GDF5+ chondroprogenitors derived from human pluripotent stem cells, which resemble embryonic teno/ligamento-genic cells, preferentially form permanent chondrocytes

Background: Human pluripotent stem cells (hPSCs) give rise to chondrogenic activity in culture. Such activity was found in mesodermal and neural crest like progeny of hPSCs, and readily expanded as SOX9+ msenchymal cells in a medium containing FGF2. However, once expanded, the type of chondrocytes they perfer to form is growth plate-ike transient chondrocytes that are destined to form bone. However, we have recently developed a method to generate GDF5+ mesenchymal cells from such SOX9+ cells which ehibit activity to preferentially form articular-like permanent chondrocytes. The aim of the present prospective follow-up study was to reveal the cell-type and developmental origin of the GDF5+ cells as well as the SOX9+ cells. Methods: Paraxial mesoderm was generated from human PSCs, purified by FACS, and expanded to generate SOX9+ chondroprogenitors. Then, the SOX9+ cells were further differentiated into joint progenitor-like GDF5+ chondroprogenitors. These two chondroprogenitors were subjcted to bulk RNA-seq. Results: Based on the transcriptomic data, we examined differentially expressed genes, cell-type deconvolution analysis, and cell-type correlation analysis. The results suggested that GDF5+ cells might contain a teno/ligamento-genic potential (e.g., SCX+ cells), while SOX9+ cells were related to (neural crest-derived) ectomesenchymal chondroprogenitors. The followup biological analyses indicated as follows. The fast-growing SOX9+ cells formed cartilage that expressed chondrocyte hypertrophy markers and was readily mineralized after ectopic transplantation. In contrast, the slowly-growing GDF5+ cells were derived from SOX9+ cells. They formed cartilage that tended to express low to no chondrocyte hypertrophy markers, while expressing PRG4, a marker of embryonic articular chondrocytes, and to remain largely unmineralized in vivo. Conclusions: Our results imply that GDF5+ cells specified to generate permanent-like cartilage are likely to emerge in association with the commitment of SOX9+ cells to the tendon/ligament lineage. Overall design: Bulk RNA-seq data of 4 SOX9+ chondogenic cells and 4 GDF5+ chondrogenic cells generated independently from human pluripotent stem cells were generated by deep sequencing.