Single-cell RNA sequencing analysis of human chondrocytes reveals cell–cell communication alterations mediated by interactive signaling pathways in osteoarthritis

Abstract

Objective: Osteoarthritis (OA) is a common joint disorder characterized by degenerative articular cartilage, subchondral bone remodeling, and inflammation. Increasing evidence suggests that the substantial crosstalk between cartilage and synovium is closely related to Osteoarthritis development, but the events that cause this degeneration remain unknown. This study aimed to explore the alterations in intercellular communication involved in the pathogenesis of Osteoarthritis using bioinformatics analysis.Methods: Single-cell transcriptome sequencing (scRNA-seq) profiles derived from articular cartilage tissue of patients with Osteoarthritis were downloaded from a public database. Chondrocyte heterogeneity was assessed using computational analysis, and cell type identification and clustering analysis were performed using the “FindClusters” function in the Seurat package. Intercellular communication networks, including major signaling inputs and outputs for cells, were predicted, and analyzed using CellChat.Results: Seven molecularly defined chondrocytes clusters (homeostatic chondrocytes, hypertrophic chondrocyte (HTC), pre-HTC, regulatory chondrocytes, fibro-chondrocytes (FC), pre-FC, and reparative chondrocyte) with different compositions were identified in the damaged cartilage. Compared to those in the intact cartilage, the overall cell–cell communication frequency and communication strength were remarkably increased in the damaged cartilage. The cellular communication among chondrocyte subtypes mediated by signaling pathways, such as PTN, VISFATIN, SPP1, and TGF-β, was selectively altered in Osteoarthritis. Moreover, we verified that SPP1 pathway enrichment scores increased, but VISFATIN pathway enrichment scores decreased based on the bulk rna-seq datasets in Osteoarthritis.Conclusion: Our results revealed alterations in cell–cell communication among OA-related chondrocyte subtypes that were mediated by specific signaling pathways, which might be a crucial underlying mechanism associated with Osteoarthritis progression.

Collagen and Alginate Hydrogels Support Chondrocytes Redifferentiation In Vitro without Supplementation of Exogenous Growth Factors

“…During pellet culture, cells are compacted and in close proximity to each other. It is well-known that cell-to-cell interactions can influence gene expression and matrix deposition. − This suggests that pellet culture does not fully replicate our model, in which cells within col/alg hydrogels are seeded as single cells and form aggregates only after 7 days of culture. To ensure the accuracy and integrity of our results, we opted to avoid using pellets as controls and instead designed our experiments to directly assess the impact of hydrogels on chondrocytes without the interference of external factors.…”

PTH treatment before cyclic joint loading improves cartilage health and attenuates load-induced osteoarthritis development in mice

“…Comparison of our differential gene expression and pathway analyses to recent single-cell RNA sequencing (scRNAseq) findings in cartilage (54)(55)(56)(57) allowed us to draw further insight into differential expression associated with loading and treatment. In the PTH-ALN group, cartilage had up-regulation of pathways related to extracellular matrix organization and collagen fibril organization, both associated with changes in Col2a1 and Comp gene expression.…”

“…While immune responses and regulation of inflammation in OA primarily occur through the synovial tissue signaling (58), recent transcriptomic-based studies have identified alterations in genes and signaling pathways related to immune signaling in chondrocytes (54)(55)(56)(57)59). Pathways containing genes linked to T cell receptor signaling and antigen presentation were down-regulated in cartilage at 1 week following loading in the PTH-ALN and PTH pretreatmentonly groups.…”

“…In scRNAseq, a chondrocyte phenotype, regulatory chondrocytes, was associated with early-stage OA progression and characterized by the expression of pathways related to T cell and B cell receptor signaling and antigen presentation (54). Regulatory chondrocytes play a regulatory role in OA progression and, given high expression of immune-specific markers found in this chondrocyte phenotype, are even speculated to have immunerelated capacities within the cartilage extracellular matrix (54,57). Suppression of the characteristic regulatory chondrocyte pathways with PTH-ALN treatment may suggest that modulation of regulatory chondrocyte signaling attenuates OA progression (57).…”

“…Regulatory chondrocytes play a regulatory role in OA progression and, given high expression of immune-specific markers found in this chondrocyte phenotype, are even speculated to have immunerelated capacities within the cartilage extracellular matrix (54,57). Suppression of the characteristic regulatory chondrocyte pathways with PTH-ALN treatment may suggest that modulation of regulatory chondrocyte signaling attenuates OA progression (57). Overall, PTH pretreatment suppressed gene expression related to immune signaling pathways in cartilage.…”