Low-intensity pulsed ultrasound irradiation attenuates collagen degradation of articular cartilage in early osteoarthritis-like model mice

Kojima Y, Watanabe T · Journal of Experimental Orthopaedics

At four weeks the untreated group's OARSI histological score had risen and the irradiated group's had not; at one week neither group had lost safranin-O staining. Denatured collagen reagent marked wide areas of denatured type II collagen in untreated knees and few in irradiated ones at both time points. Macrophage counts in the joint capsule were lower at one week with irradiation, and lubricin-positive cells higher at four weeks. Aggrecan-positive cells did not differ.

Population

Female ICR mice given a low dose of monoiodoacetate (0.1 mg) in one knee to model early osteoarthritis; four mice per group, the number a power calculation said was the minimum

Intervention

Low-intensity pulsed ultrasound over the knee, 30 mW/cm2 at a 20% duty cycle, 2.0 MHz, 20 minutes a day, five days a week for four weeks

Comparator

The same model with no irradiation

Limitations

Four mice per group, a single laboratory, and a chemical model: monoiodoacetate kills chondrocytes directly rather than reproducing mechanical wear. Both authors are employees of Nippon Sigmax Co. Ltd., which funded the study and made the ultrasound transducer used in it.