Collateral Vessels Have Unique Endothelial and Smooth Muscle Cell Phenotypes

Area of Science:

• Cardiovascular Biology
• Microcirculation Research
• Vascular Cell Biology

Background:

• Collateral blood vessels provide crucial alternative perfusion routes in tissues.
• Collaterals are vulnerable to rarefaction due to aging, vascular risk factors, and Alzheimer's disease.
• This vulnerability is linked to the disturbed hemodynamic environment in collateral-residing watershed regions.

Purpose of the Study:

• To investigate if collateral endothelial cells (ECs) and smooth muscle cells (SMCs) possess unique specializations.
• To compare collateral cells with similarly-sized distal-most arterioles (DMAs).
• To determine if these specializations maintain collateral integrity under adverse hemodynamic conditions.

Main Methods:

• Examination of mouse brain microcirculation.
• Morphological analysis of ECs and SMCs.
• Assessment of gene expression patterns (Pycard, Ki67, Pdgfb, Angpt2, Dll4, Ephrinb2, eNOS, Klf2/4).
• Evaluation of primary cilia presence and abundance.

Main Results:

• Collateral ECs exhibit axial alignment, unlike pro-inflammatory ECs in other vasculature.
• Primary cilia are present on collateral and DMA ECs, but less abundant on collaterals.
• Collaterals are continuously invested with SMCs and show distinct gene expression profiles compared to DMAs.
• Collateral tortuosity develops postnatally, suggesting a higher cell turnover rate.

Conclusions:

• Endothelial and smooth muscle cells in collaterals display significant morphologic and functional differences from nearby arterioles.
• These differences may represent specializations that counteract the pro-inflammatory and pro-proliferative environment.
• Further research is needed to confirm if these specializations mitigate risk factor-induced collateral rarefaction.