The observation of the PG-depletion in progressive trypsin digested articular cartilage based on conventional a-mode ultrasound

This study tried to monitor proteoglycans (PG)-depletion in progressive trypsin digested porcine articular cartilage (AC) samples with a conventional ultrasound system. 10 cartilage-bone samples were prepared from normal porcine femoral condyle cartilages and were digested with 0.25% trypsin solution for two hours. The dynamic process of the PG digestion was explored using an A-mode ultrasound experiment system with 10MHz center frequency. The speed of PG-depletion and the degree of PG-depletion were estimated from ultrasound echo signal. The results showed that 10MHz ultrasound is valuable in tracking the degree of PG-digestion. The transient speed of PG-digestion decreased with digesting time and tissue depth. The digestion speed is faster in the superficial layer of the cartilage samples (0.93 ± 0.3M/min) than that in deeper layers (0.26 ± 0.12 M/min at 50% of the full thickness). The histological image also confirmed the validity of the ultrasound observation.. This study may provide some useful information in identifying cartilage matrix integrity and osteoarthritis (OA) disease progression.