Journal of the Mechanical Behavior of Biomedical Materials ( IF 3.3 ) Pub Date : 2020-03-27 , DOI: 10.1016/j.jmbbm.2020.103732 Shannon K Walsh 1 , Stephanie E Schneider 2 , Laura A Amundson 3 , Corey P Neu 2 , Corinne R Henak 4
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Objective
Articular cartilage undergoes biological and morphological changes throughout maturation. The prevalence of osteoarthritis in the aged population suggests that maturation predisposes cartilage to degradation and/or impaired regeneration, but this process is not fully understood. Therefore, the objective of this study was to characterize the cellular and genetic profile of cartilage, as well as biological plasticity in response to mechanical and culture time stimuli, as a function of animal maturity.
Methods/design
Porcine articular cartilage explants were harvested from stifle joints of immature (2–4 weeks), adolescent (5–6 months), and mature (1–5 years) animals. Half of all samples were subjected to a single compressive mechanical load. Loaded samples were paired with unloaded controls for downstream analyses. Expression of cartilage progenitor cell markers CD105, CD44, and CD29 were determined via flow cytometry. Expression of matrix synthesis genes Col1, Col2, Col10, ACAN, and SOX9 were determined via qPCR. Tissue morphology and matrix content were examined histologically. Post-loading assays were performed immediately and following 7 days in culture.
Results
CD105 and CD29 expression decreased with maturity, while CD44 expression was upregulated in cartilage from mature animals. Expression of matrix synthesis genes were generally upregulated in cartilage from mature animals, and adolescent animals showed the lowest expression of several matrix synthesizing genes. Culture time and mechanical loading analyses revealed greater plasticity to mechanical loading and culture time in cartilage from younger animals. Histology confirmed distinct structural and biochemical profiles across maturity.
Conclusion
This study demonstrates differential, nonlinear expression of chondroprogenitor markers and matrix synthesis genes as a function of cartilage maturity, as well as loss of biological plasticity in aged tissue. These findings have likely implications for age-related loss of regeneration and osteoarthritis progression.
中文翻译：
依赖于成熟度的软骨细胞可塑性和对外部扰动的敏感性。
目的
关节软骨在整个成熟过程中都会经历生物学和形态学变化。老年人中骨关节炎的流行表明成熟易使软骨退化和/或再生受损，但这一过程尚未完全明了。因此，本研究的目的是表征软骨的细胞和遗传特征，以及对机械和培养时间刺激的响应，作为动物成熟度的函数的生物可塑性。
方法/设计
猪关节软骨外植体是从不成熟（2-4周），青春期（5-6个月）和成熟（1-5岁）的动物的窒息关节中收获的。所有样品的一半都经受了一次压缩机械载荷。将已加载的样品与未加载的对照配对以进行下游分析。通过流式细胞术确定软骨祖细胞标志物CD105，CD44和CD29的表达。通过qPCR确定基质合成基因Col1，Col2，Col10，ACAN和SOX9的表达。组织学检查组织形态和基质含量。立即进行加载后测定，并在培养7天后进行。
结果
CD105和CD29表达随着成熟而降低，而CD44表达在成熟动物的软骨中上调。基质合成基因的表达通常在成熟动物的软骨中上调，而青春期动物显示几种基质合成基因的最低表达。培养时间和机械负荷分析显示，幼小动物的软骨对机械负荷和培养时间具有更大的可塑性。组织学证实了整个成熟过程中独特的结构和生化特征。
结论
这项研究证明了软骨生成器标志物和基质合成基因的差异性，非线性表达与软骨成熟以及衰老组织中生物可塑性的丧失有关。这些发现可能与年龄相关的再生丧失和骨关节炎的进展有关。
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