The immune system and postmenopausal osteoporosis

Crosstalk between bone and the immune system

Bone functions not only as a critical element of the musculoskeletal system but also serves as the primary lymphoid organ harboring hematopoietic stem cells (HSCs) and immune progenitor cells. The interdisciplinary field of osteoimmunology has illuminated the dynamic interactions between the skeletal and immune systems, vital for the maintenance of skeletal tissue homeostasis and the pathogenesis of immune and skeletal diseases. Aberrant immune activation stimulates bone cells such as osteoclasts and osteoblasts, disturbing the bone remodeling and leading to skeletal disorders as seen in autoimmune diseases like rheumatoid arthritis. On the other hand, intricate multicellular network within the bone marrow creates a specialized microenvironment essential for the maintenance and differentiation of HSCs and the progeny. Dysregulation of immune-bone crosstalk in the bone marrow environment can trigger tumorigenesis and exacerbated inflammation. A comprehensive deciphering of the complex "immune-bone crosstalk" leads to a deeper understanding of the pathogenesis of immune diseases as well as skeletal diseases, and might provide insight into potential therapeutic approaches.

Identification of differentially expressed genes, signaling pathways and immune infiltration in postmenopausal osteoporosis by integrated bioinformatics analysis

Background

Postmenopausal osteoporosis is a systemic metabolic disorder typified by an imbalance in bone turnover, where bone resorption supersedes bone formation. This imbalance primarily arises from a decline in bone mass induced by estrogen deficiency, and an elevated risk of fractures resulting from degradation of bone microstructure. Despite recognizing these changes, the precise causative factors and potential molecular pathways remain elusive. In this study, we aimed to identify differentially expressed genes (DEGs), associated pathways, and the role of immune infiltration in osteoporosis, leveraging an integrated bioinformatics approach to shed light on potential underlying molecular mechanisms.

Methods

We retrieved the expression profiles of GSE230665 from the Gene Expression Omnibus database, comprising 15 femur samples, including 12 postmenopausal osteoporosis samples and 3 normal controls. From the aggregated microarray datasets, we derived differentially expressed genes (DEGs) for further bioinformatics analysis. We used WGCNA, analyzed DEGs, PPI, and conducted GO analysis to identify pivotal genes. We then used the CIBERSORT method to explore the degree of immune cell infiltration within femur specimens affected by postmenopausal osteoporosis. To probe into the relationship between pivotal genes and infiltrating immune cells, we conducted correlation analysis.

Results

We identified a total of 12,204 DEGs. Among these, 12,157 were up-regulated, and 47 were down-regulated. GO and KEGG pathway analyses indicated that these DEGs predominantly targeted cellular protein localization activity and associated signaling pathways. The protein-protein interaction network highlighted four central hub-genes: RPL31, RPL34, EEF1G, and BPTF. Principal component analysis indicated a positive correlation between the expression of these genes and resting NK cells (as per CIBERSORT). In contrast, the expression of RPL31, RPL34, and EEF1G showed a negative correlation with T cells (gamma delta per CIBERSORT).

Conclusions

Immune infiltration plays a role in the development of osteoporosis.

Global Publication Trends and Research Hotspots of the Immune System and Osteoporosis: A Bibliometric and Visualization Analysis from 2012 to 2022

BACKGROUND

Osteoporosis (OP) is a systemic bone metabolism disorder in which the immune system and bone metabolism interact.

OBJECTIVE

The purpose of this study was to explore the research status, hot spots and trends regarding the influence of the immune system on OP and to provide a basis for research directions and applications in this field.

METHODS

We searched and collected literature about the immune system and OP published from 2012 to 2022 in the Web of Science Core Collection database. All the included studies were subjected to bibliometrics analysis using Hiplot Pro, VOSviewer and CiteSpace software to produce statistics and visual analyses of the literature output, countries, institutions, authors, keywords and journals.

RESULTS

A total of 1201 papers were included, and the number of citations of these articles reached 31,776. The number of publications and citations on the immune system and OP has increased year by year. The top three countries with the greatest number of papers published were China, the United States of America (USA) and Italy. The two institutions with the largest number of papers published were Sichuan University and Soochow University, both located in China. De Martinis Massimo (Italy) and Ginaldi Lia (Italy) are prolific authors in this field. The representative academic journals are Osteoporosis International, Frontiers in Immunology, Journal of Bone and Mineral Research, PloS One and Bone. The results of the keyword cooccurrence analysis showed that the research topics in this field mainly focused on T cells, cytokines, signaling pathways, vitamin D, postmenopausal OP and immune diseases. The keyword burst results showed that zoledronic acid, chain fatty acids and gut microbiota are the frontiers and trends of future research on this topic.

CONCLUSION

The influence of the immune system on OP has been widely studied, and the current research in this field focuses on the effect or mechanism of immune-related cytokines, signaling pathways and vitamin D on OP. Future research trends in this field should focus on the immune regulation mechanism and clinical transformation of zoledronic acid, chain fatty acids and the gut microbiota in OP.

Jiangu granules ameliorate postmenopausal osteoporosis via rectifying bone homeostasis imbalance: A network pharmacology analysis based on multi-omics validation

BACKGROUND

Postmenopausal osteoporosis (PMOP) is a series of reactions to bone homeostasis dysregulation mediated by estrogen deficiency in elderly women. Jiangu granules, a traditional Chinese medicine formula, has been proven as an effective treatment approach for PMOP, which still needs more research iin its complex regulatory mechanisms.

PURPOSE

Our study aimed to identify the putative targets and regulatory mechanisms of Jiangu granules in PMOP treating.

METHODS

We utilized the NHANES database to compare the clinical information of normal population and PMOP patients. Associated with transcriptomics and proteomic data, we identified the PMOP-related genes, and further studied them with bioinformatic methods including and prognosis model. Network pharmacology was applied for confirming the action targets of Jiangu granules in PMOP. We verified the safety and effectiveness in PMOP treatments of Jiangu granules, and also demonstrated our hypothesis in rats.

RESULTS

We discovered that the PMOP patients had higher monocytes than the normal women. Moreover, the transcriptomics and proteomic analysis suggested that the dysregulation of PMOP-related genes expression was associated with monocytes, and the Notch pathway were the critical targets representing bone homeostasis imbalance highly involved in the occurrence of PMOP. We also ascertained network pharmacology results further revealing that Jiangu granules might treat PMOP via recovering the bone homeostasis imbalance identified above. In vivo experiments, we confirmed the high efficacy which mainly resulted from function in mitigating the imbalance in bone homeostasis by recovering the normal expression of PMOP-related genes associated with monocytes, Notch, and steroid pathway in the rat models.

CONCLUSION

Our finding underscored the clinical potential of Jiangu granules in treating PMOP, and enriched the comprehension of the related pathogenic and therapeutic mechanisms.

Gut microbiota and fecal metabolic signatures in rat models of disuse-induced osteoporosis

Background

Assessing the correlation between gut microbiota (GM) and bone homeostasis has increasingly attracted research interest. Meanwhile, GM dysbiosis has been found to be associated with abnormal bone metabolism. However, the function of GM in disuse-induced osteoporosis (DIO) remains poorly understood. In our research, we evaluated the characteristics of GM and fecal metabolomics to explore their potential correlations with DIO pathogenesis.

Methods

DIO rat models and controls (CON) underwent micro-CT, histological analyses, and three-point bending tests; subsequently, bone microstructures and strength were observed. ELISAs were applied for the measurement of the biochemical markers of bone turnover while GM abundance was observed using 16S rDNA sequencing. Metabolomic analyses were used to analyze alterations fecal metabolites. The potential correlations between GM, metabolites, and bone loss were then assessed.

Results

In the DIO group, the abundance of GM was significantly altered compared to that in the CON group. Moreover, DIO significantly altered fecal metabolites. More specifically, an abnormally active pathway associated with bile acid metabolism, as well as differential bacterial genera related to bone/tissue volume (BV/TV), were identified. Lithocholic acid, which is the main secondary bile acid produced by intestinal bacteria, was then found to have a relationship with multiple differential bacterial genera. Alterations in the intestinal flora and metabolites in feces, therefore, may be responsible for DIO-induced bone loss.

Conclusions

The results indicated that changes in the abundance of GM abundance and fecal metabolites were correlated with DIO-induced bone loss, which might provide new insights into the DIO pathogenesis. The detailed regulatory role of GM and metabolites in DIO-induced bone loss needs to be explored further.

Immunoporosis: Role of immune system in the pathophysiology of different types of osteoporosis

Osteoporosis is a skeletal system disease characterized by low bone mass and altered bone microarchitecture, with an increased risk of fractures. Classical theories hold that osteoporosis is essentially a bone remodeling disorder caused by estrogen deficiency/aging (primary osteoporosis) or secondary to diseases/drugs (secondary osteoporosis). However, with the in-depth understanding of the intricate nexus between both bone and the immune system in recent decades, the novel field of "Immunoporosis" was proposed by Srivastava et al. (2018, 2022), which delineated and characterized the growing importance of immune cells in osteoporosis. This review aimed to summarize the response of the immune system (immune cells and inflammatory factors) in different types of osteoporosis. In postmenopausal osteoporosis, estrogen deficiency-mediated alteration of immune cells stimulates the activation of osteoclasts in varying degrees. In senile osteoporosis, aging contributes to continuous activation of the immune system at a low level which breaks immune balance, ultimately resulting in bone loss. Further in diabetic osteoporosis, insulin deficiency or resistance-induced hyperglycemia could lead to abnormal regulation of the immune cells, with excessive production of proinflammatory factors, resulting in osteoporosis. Thus, we reviewed the pathophysiology of osteoporosis from a novel insight-immunoporosis, which is expected to provide a specific therapeutic target for different types of osteoporosis.

Roles of Altered Macrophages and Cytokines: Implications for Pathological Mechanisms of Postmenopausal Osteoporosis, Rheumatoid Arthritis, and Alzheimer's Disease

Postmenopausal osteoporosis (PMOP) is characterized by the uncoupling of bone resorption and bone formation induced by estrogen deficiency, which is a complex outcome related to estrogen and the immune system. The interaction between bone and immune cells is regarded as the context of PMOP. Macrophages act differently on bone cells, depending on their polarization profile and secreted paracrine factors, which may have implications for the development of PMOP. PMOP, rheumatoid arthritis (RA), and Alzheimer's disease (AD) might have pathophysiological links, and the similarity of their pathological mechanisms is partially visible in altered macrophages and cytokines in the immune system. This review focuses on exploring the pathological mechanisms of PMOP, RA, and AD through the roles of altered macrophages and cytokines secretion. First, the multiple effects on cytokines secretion by bone-bone marrow (BM) macrophages in the pathological mechanism of PMOP are reviewed. Then, based on the thought of "different tissue-same cell type-common pathological molecules-disease pathological links-drug targets" and the methodologies of "molecular network" in bioinformatics, highlight that multiple cytokines overlap in the pathological molecules associated with PMOP vs. RA and PMOP vs. AD, and propose that these overlaps may lead to a pathological synergy in PMOP, RA, and AD. It provides a novel strategy for understanding the pathogenesis of PMOP and potential drug targets for the treatment of PMOP.

LIGHT/TNFSF14 regulates estrogen deficiency-induced bone loss

Bone loss induced by ovariectomy is due to the direct activity on bone cells and mesenchymal cells and to the dysregulated activity of bone marrow cells, including immune cells and stromal cells, but the underlying mechanisms are not completely known. Here, we demonstrate that ovariectomy induces the T-cell co-stimulatory cytokine LIGHT, which stimulates both osteoblastogenesis and osteoclastogenesis by modulating osteoclastogenic cytokine expression, including TNF, osteoprotegerin, and the receptor activator of nuclear factor-κB ligand (RANKL). Predictably, LIGHT-deficient (Tnfsf14^-/- ) mice are protected from ovariectomy-dependent bone loss, whereas trabecular bone mass increases in mice deficient in both LIGHT and T and B lymphocytes (Rag ^-/- Tnfsf14 ^-/- ) and is associated with an inversion of the TNF and RANKL/OPG ratio. Furthermore, women with postmenopausal osteoporosis display high levels of LIGHT in circulating T cells and monocytes. Taken together, these results indicate that LIGHT mediates bone loss induced by ovariectomy, suggesting that patients with postmenopausal osteoporosis may benefit from LIGHT antagonism. © 2020 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Antiresorptive Agents are More Effective in Preventing Titanium Particle-Induced Calvarial Osteolysis in Ovariectomized Mice Than Anabolic Agents in Short-Term Administration

Aseptic loosening due to wear particle‐induced osteolysis is the main cause of arthroplasty failure and the influence of postmenopausal osteoporosis and anti‐osteoporosis treatment on Titanium (Ti) particle‐induced osteolysis remains unclear. 66 C57BL/6J female mice were used in this study. Ovariectomy (OVX) was performed to induce osteopenia mice and confirmed by micro‐CT. The Ti particle‐induced mouse calvaria osteolysis model was established subsequently and both OVX and Sham‐OVX mice were divided into four groups, respectively: Ti (‐) group, Ti group, Ti + zoledronic acid (ZOL) group (50ug/kg, local administration, single dose) and Ti + teriparatide (TPTD) group (40ug/kg/d, subcutaneous injection*14d). Mice calvarias were collected for micro‐CT and histomorphometric analysis 2 weeks after particle induction. 8 weeks after bilateral OVX, significantly reduced BMD and microstructure parameters in both proximal tibia and calvaria were observed in OVX mice when comparing with Sham‐OVX mice. OVX mice in Ti group had not only markly decreased BMD and BV/TV, but also significantly increased total porosity, eroded surface area and osteoclast numbers when comparing with Sham‐OVX mice. Shown by Two‐way ANOVA analysis, the interaction terms between OVX and Ti implantation on micro‐CT and histomorphometry parameters didn’t reach significant difference. As illustrated by micro‐CT and histological analysis, ZOL treatment markedly inhibited Ti particle‐induced osteolysis in OVX mice and Sham‐OVX mice, and there were significant differences when comparing to both Ti and Ti+TPTD group. The combination of osteoporosis and Ti particle implantation result in aggravated bone resorption, accompanied with increased osteoclasts and excessive inflammation response. ZOL was more effective in preventing Ti particle‐induced osteolysis in both OVX mice and Sham‐OVX mice than TPTD in short‐term administration. ZOL exert the protective effects on Ti particle‐induced bone loss via the suppression of osteoclasts.

Fractures and the gut microbiome

PURPOSE OF REVIEW

The role of the gut microbiome in the pathogenesis of several inflammatory, non-AIDS comorbidities, such as cardiovascular disease, cognitive impairment and liver disease has become a focus of recent research. Low bone mineral density (BMD) and increased fracture incidence in people living with HIV (PLWH) is also widely reported, however, the relationship between alterations in the gut microbiome and bone disease in PLWH has not been previously reviewed.

RECENT FINDINGS

Murine models that manipulate the gut microbiome, either through breeding of 'germ-free' mice or antibiotic-depleted gut microbiome, show differences in bone mineral density and bone mass in those with altered gut microbiome. This effect is reported to be driven via changes in the gut-immune-skeletal axis, with changes favouring bone resorption. Several inflammatory conditions wherever bone loss is a prominent feature, such as rheumatoid arthritis and inflammatory bowel disease, have also reported alterations in the gut microbiome, which are associated with bone loss, again through changes in the gut-immune-skeletal axis.

SUMMARY

The interplay between the gut microbiome and the immune-skeletal axis in HIV represents a complex relationship. Alterations in the gut microbiome, which induce an activated immune phenotype and inflammatory milieu are associated with non-AIDS comorbidities in PLWH and bone loss in several other conditions characterized by chronic immune activation and inflammation. It is, therefore, likely that there are comparable effects between altered gut microbiome and bone loss in HIV, however, further research is required to better define this relationship in populations of PLWH.

Lack of Adrenomedullin Aggravates Acute TNBS-Induced Colitis Symptoms in Mice, Especially in Females

Adrenomedullin (AM) is a biologically active peptide which has been tested as a new therapy for inflammatory bowel disease (IBD) in animal models and in patients with severe ulcerative colitis. We used an inducible knockout (KO) mouse model for AM to evaluate the effects of endogenous levels of this peptide on the development and degree of pathogenesis of IBD. Acute colitis was induced in mice of both sexes by rectal instillation of 3 mg 2,4,6-trinitrobenzenesulfonic acid (TNBS) in 100 μL of 50% ethanol. Control mice received the same volume of saline in 50% ethanol. During the following 5 days, the weight and the disease severity index of all animals were recorded. After sacrifice, the inflammatory response was macroscopically assessed by analyzing the weight of the colon; by histomorphometrical analysis on histological sections; and by qRT-PCR determination of different inflammatory, adhesion, and regeneration molecules. TNBS administration caused a significantly more severe colitis in KO mice, and especially in females, when compared to wild type (WT) animals. Abrogation of the AM gene caused more severe diarrhea, accompanied by rectal bleeding, anorexia, and a significant increase of colon weight. Histological analysis of TNBS-treated KO mice showed large areas of lymphocyte infiltrates in the mucosa and submucosa, with loss of tissue architecture. No alterations were observed in the expression levels of inflammatory cytokines at the time of sacrifice; meanwhile lack of AM resulted in lower levels of some adhesion molecules and regeneration markers. Taken together, these results support the protective role of endogenous AM against the development of acute colitis, and that its effects are particularly beneficial on females.

Biochemistry of the menopause

The life of a human female is characterized from teenage years by monthly menstruation which ceases (the menopause) typically between the age of 40 and 60 years. The potential for reproduction declines and ceases as the ovaries become depleted of follicles. A transition period in mid-life, for 2 to 10 years, when menstruation is less regular is called the perimenopause. The menopause is associated with a significant decline in plasma concentrations of sex hormones, an increase in the concentrations of the gonadotrophins and changes in other hormones such as the inhibins. These changes are superimposed with effects of aging, social and metabolic factors, daily activity and well-being. Although the menopause is entirely natural, in some cases ovarian failure can occur earlier than usual; this is pathological and warrants careful biochemical investigations to distinguish it from conditions causing infertility. Elderly females are affected by a range of clinical disorders including endocrine, cardiovascular, skeletal, urogenital tract and immunological systems, body mass, vasomotor tone, mood and sleep pattern. Reference intervals for many diagnostic biochemical tests for the menopause need to be used when interpreting results in clinical investigations for patient management. The standardization and harmonization of assays are being addressed. Many women now choose to develop their career before bearing children, and the health service has had to change services around this. This review does not cover screening for and tests during pregnancy. The review is timely since the population is aging and there will be more demand on healthcare services.

Osteoimmunology: The Conceptual Framework Unifying the Immune and Skeletal Systems

The immune and skeletal systems share a variety of molecules, including cytokines, chemokines, hormones, receptors, and transcription factors. Bone cells interact with immune cells under physiological and pathological conditions. Osteoimmunology was created as a new interdisciplinary field in large part to highlight the shared molecules and reciprocal interactions between the two systems in both heath and disease. Receptor activator of NF-κB ligand (RANKL) plays an essential role not only in the development of immune organs and bones, but also in autoimmune diseases affecting bone, thus effectively comprising the molecule that links the two systems. Here we review the function, gene regulation, and signal transduction of osteoimmune molecules, including RANKL, in the context of osteoclastogenesis as well as multiple other regulatory functions. Osteoimmunology has become indispensable for understanding the pathogenesis of a number of diseases such as rheumatoid arthritis (RA). We review the various osteoimmune pathologies, including the bone destruction in RA, in which pathogenic helper T cell subsets [such as IL-17-expressing helper T (Th17) cells] induce bone erosion through aberrant RANKL expression. We also focus on cellular interactions and the identification of the communication factors in the bone marrow, discussing the contribution of bone cells to the maintenance and regulation of hematopoietic stem and progenitors cells. Thus the time has come for a basic reappraisal of the framework for understanding both the immune and bone systems. The concept of a unified osteoimmune system will be absolutely indispensable for basic and translational approaches to diseases related to bone and/or the immune system.

Osteoimmunology and Beyond

Abstract: Objective

Osteoimmunology investigates interactions between skeleton and immune system. In the light of recent discoveries in this field, a new reading register of osteoporosis is actually emerging, in which bone and immune cells are strictly interconnected. Osteoporosis could therefore be considered a chronic immune mediated disease which shares with other age related disorders a common inflammatory background. Here, we highlight these recent discoveries and the new landscape that is emerging.

Method

Extensive literature search in PubMed central.

Results

While the inflammatory nature of osteoporosis has been clearly recognized, other interesting aspects of osteoimmunology are currently emerging. In addition, mounting evidence indicates that the immunoskeletal interface is involved in the regulation of important body functions beyond bone remodeling. Bone cells take part with cells of the immune system in various immunological functions, configuring a real expanded immune system, and are therefore variously involved not only as target but also as main actors in various pathological conditions affecting primarily the immune system, such as autoimmunity and immune deficiencies, as well as in aging, menopause and other diseases sharing an inflammatory background.

Conclusion

The review highlights the complexity of interwoven pathways and shared mechanisms of the crosstalk between the immune and bone systems. More interestingly, the interdisciplinary field of osteoimmunology is now expanding beyond bone and immune cells, defining new homeostatic networks in which other organs and systems are functionally interconnected. Therefore, the correct skeletal integrity maintenance may be also relevant to other functions outside its involvement in bone mineral homeostasis, hemopoiesis and immunity.

Changes in the Level of Immunoglobulins and CD4/CD8 Ratio in Young and Aged Mice with Estradiol Deficiency

Studies demonstrated that deficiency in 17β-estradiol (E₂) in postmenopausal women influences their immune system. However, few studies have reported alterations in immunologic presentation during nonnatural menopause in young females. Here we compared the differences in immune response between young C57BL/6N mice with surgical or medical variectomy and aged C57BL/6N mice with the common feature of E₂ deficiency following Con A stimulation. We observed inverted CD4/CD8 ratios in the aged group and apparent reduced production of serum immunoglobin (Ig)G, IgA, and IgM in the surgical group, whereas changes in immune parameters in the medical group were moderate. These data suggested that the immunological response to Con A stimulus differed among the three groups and that E₂ deficiency was only partially responsible for the development of immune deficiency in aged mice.

Serum CX3CL1/fractalkine concentrations are positively associated with disease severity in postmenopausal osteoporotic patients

BACKGROUND

The chemokine (C-X3-C motif) ligand 1 (CX3CL1), also called fractalkine (FKN), has recently been reported to be involved in osteoclastogenic process and pathological bone destruction.

OBJECTIVE

This study aimed to investigate the link between serum CX3CL1/FKN levels with disease progression of postmenopausal osteoporotic patients.

METHODS

A total of 53 women with postmenopausal osteoporosis (PMOP group), 51 postmenopausal non-osteoporotic female patients (PMNOP group) and 50 premenopausal non-osteoporotic healthy women of childbearing age (control group) were enrolled in the study. The bone mineral density (BMD) for all subjects was determined via dual-energy X-ray absorptiometry of the lumbar spine, femoral neck, internal trochanter, total hip, greater trochanter and Ward's triangle. The levels of FKN in the serum were examined using the enzyme-linked immunosorbent assay method. The serum bone resorption markers TRACP-5b, NTX levels, inflammation markers IL-1β and IL-6 as well as oestrogen-2(E2) were also detected in all participants. The visual analogue scores (VAS) and Oswestry Disability Index (ODI) for low back pain were recorded in PMOP females for evaluation of osteoporotic pain and function.

RESULTS

FKN levels were significantly higher in postmenopausal osteoporotic patients compared with postmenopausal non-osteoporotic females (139.8 ± 44.3 pg/mL VS 116.5 ± 23.1 pg/mL, p < 0.05) and healthy controls (139.8 ± 44.3 pg/mL VS 109.7 ± 19.4 pg/mL, p < 0.05). Serum FKN concentrations were negatively associated with BMD at femoral neck (r = -0.394, p = 0.004), total hip(r = -0.374, p = 0.006), internal trochanter(r = -0.340, p = 0.013), greater trochanter(r = -0.376, p = 0.006), Ward's triangle(r = -0.343, p = 0.012), L1-L4 lumbar spine(r = -0.339, p = 0.013) and positively associated with VAS (r = 0.321, p = 0.019) and ODI (r = 0.377, p = 0.005) scores, bone turnover makers (TRACP-5b:r = 0.341, p = 0.012; NTX:r = 0.364, p = 0.007)as well as inflammation markers (IL-1β: r = 0.396, p = 0.003; IL-6:r = 0.355, p = 0.009) in postmenopausal osteoporotic patients.

CONCLUSIONS

Serum FKN may serve as a novel biomarker for assessing disease progression and a new potential therapeutic target for anti-resorptive treatment in osteoporosis patients.

Increased levels of interleukin 31 (IL-31) in osteoporosis

Background

Several inflammatory cytokines play a key part in the induction of osteoporosis. Until now, involvement of the Th2 cytokine interleukin-31 (IL-31) in osteoporosis hadn’t yet been studied. IL-31 is a proinflammatory cytokine mediating multiple immune functions, whose involvement in a wide range of diseases, such as atopic dermatitis, inflammatory bowel diseases and cutaneous lymphomas, is now emerging. Given the important role of IL-31 in inflammation, we measured its serum levels in postmenopausal osteoporotic patients.

Methods and results

In fifty-six postmenopausal females with osteoporosis and 26 healthy controls, bone mineral density (BMD) measurements were performed by using calcaneal quantitative ultrasound (QUS) technique, confirmed at the lumbar spine and hip by dual energy X-ray absorptiometry (DXA). Both patients and controls were divided according to age (less or more than 65 years) and disease severity (T-score levels and presence of fractures). Serum IL-31 levels were measured by ELISA technique. Osteoporotic patients exhibited elevated levels of serum IL-31 compared with healthy controls (43.12 ± 6.97 vs 29.58 ± 6.09 pg/ml; p < 0.049). IL-31 expression was higher in over 65 years old patients compared to age-matched controls (45 ± 11.05 vs. 17.92 ± 5.92; p < 0.01), whereas in younger subjects no statistically significant differences were detected between patients and controls (37.91 ± 6.9 vs 32.08 ± 8.2). No statistically significant differences were found between IL-31 levels in patients affected by mild (T-score > -3) compared to severe (T-score < -3) osteoporosis (59.17 ± 9.22 vs 37.91 ± 10.52), neither between fractured and unfractured osteoporotic women (33.75 ± 9.16 vs 51.25 ± 8.9).

Conclusions

We showed for the first time an increase of IL-31 serum levels in postmenopausal women with decreased BMD. Although they did not reflect the severity of osteoporosis and/or the presence of fractures, they clearly correlated with age, as reflected by the higher levels of this cytokine in aged patients.

Protective effect of porcine placenta in a menopausal ovariectomized mouse

Menopause is a significant physiological phase that occurs as women's ovaries stop producing ovum and the production of estrogen declines. Human placenta and some amino acids are known to improve menopausal symptoms. In this study, we investigated that porcine placenta extract (PPE) and arginine (Arg), a main amino acid of PPE, would have estrogenic activities in ovariectomized (OVX) mice as a menopause mouse model, human breast cancer cell line (MCF-7) cells, and human osteoblast cell line (MG-63) cells. PPE or Arg significantly inhibited the body weight and increased the vagina weight compared to the OVX mice. PPE or Arg ameliorated the vaginal atrophy in the OVX mice. The levels of 17β-estradiol and the activities of alkaline phosphatase (ALP) were significantly increased by PPE or Arg in the serum of OVX mice. Trabecular bone parameters such as bone mineral density and porosity were also improved by PPE or Arg in the OVX mice. In the MCF-7 and MG-63 cells, PPE or Arg significantly increased the cell proliferation, estrogen receptor β mRNA expression, and estrogen-response elements luciferase activity. Finally, PPE or Arg increased the activations of ALP and extracellular signal-regulated kinase 1/2 in the MG-63 cells. These results indicate that PPE or Arg would have estrogenic and osteoblastic activity. Therefore, PPE or Arg may be useful as new pharmacological tools for treating menopausal symptoms including osteoporosis. Free Korean abstract: A Korean translation of this abstract is freely available at http://www.reproduction-online.org/content/150/3/173/suppl/DC1.