Effects Of Wild And Mutant Type Of WISP3 On The Modulation Of IGF Signalling In Human Chondrocytes

Objective: WISP3 is essential for maintaining cartilage integrity by regulating the expression of collagen II and aggrecan, and mutations of WISP3 linked with Spondyloepiphyseal dysplasia tarda with progressive arthropathy (SEDT-PA) can compromise this function and lead to cartilage loss. The aim of this study was to evaluate the effect of WISP3 on the IGF signalling and to determine the different characteristics between wild and mutant type of WISP3 in human articular chondrocytes.Methods: T/C-28a2 cells were treated with rhWISP3 and rhIGF-I. C20/A4 cells were transfected with wild and mutant type (1000T to C and 840delT) of WISP3 gene. The effect of WISP3 on the activation of IGF signalling was evaluated by immunoprecipitation of phosphorylated IGF-IRβ, IRS-1 and western blot analysis of phosphorylated ERK1/2 and Akt.Results: RhWISP3 reduced IGF-I induced IGF-IRβactivation and two of its main downsream signalling molecules IRS-1 and ERK1/2 kinase in T/C-28a2 cells. WISP3 reduced IGF-IR activation and IGF-IR induced IRS-1 and ERK1/2 phosphorylation in C20/A4 cells transfected with wildtype of WISP3 gene but induced IGF-IRβ,IRS-1 and ERK1/2 activation in C20/A4 cells transfected with the mutant types of WISP3 gene. Conclusions: WISP3 inhibits the activation of IGF-IR,IRS-1 and ERK kinase in human chondrocytes; mutation of WISP3 may abolish the binding with IGF-I and augment IGF signalling on human chondrocytes.