Signaling cross-talk between IGF-binding protein-3 and transforming growth factor-β in mesenchymal chondroprogenitor cell growth

Abstract

Cartilage formation is driven by mesenchymal chondroprogenitor cells (MCCs) that proliferate and differentiate into chondrocytes. The molecular mechanisms by which growth factors regulate MCC fate are not well defined. Insulin-like growth factor binding protein-3 (IGFBP-3) has intrinsic bioactivity that is independent of IGF binding. We previously reported that IGFBP-3 has IGF-independent antiproliferative and apoptotic effects in MCCs, and requires STAT-1 activation to mediate its apoptotic effect. Transforming growth factor-(TGF-) is a key chondroinductive growth factor. The objective of the study is to define the interactions between IGFBP-3 and TGF-in MCC growth and their intracellular signaling pathways. We used the RCJ3·1C5·18 mesenchymal chondrogenic cells that without biochemical or oncogenic transformation progress in culture from MCCs to differentiated chondrocytes. Cell proliferation was assessed in MCCs treated with IGFBP-3 or transfected with IGFBP-3, in the presence or absence of TGF-. To demonstrate that IGFBP-3 effects were IGF-independent an IGFBP-3 analog that lacks IGF binding was used (GGG-IGFBP-3). To determine the functional roles of the TGF--mediated signaling and the STAT-1 pathway, cells were either stably transfected with a dominant negative TGF-type II receptor (MCC-DNT RII) or treated with a STAT-1 morpholino antisense oligonucleotide. We found that in MCCs, TGF-antagonized the antiproliferative effect of IGFBP-3. IGFBP-3 increased the cyclin-dependent kinase inhibitor p21 expression and this effect was abolished by TGF-. Furthermore, TGF-inhibited STAT-1 phosphorylation induced by IGFBP-3. Similarly to TGF-, STAT-1 antisense oligonucleotide inhibited the IGFBP-3 antiproliferative action. Although TGF-in MCC-DNT RII lacked Smad-mediated signaling, it persistently antagonized the IGFBP-3 antiproliferative action. However, TGF-even in MCC-DNT RII cells induced ERK1/2 phosphorylation, and treatment with MEK inhibitor, UO126, inhibited the antagonistic effects of TGF-on IGFBP-3. Furthermore, UO126 blocked the TGF-inhibition of STAT-1 phosphorylation induced by IGFBP-3. Collectively, these results demonstrate cross-talk between the IGFBP-3-dependent STAT-1 signaling and the TGF--dependent ERK pathway that regulates MCC proliferation.

A novel adipokine C1q/TNF-related protein 1 (CTRP1) regulates chondrocyte proliferation and maturation through the ERK1/2 signaling pathway

“…We found that CTRP1 induces activation of ERK1/2 in immature proliferating chondrocytes, whereas it had no effect on the activities of JNK1/2, p38 MAPK and Akt, and none of their phosphorylated forms was detected (data not shown). Indeed, the ERK1/2 pathway is known to be involved in controlling proliferation of immature proliferating chondrocytes (O'Rear et al, 2005;Akiyama et al, 2006). We next investigated the effects of the MEK1/2 inhibitor U0126 on the proliferation of CTRP1-stimulated immature proliferating chondrocytes.…”

Pentosan polysulfate promotes proliferation and chondrogenic differentiation of adult human bone marrow-derived mesenchymal precursor cells

“…Furthermore, enhanced proteolysis of IGFBP-3 by ADAM12 would increase the bioavailability of IGF-1, thereby also supporting MPC proliferation and chondrogenic differentiation. On the other hand, it has also been shown that the apoptosis-potentiating and anti-proliferative activity of IGFBP-3 on MSCs may be antagonised through a TGF-β-dependent ERK pathway [52], suggesting that the proliferative, chondrogenic and anti-apoptotic effects of PPS on MPCs could be mediated by their increased production of TGF-β.…”

Inhibition of adipocyte differentiation by insulin-like growth factor-binding protein-3

“…They identified the signal transducer and activator of transcription (STAT)1 to be an intracellular signaling and transcriptional target of the apoptotic effect of IGFBP-3 in chondrogenesis (45). Recently, O'Rear et al (33) have shown that there is cross talk between the IGFBP-3-dependent STAT1 signaling and the TGF-␤-dependent ERK pathway that regulate mesenchymal chondroprogenitor cell proliferation and differentiation. In adipocytes, TNF-␣ is well known to inhibit differentiation (35,52).…”