Static mechanical strain induces capillary endothelial cell cycle re-entry and sprouting.

Area of Science:

• Biomedical Engineering
• Cell Biology
• Vascular Biology

Background:

• Vascular endothelial cells (VECs) respond to biochemical and mechanical cues to regulate angiogenesis (blood vessel sprouting).
• The impact of sustained (static) mechanical forces on VECs, particularly those from contractile cells like pericytes, is less understood.
• These static forces can change with age and disease, potentially influencing vascular health.

Purpose of the Study:

• To investigate the direct effects of static tensile strain on microvascular endothelial cell monolayers.
• To determine if static mechanical cues can induce endothelial cell proliferation and angiogenesis.
• To identify the molecular mechanisms underlying the response to static strain.

Main Methods:

• Cultured human microvascular endothelial cells were subjected to 10% static tensile strain.
• Cell cycle re-entry was assessed by monitoring S-phase entry.
• Nuclear localization of p27, a cyclin-dependent kinase inhibitor, was analyzed.
• Endothelial cell sprouting was quantified in response to strain.

Main Results:

• Static tensile strain (10%) rapidly induced cell cycle re-entry in growth-arrested endothelial cells.
• Strain-induced S-phase entry correlated with reduced nuclear levels of p27.
• The applied mechanical strain promoted endothelial cell sprouting, indicating a novel mechanical angiogenic switch.
• These findings suggest pericyte-exerted strain can directly drive pathological angiogenesis.

Conclusions:

• Static tensile strain is a direct stimulus for endothelial cell cycle re-entry and proliferation.
• Mechanical forces, independent of biochemical signals, can initiate angiogenesis.
• This mechanical pathway implies that pericyte dysfunction or absence is not a prerequisite for endothelial cell activation in pathological angiogenesis.