Colloidal 90Y used for radiation synovectomy decreases the viability of chondrocytes in human cadaveric samples

Abstract

To analyse the early effect of colloidal 90Y beta irradiation, as used for radiation synovectomy (RSV), on the viability of human chondrocytes in an ex-vivo model. Twenty osteochondral plugs (6 mm in diameter) were procured from femoral condyles of an adult male donor and stored in normal saline at 4 degrees C. The cartilage surfaces of 10 plugs were contaminated with colloidal 90Y citrate corresponding to the standard knee RSV dose (185 MBq) matched for the sample size (430 kBq). The remaining 10 plugs served as controls. At days 1, 2, 3, 6 and 13, two osteochondral plugs from each group were stained for viability with live/dead probes and scanned under a confocal laser microscope. The ratios of viable (green channel) and non-viable (red channel) pixels were acquired in four cartilage depth regions and statistically analysed with a regression model. The irradiation did not significantly alter the viable/non-viable pixel ratio during the first 2 days, but longer exposures led to a significant and time progressive reduction from 8.7% (day 3) to 12.5% (day 13). The ratio was less affected deeper in the cartilage, where it increased about 1% for every 100 microm from the surface. Surface exposure of human cadaveric cartilage to a therapeutic dose of colloidal 90Y decreased chondrocyte viability, expressed as the viable/non-viable pixel ratio, in the early post-irradiation period. The findings established in the ex-vivo simulation may reflect the changes in knee cartilage occurring after RSV therapy.