Nfib promotes chondrocyte proliferation and inhibits differentiation by mildly regulating Sox9 and its downstream genes.

Background: Chondrocyte proliferation and differentiation play pivotal roles in regulating cartilage formation, endochondral bone formation, and repair. Cartilage damage and underdevelopment may cause severe joint diseases. Various transcription factors regulate cartilage development. Nuclear factor 1 B (Nfib) is a transcription factor that plays a regulatory role in various organs. However, the effect and mechanism of Nfib on the proliferation and differentiation of chondrocytes in cartilage are still largely unknown.

Methods And Results: In the present study, we investigated the gene expression patterns in primary chondrocytes with Nfib overexpression or silencing by RNA sequencing (RNA-seq) technology. The results showed that Nfib 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. However, with Nfib silencing, the genes involved in promoting chondrocyte differentiation were significantly up-regulated, whereas those involved in promoting chondrocyte proliferation were significantly down-regulated. Furthermore, quantitative real-time PCR (qRT-PCR), western blot, alcian blue staining and immunofluorescence staining assays further confirmed that Nfib potentially promotes chondrocyte proliferation and extracellular synthesis but inhibits differentiation.

Conclusions: The molecular mechanism of Nfib in promoting chondrocyte proliferation and inhibiting differentiation was probably achieved by stimulating Sox9 and its downstream genes. Thus, this study adds new insights regarding the underlying molecular mechanism of transcriptional regulation in cartilage.