Role of the low‐density lipoprotein receptor‐related protein‐1 in regulation of chondrocyte differentiation

Abstract

The low-density lipoprotein receptor-related protein 1 (LRP1) is known as an endocytic and signal transmission receptor. We formerly reported the gene expression and the localization of LRP1 in cartilage tissue and chondrocytes, but its roles in the differentiation of chondrocytes remained to be investigated. Here, in order to address this issue, we employed RNAi strategy to knockdown lrp1 in chondrocytic cells and obtained findings indicating a critical role therein. As a result of lrp1 knockdown, aggrecan and col2a1 mRNA levels were decreased. However, that of col10a1 or mmp13 mRNA was rather increased. Under this condition, we performed a promoter assay for Axin2, which is known to be induced by activation of the WNT/beta-catenin (betacat) signaling pathway. Thereby, we found that Axin2 promoter activity was enhanced in the lrp1 knockdown cells. Furthermore, when the WNT/beta-catenin pathway was activated in chondrocytic cells by WNT3a or SB216763, which inhibits the phosphorylation of GSK3beta, the mRNA levels of aggrecan and col2a1 were decreased, whereas that of mmp13 was increased. Additionally, the level of phosphorylated protein kinase C (PKC) zeta was also decreased in the lrp1 knockdown cells. When the phosphorylation of PKCzeta was selectively inhibited, aggrecan and col2a1 mRNA levels decreased, whereas the mmp13 mRNA level increased. These data demonstrate that LRP1 exerts remarkable effects to retain the mature phenotype of chondrocytes as a critical mediator of cell signaling. Our findings also indicate that the onset of hypertrophy during endochondral ossification appears to be particularly dependent on the WNT and PKC signaling initiated by LRP1.

Role of low-density lipoprotein receptor related protein 1 (LRP1) in CCN2/connective tissue growth factor (CTGF) protein transport in chondrocytes

“…Effect of LRP1 knockdown on CCN2 association with chondrocytic HCS-2/8 cells First, to examine whether LRP1 participates in the association of CCN2 with chondrocytes or not, we performed RNA interference (RNAi) experiments to knockdown LRP1 in HCS-2/8 cells, a human chondrocytic cell line, as previously performed (Kawata et al, 2010). We confirmed that the production of LRP1 protein was substantially knocked down by si-1163 and si-13157 (Fig.…”

“…We have previously reported the distribution of LRP1 in normal cartilage (Kawata et al, 2006) and shown that LRP1 initiates the hypertrophy of chondrocytes during endochondral ossification through WNT-b-catenin and PKC signaling (Kawata et al, 2010). Vertebrate cartilage is of two distinct types, permanent cartilage represented by articular cartilage, and temporary cartilage represented by the growth plate cartilage, which is where endochondral ossification occurs.…”

Enhanced Chondrogenic Differentiation of Human Umbilical Cord Wharton's Jelly Derived Mesenchymal Stem Cells by GSK-3 Inhibitors

“…The β-catenin signaling pathway often crosstalks with other signaling pathways to modulate chondrogenesis [13–18]. However, the Wnt/β-catenin signaling pathway plays a crucial role in the hypertrophic maturation of chondrocytes during the endochondral ossification process [19]. Another key regulator of the Wnt signaling pathway is glycogen synthase kinase 3 (GSK-3) that mediates β-catenin phosphorylation [20].…”

Low Density Lipoprotein Receptor-related Protein 1 (LRP1)-mediated Endocytic Clearance of a Disintegrin and Metalloproteinase with Thrombospondin Motifs-4 (ADAMTS-4)

“…LRP1 interacts with frizzled-1 and down-regulates the canonical Wnt-␤-catenin signaling pathway (32). It also represses the hypertrophy of chondrocytes during endochondral ossification by removing connective tissue growth factor (33,34). LRP1 is, therefore, an important regulator of skeletal development and maintenance of cartilage homeostasis.…”