Influence of cryopreservation methods of ex vivo rat and pig skin on the results of in vitro permeation test

In vitro permeation test (IVPT) is a frequently used method for in vitro assessment of topical preparations and transdermal drug delivery systems. However, the storage of ex vivo skin for IVPT remains a challenge. Here, two cryopreservation media were chosen to preserve rat and pig skin at -20 °C and -80 °C for further IVPT, namely, 10 % DMSO and 10 % GLY. The skin viability test confirmed that the skin protective capacity of 10 % DMSO and 10 % GLY was almost equal. The results of skin viability and IVPT showed that the skin viability and permeability of rat skin in 10 %DMSO or 10 % GLY were maintained for at least 7 and 30 days at -20 °C and -80 °C compared to fresh skin, respectively; in contrast, those of porcine skin were just maintained for <7 days at -20 °C and -80 °C. These results indicated that ex vivo skin for IVPT preserved at -80 °C in 10 % DMSO or 10 % GLY was optimal. Furthermore, skin permeability was independent of skin barrier integrity. Our study provides reference conditions for preserving IVPT skin, and skin viability can be a potential indicator of IVPT skin.