Mutations in Slc26a2 cause a spectrum of autosomal-recessive chondrodysplasia with a significant and negligible influence on the quality of life. It has been reported that Slc26a2 deficiency triggers the ATF6 branch of the UPR, which may, in turn, activate the negative regulator of the FGFR3 signaling pathway. However, the correlation between the deletion of Slc26a2 and the augmentation of downstream phosphorylation of FGFR3 has not been investigated in vivo. First, we constructed Slc26a2 and Fgfr3 double knockout mouse lines and observed gross views of the born mice and histological staining of the tibial growth plates. The second approach was to construct tamoxifen-inducible Cre-ER^T2 mouse models to replicate SLC26A2-related non-lethal dysplastic conditions. Pharmacological intervention was performed by administering the FGFR3 inhibitor NVP-BGJ398. The effect of NVP-BGJ398 on chondrocytes was assessed by Alcian blue staining, proliferation, apoptosis, and chondrocyte-specific markers and then verified by western blotting for variations in the downstream markers of FGFR3. The growth process was detected using X-rays, micro-CT examination, histomorphometry staining of growth plates, and immunofluorescence. Genetic ablation of Fgfr3 in embryonic Slc26a2-deficient chondrocytes slightly attenuated chondrodysplasia. Subsequently, in the constructed mild dysplasia model, we found that postnatal intervention with Fgfr3 gene in Slc26a2-deficient chondrocytes partially alleviated chondrodysplasia. In chondrocyte assays, NVP-BGJ398 suppressed the defective phenotype of Slc26a2-deficient chondrocytes and restored the phosphorylation downstream of FGFR3 in a concentration-dependent manner. In addition, in vivo experiments showed significant alleviation of impaired chondrocyte differentiation, and micro-CT analysis showed a clear improvement in trabecular bone microarchitectural parameters. Our results suggested that inhibition of FGFR3 signaling pathway overactivation and NVP-BGJ398 has promising therapeutic implications for the development of SLC26A2-related skeletal diseases in humans. Our data provide genetic and pharmacological evidence that targeting FGFR3 signaling via NVP-BGJ398 could be a route for the treatment of SLC26A2-associated skeletal disorders, which promisingly advances translational applications and therapeutic development.

Articular cartilage, a highly specialized avascular connective tissue, forms a smooth, load-bearing surface on articulating bone ends to facilitate frictionless joint movement. While cell-derived small extracellular vesicles (sEVs) have emerged as promising therapeutic biomaterials for cartilage regeneration, two major limitations impede their clinical translation: the scarcity of autologous donor cells, and suboptimal functional efficacy of conventional sEVs preparations. We established an induced pluripotent stem cell (iPSC)-based approach by differentiating iPSCs into chondrocytes (designated iChondrocytes). After characterizing the derived iChondrocytes, we isolated their secreted sEVs (iChondrocyte-sEVs) and systematically evaluated their therapeutic effects and underlying mechanisms in cartilage regeneration through in vitro and in vivo experiments. Functional assays revealed that iChondrocyte-sEVs significantly enhanced chondrogenic differentiation, stimulated extracellular matrix (ECM) deposition, and maintained chondrocyte homeostasis. In murine osteoarthritis (OA) models, intra-articularly administered iChondrocyte-sEVs efficiently penetrated deep cartilage layers, alleviated OA-associated pathological changes, and restored cartilage microstructure and biomechanical properties to near-normal levels. Furthermore, therapeutic intervention with iChondrocyte-sEVs resulted in significant improvements in joint mobility and motor function in OA-affected mice. Proteomic profiling identified serine racemase (SRR) as a key upregulated protein in iChondrocyte-sEVs. Mechanistic studies suggested that SRR may contribute to cartilage regeneration by suppressing the P38/ERK signaling pathway. This study highlights the significant therapeutic potential of iChondrocyte-sEVs, demonstrating their ability to promote both structural and functional regeneration of articular cartilage. These findings suggest a promising novel strategy for OA treatment. This study highlights the therapeutic potential of iChondrocyte-sEVs, demonstrating their ability to promote both structural and functional regeneration of articular cartilage. These findings indicate a clinical conversion potential for OA treatment.