S in the Tyrphostin AG 490 clinical trials growth-factor-treated ligament fibroblasts. Moreover, transcription analysis of stimulated
S in the growth-factor-treated ligament fibroblasts. Moreover, transcription analysis of stimulated ligament fibroblasts demonstrated an upregulation of chondrogenic markers (aggrecan, collagen type II, type IX and type X) but not of osteogenic markers. PubMed ID:https://www.ncbi.nlm.nih.gov/pubmed/28607003 Conclusion CDMP-1 and CDMP-2 induce matrix synthesis and cell proliferation in cells derived from bovine ligament. The expression of chondrocyte markers suggests that adult cells from ligaments and tendons have the capability of differentiation into chondrocytes under the influence of CDMPs. Given our current dilemma in the treatment of osteoarthritis, CDMP-1 and CDMP-2 could therefore contribute an interesting therapeutic molecule for osteoarthritis.63 Altered phosphorylation of Syp may be responsible for abnormal insulin-like growth factor-1 signaling in human osteoarthritic osteoblastsD Lajeunesse, F Massicotte, I Aubry, J Martel-Pelletier, J Pelletier Rheumatic Disease Unit, Centre Hospitalier de l’Universit?de Montr l, H ital Notre-Dame, Montr l, Qu ec, Canada Arthritis Res Ther 2003, 5(Suppl 3):63 (DOI 10.1186/ar864) Introduction The subchondral bone plays a prominent role in the pathophysiology of osteoarthritis (OA), possibly related to abnormal osteoblast metabolism. In particular, abnormal responses to insulin-like growth factor-1 (IGF-1) were noted in OA osteoblasts. Objectives To investigate whether IGF-1 signaling is abnormal in OA osteoblasts compared with normal osteoblasts. Methods We used primary human subchondral osteoblasts from normal and OA individuals. Cells were stimulated, or not, with 100 ng/ml IGF-1 for up to 5 min. Proteins were separated by SDSPAGE or immunoprecipitated with anti-insulin receptor substrate-1 (anti-IRS-1) antibodies followed by SDS-PAGE, and detected with selective antibodies. Results Upon binding to its receptor (IGF-1R), IGF-1 activates the p42/44 mitogen-activated protein kinase (MAPK) pathway using SHC or phosphorylation of IRS-1 via Grb2. The interaction of IRS-1 with IGF-1R is also modulated via the binding of a tyrosine phosphatase, Syp. IGF-1R -subunits, SHC, IRS-1, Syp, Grb2 and p42/44 MAPK levels, by Western blot analysis, were similar in normal and OA osteoblasts under basal condition and following IGF-1 treatment. IGF-1 stimulated IGF-1R autophosphorylation in normal and OA osteoblasts similarly. However, IRS-1 phosphorylation was reduced whereas p42/44 MAPK phosphorylation was higher in OA osteoblasts than normal osteoblasts in response to IGF-1. PubMed ID:http://www.ncbi.nlm.nih.gov/pubmed/26437915 In normal osteoblasts, Syp was poorly phosphorylated under basal conditions and rapidly became phosphorylated upon IGF-1 stimulation, while Syp was already highly phosphorylated under basal conditions in OA osteoblasts and was dephosphorylated upon IGF-1 stimulation. Co-immunoprecipitation of Syp using IRS-1 antibodies showed that this interaction is poor under basal conditions in normal cells yet increases following IGF-1 treatment, while in OA osteoblasts this interaction was very strong and rapidly dropped with IGF-1 treatments, indicating that phospho-Syp is the trigger. Co-immunoprecipitation of Grb2 using IRS-1 antibodies showed that Grb2 interaction with IRS-1 was increased in OA osteoblasts compared with normal osteoblasts under basal conditions and following IGF-1 stimulation. Conclusion These results suggest that an abnormal interaction of phospho-Syp with IRS-1 in OA osteoblasts leads to a reduced activity of IRS-1-dependent pathways. In addition, the increased interaction of Gr.
