Orthopaedic Biomechanics Group, Department of Biomedical Engineering, Eindhoven University of Technology (TU/e), Eindhoven, The Netherlands.
Osteoarthritis Cartilage. 2013 Jan;21(1):136-43. doi: 10.1016/j.joca.2012.09.002. Epub 2012 Sep 23.
Because collagen damage and cartilage softening have not yet been determined simultaneously in one study for the very early onset of osteoarthritis (OA), it remains questionable whether they are associated. The aim of the present study is therefore to evaluate whether indeed, initial collagen damage can be found when tissue softening occurs as a result of excessive mechanical loading.
To investigate this aim, a series of specific indentation loading protocols were designed to induce and monitor cartilage softening in osteochondral explants of bovine carpometacarpal joints. The experiment contained one control group (n = 6) in which no damage was induced and four experimental groups in which samples received either a constant load of 3 (n = 5), 6 (n = 5) or 15 N (n = 6), or an increasing load (n = 7) from 2 to 13 N in 11 steps. Moreover, to determine mechanically induced collagen damage, Col2-3/4M (cumulative collagen damage) and Col2-3/4C(short) (only enzymatic damage) staining were compared.
The normalized peak and equilibrium reaction forces decreased in the groups that received increasing and 15 N peak loading. However, Col2-3/4M staining was negative in all samples, while enzymatic damage (Col2-3/4C(short)) appeared similar in experiments and in unloaded control groups.
It was shown that a loading magnitude threshold exists above which softening occurs in cartilage. However, in samples that did show softening, we were unable to detect collagen damage. Thus, our results demonstrate that cartilage softening most likely precedes collagen damage.
由于一项关于骨关节炎（OA）早期发病的研究尚未同时确定胶原损伤和软骨软化，因此仍不清楚它们是否相关。本研究的目的是评估在由于过度机械加载而导致组织软化时，是否确实会出现初始胶原损伤。
为了研究这个目的，设计了一系列特定的压痕加载方案，以诱导和监测牛腕掌关节骨软骨标本的软骨软化。该实验包含一个对照组（n=6），其中不诱导损伤，以及四个实验组，其中样本分别接受 3N（n=5）、6N（n=5）或 15N（n=6）的恒定载荷，或从 2N 到 13N 以 11 步递增的载荷。此外，为了确定机械诱导的胶原损伤，比较了 Col2-3/4M（累积胶原损伤）和 Col2-3/4C（短）（仅酶损伤）染色。
接受递增和 15N 峰值载荷的组的归一化峰值和平衡反应力降低。然而，所有样本的 Col2-3/4M 染色均为阴性，而酶损伤（Col2-3/4C（短））在实验和未加载对照组中表现相似。
研究表明，软骨软化发生在加载量超过一定阈值之上。然而，在确实出现软化的样本中，我们未能检测到胶原损伤。因此，我们的结果表明，软骨软化很可能先于胶原损伤发生。
