Assessment of OPG/RANK/RANKL gene expression levels in peripheral blood mononuclear cells (PBMC) after treatment with strontium ranelate and ibandronate in patients with postmenopausal osteoporosis

Advanced applications of strontium-containing biomaterials in bone tissue engineering

Strontium (Sr) and strontium ranelate (SR) are commonly used therapeutic drugs for patients suffering from osteoporosis. Researches have showed that Sr can significantly improve the biological activity and physicochemical properties of materials in vitro and in vivo. Therefore, a large number of strontium containing biomaterials have been developed for repairing bone defects and promoting osseointegration. In this review, we provide a comprehensive overview of Sr-containing biomaterials along with the current state of their clinical use. For this purpose, the different types of biomaterials including calcium phosphate, bioactive glass, and polymers are discussed and provided future outlook on the fabrication of the next-generation multifunctional and smart biomaterials.

A Mixture of Cervus elaphus sibiricus and Glycine max (L.) Merrill Inhibits Ovariectomy-Induced Bone Loss Via Regulation of Osteogenic Molecules in a Mouse Model

Osteoporosis is a metabolic skeletal disease characterized by lowered bone mineral density and quality, which lead to an increased risk of fracture. The aim of this study was to evaluate the anti-osteoporosis effects of a mixture (called BPX) of Cervus elaphus sibiricus and Glycine max (L.) Merrill and its underlying mechanisms using an ovariectomized (OVX) mouse model. BALB/c female mice (7 weeks old) were ovariectomized. From 12 weeks of ovariectomy, mice were administered BPX (600 mg/kg) mixed in a chow diet for 20 weeks. Changes in bone mineral density (BMD) and bone volume (BV), histological findings, osteogenic markers in serum, and bone formation-related molecules were analyzed. Ovariectomy notably decreased the BMD and BV scores, while these were significantly attenuated by BPX treatment in the whole body, femur, and tibia. These anti-osteoporosis effects of BPX were supported by the histological findings for bone microstructure from H&E staining, increased activity of alkaline phosphatase (ALP), but a lowered activity of tartrate-resistant acid phosphatase (TRAP) in the femur, along with other parameters in the serum, including TRAP, calcium (Ca), osteocalcin (OC), and ALP. These pharmacological actions of BPX were explained by the regulation of key molecules in the bone morphogenetic protein (BMP) and mitogen-activated protein kinase (MAPK) pathways. The present results provide experimental evidence for the clinical relevance and pharmaceutical potential of BPX as a candidate for anti-osteoporosis treatment, especially under postmenopausal conditions.

The potential benefits and mechanisms of protein nutritional intervention on bone health improvement

Osteoporosis commonly occurs in the older people and severe patients, with the main reason of the imbalance of bone metabolism (the rate of bone resorption exceeding the rate of bone formation), resulting in a decrease in bone mineral density and destruction of bone microstructure and further leading to the increased risk of fragility fracture. Recent studies indicate that protein nutritional support is beneficial for attenuating osteoporosis and improving bone health. This review summarized the classical mechanisms of protein intervention for alleviating osteoporosis on both suppressing bone resorption and regulating bone formation related pathways (promoting osteoblasts generation and proliferation, enhancing calcium absorption, and increasing collagen and mineral deposition), as well as the potential novel mechanisms via activating autophagy of osteoblasts, altering bone related miRNA profiles, regulating muscle-bone axis, and modulating gut microbiota abundance. Protein nutritional intervention is expected to provide novel approaches for the prevention and adjuvant therapy of osteoporosis.

Assessment of Wnt pathway selected gene expression levels in peripheral blood mononuclear cells (PBMCs) of postmenopausal patients with low bone mass

The purpose of the study was to assess the expression of selected genes of the Wnt pathway: APC, AXIN1, CTNNB1, DKK1, GSK3B, KREMEN1, SFRP1, and WNT1 in peripheral blood mononuclear cells (PBMC) of patients, selected in consideration of their bone mineral density (BMD), and the occurrence of low-energy fractures. The study involved 45 postmenopausal women, divided into four groups, according to BMD and fracture history. Measurements of laboratory parameters and RNA expression in PBMC cells were carried out in material, collected once at the inclusion visit. The densitometric examination was performed on all participants. In the analysis of the relative expression levels (RELs) of the studied genes in the entire population, we observed an overexpression for SFRP1 in 100% of samples and WNT1. In addition, the REL of DKK1, APC, and GSK3B genes were slightly elevated versus the calibrator. In contrast, CTNNB1 and AXIN1 presented with a slightly decreased RELs. Analysis did not show any significant differences among the groups in the relative gene expression levels (p < 0.05) of particular genes. However, we have observed quite numerous interesting correlations between the expression of the studied genes and BMD, the presence of fractures, and laboratory parameters, both in the whole studied population as well as in selected groups. In conclusion, the high level of CTNNB1 expression maintains normal BMD and/or protects against fractures. It also appears that the changes in expression levels of the Wnt pathway genes in PBMCs reflect the expected changes in bone tissue.

Identification and comparison of novel circular RNAs with associated co-expression and competing endogenous RNA networks in postmenopausal osteoporosis

BACKGROUND

Circular RNAs (circRNAs) are emerging as crucial regulators in various human diseases. So far, the expression profile and regulatory mechanism of circRNAs in postmenopausal osteoporosis (PMOP) are less studied and should be deciphered urgently. Herein, we aimed to reveal key circRNAs affecting PMOP and clarify their compounding regulatory actions.

METHODS

To reveal key circRNAs affecting PMOP and clarify their compounding regulatory actions, whole transcriptome sequencing and bioinformatics analysis were performed to identify differentially expressed circRNAs (DECs). The expression pattern and regulatory networks of DECs in peripheral blood mononuclear cells (PBMCs) were unearthed.

RESULTS

A total of 373 DECs comprising 123 intronic, 100 antisense, 70 exonic, 55 intergenic, and 25 sense-overlapping circRNAs were identified. Among these, 73 circRNAs were upregulated and 300 were downregulated. These DECs exerted pivotal functions in the pathogenesis of PMOP as demonstrated by Gene Ontology (GO) annotation and the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis. The circRNA-miRNA-mRNA co-expression network comprising 28 DECs, 145 miRNAs, and 175 differentially expressed mRNAs predicted the possible mechanism of the pathogenesis and progression of PMOP.

CONCLUSION

The results of the present study provided a further comprehension of circRNA-associated competing endogenous RNA regulatory mechanism in PMOP. The steadily expressed and disease-specific DECs may serve as promising diagnostic and prognostic biomarkers for PMOP.

Identification of a key gene module associated with glucocorticoid- induced derangement in bone mineral density in patients with asthma

Derangement in bone mineral density (BMD) caused by glucocorticoid is well-known. The present study aimed to find key biological pathways associated with low BMD after glucocorticoid treatment in asthmatics using gene expression profiles of peripheral blood cells. We utilized immortalized B cells (IBCs) from 32 childhood asthmatics after multiple oral glucocorticoid bursts and peripheral blood mononuclear cells (PBMCs) from 17 adult asthmatics after a long-term use of oral glucocorticoid. We searched co-expressed gene modules significantly related with the BMD Z score in childhood asthmatics and tested if these gene modules were preserved and significantly associated with the BMD Z score in adult asthmatics as well. We identified a gene module composed of 199 genes significantly associated with low BMD in both childhood and adult asthmatics. The structure of this module was preserved across gene expression profiles. We found that the cellular metabolic pathway was significantly enriched in this module. Among 18 hub genes in this module, we postulated that 2 genes, CREBBP and EP300, contributed to low BMD following a literature review. A novel biologic pathway identified in this study highlighted a gene module and several genes as playing possible roles in the pathogenesis of glucocorticoid- induced derangement in BMD.

Abnormal sub-pathways competitively regulated by lncRNAs contribute to postmenopausal osteoporosis

Abnormal sub-pathways competitively regulated by long non-coding RNAs (lncRNAs) for postmenopausal osteoporosis (PO) based on integration of lncRNA-mRNA expression data and pathway network topologies were investigated. Interesting lncRNA-mRNA pairs were selected by Pearsons correlation coefficient (PCC) algorithm on the basis of lncRNA-miRNA and miRNA-mRNA interactions and gene expression profiles. Then, lncRNAs in interesting pairs were embedded into pathway graphs as signature nodes by linking to their regulated-mRNAs, and lncRNA competitively regulated pathways (LCRPs) were gained for PO patients. Moreover, sub-pathways were detected dependent on the shortest distance similarity and the pathway topology. The abnormal sub-pathways were determined utilizing the Wallenius approximation methods through evaluating the statistical significance of sub-pathways. In total 75 interesting lncRNA-mRNA pairs (representing 17 lncRNAs and 74 mRNAs) were identified. Subsequently, 42 LCRPs were extracted from pathway graphs by signature lncRNA regulated mRNAs. Moreover, 14 abnormal sub-pathways with P<0.05 were obtained between PO patients and controls, such as sub-pathways of PI3K-Akt signaling pathway and long-term potentiation. This finding may facilitate understanding the molecular mechanism of PO, and point a new direction to identify potential biomarkers for treatment and prevention of the disease.

Experimental research into the potential therapeutic effect of GYY4137 on Ovariectomy-induced osteoporosis

BACKGROUND

Evidence has shown that endogenous H2S plays an important role in the physiological and pathophysiological processes of many organs. The study aimed to explore whether exogenous H2S has a potential therapeutic effect on a rat ovariectomy-induced model of osteoporosis.

METHODS

The OVX osteoporosis model was established in female Sprague-Dawley rats by full bilateral ovariectomy. The rats were randomly divided into four groups, with the two experimental groups receiving an intraperitoneal injection of GYY4137 or sodium alendronate. The level of H2S in the plasma was determined and common laboratory indicators to diagnose osteoporosis, such as alkaline phosphatase (ALP) activity and the levels of osteocalcin (OCN), calcitonin, parathyroid hormone and leptin were measured. The bone mineral density (BMD) of the 4th and 5th lumbar vertebrae was measured using dual-energy X-ray absorptiometry. The maximum stress of femoral fracture was obtained through a three-point bending test of the femur.

RESULTS

The OVX osteoporosis model was successfully established. GYY4137 was injected to increase the level of H2S in the plasma in one group, designated OVX-GYY during the observation period (p < 0.05). At 12 weeks, the BMD value of the fourth lumbar vertebra in the OVX-GYY group had increased (p < 0.05). The BMD femur value in the OVX-vehicle group had decreased (p < 0.05). Bilateral ovariectomy leads to biochemical disorders related to bone metabolism and hormone levels in rat plasma (all p < 0.05). Ovariectomy also reduced blood calcium, blood phosphate and calcitonin, and increased parathyroid hormone and leptin. The opposite results were obtained for the groups with alendronate sodium or GYY4137 treatment (all p < 0.05).

CONCLUSIONS

Through the slow release of H2S, GYY4137 did an excellent job of simulating endogenous neuroendocrine gaseous signaling molecules. Exogenous H2S had a regulatory effect on osteoporosis in ovariectomized rats, showing potential value for the treatment of human postmenopausal osteoporosis.

MicroRNA‑148a inhibition protects against ovariectomy‑induced osteoporosis through PI3K/AKT signaling by estrogen receptor α

The present study aimed to investigate the effect of microRNA‑148a downregulation on osteoporosis by using an ovariectomized rat model. Reverse transcription‑quantitative polymerase chain reaction was used to analyze microRNA‑148a expression levels, MTT and flow cytometry assays were used to examine cytotoxicity and apoptosis, respectively. The gap‑associated proteins were quantified using western blotting. The expression of microRNA‑148a was significantly increased in osteoporosis rat following ovariectomy. Overexpression of microRNA‑148a significantly promoted apoptosis and inhibited cell growth, whereas downregulation of microRNA‑148a significantly reduced apoptosis and increased cell growth. Overexpression of microRNA‑148a significantly reduced estrogen receptor a (ERα) protein expression and suppressed phosphoinositide‑3‑kinase regulatory subunit 1 (PI3K) and phosphorylated‑protein kinase B (AKT) protein expression in osteoblasts in vitro. The inhibition of ERα increased the microRNA‑148a effect on apoptosis in osteoblasts in vitro. Subsequently, LY294002, an PI3K inhibitor, significantly increased the effect of microRNA‑148a on apoptosis in osteoblasts in vitro. The findings of the present study revealed that anti‑microRNA‑148a protected cells against ovariectomy‑induced osteoporosis through ERα by PI3K/AKT signaling.

Bioavailable 25(OH)D but Not Total 25(OH)D Is an Independent Determinant for Bone Mineral Density in Chinese Postmenopausal Women

Total 25(OH)D levels were determined to assess bone health in elderly populations; however, the bioavailability of 25(OH)D is regulated by the albumin and vitamin D binding protein (DBP) levels and DBP variations. Whether bioavailable 25(OH)D level is a superior biomarker for vitamin D than total 25(OH)D level regarding the BMD and the bone metabolism were not yet fully understood. With a community based cross-sectional study of 967 postmenopausal women, we found that the variant rs7041, but not rs4588, of DBP was significantly associated with the blood DBP level, which was positively correlated with the total 25(OH)D level but negatively associated with bioavailable 25(OH)D levels. Both total and bioavailable 25(OH)D levels were significantly correlated with the BMD value in postmenopausal women; however, only the bioavailable 25(OH)D level was an independent determinant of the BMD values when adjusted for age, body mass index and bone turnover biomarkers (OST and β-CTX). The bioavailable and total 25(OH)D were negatively correlated with bone formation biomarkers (OST, PINP and ALP) and PTH levels, while they were positively correlated with osteoprotegerin (OPG) level; however, the bone resorption biomarker (β-CTX) was not correlated with the 25(OH)D levels. An increment of PTH level, along with reduced bioavailable 25(OH)D levels, was evident when the bioavailable 25(OH)D level was < 5 ng/mL, which may be the optimal cutpoint for sufficient vitamin D in Chinese elderly women. The blood calcium, magnesium, ALP, TSH, FGF23, and phosphorus levels were not correlated with the total or the bioavailable 25(OH)D levels. These results suggested that high bioavailable 25(OH)D levels were correlated with reduced bone turnover processes and were a biomarker superior to total 25(OH)D for vitamin D in assessing the risks of bone-related diseases. The results indicate that the bioavailable 25(OH)D level should be determined in assessing the bone health.

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DBP levels and variants on DBP were associated with the total and bioavailable 25(OH)D levels in the elderly populations.

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Both the total and bioavailable 25(OH)D levels were correlated with the BMD in postmenopausal women.

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Multivariate analyses suggested that the bioavailable but not total 25(OH)D was an independent determinant for the BMD.

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Higher bioavailable 25(OH)D levels were correlated with reduced bone turnover and lower PTH in postmenopausal women.

With a cross-sectional community study, we found that the variant rs7041, but not rs4588, of DBP was significantly associated with the blood DBP level, which was positively correlated with the total 25(OH)D levels but negatively associated with the bioavailable 25(OH)D levels. The bioavailable 25(OH)D level was an independent determinant for BMD but not total 25(OH)D. Higher vitamin D levels were correlated with the reduced bone turnover process and lower PTH levels, which might lead to the higher BMD value in postmenopausal women. These results suggested that bioavailable 25(OH)D was a superior biomarker than total 25(OH)D regarding the bone metabolism, and that vitamin D intervention may improve the bone health in elderly populations.

Mechanism of chlorogenic acid treatment on femoral head necrosis and its protection of osteoblasts

The aim of the present study was to investigate the therapeutic effect of chlorogenic acid on hormonal femoral head necrosis and its protection of osteoblasts. The study established a femoral head necrosis model in Wistar rats using Escherichia coli endotoxin and prednisolone acetate. The rats were divided into five groups and were treated with different concentrations of chlorogenic acid (1, 10 and 20 mg/kg). The main detected indicators were the blood rheology, bone mineral density, and the hydroxyproline and hexosamine (HOM) contents. At a cellular level, osteoblasts were cultured and treated by drug-containing serum. Subsequently, cell proliferation and the osteoblast cycle were measured using flow cytometry, and the protein expression levels of Bax and B-cell lymphoma 2 (Bcl-2) were detected using western blotting. Chlorogenic acid at a concentration of 20 mg/kg (high-dose) enhanced the bone mineral density of the femoral head and femoral neck following ischemia. Simultaneously, blood flow following the injection of prednisolone acetate was significantly improved, and the HOM contents of the high-dose chlorogenic acid group were significantly different. The results from the flow cytometry analysis indicated that chlorogenic acid can efficiently ameliorate hormone-induced necrosis. The osteoblasts were isolated and cultured. The MTT colorimetric assay showed that chlorogenic acid at different densities can increase the proliferation capabilities of osteoblasts and accelerate the transition process of G₀/G₁ phase to S phase, as well as enhance mitosis and the regeneration of osteoblasts. Western blotting detection indicated that chlorogenic acid may prohibit the decrease of Bcl-2 and the increase of Bax during apoptosis, thereby inhibiting osteoblast apoptosis and preventing the deterioration of femoral head necrosis. In conclusion, chlorogenic acid at the density of 20 mg/kg is effective in the treatment of hormonal femoral head necrosis, which may be applicable for future treatment.

Expression Signatures of Long Noncoding RNAs in Adolescent Idiopathic Scoliosis

Purpose. Adolescent idiopathic scoliosis (AIS), the most common pediatric spinal deformity, is considered a complex genetic disease. Causing genes and pathogenesis of AIS are still unclear. This study was designed to identify differentially expressed long noncoding RNAs (lncRNAs) involving the pathogenesis of AIS. Methods. We first performed comprehensive screening of lncRNA and mRNA in AIS patients and healthy children using Agilent human lncRNA + mRNA Array V3.0 microarray. LncRNAs expression in different AIS patients was further evaluated using quantitative PCR. Results. A total of 139 lncRNAs and 546 mRNAs were differentially expressed between AIS patients and healthy control. GO and Pathway analysis showed that these mRNAs might be involved in bone mineralization, neuromuscular junction, skeletal system morphogenesis, nucleotide and nucleic acid metabolism, and regulation of signal pathway. Four lncRNAs (ENST00000440778.1, ENST00000602322.1, ENST00000414894.1, and TCONS_00028768) were differentially expressed between different patients when grouped according to age, height, classification, severity of scoliosis, and Risser grade. Conclusions. This study demonstrates the abnormal expression of lncRNAs and mRNAs in AIS, and the expression of some lncRNAs was related to clinical features. This study is helpful for further understanding of lncRNAs in pathogenesis, treatment, and prognosis of AIS.

Effect of serum from postmenopausal women with osteoporosis exhibiting the Kidney-Yang deficiency pattern on bone formation in an hFOB 1.19 human osteoblastic cell line

The aim of the present study was to investigate the underlying mechanism of the Kidney-Yang deficiency (KYD) pattern of osteoporosis in postmenopausal women of a certain age range by comparing the effect of serum from postmenopausal women with osteoporosis exhibiting the KYD pattern with that of serum from postmenopausal women without osteoporosis on bone formation in an hFOB 1.19 human osteoblastic cell line. A random selection of 30 female, postmenopausal volunteers aged 60-70 years, including 15 cases without osteoporosis and 15 cases with the KYD pattern of osteoporosis, were enrolled at the Physical Examination Center of the Second Affiliated Hospital of Fujian University of Traditional Chinese Medicine. Venous blood was extracted and the serum was separated. The hFOB 1.19 cells were treated with 10% KYD pattern-serum or control serum from postmenopausal women of the same age range without osteoporosis. It was found that the KYD pattern-serum significantly decreased the cell viability, activity of alkaline phosphatase and number of calcified nodules, as well as downregulated the expression of osteocalcin and osteoprotegerin (OPG) and upregulated that of receptor activator of nuclear factor κB ligand (RANKL) in the hFOB 1.19 cells. In addition, the present results showed that the concentrations of estradiol (E₂), OPG and insulin-like factor-1 (IGF-1) in the KYD pattern-serum were lower than those in the control serum. In combination, these findings suggest that the downregulation of E₂, OPG and IGF-1 in the KYD pattern-serum inhibits the OPG/RANKL system, leading to a decrease in bone formation in the hFOB 1.19 cells. This indicates that the alterations in E₂, OPG and IGF-1 may account for the susceptibility of certain postmenopausal women to the KYD pattern of osteoporosis.

New developments in biological markers of bone metabolism in osteoporosis

Over the last 15 years several biological markers of bone turnover have been developed with increased specificity and sensitivity. In osteoporosis clinical studies, the IOF and IFCC organizations have recently recommended the measurements of serum type I collagen N-propeptide (PINP) and the crosslinked C-terminal telopeptide (serum CTX) as markers of bone formation and bone resorption, respectively. However these markers have some limitations including a lack of specificity for bone tissue, their inability to reflect osteocyte activity or periosteal apposition. In addition they do not allow the investigation of bone tissue quality an important determinant of skeletal fragility. To address these limitations, new developments in markers of bone metabolism have been recently achieved. These include assays for periostin, a matricellular protein preferentially localized in the periosteal tissue, sphingosine 1-phosphate, a lipid mediator which acts mainly on osteoclastogenesis and the osteocyte factors such as sclerostin and FGF-23. Recent studies have shown an association between the circulating levels of these biological markers and fracture risk in postmenopausal women or elderly men, although data require confirmation in additional prospective studies. Finally, recent studies suggest that the measurements of circulating microRNAs may represent a novel class of early biological markers in osteoporosis. It is foreseen that with the use of genomics and proteomics, new markers will be developed to ultimately improve the management of patients with osteoporosis.