Function and regulation of nuclear factor 1 X-type on chondrocyte proliferation and differentiation.

Nuclear factor 1 X-type (Nfix) is a transcription factor related to mental and physical development. However, very few studies have reported the effects of Nfix on cartilage. This study aims to reveal the influence of Nfix on the proliferation and differentiation of chondrocytes, and to explore its potential action mechanism. We isolated primary chondrocytes from the costal cartilage of newborn C57BL/6 mice and with Nfix overexpression or silencing treatment. We used Alcian blue staining and found that Nfix overexpression significantly promoted ECM synthesis in chondrocytes while silencing inhibited ECM synthesis. Using RNA-seq technology to study the expression pattern of Nfix in primary chondrocytes. We found that Nfix overexpression significantly up-regulated genes that are related to chondrocyte proliferation and extracellular matrix (ECM) synthesis and significantly down-regulated genes related to chondrocyte differentiation and ECM degradation. Nfix silencing, however, significantly up-regulated genes associated with cartilage catabolism and significantly down-regulated genes associated with cartilage growth promotion. Furthermore, Nfix exerted a positive regulatory effect on Sox9, and we propose that Nfix may promote chondrocyte proliferation and inhibit differentiation by stimulating Sox9 and its downstream genes. Our findings suggest that Nfix may be a potential target for the regulation of chondrocyte proliferation and differentiation.