Long-term expandable SOX9+ chondrogenic ectomesenchymal cells from human pluripotent stem cells

Purpose: We have succeeded in the generation and long-term expansion of SOX9-expressing CD271+PDGFRa+CD73+ chondrogenic ectomesenchymal cells from the PAX3/SOX10/FOXD3-expressing MIXL1-CD271hiPDGFRaloCD73- neural crest-like progeny of human pluripotent stem cells in a chemically defined medium supplemented with Nodal/Activin/TGFb inhibitor (SB) and FGF2 (hereafter called FSB). When “primed” with TGFb, such cells efficiently formed translucent cartilage particles, which were completely mineralized in 12 weeks in immunocompromized mice. Under the FSB condition, ectomesenchymal cells were expandable without loss of chondrogenic potential for at least 16 passages, maintained normal karyotype for at least 10 passages, which any conditions deviated from it (e.g. FGF2 alone or SB alone) failed to support. In order to address the molecular basis of such effects of FSB, a series of RNA-seq experiments were carried out. Methods: We generated and compared the transcriptome profiles of human ectomesenchymal cells expanded under FSB with those cultured under FSB first then under FGF2 alone (F). As a control, we also generated transcriptome of ectomesenchymal cells expanded from the begining under F conditions. RNA-sequencing libraries were prepared using a SureSelect Strand Specific RNA Library Preparation kit (Agilent technologies, Santa Clara, CA). Sequencing was performed on an Illumina HiSeq 1500 using a TruSeq Rapid SBS kit (Illumina, San Diego, CA) in a 50-base single-end mode. Sequenced reads were mapped against the human reference genome (GRCh37), using TopHat v2.0.12 (