Exploring the Mechanism of Microfracture in the Treatment of Porcine Full-Thickness Cartilage Defect

Background: Microfracture has the most extensive clinical application because of its advantages of a single operation, unified process, and low operation cost. Because research on the repair mechanism of microfractures in the treatment of cartilage defects is not in-depth, this study aimed to elucidate the mechanism. Purpose: To identify the characteristic cell subsets at different repair stages after microfracture, systematically analyze the repair process of the defect area after microfracture, and investigate the mechanism of fibrocartilage repair. Study Design: Descriptive laboratory study. Methods: Full-thickness articular cartilage defects and microfractures was established in the right knee of Bama miniature pigs. Single-cell transcriptional assays were used to identify the characteristics of cells isolated from healthy articular cartilage and regenerated tissues. Results: Microfractures induced mature fibrous repair in the full-thickness cartilage defect six months after surgery, while early stages of repair occurred within six weeks. Based on single-cell sequencing results, eight subsets and specific marker genes were identified. Two processes may occur after microfracture: normal hyaline cartilage regeneration and abnormal fibrocartilage repair. Regulatory chondrocytes, proliferative chondrocytes and cartilage progenitor cells (CPCs) may play important roles in the normal regeneration process. During abnormal repair, CPCs and skeletal stem cells may have different functions, and macrophages and endothelial cells may play important regulatory roles in the formation of fibrochondrocytes. Conclusions: Using single-cell transcriptome sequencing, this study investigated the tissue regeneration process and identified key cell subsets after microfracture. Clinical Relevance: These results provide future targets for optimizing the repair effect of microfracture.