Single-cell transcriptomics identifies chondrocyte differentiation dynamics in vivo and in vitro.

Area of Science:

• Developmental Biology
• Regenerative Medicine
• Stem Cell Biology

Background:

• Current in vitro chondrogenesis methods yield heterogeneous cell states due to off-target differentiation.
• Lack of comparison with human embryonic tissue hinders detailed evaluation of in vitro chondrocytes.
• Advancing musculoskeletal disease modeling and regenerative medicine requires robust in vitro models.

Purpose of the Study:

• To create an atlas of endochondral ossification using single-cell RNA sequencing (scRNA-seq) of embryonic long bones.
• To evaluate existing in vitro chondrogenesis protocols and identify sources of off-target differentiation.
• To develop a strategy for improving in vitro chondrocyte development by targeting specific transcription factors.

Main Methods:

• Performed scRNA-seq on embryonic long bones and integrated public datasets to build an endochondral ossification atlas.
• Evaluated human cell line-based chondrogenesis protocols and applied single-nuclear RNA sequencing (snRNA-seq) to a human embryonic stem cell protocol.
• Utilized trajectory alignment with in vivo data to analyze in vitro differentiation pathways and identified FOXO1 as a key regulator.

Main Results:

• Discovered significant variability in cell states produced by different in vitro chondrogenesis protocols.
• Identified off-target differentiation in vitro by comparing with the developmental atlas.
• Inhibition of FOXO1, a transcription factor found in embryonic osteoblasts and in vitro cells, increased chondrocyte transcripts.

Conclusions:

• Established a framework for enhancing in vitro chondrogenesis by leveraging developmental data.
• The study provides insights into improving the fidelity of lab-grown chondrocytes for research and therapeutic applications.
• Targeting specific developmental pathways, like FOXO1, can optimize in vitro cell differentiation for regenerative medicine.