Efficient Production of Chondrocyte Particles from Human iPSC-Derived Chondroprogenitors Using a Plate-Based Cell Self-Aggregation Technique

The limited capacity of articular cartilage for self-repair is a critical challenge in orthopedic medicine. Here, we aimed to develop a simplified method of generating chondrocyte particles from human-induced pluripotent stem cell-derived expandable limb-bud mesenchymal cells (ExpLBM) using a cell self-aggregation technique (CAT). ExpLBM cells were induced to form chondrocyte particles through a stepwise differentiation protocol performed on a CAT plate (prevelex-CAT (R)), which enables efficient and consistent production of an arbitrary number of uniformly sized particles. Histological and immunohistochemical analyses confirmed that the generated chondrocyte particles expressed key cartilage markers, such as type II collagen and aggrecan, but not hypertrophic markers, such as type X collagen. Additionally, when these particles were transplanted into osteochondral defects in rats with X-linked severe combined immunodeficiency, they demonstrated successful engraftment and extracellular matrix production, as evidenced by Safranin O and Toluidine Blue staining. These data suggest that the plate-based CAT system offers a robust and scalable approach to produce a large number of chondrocyte particles in a simplified and efficient manner, with potential application to cartilage regeneration. Future studies will focus on refining the system and exploring its clinical applications to the treatment of cartilage defects.