Single-Cell RNA Sequencing of In Vitro Expanded Chondrocytes: MSC-Like Cells With No Evidence of Distinct Subsets:

ObjectiveTo investigate the heterogeneity of in vitro expanded chondrocytes used for autologous chondrocyte implantation.MethodsHuman articular chondrocytes were expanded in vitro for 14 days, sorted into 86 single cells using fluorescence-activated cell sorting and subjected to single-cell RNA sequencing. Principal component, Cross R2 hierarchical clustering, and differential gene expression analyses were used for data evaluation. Flow cytometry and single-cell RT-qPCR (reverse transcriptase quantitative polymerase chain reaction) was used to validate the results of the RNA sequencing data Polyclonal chondrocyte populations from the same donor were differentiated in vitro toward the osteogenic and adipogenic lineages.ResultsThere was considerable variation in gene expression between individual cells, but we found no evidence for separate cell subpopulations based on principal component, hierarchical clustering, and differential gene expression analysis. Most of the cells expressed all the markers definin...