Sorbonne Université, INSERM, Centre de Recherche Saint-Antoine (CRSA), F-75012, Paris, France.
Servier Research Institute, F-78290, Croissy-sur-Seine, France.
Osteoarthritis Cartilage. 2021 Feb;29(2):257-268. doi: 10.1016/j.joca.2020.10.013. Epub 2020 Dec 7.
We hypothesize that chondrocytes from the deepest articular cartilage layer are pivotal in maintaining cartilage integrity and that the modification of their prehypertrophic phenotype to a hypertrophic phenotype will drive cartilage degradation in osteoarthritis.
Murine immature articular chondrocytes (iMACs) were successively cultured into three different culture media to induce a progressive hypertrophic differentiation. Chondrocyte were phenotypically characterized by whole-genome microarray analysis. The expression of IL-34 and its receptors PTPRZ1 and CSF1R in chondrocytes and in human osteoarthritis tissues was assessed by RT-qPCR, ELISA and immunohistochemistry. The expression of bone remodeling and angiogenesis factors and the cell response to IL-1β and IL-34 were investigated by RT-qPCR and ELISA.
Whole-genome microarray analysis showed that iMACs, prehypertrophic and hypertrophic chondrocytes each displayed a specific phenotype. IL-1β induced a stronger catabolic effect in prehypertrophic chondrocytes than in iMACs. Hypertrophic differentiation of prehypertrophic chondrocytes increased Bmp-2 (95%CI [0.78; 1.98]), Bmp-4 (95%CI [0.89; 1.59]), Cxcl12 (95%CI [2.19; 5.41]), CCL2 (95%CI [3.59; 11.86]), Mmp 3 (95%CI [10.29; 32.14]) and Vegf mRNA expression (95%CI [0.20; 1.74]). Microarray analysis identified IL-34, PTPRZ1 and CSFR1 as being strongly overexpressed in hypertrophic chondrocytes. IL-34 was released by human osteoarthritis cartilage; its receptors were expressed in human osteoarthritis tissues. IL-34 stimulated CCL2 and MMP13 in osteoblasts and hypertrophic chondrocytes but not in iMACs or prehypertrophic chondrocytes.
Our results identify prehypertrophic chondrocytes as being potentially pivotal in the control of cartilage and subchondral bone integrity. Their differentiation into hypertrophic chondrocytes initiates a remodeling program in which IL-34 may be involved.
我们假设来自最深处关节软骨层的软骨细胞对于维持软骨完整性至关重要，并且它们的预肥大表型向肥大表型的转变将驱动骨关节炎中的软骨降解。
我们连续将幼稚关节软骨细胞（iMAC）培养到三种不同的培养基中，以诱导其进行渐进性肥大分化。通过全基因组微阵列分析对软骨细胞的表型进行特征分析。通过 RT-qPCR、ELISA 和免疫组织化学评估软骨细胞和人骨关节炎组织中 IL-34 及其受体 PTPRZ1 和 CSF1R 的表达。通过 RT-qPCR 和 ELISA 研究骨重塑和血管生成因子的表达以及细胞对 IL-1β 和 IL-34 的反应。
全基因组微阵列分析显示，iMAC、预肥大和肥大软骨细胞各自表现出特定的表型。与 iMAC 相比，IL-1β 在预肥大软骨细胞中引起更强的分解代谢作用。预肥大软骨细胞的肥大分化增加了 Bmp-2（95%CI [0.78；1.98]）、Bmp-4（95%CI [0.89；1.59]）、Cxcl12（95%CI [2.19；5.41]）、CCL2（95%CI [3.59；11.86]）、Mmp3（95%CI [10.29；32.14]）和 Vegf mRNA 表达（95%CI [0.20；1.74]）。微阵列分析鉴定出 IL-34、PTPRZ1 和 CSFR1 在肥大软骨细胞中强烈过表达。IL-34 由人骨关节炎软骨释放；其受体在人骨关节炎组织中表达。IL-34 刺激成骨细胞和肥大软骨细胞中的 CCL2 和 MMP13，但不刺激 iMAC 或预肥大软骨细胞。
我们的研究结果确定预肥大软骨细胞在控制软骨和软骨下骨完整性方面具有潜在的关键作用。它们向肥大软骨细胞的分化启动了一个重塑程序，其中 IL-34 可能参与其中。
