Single-cell RNA-seq analysis identifies meniscus progenitors and reveals the progression of meniscus degeneration

We identified seven clusters in healthy human meniscus, including five empirically-defined populations and two novel populations. Pseudotime analysis showed EC and FCP existed at the pseudospace trajectory start. MCAM (CD146) was highly expressed in two clusters. CD146+ meniscus cells differentiated into osteoblasts and adipocytes and formed colonies. We identified changes in the proportions of degenerated meniscus cell clusters and found a cluster specific to degenerative meniscus with progenitor cell characteristics. The reconstruction of four progenitor cell clusters indicated that FCP differentiation into DegP was an aberrant process. Interleukin-1ß stimulation in healthy human meniscus cells decreased CD146+ cells and increased CD318+ cells, while TGFß1 attenuated the increase in CD318+ cells in degenerated meniscus cells. Overall design: scRNA-seq was used to identify cell subsets and their gene signatures in healthy human and degenerated meniscus cells