Serum Circulating MicroRNAs as Biomarkers of Osteoporotic Fracture

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.