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Published on: September 14, 2021

Transforming growth factor-beta prevents osteoblast apoptosis induced by skeletal unloading via PI3K/Akt, Bcl-2, and

Cécilie Dufour1, Xavier Holy, Pierre J Marie

  • 1Unit 606 Institut National de la Santé et de la Recherche Médicale, Paris, France.

American Journal of Physiology. Endocrinology and Metabolism
|April 2, 2008
PubMed

Insights

Transforming growth factor-beta2 (TGF-β2) administration prevents bone loss in unloaded rats by inhibiting osteoblast apoptosis. TGF-β2 activates the alpha(5)beta(1)/PI3K/Akt pathway, protecting bone cells.

Area of Science:

  • Bone biology and skeletal metabolism
  • Cell signaling and apoptosis
  • Integrin and growth factor signaling

Background:

  • Mechanical unloading causes significant bone loss by increasing osteoblast apoptosis.
  • The underlying molecular mechanisms linking mechanical unloading to bone loss are not fully understood.
  • Previous research indicated phosphatidylinositol 3-kinase (PI3K) signaling is reduced during unloading-induced bone loss.

Purpose of the Study:

  • To investigate the potential of transforming growth factor-beta2 (TGF-β2) to prevent osteoblast apoptosis and altered signaling caused by skeletal unloading.
  • To elucidate the signaling pathways involved in TGF-β2's protective effects against unloading-induced bone loss.

Main Methods:

  • Hindlimb suspension model in rats to induce skeletal unloading.
  • Administration of TGF-β2 via osmotic minipumps.
  • Assessment of bone volume, alpha(5)beta(1)-integrin expression, PI3K/Akt signaling, Bcl-2 levels, and phosphorylated Bad (inactive Bad).

Main Results:

  • Skeletal unloading decreased bone volume, alpha(5)beta(1)-integrin, and PI3K/Akt signaling, leading to osteoblast apoptosis.
  • Continuous TGF-β2 administration prevented these decreases, preserving bone volume and inhibiting osteoblast apoptosis.
  • TGF-β2 administration also prevented reductions in Bcl-2 and increased phosphorylated Bad, indicating a role in regulating apoptosis-related proteins.

Conclusions:

  • TGF-β2 plays a protective role against mechanical unloading-induced osteoblast apoptosis in vivo.
  • This protection is mediated through the alpha(5)beta(1)/PI3K/Akt signaling cascade.
  • TGF-β2 regulates downstream survival proteins Bcl-2 and phospho-Bad, offering a novel therapeutic target for unloading-induced bone loss.

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