Transforming growth factor beta1 induces angiogenesis in vivo with a threshold pattern

Area of Science:

• Cell Biology
• Biochemistry
• Immunology

Background:

• The role of transforming growth factor beta1 (TGFbeta) in angiogenesis is debated, with conflicting in vitro and in vivo findings.
• In vitro studies show TGFbeta can inhibit or stimulate endothelial cell (EC) proliferation and tube formation.
• In vivo studies present discrepancies, with some reporting angiogenic induction and others inhibition.

Purpose of the Study:

• To investigate the in vivo angiogenic effects of TGFbeta using the disc angiogenesis system (DAS).
• To assess the contribution of endogenous TGFbeta to spontaneous angiogenesis during wound healing.
• To examine the combined effects of TGFbeta and basic fibroblast growth factor (bFGF) on angiogenesis.

Main Methods:

• Subcutaneous implantation of discs containing varying doses of TGFbeta (1 ng to 2000 ng) in mice.
• Measurement of angiogenesis using vessel growth, fibrovascular area, and tritiated thymidine incorporation.
• Inhibition of endogenous TGFbeta using a monoclonal anti-TGFbeta antibody.
• Co-administration of suboptimal doses of TGFbeta and bFGF.

Main Results:

• TGFbeta induced significant angiogenesis at doses of 1000 ng and 2000 ng, but not at lower doses (1-500 ng).
• Anti-TGFbeta antibody reduced spontaneous vascular growth, indicating a role for endogenous TGFbeta in wound healing.
• Suboptimal doses of TGFbeta and bFGF did not show a combined angiogenic effect.
• TGFbeta-treated discs exhibited increased collagen and neutrophil accumulation.

Conclusions:

• TGFbeta1 is angiogenic in vivo above a threshold of 1 microg, with lower doses being ineffective.
• Endogenous TGFbeta contributes to spontaneous angiogenesis, particularly in wound healing.
• The angiogenic effect of TGFbeta appears to be indirect, mediated by leukocyte recruitment and subsequent release of angiogenic factors.