Cryopreservation increases apoptosis in human menisci

Removal of the meniscus leads to progressive degenerative arthritis of the knee on a long-term basis; therefore, meniscal allograft transplantation has been proposed as an alternative to meniscectomy. Preservation methods are required to build up operational stocks and to provide living grafts of a practical size at the right time for patients. Methods for meniscus preservation have been published, and relevant literature confirms that using standard cryopreservation, the chondrocyte survival in situ is inadequate and extremely variable and the cryoinjury mechanisms are not completely established. The aim of the present study is to further investigate possible cellular injury caused by cryopreservation by analysing apoptosis and ultrastructural damage to menisci.

Seven human menisci that were cryopreserved by standard method were used. All tissue samples were processed simultaneously for routine light microscopy, scanning and transmission electron microscopy as well as apoptosis assessment by the use of ISOL method.

With respect to cellularity, significant differences (P < 0.05) between the fresh (14.6 ± 3.5) (mean ± SD) and cryopreserved menisci (9.2 ± 2.8) (mean ± SD) were observed. Apoptosis using ISOL method was observed in fibrochondrocytes of fresh and cryopreserved menisci. The quantitative analysis revealed significant differences (P < 0.05) between fresh meniscus samples, where the apoptotic index was 0.8 ± 2.3% (mean ± SD), and cryopreserved meniscus samples, where this index was 50 ± 18.1% (mean ± SD).

The results suggest that apoptosis occurs during meniscus cryopreservation. The major findings of this study are cellular damage in meniscus cryopreservation suggesting apoptosis-mediated cell loss. The findings reported herein encourage to further investigations in preservation procedures to enhance maximum long-term clinical survival.