Smooth Muscle Dysfunction Drives Cerebrovascular Reserve Failure and End-Organ Brain Injury.

Area of Science:

• Neurology
• Vascular Biology
• Genetics

Background:

• Cerebrovascular reserve failure is key to ischemic vulnerability.
• Mechanisms linking vascular smooth muscle dysfunction to brain injury are unclear.
• ACTA2 mutation causes multisystemic smooth muscle dysfunction.

Purpose of the Study:

• To determine if pathogenic ACTA2 mutation causes baseline cerebrovascular reserve failure.
• To assess brain vulnerability to hypoperfusion in the absence of arterial occlusion.

Main Methods:

• Examined cerebrovascular structure, hemodynamics, and reserve in a mouse model of ACTA2 mutation.
• Assessed cerebral artery morphology via angiography.
• Measured blood pressure reactivity and cerebral blood flow (CBF) during vasoactive challenges and hypotension.
• Evaluated downstream brain effects using histology, functional connectivity imaging, and behavioral tests.

Main Results:

• Impaired smooth muscle contractility led to cerebral artery narrowing and reduced vasoreactivity.
• Mutant mice showed blunted cerebrovascular reserve, with reduced baseline CBF.
• Hypotension and stress impaired compensatory perfusion, worsening behavioral outcomes and causing brain injury (white matter loss, neuronal loss).

Conclusions:

• ACTA2 mutation causes baseline cerebrovascular reserve failure, increasing brain vulnerability to hypoperfusion and ischemic injury.
• This establishes reserve failure as a mechanism linking vascular dysfunction to brain injury.
• Preserving cerebrovascular reserve is critical for brain health in hypotension-prone vascular diseases.