Five freely circulating miRNAs and bone tissue miRNAs are associated with osteoporotic fractures

Osteoporosis as a systemic skeletal disorder is characterized by increased bone fragility and the risk of fractures. According to the World Health Organization, osteoporosis is one of the 10 most common diseases and affects approximately 75 million people in Europe, the United States, and Japan. In this context, the identification of specific microRNA (miRNA) signatures is an important step for new diagnostic and therapeutic approaches. The focus of interest on miRNAs as biomarkers came with new publications identifying free circulating extracellular miRNAs associated with various types of cancer. This study aimed to identify specific miRNAs in patients with osteoporotic fractures compared with nonosteoporotic fractures. For the array analysis, miRNAs were isolated from the serum of 20 patients with hip fractures, transcribed, and the samples were pooled into 10 osteoporotic and 10 nonosteoporotic specimens. With each pool of samples, human serum and plasma miRNA PCR arrays were performed, which are able to identify 83 different miRNAs. Subsequently, a separate validation analysis of each miRNA found to be regulated in the array followed with miRNA samples isolated from the serum of 30 osteoporotic and 30 nonosteoporotic patients and miRNA samples isolated from the bone tissue of 20 osteoporotic and 20 nonosteoporotic patients. With the validation analysis of the regulated miRNAs, we identified 9 miRNAs, namely miR-21, miR-23a, miR-24, miR-93, miR-100, miR-122a, miR-124a, miR-125b, and miR-148a, that were significantly upregulated in the serum of patients with osteoporosis. In the bone tissue of osteoporotic patients, we identified that miR-21, miR-23a, miR-24, miR-25, miR-100, and miR-125b displayed a significantly higher expression. A total of 5 miRNAs display an upregulation both in serum and bone tissue. This study reveals an important role for several miRNAs in osteoporotic patients and suggested that they may be used as biomarkers for diagnostic purposes and may be a target for treating bone loss and optimizing fracture healing in osteoporotic patients.