A tight squeeze: how do we make sense of small changes in microvascular diameter?

Area of Science:

• Neuroscience
• Physiology
• Vascular Biology

Background:

• The brain requires precise blood flow regulation for its high energy demands.
• Traditionally, arterioles were considered the primary regulators of cerebral blood flow.
• Recent evidence suggests capillary pericytes also play a significant contractile role.

Purpose of the Study:

• To explain the privileged position of capillary pericytes in controlling cerebral blood flow.
• To compare the regulatory roles of capillary pericytes and arterioles.
• To highlight the mechanisms by which pericytes influence blood flow.

Main Methods:

• Review of existing evidence on pericyte function.
• Analysis of fundamental equations governing vascular resistance.
• Discussion of experimental observations on pericyte-mediated blood flow changes.

Main Results:

• Capillary pericytes exert greater control over total cerebral vascular resistance due to the smaller diameter of capillaries compared to arterioles.
• Low-order capillary pericytes respond faster to local energy demands, offering a distinct regulatory role.
• Pericyte contraction can induce capillary stalling, transiently impeding blood cell circulation and further impacting blood flow.

Conclusions:

• Capillary pericytes are crucial regulators of cerebral blood flow, complementing the role of arterioles.
• The unique physical and temporal characteristics of pericytes provide a specialized mechanism for fine-tuning brain energy supply.
• Understanding pericyte function is essential for comprehending cerebral blood flow control and its implications for brain health.