Mistry D, Oue Y, Chambers M G, Kayser M V, Mason R M
Department of Experimental Biology, William Harvey Research Institute, St. Bartholomew's and The Royal London School of Medicine and Dentistry, Charterhouse Square, EC1M 6BQ, London, UK.
Osteoarthritis Cartilage. 2004 Feb;12(2):131-41. doi: 10.1016/j.joca.2003.10.006.
To determine whether chondrocyte apoptosis occurs during the progression of osteoarthritis (OA) in the STR/ort mouse model of OA.
Serial cryostat sections were cut (10 microns) through the knee joint of young and old male STR/ort mice and graded for the severity of OA lesions. Age- and sex-matched CBA mice were used as controls. Apoptotic chondrocytes were detected using the TUNEL assay. Ultrastructural changes were examined using electron microscopy (EM). Expression of biochemical markers associated with apoptosis (bax, bcl-2 and caspases-3, -8 & -9) was investigated using immunohistochemistry.
TUNEL assays on histological sections of STR/ort knee joints showed that the number of TUNEL-positive chondrocytes in the tibial medial articular cartilage correlated with the severity of the OA damage. These cells were located close to the lesional area. Only very occasional TUNEL positive chondrocytes were detected in either morphologically normal STR/ort cartilage or in control CBA cartilage. Ultrastructural analysis of chondrocytes neighboring focal osteoarthritic lesions in STR/ort tibial cartilage revealed an abundance of abnormal cells exhibiting numerous morphological changes. These resembled, but in some cases differed, from changes reported in classical apoptosis. The changes include abnormal distribution of chromatin, cell shrinkage, membrane blebbing and deposition of cell remnants (apoptotic bodies) in the lacuna space. Despite the TUNEL and EM changes, immunohistochemistry failed to detect any changes in the ratio of bax to bcl-2 in tibial chondrocytes of STR/ort mice. Both bcl-2 and bax levels decreased with age in morphologically normal STR/ort and control CBA cartilage. None of the caspases tested for was detected in tibial chondrocytes of either strain.
Chondrocyte cell death is correlated with the progression of OA in STR/ort mice and has many of the morphological characteristics of classical apoptosis. Absence of changes in bax to bcl-2 ratio in STR/ort chondrocytes indicate that the mitochondrial pathway of apoptosis is unlikely to be involved. Failure to detect caspases could be due to low levels of enzyme expression, expression within a very brief time period, or to a caspase-independent mechanism of cell death.
确定在STR/ort骨关节炎（OA）小鼠模型中，软骨细胞凋亡是否在OA进展过程中发生。
对年轻和年老雄性STR/ort小鼠的膝关节进行连续冰冻切片（10微米），并对OA病变的严重程度进行分级。年龄和性别匹配的CBA小鼠用作对照。使用TUNEL法检测凋亡软骨细胞。使用电子显微镜（EM）检查超微结构变化。使用免疫组织化学研究与凋亡相关的生化标志物（bax、bcl-2和半胱天冬酶-3、-8和-9）的表达。
对STR/ort膝关节组织切片进行的TUNEL检测显示，胫骨内侧关节软骨中TUNEL阳性软骨细胞的数量与OA损伤的严重程度相关。这些细胞位于病变区域附近。在形态正常的STR/ort软骨或对照CBA软骨中仅偶尔检测到TUNEL阳性软骨细胞。对STR/ort胫骨软骨中局灶性骨关节炎病变附近的软骨细胞进行超微结构分析，发现大量异常细胞呈现出许多形态学变化。这些变化与经典凋亡中报道的变化相似，但在某些情况下有所不同。变化包括染色质分布异常、细胞收缩、膜泡形成以及细胞残余物（凋亡小体）在腔隙空间中的沉积。尽管有TUNEL和EM变化，但免疫组织化学未能检测到STR/ort小鼠胫骨软骨中bax与bcl-2比值的任何变化。在形态正常的STR/ort和对照CBA软骨中，bcl-2和bax水平均随年龄下降。在两种品系的胫骨软骨中均未检测到所检测的任何半胱天冬酶。
软骨细胞死亡与STR/ort小鼠OA的进展相关，并且具有许多经典凋亡的形态学特征。STR/ort软骨细胞中bax与bcl-2比值无变化表明凋亡的线粒体途径不太可能参与其中。未能检测到半胱天冬酶可能是由于酶表达水平低、在非常短的时间段内表达，或者是由于细胞死亡的半胱天冬酶非依赖性机制。
