Osteoporosis is a common skeletal disorder characterized by increased risk of bone fracture (BF) due to fragility. BFs, particularly hip fracture, are a major concern in health care because of the associated morbidity and mortality, mainly in the elderly. Lately the involvement of epigenetic mechanisms in the pathophysiology of many diseases has been recognized. In this context, the identification of microRNAs (miRNAs) specific to BF should represent a substantial step forward in diagnostics and therapeutics. The present study aimed to identify specific miRNAs in osteoporotic BF patients compared to those in osteoarthritic controls. In the profiling stage, total RNA was extracted from serum, two pools were prepared, and then retro-transcribed in triplicate. Levels of 179 serum miRNAs were analyzed by real-time PCR, and 42 of them showed significance (P < 0.05), and 12 passed the false discovery rate test for multiple comparisons. Six miRNAs were selected for the replication stage and individually analyzed in sera from 15 BF patients and 12 controls. Results showed that 3 miRNAs (miR-122-5p, miR-125b-5p, and miR-21-5p) were valuable upregulated biomarkers in BF with respect to controls and, significantly, their levels were not affected by hemolysis. For miR-21-5p, the difference detected between groups was independent of age (P = 0.005) and its levels correlated to those of CTx (r = 0.76; P < 0.00001), a marker of bone resorption. In conclusion, several miRNAs may be biomarkers of BF, particularly miR-21-5p. Further studies are needed in order to better characterize the levels of these miRNAs in other bone diseases and to elucidate the mechanism involved in the association of these three miRNAs with osteoporotic BF.

These results show that the use of animal models is an appropriate method for identifying genes associated with human bone phenotypes.

No abstract

No abstract

To identify new candidate genes in osteoporosis, mainly involved in epigenetic mechanisms, we compared whole gene-expression in osteoblasts (OBs) obtained from women undergoing hip replacement surgery due to fragility fracture and severe osteoarthritis. Then, we analyzed the association of several SNPs with BMD in 1028 women. Microarray analysis yielded 2542 differentially expressed transcripts belonging to 1798 annotated genes, of which 45.6% (819) were overexpressed, and 54.4% (979) underexpressed (fold-change between − 7.45 and 4.0). Among the most represented pathways indicated by transcriptome analysis were chondrocyte development, positive regulation of bone mineralization, BMP signaling pathway, skeletal system development and Wnt signaling pathway. In the translational stage we genotyped 4 SNPs in DOT1L, HEY2, CARM1 and DNMT3A genes. Raw data analyzed against inheritance patterns showed a statistically significant association between a SNP of DNMT3A and femoral neck-(FN) sBMD and primarily a SNP of CARM1 was correlated with both FN and lumbar spine-(LS) sBMD. Most of these associations remained statistically significant after adjusting for confounders. In analysis with anthropometric and clinical variables, the SNP of CARM1 unexpectedly revealed a close association with BMI (p = 0.000082), insulin (p = 0.000085), and HOMA-IR (p = 0.000078). In conclusion, SNPs of the DNMT3A and CARM1 genes are associated with BMD, in the latter case probably owing to a strong correlation with obesity and fasting insulin levels.