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Vol. 26, No. 6, 2010
Issue release date: 2010
Section title: Original Paper
Cell Physiol Biochem 2010;26:1093–1102
(DOI:10.1159/000323987)

Involvement of BMPs/Smad Signaling Pathway in Mechanical Response in Osteoblasts

Wang L. · Zhang X. · Guo Y. · Chen X. · Li R. · Liu L. · Shi C. · Guo C. · Zhang Y.
Tianjin Institute of Medical Equipment, Tianjin
email Corresponding Author

Abstract

Background/Aims: Mechanical strain plays an important role in osteoblasts differentiation and bone formation but the underlying mechanism remains unclear. The aim of this study was to determine whether Bone Morphogenetic Proteins (BMPs)/Smad signaling pathway is involved in mechanical response in osteoblasts. Methods: MC3T3-E1 cells were exposed to mechanical strain via a four-point bending system. mRNA levels and protein levels of BMP-2, BMP-4, Smad1, Smad5, Smurf1, and Smurf2 were assessed using RT-PCR and immunoblotting. Protein levels of BMP-2 and BMP-4 in the culture medium were also determined using Enzyme-linked Immunosorbent Assay (ELISA). Pretreatment with Noggin and transfection with Smad4 siRNA were carried out to block the BMPs/Smad signaling pathway and MG132 was used to inhibit the proteasome pathway. Results: We found that mechanical strain enhanced alkaline phosphatase (ALP) expression and activated BMPs/Smad signaling pathway. Mechanical strain induced expression of ALP was attenuated by Noggin and by Smad4 siRNA. The protein levels of Smad1 and Smad5, but not their mRNA levels, were up-regulated by mechanical strain. This finding could be explained by the down-regulation of Smurf1. The protein degradation of Smad might be inhibited by mechanical strain through down-regulation of Smuf1 expression. The addition of MG132 further enhanced the mechanical strain induced activation of Smad proteins and the increased expression of ALP. Conclusions: Mechanical strain might promote osteoblasts differentiation through BMPs/Smad signaling pathway. The strain causes a drop in Smurf1 levels, leading to accumulation of Smad proteins and, subsequently, to enhanced BMPs/Smad signaling.

© 2010 S. Karger AG, Basel


  

Key Words

  • Osteoblasts
  • Mechanical strain
  • Bone morphogenetic proteins
  • Smad
  • Smurf1

  

Author Contacts

Prof. Xizheng Zhang
Tianjin Institute of Medical Equipment
No.106, Wandong Road, Tianjin 300161 (China)
Tel./Fax +862284656717
E-Mail zxz56787@163.com

  

Article Information

Accepted: November 18, 2010
Published online: January 04, 2011
Number of Print Pages : 10

  

Publication Details

Cellular Physiology and Biochemistry (International Journal of Experimental Cellular Physiology, Biochemistry andPharmacology)

Vol. 26, No. 6, Year 2010 (Cover Date: 2010)

Journal Editor: F. Lang, Tübingen
ISSN: 1015–8987 (Print), eISSN: 1421–9778 (Online)

For additional information: http://www.karger.com/journals/cpb


Copyright / Drug Dosage / Disclaimer

Copyright: All rights reserved. No part of this publication may be translated into other languages, reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying, recording, microcopying, or by any information storage and retrieval system, without permission in writing from the publisher or, in the case of photocopying, direct payment of a specified fee to the Copyright Clearance Center.
Drug Dosage: The authors and the publisher have exerted every effort to ensure that drug selection and dosage set forth in this text are in accord with current recommendations and practice at the time of publication. However, in view of ongoing research, changes in goverment regulations, and the constant flow of information relating to drug therapy and drug reactions, the reader is urged to check the package insert for each drug for any changes in indications and dosage and for added warnings and precautions. This is particularly important when the recommended agent is a new and/or infrequently employed drug.
Disclaimer: The statements, opinions and data contained in this publication are solely those of the individual authors and contributors and not of the publishers and the editor(s). The appearance of advertisements or/and product references in the publication is not a warranty, endorsement, or approval of the products or services advertised or of their effectiveness, quality or safety. The publisher and the editor(s) disclaim responsibility for any injury to persons or property resulting from any ideas, methods, instructions or products referred to in the content or advertisements.

Abstract

Background/Aims: Mechanical strain plays an important role in osteoblasts differentiation and bone formation but the underlying mechanism remains unclear. The aim of this study was to determine whether Bone Morphogenetic Proteins (BMPs)/Smad signaling pathway is involved in mechanical response in osteoblasts. Methods: MC3T3-E1 cells were exposed to mechanical strain via a four-point bending system. mRNA levels and protein levels of BMP-2, BMP-4, Smad1, Smad5, Smurf1, and Smurf2 were assessed using RT-PCR and immunoblotting. Protein levels of BMP-2 and BMP-4 in the culture medium were also determined using Enzyme-linked Immunosorbent Assay (ELISA). Pretreatment with Noggin and transfection with Smad4 siRNA were carried out to block the BMPs/Smad signaling pathway and MG132 was used to inhibit the proteasome pathway. Results: We found that mechanical strain enhanced alkaline phosphatase (ALP) expression and activated BMPs/Smad signaling pathway. Mechanical strain induced expression of ALP was attenuated by Noggin and by Smad4 siRNA. The protein levels of Smad1 and Smad5, but not their mRNA levels, were up-regulated by mechanical strain. This finding could be explained by the down-regulation of Smurf1. The protein degradation of Smad might be inhibited by mechanical strain through down-regulation of Smuf1 expression. The addition of MG132 further enhanced the mechanical strain induced activation of Smad proteins and the increased expression of ALP. Conclusions: Mechanical strain might promote osteoblasts differentiation through BMPs/Smad signaling pathway. The strain causes a drop in Smurf1 levels, leading to accumulation of Smad proteins and, subsequently, to enhanced BMPs/Smad signaling.

© 2010 S. Karger AG, Basel


  

Author Contacts

Prof. Xizheng Zhang
Tianjin Institute of Medical Equipment
No.106, Wandong Road, Tianjin 300161 (China)
Tel./Fax +862284656717
E-Mail zxz56787@163.com

  

Article Information

Accepted: November 18, 2010
Published online: January 04, 2011
Number of Print Pages : 10

  

Publication Details

Cellular Physiology and Biochemistry (International Journal of Experimental Cellular Physiology, Biochemistry andPharmacology)

Vol. 26, No. 6, Year 2010 (Cover Date: 2010)

Journal Editor: F. Lang, Tübingen
ISSN: 1015–8987 (Print), eISSN: 1421–9778 (Online)

For additional information: http://www.karger.com/journals/cpb


Article / Publication Details

First-Page Preview
Abstract of Original Paper

Accepted: 11/18/2010
Published online: 1/4/2011
Issue release date: 2010

Number of Print Pages: 10
Number of Figures: 0
Number of Tables: 0

ISSN: 1015-8987 (Print)
eISSN: 1421-9778 (Online)

For additional information: http://www.karger.com/CPB


Copyright / Drug Dosage

Copyright: All rights reserved. No part of this publication may be translated into other languages, reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying, recording, microcopying, or by any information storage and retrieval system, without permission in writing from the publisher or, in the case of photocopying, direct payment of a specified fee to the Copyright Clearance Center.
Drug Dosage: The authors and the publisher have exerted every effort to ensure that drug selection and dosage set forth in this text are in accord with current recommendations and practice at the time of publication. However, in view of ongoing research, changes in goverment regulations, and the constant flow of information relating to drug therapy and drug reactions, the reader is urged to check the package insert for each drug for any changes in indications and dosage and for added warnings and precautions. This is particularly important when the recommended agent is a new and/or infrequently employed drug.
Disclaimer: The statements, opinions and data contained in this publication are solely those of the individual authors and contributors and not of the publishers and the editor(s). The appearance of advertisements or/and product references in the publication is not a warranty, endorsement, or approval of the products or services advertised or of their effectiveness, quality or safety. The publisher and the editor(s) disclaim responsibility for any injury to persons or property resulting from any ideas, methods, instructions or products referred to in the content or advertisements.