| Autor: |
Sabrina Ehnert, Johannes Baur, Andreas Schmitt, Markus Neumaier, Martin Lucke, Steven Dooley, Helen Vester, Britt Wildemann, Ulrich Stöckle, Andreas K Nussler |
| Jazyk: |
angličtina |
| Rok vydání: |
2010 |
| Předmět: |
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| Zdroj: |
PLoS ONE, Vol 5, Iss 11, p e14073 (2010) |
| Druh dokumentu: |
article |
| ISSN: |
1932-6203 |
| DOI: |
10.1371/journal.pone.0014073 |
| Popis: |
BACKGROUND: The TGF family plays a key role in bone homeostasis. Systemic or topic application of proteins of this family apparently positively affects bone healing in vivo. However, patients with chronic inflammation, having increased TGF-β(1) serum-levels, often show reduced bone mineral content and disturbed bone healing. Therefore, we wanted to identify intracellular mechanisms induced by chronic presence of TGF-β(1) and their possible role in bone homeostasis in primary human osteoblasts. METHODOLOGY/PRINCIPAL FINDINGS: Osteoblasts were isolated from femur heads of patients undergoing total hip replacement. Adenoviral reporter assays showed that in primary human osteoblasts TGF-β(1) mediates its signal via Smad2/3 and not Smad1/5/8. It induces proliferation as an intermediate response but decreases AP-activity and inorganic matrix production as a late response. In addition, expression levels of osteoblastic markers were strongly regulated (AP↓; Osteocalcin↓; Osteopontin↑; MGP↓; BMP 2↓; BSP2↓; OSF2↓; Osteoprotegerin↓; RANKL↑) towards an osteoclast recruiting phenotype. All effects were blocked by inhibition of Smad2/3 signaling with the Alk5-Inhibitor (SB431542). Interestingly, a rescue experiment showed that reduced AP-activities did not recover to base line levels, even 8 days after stopping the TGF-β(1) application. CONCLUSIONS/SIGNIFICANCE: In spite of the initial positive effects on cell proliferation, it is questionable if continuous Smad2/3 phosphorylation is beneficial for bone healing, because decreased AP-activity and BMP2 levels indicate a loss of function of the osteoblasts. Thus, inhibition of Smad2/3 phosphorylation might positively influence functional activity of osteoblasts in patients with chronically elevated TGF-β(1) levels and thus, could lead to an improved bone healing in vivo. |
| Databáze: |
Directory of Open Access Journals |
| Externí odkaz: |
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