Comparison of High‐Hydrostatic‐Pressure Decellularized Versus Freeze‐Thawed Porcine Menisci

ABSTRACT The meniscus functions as a load distributor and secondary stabilizer in the knee, and the loss of the meniscus increases the risk of osteoarthritis. Freeze‐thawed menisci are used in clinical practice to replace defective menisci; however, the disadvantages of freeze‐thawed tissues include disease transmission and immune rejection. In this study, we decellularized menisci using high hydrostatic pressure (HHP) and compared the decellularized menisci with freeze‐thawed menisci. Porcine menisci were either pressurized at 1,000 MPa for 10 min and then washed with DNase solution or frozen at −80°C for 2 days and thawed. These menisci then underwent in vitro histological, biochemical, and biomechanical comparisons with native menisci. The HHP‐treated and freeze‐thawed menisci were also subcutaneously implanted in a pig, and later harvested for histological analysis. The numbers of histologically detected cells were significantly lower and the amount of biochemically detected DNA was approximately 100‐fold lower in HHP‐treated than in native and freeze‐thawed menisci. The compression strength of the HHP‐decellularized menisci was decreased after 1 and 50 cycles at 20% strain but was unchanged in the freeze‐thawed menisci. After implantation, the numbers of multinucleated giant cells were significantly lower around the HHP‐treated menisci than around the freeze‐thawed menisci. Recellularization of the HHP‐decellularized menisci was confirmed. Thus, although the HHP‐decellularized menisci were mechanically inferior to the freeze‐thawed meniscus in vitro, they were immunologically superior. Our study is the first to demonstrate the use of HHP for decellularization of the meniscus. © 2019 The Authors. Journal of Orthopaedic Research® published by Wiley Periodicals, Inc. on behalf of Orthopaedic Research Society. J Orthop Res 37:2466–2475, 2019 Freeze‐thawed menisci are used in clinical practice to replace defective menisci. However, the disadvantages of using freeze‐thawed tissues include disease transmission and immune rejection. In this study, we decellularized menisci with high hydrostatic pressure (HHP) and compared these decellularized menisci with freeze‐thawed menisci. The in vitro mechanical properties were slightly inferior for the HHP‐decellularized menisci when compared with the freeze‐thawed menisci, but the immunological properties were superior. Our study is the first to demonstrate meniscus decellularization using HHP.