Significance was accepted at the 0. 05 level of probability. Results Lrp5 is upregulated via JNK and NF ��B sellectchem pathways during IL 1B mediated pathogenesis of chondrocytes We first examined the expression levels Inhibitors,Modulators,Libraries of Lrp5 and Lrp6 during the chondrogenic differentiation of mesen chymal cells obtained from mouse embryonic limb buds and subjected to micromass culture. We found that Col2a1 peaked on day 6 of micromass culture, Lrp6 expression decreased beginning on day 6 and Lrp5 expression was constant during chondrocyte differen tiation. The basal levels of Lrp5 and Lrp6 mRNA were very low in mouse articular chondrocytes. In pathogenic primary culture Inhibitors,Modulators,Libraries chondrocytes treated with IL 1B, however, Lrp5 expression was drama tically increased in a dose dependent manner and a time dependent manner, whereas Lrp6 expression was constant.

Consistent with our previous observations, IL 1B treatment increased the levels of Mmp13 while abrogating Col2a1 expression. Inhibitors,Modulators,Libraries Our qRT PCR analysis revealed that IL 1B treatment triggered an approximately tenfold increase of Lrp5 expression, but had no effect on Lrp6 expression. IL 1B treatment of chondrocytes triggered the activation of nuclear factor ��B and various mitogen activated protein kinase subtypes, including ERK, p38 kinase and JNK. Inhibition of ERK or p38 kinase had no effect on LRP5 expression, but the blockade of JNK or NF ��B signaling markedly inhi bited the IL 1B induced increase in LRP5 expression. These data indicate that LRP5 is increased during IL 1B induced chondrocyte dedifferentiation and that this upregulation of LRP5 is mediated via the JNK and NF ��B signaling pathways.

LRP5 expression is elevated in human and mouse osteoarthritic cartilage Because Lrp5 expression was distinctly regulated during IL 1B induced chondrocyte dedifferentiation, we examined whether LRP5 plays a role Inhibitors,Modulators,Libraries in OA cartilage destruction in vivo. We initially examined LRP5 levels in OA affected human cartilage obtained from individuals who had under gone Inhibitors,Modulators,Libraries arthroplasty. The degree of cartilage damage in the human OA samples was ICRS grade 4 as confirmed by Alcian blue staining. In these samples, LRP5 was significantly expressed in OA affected human cartilage but barely detectable in normal cartilage. This upregulation of Lrp5 mRNA in human OA cartilage was confirmed by RT PCR and qRT PCR analyses. We also found that the protein and mRNA levels of LRP5 were increased in cartilage from STR ort mice compared with that from control CBA CaCrl mice. We also observed increased LRP5 expression furthermore in mouse OA cartilage following collagenase injection and DMM surgery. Thus, LRP5 expression was significantly elevated in all human and mouse OA cartilage samples examined in the present study.