MicroRNAs are important regulators of gene expression with documented role in bone metabolism and osteoporosis. Moreover, the use of miRNAs constitutes potential therapeutic targets. Our aim was to identify miRNAs differentially expressed in fractured compared to healthy bone. Additionally, we performed a miRNA profiling of primary osteoblasts to assess the origin of the differentially expressed miRNAs. Total RNA was extracted from fresh femoral neck trabecular bone from women undergoing hip replacement due to either osteoporotic fracture (n=6) or osteoarthritis (n=6) in the absence of osteoporosis (according to BMD measurements), age and BMI matched, and from primary osteoblasts (at passage 0) obtained from knee replacement due to osteoarthritis (n=4). Samples were hybridized to the miRCURY LNATM microRNA Array 7th (Exiqon, Denmark), in the manufacturers facilities. QC tests, PCA plots and heat map hierarchical clustering were performed. For comparison of expression levels, the threshold was set at log fold change >1.5 and a P-value <0.05 (corrected for multiple-testing).
Both PCA and heat map analyses showed that the samples clustered according to their biological group (fracture vs non-fracture). However, one osteoporotic sample appeared as outlier and was excluded. Overall, 792 and 315 different miRNAs were detected in fresh bone samples and in primary osteoblats, respectively, 284 of which were shared (i.e. 35.8% of bone miRNAs were from osteoblasts).
A subset of 82 microRNAs was found to be significantly differentially expressed between osteoporotic and control samples. Upon validation of ten miRNAs with the lowest p-values, and for which an validated assay was available, using the miRCURY LNATM Universal RT microRNA qPCR assay, two of them were confirmed: miR-320a and miR-483-5p. They are both over-expressed in the osteoporotic samples (and expressed in primary osteoblasts). In conclusion, two osteoblast miRNAs are over-expressed in osteoporotic fractures, which open novel prospects for research and therapy.
17 May 2014 - 20 May 2014