Expression profiles of the Wnt/ß-catenin signaling-related extracellular antagonists during proliferation and differentiation in human osteoblast-like cells.

Bone formation is a dynamic process directed by osteoblast activity. The transition from the proliferation to differentiation stage during osteoblast maturation involves the downregulation of the Wnt/ß-catenin signaling pathway, and extracellular antagonists are important for the regulation of Wnt signaling. However, the expression levels of Wnt antagonists in these stages of human osteoblast maturation have not been fully elucidated. Therefore, the aim of the present study was to investigate the expression levels of extracellular Wnt antagonists during proliferation and differentiation in osteoblast-like cell lines. The results demonstrated an overlap between the differential expression of secreted Frizzled-related protein (SFPR)2, SFRP3, SFRP4 and Dickkopf (DKK) 2 genes during the differentiation stage in the MG-63 and Saos-2 cells. Furthermore, high expression levels of DKK3 in MG-63 cells, Wnt inhibitory factor 1 (WIF1) in Saos-2 cells and DKK4 in hFOB 1.19 cells during the same stage (differentiation), were observed. The upregulated expression levels of Wnt antagonists were also correlated with the high expression of anxin 2 during the differentiation stage. These findings suggested that Wnt-related antagonists could modulate the Wnt/ß-catenin signaling pathway. By contrast, DKK1 was the only gene that was found to be upregulated during the proliferation stage in hFOB 1.19 and Saos-2 cells. To the best of our knowledge, the present study provides, for the first time, the expression profile of Wnt antagonists during the proliferation stage and the initial phases of differentiation in osteoblast-like cell lines. The current results offer a basis to investigate potential targets for bone-related Wnt-signaling modulation in bone metabolism research.

Identification of microRNAs in human circulating monocytes of postmenopausal osteoporotic Mexican-Mestizo women: A pilot study.

MicroRNAs (miRNAs or miRs) are a class of short non-coding RNAs that serve an important regulatory role in living organisms. These molecules are associated with multiple biological processes and are potential biomarkers in multiple diseases. The present study aimed to further identify miRNAs that are differentially expressed in circulating monocytes (CMCs) from postmenopausal Mexican-Mestizo women. Microarray analyses of monocytes using Affymetrix miRNA 4.0 and Human Genome U133 Plus 2.0 arrays were performed in 6 normal and 6 osteoporotic women, followed by reverse transcription-quantitative polymerase chain reaction (RT-qPCR) validation. The overexpression of miR-1270, miR-548×-3p and miR-8084 were detected in the osteoporosis compared with the normal group according to the microarray analysis; miR-1270, a miRNA with several target genes associated with bone remodeling, was validated by RT-qPCR. Bioinformatics analysis identified that interferon regulatory factor 8 (IRF8) is the most likely target gene of miR-1270, which is associated with osteoclastogenesis. Furthermore, the findings of the present study demonstrate that an upregulation of miR-1270 may reduce the gene expression of IRF8 in CMCs (osteoclast precursors), implicating its potential role in leading to low bone mineral density and contributing to osteoporosis development in postmenopausal women.

A Pilot Genome-Wide Association Study in Postmenopausal Mexican-Mestizo Women Implicates the RMND1/CCDC170 Locus Is Associated with Bone Mineral Density.

To identify genetic variants influencing bone mineral density (BMD) in the Mexican-Mestizo population, we performed a GWAS for femoral neck (FN) and lumbar spine (LS) in Mexican-Mestizo postmenopausal women. In the discovery sample, 300,000 SNPs were genotyped in a cohort of 411 postmenopausal women and seven SNPs were analyzed in the replication cohort (n = 420). The combined results of a meta-analysis from the discovery and replication samples identified two loci, RMND1 (rs6904364, P = 2.77 × 10-4) and CCDC170 (rs17081341, P = 1.62 × 10-5), associated with FN BMD. We also compared our results with those of the Genetic Factors for Osteoporosis (GEFOS) Consortium meta-analysis. The comparison revealed two loci previously reported in the GEFOS meta-analysis: SOX6 (rs7128738) and PKDCC (rs11887431) associated with FN and LS BMD, respectively, in our study population. Interestingly, rs17081341 rare in Caucasians (minor allele frequency < 0.03) was found in high frequency in our population, which suggests that this association could be specific to non-Caucasian populations. In conclusion, the first pilot Mexican GWA study of BMD confirmed previously identified loci and also demonstrated the importance of studying variability in diverse populations and/or specific populations.

Analysis of association of MEF2C, SOST and JAG1 genes with bone mineral density in Mexican-Mestizo postmenopausal women.

BACKGROUND: Osteoporosis, a disease characterized by low bone mineral density (BMD), is an important health problem in Mexico. BMD is a highly heritable trait, with heritability estimates of 50-85%. Several candidate genes have been evaluated to identify those involved in BMD variation and the etiology of osteoporosis. This study investigated the possible association of single-nucleotide polymorphisms (SNPs) in the MEF2C, SOST and JAG1genes with bone mineral density (BMD) variation in postmenopausal Mexican-Mestizo women. METHODS: Four hundred unrelated postmenopausal women were included in the study. Risk factors were recorded and BMD was measured in total hip, femoral neck and lumbar spine using dual-energy X-ray absorptiometry. In an initial stage, a total of twenty-five SNPs within or near SOST gene and seven SNPs in the JAG1 gene were genotyped using a GoldenGate assay. In a second stage, three MEF2C gene SNPs were also genotyped and SOST and JAG1 gene variants were validated. Real time PCR and TaqMan probes were used for genotyping. RESULTS: Linear regression analyses adjusted by age, body mass index and ancestry estimates, showed that five SNPs in the SOST gene were significantly associated with BMD in total hip and femoral neck but not lumbar spine. The lowest p value was 0.0012, well below the multiple-test significance threshold (p=0.009), with mean effect size of -0.027 SD per risk allele. We did not find significant associations between BMD and MEF2C/JAG1 gene variants [rs1366594 "A" allele: ß=0.001 (95% CI -0.016; 0.017), P=0.938; rs2273061 "G" allele: ß=0.007 (95% CI -0.007; 0.023), p=0.409]. CONCLUSIONS: SOST polymorphisms may contribute to total hip and femoral neck BMD variation in Mexican postmenopausal women. Together, these and prior findings suggest that this gene may contribute to BMD variation across populations of diverse ancestry.