Serum factors involved in human microvascular endothelial cell morphogenesis

Area of Science:

• Cell Biology
• Angiogenesis Research
• Biochemistry

Background:

• Lipid and protein angiogenic factors are known to work together to induce optimal angiogenic responses in vivo.
• Human serum exhibits a remarkable ability to promote capillary morphogenesis in vitro.

Purpose of the Study:

• To clarify the specific substances in human serum responsible for promoting capillary morphogenesis in vitro.
• To investigate the synergistic roles of lipid and protein factors in angiogenesis.

Main Methods:

• Human serum was treated with activated charcoal to remove lipid growth factors.
• Serum was heated to 60°C for 60 minutes to inactivate protein components.
• The effects of sphingosine 1-phosphate (SPP) and basic fibroblast growth factor (bFGF) on endothelial cell morphogenesis were assessed.
• Cellular responses to SPP and bFGF were evaluated in the presence of pertussis toxin.

Main Results:

• Activated charcoal treatment depleted over 50% of serum's capillary morphogenesis activity, indicating the role of lipids.
• Heating serum inactivated the remaining activity, suggesting a protein involvement.
• Sphingosine 1-phosphate (SPP) restored activity in charcoal-treated serum, while bFGF restored activity in heat-treated serum.
• SPP and bFGF together were as effective as whole serum, with SPP responses being pertussis toxin-sensitive and bFGF responses being pertussis toxin-resistant.
• Serum-induced responses were inhibited by approximately 50% with pertussis toxin, supporting the involvement of two distinct factors.

Conclusions:

• Platelet-released sphingosine 1-phosphate (SPP) acts in conjunction with circulating basic fibroblast growth factor (bFGF) to promote capillary formation by microvascular endothelial cells.
• Lipid (SPP) and protein (bFGF) growth factors exert complementary roles in the angiogenic response.
• These factors promote chemotaxis, angiogenic differentiation, and angiogenesis in vivo.