Core binding factor β preserves early chondrogenic identity and prevents hypertrophic transition in cartilage organoids formation

Human-induced pluripotent stem cells (hiPSCs) represent a promising cell source for cartilage regeneration because of their self-renewal capacity and chondrogenic potential. However, the propensity of hiPSC-derived chondrocytes to undergo hypertrophic maturation remains a major obstacle to generating stable articular cartilage. Here, we identified core binding factor β (CBFβ) as a critical regulator of early chondrogenic identity and a suppressor of hypertrophic transition during hiPSC-derived cartilage organoid formation. CBFβ expression was markedly diminished in degenerative articular cartilage from both human osteoarthritis (OA) specimens and mouse OA models, and cartilage-specific ablation of Cbfβ accelerated cartilage structural deterioration and matrix loss. Notably, CBFβ was secreted by non-mineralizing cells, including chondrocytes and vascular smooth muscle cells, suggesting an autocrine/paracrine regulatory role. Pharmacological inhibition with Brefeldin A reduced extracellular CBFβ levels, whereas blockade of exosome release by GW4869 had minimal effect, indicating a secretion-associated mechanism independent of exosomes. Recombinant human CBFβ (rhCBFβ) treatment enhanced the chondrocyte phenotype by upregulating early chondrogenic markers (SOX9, COL2A1) while suppressing hypertrophic and catabolic markers ( RUNX2, MMP13). In hiPSC-derived cartilage organoids, rhCBFβ enhanced matrix deposition and increased COL2A1 and SOX9 expression. Transcriptomic profiling and qRT-PCR validation further demonstrated that rhCBFβ activated cartilage matrix-associated and anti-hypertrophic transcriptional programs, including upregulation of PTHRP , HIF1α , HDAC4, MGP , CILP , and ALK5 , together with suppression of RUNX2. Collectively, these findings establish CBFβ as a key regulator of articular cartilage homeostasis and highlights its therapeutic potential for cartilage regeneration in OA. The ability of rhCBFβ to preserve early chondrogenic identity while preventing hypertrophic maturation offers a promising strategy for cartilage tissue engineering. Further preclinical studies are warranted to evaluate its efficacy and accelerate clinical translation for OA therapy.