Novel Reactive Regeneration Chondrocytes Subpopulation with Microtubule Stabilization in Human Osteoarthritic Cartilage

Background: Chondrocytes (CHs) resident in cartilage suffer several detrimental events during the development of osteoarthritis (OA). Little is known regarding the complex cellular programs involved in the development of human OA. The aim of this study was to explore the underlying mechanism of regeneration of CHs involved in the pathological condition and the potential therapeutic stragegies of cartilage repair. Method: CHs were isolated from human cartilage in different OA stages and the high-resolution cellular architecture of human osteoarthritis was examined by applying single-cell RNA sequencing. The analysis of gene diffierential expression and gene set enrichment was untilized to reveal the relationship of cartilage regeneration and microtubule stabilization. Microtubule disatbilizer (nocodazole) and microtubule stabilizer (docetaxel) treated-human primary CHs and rats cartilage defect model were used to investige the effects and downstream signaling pathway of microtubule stabilization on cartilage regeneration.Finding: CHs were mapped to six types of subpopulations and the data indicated the imbalance between an increase degeneration and disruption of regeneration involved in OA progression. Surperisely, a novel cell subpopulation was identified, namely reactive regeneration CH (ReRegC), which was characterized by the CH regenerative capability, stem cell potency and the activated microtubule (MT) process in the situation of injury. Furthermore, the data indicated that MT stabilization could be viewed as an effective strategy to promote cartilage regeneration by inhibition of YAP activity.Interpretion: The identification of ReRegC and the its association with MT stabilization highlighted a novel mechanism for cartilage regeneration and chondrogenesis.Funding: This work was supported by National Key R&D Program of China (2018YFC1105904), Key Program of NSFC (81730067), National Science Foundation of China (81772335, 81941009, 81802196), Natural Science Foundation of Jiangsu Province, China (BK20180127), Jiangsu Provincial Key Medical Talent Foundation, Six Talent Peaks Project of Jiangsu Province (WSW- 079).Declaration of Interest: None declared.Ethical Approval: The collection of and experimental protocols using human articular cartilage and synovium were approved by the Ethical Committee of the Nanjing Drum Tower Hospital, the Affiliated Hospital of Nanjing University Medical School (2020-156-01).