BCN MedTech, Universitat Pompeu Fabra, C/ de la Mercè, 12, Barcelona, 08002, Catalonia, Spain.
Tissue Engineering for Orthopaedics & Mechanobiology, Bone & Joint Program, Department for BioMedical Research (DBMR), Medical Faculty, University of Bern, Murtenstrasse 35, Bern, 3008, Bern, Switzerland; Graduate School for Cellular and Biomedical Sciences (GCB), University of Bern, Mittelstrasse 43, Bern, 3012, Bern, Switzerland.
Phys Life Rev. 2024 Mar;48:205-221. doi: 10.1016/j.plrev.2024.02.003. Epub 2024 Feb 12.
In primary or idiopathic osteoarthritis (OA), it is unclear which factors trigger the shift of articular chondrocyte activity from pro-anabolic to pro-catabolic. In fact, there is a controversy about the aetiology of primary OA, either mechanical or inflammatory. Chondrocytes are mechanosensitive cells, that integrate mechanical stimuli into cellular responses in a process known as mechanotransduction. Mechanotransduction occurs thanks to the activation of mechanosensors, a set of specialized proteins that convert physical cues into intracellular signalling cascades. Moderate levels of mechanical loads maintain normal tissue function and have anti-inflammatory effects. In contrast, mechanical over- or under-loading might lead to cartilage destruction and increased expression of pro-inflammatory cytokines. Simultaneously, mechanotransduction processes can regulate and be regulated by pro- and anti-inflammatory soluble mediators, both local (cells of the same joint, i.e., the chondrocytes themselves, infiltrating macrophages, fibroblasts or osteoclasts) and systemic (from other tissues, e.g., adipokines). Thus, the complex process of mechanotransduction might be altered in OA, so that cartilage-preserving chondrocytes adopt a different sensitivity to mechanical signals, and mechanic stimuli positively transduced in the healthy cartilage may become deleterious under OA conditions. This review aims to provide an overview of how the biochemical exposome of chondrocytes can alter important mechanotransduction processes in these cells. Four principal mechanosensors, i.e., integrins, Ca channels, primary cilium and Wnt signalling (canonical and non-canonical) were targeted. For each of these mechanosensors, a brief summary of the response to mechanical loads under healthy or OA conditions is followed by a concise overview of published works that focus on the further regulation of the mechanotransduction pathways by biochemical factors. In conclusion, this paper discusses and explores how biological mediators influence the differential behaviour of chondrocytes under mechanical loads in healthy and primary OA.
在原发性或特发性骨关节炎(OA)中,尚不清楚哪些因素会引发关节软骨细胞活动从合成代谢向分解代谢转变。事实上,原发性 OA 的病因存在争议,既有机械性的也有炎症性的。软骨细胞是机械敏感细胞,它们将机械刺激整合到细胞反应中,这个过程称为机械转导。机械转导是通过机械感受器的激活来实现的,机械感受器是一组专门的蛋白质,可将物理线索转化为细胞内信号级联。适度的机械负荷水平可维持正常组织功能并具有抗炎作用。相比之下,过度或不足的机械负荷可能导致软骨破坏和促炎细胞因子表达增加。同时,机械转导过程可以被促炎和抗炎可溶性介质调节和调控,这些介质既有局部的(同一关节的细胞,即软骨细胞本身、浸润的巨噬细胞、成纤维细胞或破骨细胞)也有全身的(来自其他组织,如脂肪细胞因子)。因此,OA 中机械转导的复杂过程可能会发生改变,从而使具有软骨保护作用的软骨细胞对机械信号的敏感性不同,在健康软骨中被积极转导的机械刺激在 OA 条件下可能变得有害。本综述旨在概述软骨细胞的生化外显子组如何改变这些细胞中重要的机械转导过程。本文针对四个主要的机械感受器,即整合素、Ca 通道、初级纤毛和 Wnt 信号(经典和非经典)进行了探讨。对于每个机械感受器,简要总结了在健康和 OA 条件下对机械负荷的反应,然后简要概述了专注于生化因子对机械转导途径的进一步调控的已发表研究工作。总之,本文讨论并探讨了生物介质如何影响健康和原发性 OA 下软骨细胞在机械负荷下的差异行为。