Pre-transplantational Control of the Post-transplantational Fate of Human Pluripotent Stem Cell-Derived Cartilage

Summary: Cartilage pellets generated from ectomesenchymal progeny of human pluripotent stem cells (hPSCs) in vitro eventually show signs of commitment of chondrocytes to hypertrophic differentiation. When transplanted subcutaneously, most of the surviving pellets were fully mineralized by 8 weeks. In contrast, treatment with the adenylyl cyclase activator, forskolin, in vitro resulted in slightly enlarged cartilage pellets containing an increased proportion of proliferating immature chondrocytes that expressed very low levels of hypertrophic/terminally matured chondrocyte-specific genes. Forskolin treatment also enhanced hyaline cartilage formation by reducing type I collagen gene expression and increasing sulfated glycosaminoglycan accumulation in the developed cartilage. Chondrogenic mesoderm from hPSCs and dedifferentiated nasal chondrocytes responded similarly to forskolin. Furthermore, forskolin treatment in vitro increased the frequency at which the cartilage pellets maintained unmineralized chondrocytes after subcutaneous transplantation. Thus, the post-transplantational fate of chondrocytes originating from hPSC-derived chondroprogenitors can be controlled during their genesis in vitro. : In this article, Naoki Nakayama and colleagues show that suppression of hypertrophic differentiation and terminal maturation of chondrocytes by forskolin/cAMP treatment during in vitro chondrogenesis from human pluripotent stem cell-derived chondroprogenitors leads to the formation of cartilage consisting of an increased proportion of proliferating, immature chondrocytes with significantly improved ability to be maintained in an unmineralized state in vivo. Keywords: pluripotent stem cell, neural crest, paraxial mesoderm, chondrocyte, hypertrophy, cAMP, forskolin, cartilage, mineralization, endochondral ossification