Department of Biomedical Engineering, Columbia University, New York, NY, United States.
Department of Mechanical Engineering, Columbia University, New York, NY, United States.
J Biomech. 2024 Nov;176:112340. doi: 10.1016/j.jbiomech.2024.112340. Epub 2024 Sep 24.
Interstitial fluid load support (FLS) is a dominant mechanism of lubrication in cartilage, producing a low friction coefficient while enhancing the tissue's load bearing capabilities. Due to its viscosity, synovial fluid (SF) may retard loss of FLS by slowing the exudation of interstitial fluid from the cartilage. This study tested this hypothesis by comparing the stress-relaxation (SRL) response of immature bovine articular cartilage immersed either in phosphate buffered saline (PBS) or in healthy mature bovine SF, under unconfined compression (fluid exudation across cut lateral tissue boundary) and indentation testing (fluid exudation across articular surface). To investigate the influence of diffusion of SF molecular constituents into cartilage, the effect of incubation time in SF on SRL was also investigated. The SRL response in unconfined compression was not significantly different in PBS versus SF when compared directly (p = 0.98) and had a slope ofm = 1.00 ± 0.04 (R = 0.989 ± 0.007). Samples tested in PBS exhibited characteristic relaxation times, τ=42.6 ± 5.3 s andτ = 40.8 ± 4.7 s, that were not significantly different (p = 0.40). Incubation time of 24 h in SF resulted in no significant difference in the SRL response (p = 0.39, m=1.03 ± 0.12; R=0.983 ± 0.011, andτ = 43.4 ± 10.7 s versusτ = 41.5 ± 4.8 s, p = 0.59). Indentation testing showed some statistically significant, but functionally insignificant, difference in SRL responses in PBS versus SF with a slope ofm = 0.958 ± 0.060 (R = 0.957 ± 0.020, p = 0.029, andτ = 16.9 ± 2.6 s versusτ = 19.4 ± 3.3 s, p = 0.073). Based on these results, we reject the hypothesis that healthy SF can retard the loss of FLS in cartilage due to its viscosity.
间质液负载支持（FLS）是软骨润滑的主要机制，在提高组织承载能力的同时产生低摩擦系数。由于滑液的粘性，滑液（SF）可能会通过减缓间质液从软骨中渗出来延迟 FLS 的丧失。本研究通过比较浸泡在磷酸盐缓冲盐水（PBS）或健康成熟牛 SF 中的未成熟牛关节软骨在无约束压缩（通过切开的侧向组织边界渗出间质液）和压痕测试（通过关节表面渗出间质液）下的应力松弛（SRL）响应，来验证这一假设。为了研究 SF 分子成分扩散到软骨中的影响，还研究了在 SF 中孵育时间对 SRL 的影响。与 SF 相比，PBS 中未约束压缩下的 SRL 响应直接比较时没有显著差异（p=0.98），斜率 m=1.00±0.04（R=0.989±0.007）。在 PBS 中测试的样品表现出特征松弛时间τ=42.6±5.3 s 和τ=40.8±4.7 s，没有显著差异（p=0.40）。在 SF 中孵育 24 小时不会导致 SRL 响应有显著差异（p=0.39，m=1.03±0.12；R=0.983±0.011，τ=43.4±10.7 s 与τ=41.5±4.8 s，p=0.59）。压痕测试显示，在 PBS 与 SF 之间的 SRL 响应存在一些具有统计学意义但功能上无意义的差异，斜率 m=0.958±0.060（R=0.957±0.020，p=0.029，τ=16.9±2.6 s 与τ=19.4±3.3 s，p=0.073）。基于这些结果，我们拒绝了健康 SF 由于其粘性而能减缓软骨中 FLS 丧失的假设。
