We found that LiCl treat ment of chondrocytes from WT mice further enhanced the Wnt3a mediated upregulation of Mmp13 and the Wnt7a mediated http://www.selleckchem.com/products/Vandetanib.html upregulation of Mmp3 and Mmp13, whereas these parameters were unchanged in LiCl treated Lrp5 mice. LRP5 Inhibitors,Modulators,Libraries potentiates Wnt B catenin signaling during osteoarthritis pathogenesis Because GSK3B activity is primarily responsible for the degradation of B catenin, we next examined whether the expression and or activity levels of B catenin could be reg ulated by LRP5. Ectopic expression of LRP5 in chondro cytes increased the transcriptional activation of B catenin as determined by a Tcf Lef reporter Inhibitors,Modulators,Libraries gene assay using TOPflash and FOPflash. Treatment of chondrocytes from WT mice with IL 1B, Wnt3a or Wnt7a also increased the transcrip tional activity of the B catenin Tcf Lef complex, whereas this activity was completely blocked in cells from Lrp5 mice.

Consistent with these observations, the expression levels of B catenin and LRP5 were remarkably increased in OA cartilage induced by DMM surgery, and the B catenin expressing cells largely overlapped with the LRP5 expressing cells. Moreover, the ex pression levels of B catenin and MMP13 were Inhibitors,Modulators,Libraries increased in OA affected human cartilage compared to healthy control cartilage. Interestingly, the increases in B catenin, MMP3 and MMP13 found in the OA cartilage of WT mice subjected to aging or DMM sur gery were not observed in experimental OA cartilage samples from Lrp5 mice.

To control for unexpected effects from the lack of Inhibitors,Modulators,Libraries Lrp5 in noncartilage tissues, we generated chondrocyte specific conditional KO mice, whereby the cre recombinase gene specifically deleted the Lrp5 gene from cartilage, but not other tissues, such as brain, heart and bone. Lrp5fl fl,Col2a1 cre and correspon ding Lrp5fl fl control mice were subjected to induced OA by DMM surgery. Consistent with our data from the total KO mice, Lrp5fl fl,Col2a1 cre mice exhibited significantly reduced cartilage destruction following DMM surgery compared with control Lrp5fl fl mice and did not show DMM surgery induced upregulation of B catenin, MMP3 and MMP13 expression levels in OA cartil age samples. We also examined whether the upregulation of LRP5 could potentiate chondrocyte apop tosis and found that chondrocyte apoptosis induced by 1 Inhibitors,Modulators,Libraries ug ml anti Fas antibody was not altered by Lrp5 defi ciency.

However, stimulation of apoptosis by IL 1B treatment in the presence of a low concentration of anti Fas antibody was slightly but signifi cantly reduced in Lrp5 deficient chondrocytes. As determined by TUNEL exactly assay, apoptotic cells were also relatively reduced in DMM induced OA cartilage from Lrp5fl fl,Col2a1 cre mice compared to Lrp5fl fl mice. Taken together, our results suggest that LRP5 induces chondrocyte dedifferentiation and promotes the expression of catabolic genes by potentiating the Wnt B catenin signaling pathway.