骨关节炎(OA)是老年人的常见疾病,对生活质量和寿命产生不利影响。其特征在于关节软骨的疼痛性丧失,并且是多基因和多因素的。全基因组关联扫描已经突出显示了90多个骨关节炎遗传信号,其中一些位于或接近高度可信的候选基因。一个实例是与基质Gla蛋白基因MGP内和附近的多态性的关联。我们着手对该基因进行功能研究。
从软骨中提取核酸,髌下脂肪垫,滑膜,骨小梁,来自OA患者以及接受软骨形成的间充质干细胞(MSC)的梯形和外周血。通过定量PCR(qPCR)检测MGP的表达,RNA测序和等位基因表达失衡(AEI)分析。通过使用RNA干扰(RNAi)敲低MGP表达和通过qPCR评估对一系列基因的影响,在软骨细胞中去除基质Gla蛋白。
MGP在关节组织中表达,从MSCs培养的血液和软骨细胞。在患病的软骨与非患病的软骨中存在较高的表达。与OA相关的多态性也与MGP的表达相关,赋予OA风险的等位基因在软骨中的表达显着降低,脂肪垫和滑膜,但在血液中的表达增加。基质Gla蛋白的耗尽对大多数测试的基因有显著影响,随着编码降解软骨的酶的分解代谢基因的表达增加。
MGP表达受到与OA缔合信号相关的顺式作用调节剂的影响。这些在一系列关节组织中具有活性,但在软骨中具有特别强的作用。在血液中观察到相反的效果,突出了该基因表达调控的上下文特异性。软骨软骨细胞遗传缺陷的重述是促分解代谢。
Osteoarthritis (OA) is a common disease of older individuals that impacts detrimentally on the quality and the length of life. It is characterised by the painful loss of articular cartilage and is polygenic and multifactorial. Genome-wide association scans have highlighted over 90 osteoarthritis genetic signals, some of which reside within or close to highly plausible candidate genes. An example is an association to polymorphisms within and adjacent to the matrix Gla protein gene MGP. We set out to undertake a functional study of this gene.
Nucleic acid was extracted from cartilage, infrapatellar fat pad, synovium, trabecular bone, trapezium and peripheral whole blood from OA patients and also from mesenchymal stem cells (MSCs) subjected to chondrogenesis. Expression of MGP was measured by quantitative PCR (qPCR), RNA-sequencing and allelic expression imbalance (AEI) analysis. Matrix Gla protein was depleted in chondrocytes by knocking down MGP expression using RNA interference (RNAi) and the effect on a range of genes assessed by qPCR.
MGP is expressed in joint tissues, blood and chondrocytes cultured from MSCs. There is a higher expression in diseased versus non-diseased cartilage. Polymorphisms that are associated with OA also correlate with the expression of MGP, with the OA risk-conferring allele showing significantly reduced expression in cartilage, fat pad and synovium but increased expression in blood. Depletion of Matrix Gla protein had a significant effect on the majority of genes tested, with an increased expression of catabolic genes that encode enzymes that degrade cartilage.
MGP expression is subject to cis-acting regulators that correlate with the OA association signal. These are active in a range of joint tissues but have effects which are particularly strong in cartilage. An opposite effect is observed in blood, highlighting the context-specific nature of the regulation of this gene\'s expression. Recapitulation of the genetic deficit in cartilage chondrocytes is pro-catabolic.