Runx2 and Runx3 differentially regulate articular chondrocytes during surgically induced osteoarthritis development
Abstract The Runt-related transcription factor (Runx) family plays various roles in the homeostasis of cartilage. Here, we examined the role of Runx2 and Runx3 for osteoarthritis (OA) development in vivo and in vitro. Runx3 knockout mice accelerated OA by surgical induction, accompanied with decreased expression of lubricin and aggrecan. Meanwhile, Runx2 conditional knockout mice showed biphasic phenotypes; OA was inhibited by hetero-knockout accompanied with decreased matrix metallopeptidase 13 (Mmp13) expression, but accelerated in homo-knockout of Runx2 accompanied with reduction of type II collagen (Col2a1) expression. Comprehensive transcriptional analyses revealed lubricin and aggrecan as transcriptional target genes of Runx3, and indicated that Runx2 sustained Col2a1 expression through an intron 6 enhancer when Sox9 was decreased. Intra-articular administration of Runx3 adenovirus ameliorated development of surgically induced OA. Runx3 protects adult articular cartilage through extracellular matrix protein production under the normal condition, while Runx2 exerts both catabolic and anabolic effects under the inflammatory condition.