miRNAs as novel biomarkers for bone related diseases

MicroRNAs (miRNAs) are single stranded, non-coding RNAs that regulate mRNA expression and the amount of gene products. miRNAs regulate mRNA expression through direct binding and influence various signalling pathways in the organism. miRNAs have been found to play key roles in cell proliferation, differentiation, organ and tissue development and the regulation of bone homeostasis. They contribute to bone formation and resorption, bone remodelling and the differentiation of bone cells. Therefore, altered expression of distinct miRNAs may influence the pathology of bone diseases, such as osteoporosis, renal osteodystrophy and malignant bone tumours. miRNAs are released into the bloodstream, partly through active secretion, and are bound to structures, such as proteins and exosomes, that protect the miRNAs from degradation. Therefore, miRNAs are easy to sample, and they are stable with great potential as biomarkers for several diseases, including osteoporosis. This review is giving a short overview on the background and the features of the miRNAs and other non-coding RNAs, highlighting examples for their relevance in bone diseases and summarizing knowledge on miRNAs as biomarkers for osteoporosis.