Brain capillary pericytes exert a substantial but slow influence on blood flow

The majority of the brain's vasculature is composed of intricate capillary networks lined by capillary pericytes. However, it remains unclear whether capillary pericytes influence blood flow. Using two-photon microscopy to observe and manipulate brain capillary pericytes in vivo, we find that their optogenetic stimulation decreases lumen diameter and blood flow, but with slower kinetics than similar stimulation of mural cells on upstream pial and precapillary arterioles. This slow vasoconstriction was inhibited by the clinically used vasodilator fasudil, a Rho-kinase inhibitor that blocks contractile machinery. Capillary pericytes were also slower to constrict back to baseline following hypercapnia-induced dilation, and slower to dilate towards baseline following optogenetically induced vasoconstriction. Optical ablation of single capillary pericytes led to sustained local dilation and a doubling of blood cell flux selectively in capillaries lacking pericyte contact. These data indicate that capillary pericytes contribute to basal blood flow resistance and slow modulation of blood flow throughout the brain. Vast networks of capillaries feed the brain. Hartmann et al. show that pericyte contractility is critical for maintenance of enduring capillary tone, which sets an optimized rate and distribution of blood flow through brain capillary networks.

Automated summary

Capillary pericytes play a role in regulating blood flow by influencing vasoconstriction and dilation. Optogenetic stimulation of these cells leads to decreased luminal diameter and blood flow, affecting the overall modulation of blood flow in the brain.