Multiple ADAMTSs from different sub-groupings exert either positive or negative effects on tumorigenesis and metastasis, with both metalloproteinase-dependent and -independent actions known to occur. The basic ADAMTS structure comprises a metalloproteinase catalytic domain and a carboxy-terminal ancillary domain, the latter determining substrate specificity and the localization of the protease and its interaction partners; ancillary domains probably also have independent biological functions. Focusing primarily on the aggrecanases and proteoglycanases, this review provides a perspective on the evolution of the ADAMTS family, their links with developmental and disease mechanisms, and key questions for the future.

Intra-articular transplantation of atsttrin-transduced mesenchymal stem cells ameliorate osteoarthritis development

Osteoarthritis (OA) remains an intractable clinical challenge. Few drugs are available for reversing this degenerative disease, although some promising candidates have performed well in preclinical studies. Tumor necrosis factor α (TNFα) has been identified as a crucial effector modulating OA pathogenesis. This study aimed to investigate the therapeutic effects of Atsttrin, a novel TNFα blocker, on OA treatment. We developed genetically modified mesenchymal stem cells (MSCs) that expressed recombinant Atsttrin (named as MSC-Atsttrin). Expression levels of ADAMTS-5, MMP13, and iNOS of human chondrocytes were analyzed when cocultured with MSC-GFP/Atsttrin. OA animal models were induced by anterior cruciate ligament transection, and MSC-GFP/Atsttrin were injected into the articular cavity 1 week postsurgery. The results showed that MSC-Atsttrin significantly suppressed TNFα-driven up-regulation of matrix proteases and inflammatory factors. Intra-articular injection of MSC-Atsttrin prevented the progression of degenerative changes in the surgically induced OA mouse model. Additionally, levels of detrimental matrix hydrolases were significantly diminished. Compared with nontreated OA samples at 8 weeks postsurgery, the percentages of MMP13- and ADAMTS-5-positive cells were significantly reduced from 91.33% ± 9.87% to 24.33% ± 5.7% (p < .001) and from 91.33% ± 7.1% to 16.67% ± 3.1% (p < .001), respectively. Our results thus indicated that suppression of TNFα activity is an effective strategy for OA treatment and that intra-articular injection of MSCs-Atsttrin could be a promising therapeutic modality.