兔膝关节软骨单位微管吸吮黏弹性力学分析

摘要

目的 探讨体外急性消化软骨单位的生物力学特性.方法 成年8月龄新西兰白兔8只,随机分为两组,各4只.无菌条件下剖取双膝关节全层软骨,一组采用常规质量浓度0.4%的pronase酶和质量浓度0.025%的Ⅱ型胶原酶依次消化为软骨细胞;另一组采用质量浓度0.3%的dispase酶和质量浓度0.2%的Ⅱ型胶原酶联合搅拌消化3 h为软骨单位.利用微管吸吮结合半无限体细胞力学模型定量分析急性消化软骨细胞及软骨单位黏弹性力学特性,包括平衡模量(E∞)、瞬间模量(E0)和表观黏性(μ)等黏弹性参数.结果 成年软骨细胞在0.2-0.4 kPa恒定微管负压下,表现为典型黏弹性固体特征,即在微管中产生瞬间微小变形,随后发生形率单调减小的蠕变过程,其到达平衡状态时间为(110±18)s.成年软骨单位在微管吸吮负压提高到1.0～1.2 kPa时,与软骨细胞发生同样的黏弹性蠕变行为,但其瞬间吸入微管内的长度明显减少,且到达平衡状态的时间缩短为(36.5±4.5)s.同时,软骨单位黏弹性参数平衡模量(E∞)、瞬间模量(E0)和表观黏性(μ)均明显高于软骨细胞.结论 与软骨细胞相比,成年软骨单位同样表现为黏弹性固体特征,但其黏弹性力学特性明显提高.%Objective To characterize the biomechanical behavior and properties of the chondrons enzymatically isolated from rabbit knee articular cartilage in virto. Methods Eight months old New Zealand white rabbits were randomly divided into chondroctye and chondron groups (4 rabbits in each group). In chondrocyte groups, the full articular cartilages from both knees were enzymatically isolated to chondrocytes by 0.4% pronase and 0.025% collagenase type-Ⅱ in turn. In chondron groups, chondrons were obtained from articular cartilage using the mixture of 0.3% dispase (a neutral protease) and 0.2% collagenase type-Ⅱin at 37C for 3 h. The micropipette aspiration was used to quantify changes in biomechanical properties of chondrons and chondrocytes and the viscoelastic parameters, including K1, K2, E∞ (equilibrium modulus), E0(instantaneous modulus), and μ (apparent viscosity), were calculated coupled with standard linear half-space viscoelastic solid model. Results In response to a constant negative pressure of 0.2-0.4 kPa, the chondrocytes exhibited standard linear viscoelastic solid properties. Namely, the cells showed an initial elastic response followed by a viscoelastic creep response. then cells continued to enter into the micropipette with a monotonically decreasing rate of deformation, until reaching equilibrium within about (110±18) s. Comparing with chondrocytes, the chondrons exhibited significant viscoelasticity under a greater negative pressure of 1.0-1.2 kPa. But the instantaneous length deformed into the micropipette significantly reduced, and the equilibrium time reduced to (36.5±4.5) s. The equilibrium modulus (E∞), the instantaneous modulus (E0) and the apparent viscosity (μ) of chondrons were significantly higher than the those of chondrocytes. Conclusion Comparing with chondrocytes, the chondrons exhibited significant viscoelastic properties, and viscoelastic properties of chondrons have increased in vitro.