ESPE Yearbook of Paediatric Endocrinology

Nat Commun. 2021 Jan 13;12(1):362 Abstract: https://pubmed.ncbi.nlm.nih.gov/33441552/

In brief: Heterogenous differentiation patterns and low yields limit the use of human induced pluripotent stem cells (hiPSCs) for the generation of cartilage. In the present work, bulk- and single cell RNA sequencing during chondrogenic differentiation were used to identify regulatory networks responsible for these unintended effects. An improved protocol for highly specific chondrocyte differentiation was established based on these data.

Comment: The discovery of human induced pluripotent stem cells has revolutionized the field of regenerative therapies. While major progress has been made in conditions such as macular degeneration or type I diabetes, generation of chondrocytes and functional cartilage remains a major challenge. Low cellular yield, hypertrophy and non-cartilaginous populations limit advances in hiPSC-based applications for cartilage regeneration.

Wu et al. systematically analyzed hiPSC cultures under chondrogenic differentiation and identified neural- and melanocyte-like cells as major off-target populations under current standard protocols. Interestingly, specific WNT signaling at major differentiation branchpoints was shown to be causative for both off-target differentiation as well as for unintended effects such as chondrocyte hypertrophy. By application of a WNT-inhibitor during hiPSC pellet cultures, improved homogeneity and GAG production could be achieved. In addition, the purity of chondrocyte cultures allowed the identification of novel hub genes associated with chondrogenesis such as C1QL1.

In summary, the presented work tackled several limitations of hiPSC-based chondrocyte generation in a targeted experimental setup based on state-of-the art methodology including single cell transcriptomics. In addition to the achieved progress in cartilage regeneration research, they describe a prototype study for analytic optimization of suboptimal results in the use of hiPSCs that may further progress in other fields of stem cell research.