First ex vivo study demonstrating that ^sup 99m^Tc-NTP 15-5 radiotracer binds to human articular cartilage

Preclinical data pointed to ^sup 99m^Tc-NTP 15-5 as a good candidate for single photon emission computed tomography (SPECT) imaging of cartilaginous disease. We set out to investigate and quantify ^sup 99m^Tc-NTP 15-5 ex vivo uptake by human articular cartilage relative to bone ^sup 99m^Tc-hydroxymethylene diphosphonate (HMDP) radiotracer. Three osteoarthritic human tibial plateaux and four tibiofemoral joints were incubated with ^sup 99m^Tc-NTP 15-5 and ^sup 99m^Tc-HMDP for 2 h. Affinity of tracers for cartilage was determined by visual analysis of SPECT/CT acquisitions and measurement of cartilage to cortical bone uptake ratios. Cartilage to cortical bone uptake ratios were 3.90±2.35 and 0.76±0.24, respectively, for ^sup 99m^Tc-NTP 15-5 and ^sup 99m^Tc-HMDP radiotracers. Visual analysis of fused SPECT/CT slices showed selective, intense ^sup 99m^Tc-NTP 15-5 accumulation in articular cartilage, whereas ^sup 99m^Tc-HMDP binding was low. Interestingly, a cartilage defect visualized on CT was clearly associated with focal decreased uptake of ^sup 99m^Tc-NTP 15-5. The tracer ^sup 99m^Tc-NTP 15-5 is of major interest for human cartilage molecular imaging and could find clinical applications in osteoarthritis staging and monitoring.[PUBLICATION ABSTRACT]