In vivo imaging of MMP-13 activity using a specific polymer-FRET peptide conjugate detects early osteoarthritis and inhibitor efficacy

Imaging early molecular changes in osteoarthritic (OA) joints is instrumental for the development of disease‐modifying drugs. To this end, a fluorescent resonance energy transfer-based peptide probe that is cleavable by matrix metalloproteinase 13 (MMP-13) has been developed. This protease degrades type II collagen, a major matrix component of cartilage. The probe exhibits high catalytic efficiency (kcat/KM = 6.5 × 105m-1 s-1) and high selectivity for MMP-13 over a set of nine MMPs. To achieve optimal in vivo pharmacokinetics and tissue penetration, the probe has been further conjugated to a linear l-polyglutamate chain of 30 kDa. The conjugate detects early biochemical events that occur in a surgically induced murine model of OA before major histological changes. The nanometric probe is suitable for the monitoring of in vivo efficacy of an orally bioavailable MMP-13 inhibitor, which effectively blocks cartilage degradation during the development of OA. This new polymer-probe can therefore be a useful tool in detecting early OA, disease progression, and in developing MMP-13-based disease-modifying drugs for OA.