A novel method to measure cryoprotectant permeation into intact articular cartilage

Successful cryopreservation of articular cartilage (AC) could improve clinical results of osteochondral allografting and provide a useful treatment alternative for large cartilage defects. However, successful cartilage cryopreservation is limited by the time required for cryoprotective agent (CPA) permeation into the matrix and high CPA toxicity. This study describes a novel, practical method to examine the time-dependent permeation of CPAs [dimethyl sulfoxide (DMSO) and propylene glycol (PG)] into intact porcine AC. Dowels of porcine AC (10 mm diameter) were immersed in solutions containing high concentrations of each CPA for different times (0, 15, 30, 60 min, 3, 6, and 24 h) at three temperatures (4, 22, and 37 °C), with and without cartilage attachment to bone. The cartilage was isolated and the amount of cryoprotective agent within the matrix was determined. The results demonstrated a sharp rise in the CPA concentration within 15–30 min exposure to DMSO and PG. The concentration plateaued between 3 and 6 h of exposure at a concentration approximately 88–99% of the external concentration (6.8 M). This observation was temperature-dependent with slower permeation at lower temperatures. This study demonstrated the effectiveness of a novel technique to measure CPA permeation into intact AC, and describes permeation kinetics of two common CPAs into intact porcine AC.