L-Type Ca 2+ channels and TRPC3 channels shape brain pericyte Ca 2+ signaling and hemodynamics throughout the arteriole to capillary network in vivo
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Pericytes play a crucial role in regulating cerebral blood flow (CBF) through processes like vasomotion and neurovascular coupling (NVC). Recent work has identified different pericyte types at distinct points in the cerebrovascular network, such as the arteriole-capillary transition zone (ACT) and distal capillaries, sparking debate about their functional roles in blood flow control. Part of this discussion has comprised the possible mechanisms that may regulate pericyte Ca 2+ signaling. Using in vivo two-photon Ca 2+ imaging and a pharmacological approach with Ca 2+ channel blockers (nimodipine and Pyr3), we assessed the contribution of L-type voltage-gated Ca 2+ channels (VGCC) and transient receptor potential canonical 3 (TRPC3) channels to Ca 2+ signaling in different pericyte types, ensheathing and capillary pericytes. We also measured local hemodynamics such as vessel diameter, blood cell velocity and flux during vasomotion, and following somatosensory stimulation to evoke NVC. We report that VGCC and TRPC3 channels underlie spontaneous fluctuations in ensheathing pericyte Ca 2+ that trigger vasomotor contractions, but the contribution of each of these mechanisms to vascular tone depends on the specific branch of the ACT. Distal capillary pericytes also express L-type VGCCs and TRPC3 channels and they mediate spontaneous Ca 2+ signaling in these cells. However, only TRPC3 channels maintain resting capillary tone, possibly by a receptor-operated Ca 2+ entry mechanism. By applying the Ca 2+ channel blockers during NVC, we found a significant involvement of L-type VGCCs in both pericyte types, influencing their ability to dilate during functional hyperemia. These findings provide new evidence of VGCC and TRPC3 activity in pericytes in vivo and establish a clear distinction between brain pericyte types and their functional roles, opening avenues for innovative strategies to selectively target their Ca 2+ dynamics for CBF control.
Significance Statement
Although brain pericytes contribute to the regulation of CBF, there is uncertainty about how different types of pericytes are involved in this process. Ca 2+ signaling is believed to be important for the contractility and tone of pericytes, but there is a limited understanding of the Ca 2+ pathways in specific pericyte types. Here, we demonstrate that both VGCC and TRPC3 channels are active in distinct types of pericytes throughout the cerebrovascular network, but have different roles in pericyte tone depending on the pericyte location. This has important implications for how pericytes influence vasomotion and neurovascular coupling, which are central processes in CBF regulation. This work also provides the first evidence of TRPC3 channel activity in pericytes in vivo , furthering our understanding of the diverse signaling pathways within these brain mural cells.
