Chondrocyte death after mechanically overloading degenerated human intervertebral disk explants is associated with a structurally impaired pericellular matrix

A type VI collagen‐rich pericellular matrix (PCM) encloses both intervertebral disk (IVD) and articular cartilage chondrocytes. In the latter, the PCM protects the chondrocytes from mechanical overload, whereas tissue degeneration is associated with PCM destruction. As little is known about the IVD PCM, we investigated chondrocyte survival after mechanical overload as well as PCM structural integrity as a function of clinical tissue degeneration. The hypothesis was that IVD degeneration may affect PCM integrity and overload‐related chondrocyte survival. Cylindrical human IVD explants from patients undergoing surgical procedures for lumbar disk degeneration, disk prolapse, or spinal trauma were generated and scored. Mechanical overload was applied by single uniaxial 50% compression followed by immediate release, and the explants were live–dead stained (n = 20 explants). Type VI collagen, the major PCM component, was fluorescent stained and the extent was determined, in which individual cells were enclosed by a recognizable PCM; this was termed PCM fraction. More than 50% of chondrocytes in all degenerative IVD explants displayed <25% PCM fraction and a lower PCM fraction correlated with higher cell numbers (p < 0.001), suggesting a PCM structural impairment in IVD degeneration that is associated with chondrocyte clustering. Mechanical overload‐induced significantly increased cell death (p = 0.005), and the PCM fraction was significantly lower in overload‐induced cell death than in live cells (p = 0.042), suggesting that a fully present PCM has a protective role in mechanical overload. Collectively, human IVD degeneration is associated with a structural impairment of the PCM, which may promote cell death under mechanical overload.     

浙江省新生儿异戊酸血症筛查及临床分析

目的: 了解浙江省新生儿异戊酸血症（IVA）的患病率、临床特征及基因突变特点。方法: 采用串联质谱技术对2009年1月至2019年12月浙江省新生儿疾病筛查中心的3 510 004名新生儿进行遗传代谢病筛查,结合尿有机酸分析及IVD基因检测进行IVA诊断。IVA确诊患儿进行饮食和生活管理,补充左卡尼汀和甘氨酸治疗,长期随访观察并评估患儿的生长和智能发育情况。结果: 共确诊IVA患儿15例,3例为急性新生儿型,其余无临床症状,患病率为1/234 000。所有患儿的血异戊酰基肉碱浓度均不同程度增加。12例患儿进行尿有机酸分析,其中11例异戊酰甘氨酸升高,4例伴3-羟基异戊酸升高。11例患儿进行基因检测,9例为IVD基因复合杂合突变,1例为IVD基因纯合突变,1例只检测出一个IVD基因位点。发现IVD基因突变19种（错义突变14种、内含子突变3种、移码突变1种、同义突变1种）,其中11种突变未见报道。15例患儿中1例死亡,2例在当地随访,其余暂未发现明显临床症状（随访时间2~79个月）,其中3例生长发育落后,其他患儿体格和智力发育均正常。结论: IVA临床表现无特异性,基因谱分散。使用串联质谱开展IVA新生儿筛查,实现早期诊断和治疗能纠正代谢缺陷及其引发的病理生理改变。