Division of Biomedical Sciences, St. George's, University of London, London, UK.
BMC Musculoskelet Disord. 2010 Oct 8;11:231. doi: 10.1186/1471-2474-11-231.
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. 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.
Both 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.
Stiffness 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.
Mechanical 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.
作为一种相对不可再生的组织，关节软骨一直是冷冻保存的目标，以缓解移植手术中供体组织不足的问题。此外，关节软骨的亚零储存长期以来一直用于各种储存温度的生物医学研究。目前的研究通过直接比较各种亚零储存温度，研究了冻融对关节软骨力学性能的潜在影响。
使用对照样本（4°C）以及储存在-20°C 或-80°C 的样本以及先在液氮（-196°C）中冷冻再储存在-80°C 的样本，比较了亚零储存温度和冷冻速率。所有样本均在 37.5°C 下解冻至测试温度（22°C）。采用非破坏性、低力幅值、动态压痕协议，对复杂刚度和滞后性进行了研究，以表征负载阻力和阻尼特性，该协议跨越广泛的加载速率范围，以识别软骨的动态粘弹性特性。
在暴露于各种亚零温度下，刚度水平保持不变。在-196°C 冷冻并储存在-80°C 的样本中，滞后性增加，但在暴露于其他储存温度下保持不变。
显示的机械变化可能是由于冰晶的形成，霜胀效应可能导致胶原损伤。储存在-20°C 和-80°C 并未改变关节软骨的机械性能，这表明当与 37.5°C 的快速解冻方案结合使用时，组织可以成功地在亚零温度下储存。
