Heparin-binding EGF-like growth factor synthesis by smooth muscle cells

Area of Science:

• Cell Biology
• Molecular Biology
• Vascular Biology

Background:

• Heparin-binding epidermal growth factor-like growth factor (HB-EGF) is a known mitogen for smooth muscle cells.
• The autocrine or paracrine roles of HB-EGF in vascular smooth muscle cells are not fully understood.

Purpose of the Study:

• To investigate whether vascular smooth muscle cells synthesize HB-EGF.
• To characterize the biological activity of HB-EGF produced by smooth muscle cells.
• To determine if smooth muscle cells respond to HB-EGF through autocrine signaling.

Main Methods:

• Cultured fetal human vascular smooth muscle cells were used.
• HB-EGF mRNA expression was analyzed using Northern blotting.
• HB-EGF-like activity in cell-conditioned media was assessed by proliferation assays.
• Heparin affinity chromatography and Western blotting were employed to characterize the secreted activity and its interaction with the EGF receptor.

Main Results:

• Vascular smooth muscle cells express 2.5-kb HB-EGF mRNA.
• Conditioned media stimulated smooth muscle cell and BALB/c 3T3 cell proliferation but not endothelial cells.
• The secreted activity bound to heparin affinity columns and eluted at high salt concentrations.
• 125I-HB-EGF cross-linked to the 170-kD EGF receptor on smooth muscle cells, indicating receptor activation.

Conclusions:

• Vascular smooth muscle cells synthesize and secrete HB-EGF.
• Smooth muscle cells possess functional HB-EGF receptors and respond to the secreted factor.
• HB-EGF may mediate autocrine regulation of vascular smooth muscle cell growth and function.