Mechanisms of osteoblastic induction of mesenchymal stem cells by mechanical loading

Hochschulschrift

Zusammenfassung: Understanding the factors that regulate bone formation through osteoblastic differentiation of mesenchymal stem cells (MSCs) is of considerable importance for regenerative dentistry. Mechanical loading can be a stimulator of osteoblastic differentiation via the induction of MSCs promoting the expression of early and late response genes. One early response gene that has been described is Sprouty2 (Spry2), a profound inhibitor of the MAPkinase pathway. The latter is known to be important in bone homeostasis and osteoblastogenesis. The aims of this study were to test if and how Spry2 expression regulates osteoblastic differentiation of MSCs and whether it mediates the expression of late response genes involved in osteoblast differentiation under mechanical loading.To assess Spry2 expression, commercially obtained human MSCs were cultured in osteogenic medium. Spry2 and scrambled siRNA were transfected into MSCs to test the effectiveness of the knock-down (KD). To investigate the role of Spry2 in osteoblast differentiation and adipogenesis, RNA extraction and qRT-PCR were performed measuring the relative gene expression levels of Spry2, Runx2, ALP, FOSB, CEB-α, PPAR-γ and FAB4. To evaluate the effect of Spry2 on cell proliferation and mineralization, control and siRNA transfected cells were counted after 8 days using the Haemocytometer and stained after 21 days with Alizarin Red. To test mechanical loading responses, cells were loaded onto CaP scaffolds and a small amount of strain (≈ 0.5%) was applied via a bose bioreactor.When MSCs were cultured in osteogenic medium, Spry2 expression was induced within 2h. After RNAi treatment, Spry2 expression was down-regulated for up to 7 days. Culture of MSCs in osteogenic medium resulted in upregulated expression of Runx2 after 2h and ALP after 1 day. FOSB was down-regulated consistently for up to 7 days post transfection. Adipogenic differentiation and mineralization of MSCs was unaffected, whereas cell proliferation was increased by the Spry2 KD. Under mechanical loading, Spry2 and FOSB expression were both induced after 2h of loading and down-regulated by siRNA after 2h of loading. Runx2 and ALP expression responses were inconclusive.The results show that Spry2 modulates the expression of the osteoblast marker genes FOSB and Runx2 and inhibits MSC proliferation in culture. Under mechanical loading, Spry2 was identified as an upstream regulator of the early response gene FOSB. Therefore this study shows that Spry2 is not only an important early regulator of osteoblastogenesis induced by mechanical loading but also during osteoblast differentiation of MSCs with osteogenic media

Object Details

• Location: Deutsche Nationalbibliothek Frankfurt am Main
• Extent: Online-Ressource
• Language: Englisch
• Notes: Albert-Ludwigs-Universität Freiburg, Dissertation, 2016

Contributors, Places and Time

• Event: Veröffentlichung
• (where): Freiburg
• (who): Universität
• (when): 2016
• Creator: Schneider, Aniela Kristin
• Contributor: Ratka-Krüger, Petra ; Hughes, Francis

Further information

• DOI: 10.6094/UNIFR/10843
• URN: urn:nbn:de:bsz:25-freidok-108438
• Rights: Der Zugriff auf das Objekt ist unbeschränkt möglich.
• Last update: 14.08.2025, 10:50 AM CEST