Abstract
BackgroundAs a relatively non-regenerative tissue, articular cartilage has been targeted for cryopreservation as a method of mitigating a lack of donor tissue availability for transplant surgeries. In addition, subzero storage of articular cartilage has long been used in biomedical studies using various storage temperatures. The current investigation studies the potential for freeze-thaw to affect the mechanical properties of articular cartilage through direct comparison of various subzero storage temperatures.MethodsBoth subzero storage temperature as well as freezing rate were compared using control samples (4°C) and samples stored at either -20°C or -80°C as well as samples first snap frozen in liquid nitrogen (-196°C) prior to storage at -80°C. All samples were thawed at 37.5°C to testing temperature (22°C). Complex stiffness and hysteresis characterized load resistance and damping properties using a non-destructive, low force magnitude, dynamic indentation protocol spanning a broad loading rate range to identify the dynamic viscoelastic properties of cartilage.ResultsStiffness levels remained unchanged with exposure to the various subzero temperatures. Hysteresis increased in samples snap frozen at -196°C and stored at -80°C, though remained unchanged with exposure to the other storage temperatures.ConclusionsMechanical changes shown are likely due to ice lens creation, where frost heave effects may have caused collagen damage. That storage to -20°C and -80°C did not alter the mechanical properties of articular cartilage shows that when combined with a rapid thawing protocol to 37.5°C, the tissue may successfully be stored at subzero temperatures.
Highlights
As a relatively non-regenerative tissue, articular cartilage has been targeted for cryopreservation as a method of mitigating a lack of donor tissue availability for transplant surgeries
While many hurdles must be overcome before cyropreservation may be utilized for donor articular cartilage, the present investigation attempts to identify the important issue of how freeze-thaw treatment may affect the mechanical properties of articular cartilage
Hysteresis No significant changes (p > 0.5) were found immediately after thawing between samples stored at subzero temperatures and the 4°C controls (Figure 3a)
Summary
As a relatively non-regenerative tissue, articular cartilage has been targeted for cryopreservation as a method of mitigating a lack of donor tissue availability for transplant surgeries. The current investigation studies the potential for freeze-thaw to affect the mechanical properties of articular cartilage through direct comparison of various subzero storage temperatures. Degenerative diseases such as osteoarthritis involve deterioration of the extracellular matrix of articular cartilage and results in altered mechanical properties of the tissue. The healing capacity of articular cartilage is limited [1] necessitating the development of methods for repairing or replacing damaged tissue. While many hurdles must be overcome before cyropreservation may be utilized for donor articular cartilage (namely those involved with cell viability), the present investigation attempts to identify the important issue of how freeze-thaw treatment may affect the mechanical properties of articular cartilage
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