A Non-invasive , Early , and Sensitive Detection of Osteoarthritis through In Vivo Imaging of MMP-13 mRNA Levels by Molecular Beacon and Nanopieces Delivery Technology

Introduction: Osteoarthritis (OA) is one of the most common causes of disability. However, the lack of tools for early diagnosis of OA hampers the prevention and treatment of the disease to decelerate articular cartilage loss and alleviate suffering of patients. The OA Biomarker Initiative has identified a series of biomarkers, including matrix metalloproteinases (MMPs), which are elevated in articular cartilage during OA pathogenesis. However, detection of MMP protein levels or activities in serum may not be sensitive enough, while the more sensitive detection of MMP transcripts requires invasive procedure to obtain biopsy of articular joint tissue. Therefore, there is an urgent need to develop sensitive in vivo imaging technology to detect molecular changes at early stages of arthritis without harming articular cartilage. Molecular beacon (MB) technology provides an intriguing possibility to detect the changes of mRNA levels in live animals in vivo. Molecular beacons, composed of an oligonucleotide loop, double strand stem, and a fluorophore and quencher, remain nonfluorescent due to the proximity of fluorophore and quencher. Upon entering a cell and hybridizing with target mRNA, MBs emit fluorescence due to separation of the fluorophore and quencher (Fig.1). To date, there has been no report of detection of OA using MBs due to the significant challenge of in vivo delivery of MBs into joint tissues. In this study, we showed the feasibility of early detection of OA in the Destabilizing Medial Meniscus (DMM) mouse OA model using MB to detect induction of MMP-13 transcript, a major matrix proteinase that degrades interstitial collagen matrix during arthritis. In vivo delivery of MMP-13 MB was made possible by a novel nanomaterial named Nanopieces that is derived from rosette nanotubes.