Protein phosphatase SCP4 regulates temporomandibular joint cartilage development via glucose metabolism.

OBJECTIVE

Despite the growing evidence supporting the regulatory role of small carboxy-terminal domain (CTD) phosphatase 4 (SCP4) in metabolic pathways, limited knowledge exists concerning its involvement and molecular basis in temporomandibular joint (TMJ) cartilage growth, development, and homeostasis maintenance. Therefore, this study aims to investigate the role of SCP4 in chondrogenesis in condylar cartilage.

METHODS

We generated chondrocyte-specific SCP4 conditional knockout mice (SCP4Col2Cre). Whole skeletal staining, ABH/OG or HE staining, and immunohistochemistry were employed to compare chondrocyte differentiation and cartilage development between SCP4Col2Cre and Cre-negative mice during prenatal and postnatal periods. The impact of SCP4 on subchondral bone in mice was assessed using Micro-CT. Additionally, relevant biological functions were evaluated by KEGG and GO enrichment analysis, which further confirmed immunohistochemical staining, Western Blot, RT-PCR and Seahorse experiment.

RESULTS

Our findings demonstrated that the deficiency of SCP4 in chondrocytes resulted in defects in condylar chondrogenesis and impaired matrix production. Accordingly, the SCP4Col2Cre mice exhibited a significant decrease in bone volume fraction (BV/TV) and trabecular thickness (Tb.Th), with an increase in trabecular separation (Tb.Sp). Furthermore, RNA-seq analysis showed the impact of SCP4 deficiency on glucose metabolism. Subsequently, we confirmed that the deficiency of SCP4 resulted in aberrant regulation of glucose transporter 1 (Glut1) and other glucose metabolism-related gene expression throughout prenatal and postnatal development in vivo and in vitro. We further demonstrated in vitro that the deletion of SCP4 led to increased ATP production and extracellular acidification rate (ECAR) levels, while concurrently reducing oxygen consumption rate (OCR) levels.

CONCLUSION

Our study emphasizes the crucial role of SCP4 in regulating prenatal and postnatal TMJ cartilage development, partly through aberrant upregulation of Glut1-mediated glucose metabolism.