Rheumatoid arthritis in remission : Decreased myostatin and increased serum levels of periostin

Periostin and rheumatic diseases: early insights from a systematic review and meta-analysis

Periostin regulates angiogenesis, inflammation, and fibrosis, key processes in the pathophysiology of rheumatic diseases (RDs). However, its association with RDs has not been assessed. We conducted a systematic review and meta-analysis of studies reporting circulating periostin in RD patients and healthy controls. We searched electronic databases from inception to 30 November 2024 for relevant articles and assessed the risk of bias and the certainty of evidence using the JBI critical appraisal checklist and GRADE, respectively. In 12 eligible studies, there was a non-significant trend towards higher periostin concentrations in RD patients (standard mean difference, SMD = 0.46, 95% CI -0.07 to 0.98, p = 0.089; I2 = 94.2%, p < 0.001). The results were stable in sensitivity analysis. There were no significant associations between the SMD and age, male-to-female ratio, number of participants, or publication year. However, we observed significant periostin elevations in studies investigating systemic sclerosis and rheumatoid arthritis but not osteoarthritis. Significant periostin reductions were observed in studies investigating ankylosing spondylitis and dermatomyositis. Furthermore, the SMD was significant in studies conducted in America, but not Asia or Europe. Our study suggests significant periostin elevations in rheumatoid arthritis and systemic sclerosis. Such elevations may reflect a more pronounced dysregulation of angiogenesis and fibrosis when compared to other RDs. Further research is warranted to investigate periostin concentrations in a wide range of RDs with various inflammatory, angiogenic, and fibrotic features and whether periostin is useful for diagnosis, prognosis, and monitoring in this patient group (PROSPERO registration number: CRD42024623501).

Muscle Strength Comparison in Immune-Mediated Rheumatic Disease vs Healthy Adults: A Meta-Analysis

OBJECTIVES

Patients with immune-mediated rheumatic diseases (IMRDs) often exhibit reduced muscle strength. Therefore, this review aimed to evaluate muscle strength in patients with IMRDs compared with healthy control and to summarize the relationship between low muscle strength and clinical features in patients with IMRDs.

DESIGN

Systematic review with meta-analysis of case-control studies.

SETTING AND PARTICIPANTS

Patients with IMRDs.

METHODS

A comprehensive search was conducted in the Embase, MEDLINE, Web of Science, and Cochrane databases to identify relevant studies published up to November 2023 on rheumatoid arthritis, systemic lupus erythematosus, systemic sclerosis, and spondyloarthritis. Meta-analysis was performed using a random-effects model to determine the mean difference (MD) in muscle strength between patients with IMRDs and an age- and sex-matched healthy control group.

RESULTS

We identified 11,692 studies, and 760 studies were selected for screening. Ultimately, 26 studies met the inclusion criteria, composed of 2661 individuals, mostly women. The IMRDs women group had lower handgrip muscle strength (MD, -9.53; 95% CI, -11.78 to -7.28 kg) than the healthy control group, whereas the handgrip strength men groups did not differ significantly from that of the healthy control group. Similar trend was observed in lower limb muscle strength for the IMRDs women group than the healthy control group (MD, -63.10; 95% CI, -94.18 to -32.01 Nm). Four studies examined muscle strength and clinical features in rheumatoid arthritis: one associated it with age and disease activity, 2 associated it with disease duration, and 3 associated it with physical function. In systemic lupus erythematosus, only 2 studies associated low muscle strength with age, disease activity, and fatigue. No associations were found in spondyloarthritis, and none were found in systemic sclerosis.

CONCLUSIONS AND IMPLICATIONS

Patients with IMRD exhibit lower muscle strength than healthy counterparts, with low strength moderately associated with longer disease duration, worsening disease activity, and decline in physical function. Targeted interventions are crucial for preventing and managing muscle weakness in IMRDs.

Unbiased Proteomic Exploration Suggests Overexpression of Complement Cascade Proteins in Plasma from Patients with Psoriasis Compared with Healthy Individuals

Knowledge about the molecular mechanisms underlying the systemic inflammation observed in psoriasis remains incomplete. In this study, we applied mass spectrometry-based proteomics to compare the plasma protein levels between patients with psoriasis and healthy individuals, aiming to unveil potential systemically dysregulated proteins and pathways associated with the disease. Plasma samples from adult patients with moderate-to-severe psoriasis vulgaris (N = 59) and healthy age- and sex-matched individuals (N = 21) were analyzed using liquid chromatography-tandem mass spectrometry. Patients did not receive systemic anti-psoriatic treatment for four weeks before inclusion. A total of 776 protein groups were quantified. Of these, 691 were present in at least 60% of the samples, providing the basis for the downstream analysis. We identified 20 upregulated and 22 downregulated proteins in patients with psoriasis compared to controls (p < 0.05). Multiple proteins from the complement system were upregulated, including C2, C4b, C5, and C9, and pathway analysis revealed enrichment of proteins involved in complement activation and formation of the terminal complement complex. On the other end of the spectrum, periostin was the most downregulated protein in sera from patients with psoriasis. This comprehensive proteomic investigation revealed significantly elevated levels of complement cascade proteins in psoriatic plasma, which might contribute to increased systemic inflammation in patients with psoriasis.

Role of Myostatin in Rheumatoid Arthritis: A Review of the Clinical Impact

Rheumatoid arthritis (RA) is a chronic inflammatory disease that affects synovial joints and that frequently involves extra-articular organs. A multiplicity of interleukins (IL) participates in the pathogenesis of RA, including IL-6, IL-1β, transforming growth factor-beta (TGF-β), and tumor necrosis factor (TNF)-α; immune cells such as monocytes, T and B lymphocytes, and macrophages; and auto-antibodies, mainly rheumatoid factor and anti-citrullinated protein antibodies (ACPAs). Skeletal muscle is also involved in RA, with many patients developing muscle wasting and sarcopenia. Several mechanisms are involved in the myopenia observed in RA, and one of them includes the effects of some interleukins and myokines on myocytes. Myostatin is a myokine member of the TGF-β superfamily; the overproduction of myostatin acts as a negative regulator of growth and differentiates the muscle fibers, limiting their number and size. Recent studies have identified abnormalities in the serum myostatin levels of RA patients, and these have been found to be associated with muscle wasting and other manifestations of severe RA. This review analyzes recent information regarding the relationship between myostatin levels and clinical manifestations of RA and the relevance of myostatin as a therapeutic target for future research.

Periostin Is a Biomarker of Rheumatoid Arthritis-Associated Interstitial Lung Disease

Periostin was investigated as a biomarker for rheumatoid arthritis-associated interstitial lung disease (RA-ILD). This prospective study measured serum monomeric and total periostin, Klebs von den Lungen-6 (KL-6), surfactant protein D (SP-D), and lactate dehydrogenase (LDH) in 19 patients with RA-ILD, 20 RA without ILD, and 137 healthy controls (HC). All biomarkers were higher in RA-ILD than HC or RA without ILD. KL-6 accurately detected ILD in RA patients (area under curve [AUC] = 0.939) and moderately detected SP-D and monomeric and total periostin (AUC = 0.803, =0.767, =0.767, respectively). Monomeric and total periostin were negatively correlated with normal lung area and positively correlated with honeycombing, reticulation, fibrosis score, and the traction bronchiectasis grade but not inflammatory areas. Serum levels of SP-D, KL-6, and LDH did not correlate with the extent of those fibrotic areas on high-resolution CT. Serum monomeric and total periostin were higher in patients with RA-ILD with definite usual interstitial pneumonia pattern compared with other ILD patterns. Immunohistochemical analyses of biopsy or autopsy lung tissues from RA-ILD during the chronic phase and acute exacerbation showed that periostin was expressed in fibroblastic foci but not inflammatory or dense fibrosis lesions. Periostin is a potential biomarker for diagnosis, evaluating fibrosis, and deciding therapeutic strategies for patients with RA-ILD.

The plasma levels of Dickkopf-1 elevated in patients with Juvenile Idiopathic Arthritis

BACKGROUND

To explore the role of two major inhibitors of Wnt signal pathway, Dickkopf-1(DKK-1) and Sclerostin (SOST), in the pathogenesis of juvenile idiopathic arthritis (JIA).

METHODS

88 patients with JIA, which including 49 patients with enthesitis-related arthritis (ERA), 21 oligoarthritis (oJIA) and 18 polyarthritis (pJIA), and 36 age-and sex-matched children as healthy controls (HC) were enrolled in this study. The plasma levels of DKK-1 and SOST, measured using commercially available ELISA kits, were analyzed the correlation between the levels of DKK-1/SOST and JIA, and were analyzed in 14 patients with JIA during before and after treatment.

RESULTS

Plasma levels of DKK-1 were significantly higher in the patients with JIA than that in HC, the elevation of DKK-1 level was positively correlated with HLA-B27 positive JIA. DKK-1 levels dropped significantly in patient with JIA after treatment (P < 0.05). There was no significant change in SOST levels among different subtypes of JIA, patients with JIA during before and after treatment, and HC.

CONCLUSION

It was suggested that the DKK-1 may have a certain correlation with the pathogenesis of JIA, and DKK-1 levels are more closely related to the HLA-B27 positive-ERA.

IMPACT

The abnormally elevated levels of Dickkopf-1 (DKK-1) may be involved in the pathogenesis of juvenile idiopathic arthritis (JIA). DKK-1 levels were more closely related to the HLA-B27 positive-enthesitis-related arthritis (ERA). DKK-1 is an inhibitor of Wnt signaling pathway that promotes osteoblastic new bone formation; it is very rare for pediatric patients with HLA-B27 positive-ERA to manifest typical spondylitis, while sacroiliac arthritis is relatively common, which may be related to the high levels of DKK-1, which is consistent with the early stage of ankylosing spondylitis (AS).

Abnormal basement membrane results in increased keratinocyte-derived periostin expression in psoriasis similar to wound healing

The psoriatic skin resembles wound healing, and it shows abnormalities at the basement membrane (BM), also in the non-lesional skin. Fibroblast-derived dermal periostin has well-known functions in wound healing and Th2-mediated diseases, such as atopic dermatitis. Here we show that serum periostin level was elevated in psoriatic patients, remarkably in the systemically treated ones. Obvious periostin positivity was detected in basal keratinocytes of the non-lesional, lesional, and previously-lesional psoriatic vs. healthy skin. Ex vivo skin models were generated to examine how different skin injuries affect periostin expression during wound healing. Our newly developed cultured salt-split model demonstrated that BM-injury induced periostin expression in basal keratinocytes, and periostin levels in the supernatant were also increased upon healing. In wound healing models, β1-integrin expression was similarly induced. β1-integrin blocking caused reduced periostin expression in in vitro scratch assay, indicating that β1-integrin can mediate periostin production. In contrast to atopic dermatitis, psoriatic basal keratinocytes are in an activated state and show a stable wound healing-like phenotype with the overexpression of periostin. This abnormal BM-induced wound healing as a potential compensatory mechanism can be initiated already in the non-lesional skin present in the lesion and keratinocytes can remain activated in the healed skin.

Rheumatoid sarcopenia: loss of skeletal muscle strength and mass in rheumatoid arthritis

Sarcopenia, a disorder that involves the generalized loss of skeletal muscle strength and mass, was formally recognized as a disease by its inclusion in the International Classification of Diseases in 2016. Sarcopenia typically affects older people, but younger individuals with chronic disease are also at risk. The risk of sarcopenia is high (with a prevalence of ≥25%) in individuals with rheumatoid arthritis (RA), and this rheumatoid sarcopenia is associated with increased likelihood of falls, fractures and physical disability, in addition to the burden of joint inflammation and damage. Chronic inflammation mediated by cytokines such as TNF, IL-6 and IFNγ contributes to aberrant muscle homeostasis (for instance, by exacerbating muscle protein breakdown), and results from transcriptomic studies have identified dysfunction of muscle stem cells and metabolism in RA. Progressive resistance exercise is an effective therapy for rheumatoid sarcopenia but it can be challenging or unsuitable for some individuals. The unmet need for anti-sarcopenia pharmacotherapies is great, both for people with RA and for otherwise healthy older adults.

Increased circulating sclerostin levels in rheumatoid arthritis patients: an updated meta-analysis

BACKGROUND

Sclerostin, a regulator of bone metabolism and vascular calcification involved in regulating the Wnt/β-catenin signaling pathway, has been shown to be involved in the pathogenesis of rheumatoid arthritis (RA). However, current results regarding the circulating sclerostin level of RA patients are debatable. This study aimed to evaluate the circulating level of sclerostin in RA patients and briefly summarize its role.

METHOD

PubMed, EMBASE, and the Cochrane Library databases were systematically searched till May 27, 2021, for eligible articles. Useful data from all qualified papers were systematically extracted and analyzed using Stata 12.0 software (Stata Corp LP, College Station, TX, USA).

RESULTS

Overall, 13 qualifying studies including 1030 cases and 561 normal controls were analyzed in this updated meta-analysis. Forest plot of this meta-analysis showed that RA patients had higher circulating sclerostin levels (P < 0.001, standardized mean difference [SMD] = 0.916, 95% CI: 0.235-1.597) compared to normal controls. Subgroup analyses implied that age, region, and assay method were associated with sclerostin level in RA patients.

CONCLUSION

RA patients have higher circulating sclerostin levels, and these was influenced by age, region, and assay method.

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.

Therapeutic Potential of Targeting Periostin in the Treatment of Graves' Orbitopathy

Periostin is a matricellular protein that is ubiquitously expressed in normal human tissues and is involved in pathologic mechanism of chronic inflammatory and fibrotic disease. In this study we investigate periostin in the pathogenesis of Graves' orbitopathy (GO) using human orbital adipose tissue obtained from surgery and primary cultured orbital fibroblasts in vitro. POSTN (gene encoding periostin) expression in Graves' orbital tissues and healthy control tissues was studied, and the role of periostin in GO pathologic mechanism was examined through small-interfering RNA (siRNA)-mediated silencing. POSTN gene expression was significantly higher in Graves' orbital tissues than healthy control tissues in real-time PCR results, and immunohistochemical staining revealed higher expression of periostin in Graves' orbital tissues than normal tissues. Silencing periostin using siRNA transfection significantly attenuated TGF-β-induced profibrotic protein production and phosphorylated p38 and SMAD protein production. Knockdown of periostin inhibited interleukin-1 β -induced proinflammatory cytokines production as well as phosphorylation of NF-κB and Ak signaling protein. Adipocyte differentiation was also suppressed in periostin-targeting siRNA transfected GO cells. We hypothesize that periostin contributes to the pathogenic process of inflammation, fibrosis and adipogenesis of GO. Our study provides in vitro evidence that periostin may be a novel potential therapeutic target for the treatment of GO.

Periostin in Allergy and Inflammation

Matricellular proteins are involved in the crosstalk between cells and their environment and thus play an important role in allergic and inflammatory reactions. Periostin, a matricellular protein, has several documented and multi-faceted roles in health and disease. It is differentially expressed, usually upregulated, in allergic conditions, a variety of inflammatory diseases as well as in cancer and contributes to the development and progression of these diseases. Periostin has also been shown to influence tissue remodelling, fibrosis, regeneration and repair. In allergic reactions periostin is involved in type 2 immunity and can be induced by IL-4 and IL-13 in bronchial cells. A variety of different allergic diseases, among them bronchial asthma and atopic dermatitis (AD), have been shown to be connected to periostin expression. Periostin is commonly expressed in fibroblasts and acts on epithelial cells as well as fibroblasts involving integrin and NF-κB signalling. Also direct signalling between periostin and immune cells has been reported. The deposition of periostin in inflamed, often fibrotic, tissues is further fuelling the inflammatory process. There is increasing evidence that periostin is also expressed by epithelial cells in several of the above-mentioned conditions as well as in cancer. Augmented periostin expression has also been associated with chronic inflammation such as in inflammatory bowel disease (IBD). Periostin can be expressed in a variety of different isoforms, whose functions have not been elucidated yet. This review will discuss potential functions of periostin and its different isoforms in allergy and inflammation.

Pathological Roles and Clinical Usefulness of Periostin in Type 2 Inflammation and Pulmonary Fibrosis

Periostin is known to be a useful biomarker for various diseases. In this article, we focus on allergic diseases and pulmonary fibrosis, for which we and others are now developing detection systems for periostin as a biomarker. Biomarker-based precision medicine in the management of type 2 inflammation and fibrotic diseases since heterogeneity is of utmost importance. Periostin expression is induced by type 2 cytokines (interleukin-4/-13) or transforming growth factor-β, and plays a vital role in the pathogenesis of allergic inflammation or interstitial lung disease, respectively, andits serum levels are correlated disease severity, prognosis and responsiveness to the treatment. We first summarise the importance of type 2 biomarker and then describe the pathological role of periostin in the development and progression of type 2 allergic inflammation and pulmonary fibrosis. In addition, then, we summarise the recent development of assay methods for periostin detection, and analyse the diseases in which periostin concentration is elevated in serum and local biological fluids and its usefulness as a biomarker. Furthermore, we describe recent findings of periostin as a biomarker in the use of biologics or anti-fibrotic therapy. Finally, we describe the factors that influence the change in periostin concentration under the healthy conditions.

Myostatin and markers of bone metabolism in dermatomyositis

Background

In dermatomyostis (DM) patients, inflammation, reduced activity, and medication have a negative impact on the musculoskeletal system. Several endocrine factors are involved in muscle growth and bone turnover.

Objective: We aimed to investigate factors regulating myogenesis and bone metabolism and to evaluate possible associations between these endocrine factors, muscle strength, and functional tests in DM patients.

Methods

We conducted a cross-sectional study in 20 dermatomyositis patients. Serum levels of myostatin (MSTN), follistatin (FSTN), dickkopf 1 (Dkk1), sclerostin (SOST), periostin (PSTN), the receptor activator nuclear factor kB ligand (RANKL):osteoprotegerin (OPG) ratio and fibroblast growth factor 23 (FGF23) were determined. Physical function was evaluated by hand-held strength measurement, chair rising test, timed up and go test and the 3-min walking test.

Results

Serum MSTN and FGF23 levels (2.5 [1.9; 3.2] vs. 1.9 [1.6; 2.3] and 2.17 [1.45; 3.26] vs. 1.28 [0.79; 1.96], respectively; p <  0.05) were significantly higher in DM patients than in controls. Dkk1 was significantly lower (11.4 [6.9; 20.0] vs. 31.8 [14.3; 50.6], p <  0.01). Muscle strength and physical function tests correlated with each other (e.g. hip flexion – timed up and go test: r = − 0.748, p < 0.01).

Conclusion

In DM patients, biochemical musculo-skeletal markers are altered and physical function shows deficits. All these tests reflect independent of each other different deficits in long-term DM patients which is important for the assessment of DM patients as well as planning of therapeutic interventions in clinical routine.

Alterations in activin A-myostatin-follistatin system associate with disease activity in inflammatory myopathies

OBJECTIVES

The aim of this study was to investigate the systemic and skeletal muscle levels of atrophy-associated myokines in patients with idiopathic inflammatory myopathies (IIM) and their association with clinical characteristics of myositis.

METHODS

A total of 94 IIM patients and 162 healthy controls were recruited. Of those, 20 IIM patients and 28 healthy controls underwent a muscle biopsy. Circulating concentrations of myostatin, follistatin, activin A and TGF-β1 were assessed by ELISA. The expression of myokines and associated genes involved in the myostatin signalling pathway in muscle tissue was determined by real-time PCR.

RESULTS

We report decreased levels of circulating myostatin (median 1817 vs 2659 pg/ml; P = 0.003) and increased follistatin (1319 vs 1055 pg/ml; P = 0.028) in IIM compared with healthy controls. Activin A levels were also higher in IIM (414 vs 309 pg/ml; P = 0.0005) compared with controls. Myostatin was negatively correlated to muscle disease activity assessed by physician on visual analogue scale (MDA) (r = -0.289, P = 0.015) and positively to manual muscle testing of eight muscles (r = 0.366, P = 0.002). On the other hand, follistatin correlated positively with MDA (r = 0.235, P = 0.047). Gene expression analysis showed higher follistatin (P = 0.003) and myostatin inhibitor follistatin-like 3 protein (FSTL3) (P = 0.008) and lower expression of activin receptor type 1B (ALK4) (P = 0.034), signal transducer SMAD3 (P = 0.023) and atrophy marker atrogin-1 (P = 0.0009) in IIM muscle tissue compared with controls.

CONCLUSION

This study shows lower myostatin and higher follistatin levels in circulation and attenuated expression of myostatin pathway signalling components in skeletal muscle of patients with myositis, a newly emerging pattern of the activin A-myostatin-follistatin system in muscle wasting diseases.

Association of myostatin, a cytokine released by muscle, with inflammation in rheumatoid arthritis: A cross-sectional study

Myostatin is a cytokine produced and released by myocytes that might have an outstanding role not only in muscle wasting during cachexia but also in inflammation. Herein we explore the association between myostatin levels and inflammatory parameters in rheumatoid arthritis (RA).One hundred twenty-seven women without rheumatic diseases and 84 women with a diagnosis of RA were assessed in a cross-sectional study. Outcomes reflecting the activity of the arthritis including Disease Activity Score (DAS28-ESR) and impairment in functioning by the Health Assessment Questionnaire-Disability Index were assessed in RA. We obtained Skeletal muscle mass index (SMI), fat-free mass index (FFMI), and fat mass index using dual-energy x-ray absorptiometry. Serum myostatin was determined by enzyme-linked immunosorbent assay. Myostatin levels were correlated with disease activity and parameters of muscle mass.The SMI was lower and concentration of myostatin was higher in RA patients than in controls (P = .008 and P < .001, respectively). Myostatin significantly positively correlated with C-reactive protein (rho = 0.48, P < .001), erythrocyte sedimentation rate (rho  = 0.28, P = .009), and DAS28-ESR (rho = 0.22, P  = .04), and negatively correlated with SMI (rho = -0.29, P = .008), (FFMI) (rho = -0.24, P = .027). In the multivariate logistic regression analysis, levels of myostatin remained associated with disease activity in RA (P = .027).In our study, myostatin was associated with disease activity in RA patients, suggesting a mechanistic link between myostatin, muscle wasting and inflammation in RA.

The role of biochemical markers of joint tissue remodelling to predict progression and treatment efficacy in inflammatory rheumatic diseases

Structural damage is a hallmark in RA, spondyloarthropy (SpA) and psoriatric arthritis (PsA). Its progression is difficult to predict and current radiological or inflammatory biological markers lack sensitivity. Biochemical markers of bone, cartilage and synovial tissues provide a dynamic indication of the anabolism and catabolism of joint tissues and can be easily measured by immunoassays. Novel biochemical markers including post-translational modifications of matrix proteins and enzyme-generated neoepitopes with increased tissue and/or biological pathway specificity have been developed. Their evaluation in clinical trials of novel biologic therapies and epidemiological studies indicated that their measurements could be useful to predict progression of structural damage and treatment efficacy, independently of current clinical, radiological and biological indices of disease activity. In this paper we briefly describe the latest developments in biochemical markers and critically analyse the clinical data assessing the utility of established and novel biochemical markers in RA, SpA and PsA.

Myostatin as a Biomarker of Muscle Wasting and other Pathologies-State of the Art and Knowledge Gaps

Sarcopenia is a geriatric syndrome with a significant impact on older patients’ quality of life, morbidity and mortality. Despite the new available criteria, its early diagnosis remains difficult, highlighting the necessity of looking for a valid muscle wasting biomarker. Myostatin, a muscle mass negative regulator, is one of the potential candidates. The aim of this work is to point out various factors affecting the potential of myostatin as a biomarker of muscle wasting. Based on the literature review, we can say that recent studies produced conflicting results and revealed a number of potential confounding factors influencing their use in sarcopenia diagnosing. These factors include physiological variables (such as age, sex and physical activity) as well as a variety of disorders (including heart failure, metabolic syndrome, kidney failure and inflammatory diseases) and differences in laboratory measurement methodology. Our conclusion is that although myostatin alone might not prove to be a feasible biomarker, it could become an important part of a recently proposed panel of muscle wasting biomarkers. However, a thorough understanding of the interrelationship of these markers, as well as establishing a valid measurement methodology for myostatin and revising current research data in the light of new criteria of sarcopenia, is needed.

Osteostatin Inhibits Collagen-Induced Arthritis by Regulation of Immune Activation, Pro-Inflammatory Cytokines, and Osteoclastogenesis

In chronic inflammatory joint diseases, such as rheumatoid arthritis, there is an important bone loss. Parathyroid hormone-related protein (PTHrP) and related peptides have shown osteoinductive properties in bone regeneration models, but there are no data on inflammatory joint destruction. We have investigated whether the PTHrP (107-111) C-terminal peptide (osteostatin) could control the development of collagen-induced arthritis in mice. Administration of osteostatin (80 or 120 μg/kg s.c.) after the onset of disease decreased the severity of arthritis as well as cartilage and bone degradation. This peptide reduced serum IgG2a levels as well as T cell activation, with the downregulation of RORγt+CD4+ T cells and upregulation of FoxP3+CD8+ T cells in lymph nodes. The levels of key cytokines, such as interleukin(IL)-1β, IL-2, IL-6, IL-17, and tumor necrosis factor-α in mice paws were decreased by osteostatin treatment, whereas IL-10 was enhanced. Bone protection was related to reductions in receptor activator of nuclear factor-κB ligand, Dickkopf-related protein 1, and joint osteoclast area. Osteostatin improves arthritis and controls bone loss by inhibiting immune activation, pro-inflammatory cytokines, and osteoclastogenesis. Our results support the interest of osteostatin for the treatment of inflammatory joint conditions.