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Iba C, Abe Y, Tanaka KF. Optogenetic demonstration of the involvement of SMA-negative mural cells in the regulation of cerebral blood flow. Front Physiol 2023; 14:1322250. [PMID: 38187133 PMCID: PMC10771846 DOI: 10.3389/fphys.2023.1322250] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2023] [Accepted: 12/08/2023] [Indexed: 01/09/2024] Open
Abstract
Mural cells are critical components of the cerebral vasculature. They are categorized into three primary subsets: arteriole smooth muscle cells (aSMCs), pericytes (PCs) and venule smooth muscle cells (vSMCs). It is well known that aSMCs can directly regulate cerebral blood flow (CBF) with their own contraction and dilation mechanisms. On the other hand, the direct involvement of PCs or vSMCs in CBF regulation is controversial. This ambiguity is largely due to the lack of specifically manipulable tools to isolate their function. To address this issue, we employed a set-subtraction approach by using a combination of tTA-mediated gene induction and Cre-mediated gene excision. We developed transgenic mice expressing optical actuators, channelrhodopsin-2 (ChR2) and photoactivated adenylyl cyclase (PAC) in smooth muscle actin (SMA)-negative mural cells that lack the machinery for SMA-mediated vasoregulation. Using these mouse models, we assessed CBF alterations in response to optical stimulation using laser Doppler techniques. Our results showed that optical stimulation induced notable CBF changes in both models. This study provides evidence for the potential regulatory role of PCs and vSMCs in cerebral hemodynamics and introduces powerful tools to specifically manipulate these cell types in vascular neurobiology.
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Affiliation(s)
| | | | - Kenji F. Tanaka
- Division of Brain Sciences, Institute for Advanced Medical Research, Keio University School of Medicine, Tokyo, Japan
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Murata J, Unekawa M, Kudo Y, Kotani M, Kanno I, Izawa Y, Tomita Y, Tanaka KF, Nakahara J, Masamoto K. Acceleration of the Development of Microcirculation Embolism in the Brain due to Capillary Narrowing. Stroke 2023; 54:2135-2144. [PMID: 37309687 DOI: 10.1161/strokeaha.122.042416] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2022] [Accepted: 05/05/2023] [Indexed: 06/14/2023]
Abstract
BACKGROUND Cerebral microvascular obstruction is critically involved in recurrent stroke and decreased cerebral blood flow with age. The obstruction must occur in the capillary with a greater resistance to perfusion pressure through the microvascular networks. However, little is known about the relationship between capillary size and embolism formation. This study aimed to determine whether the capillary lumen space contributes to the development of microcirculation embolism. METHODS To spatiotemporally manipulate capillary diameters in vivo, transgenic mice expressing the light-gated cation channel protein ChR2 (channelrhodopsin-2) in mural cells were used. The spatiotemporal changes in the regional cerebral blood flow in response to the photoactivation of ChR2 mural cells were first characterized using laser speckle flowgraphy. Capillary responses to optimized photostimulation were then examined in vivo using 2-photon microscopy. Finally, microcirculation embolism due to intravenously injected fluorescent microbeads was compared under conditions with or without photoactivation of ChR2 mural cells. RESULTS Following transcranial photostimulation, the stimulation intensity-dependent decrease in cerebral blood flow centered at the irradiation was observed (14%-49% decreases relative to the baseline). The cerebrovascular response to photostimulation showed significant constriction of the cerebral arteries and capillaries but not of the veins. As a result of vasoconstriction, a temporal stall of red blood cell flow occurred in the capillaries of the venous sides. The 2-photon excitation of a single ChR2 pericyte demonstrated the partial shrinkage of capillaries (7% relative to the baseline) around the stimulated cell. With the intravenous injection of microbeads, the occurrence of microcirculation embolism was significantly enhanced (11% increases compared to the control) with photostimulation. CONCLUSIONS Capillary narrowing increases the risk of developing microcirculation embolism in the venous sides of the cerebral capillaries.
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Affiliation(s)
- Juri Murata
- Graduate School of Informatics and Engineering (J.M., Y.K., M.K., K.M.), University of Electro-Communications, Tokyo, Japan
| | - Miyuki Unekawa
- Department of Neurology (M.U., Y.I., Y.T., J.N.), Keio University School of Medicine, Tokyo, Japan
| | - Yuya Kudo
- Graduate School of Informatics and Engineering (J.M., Y.K., M.K., K.M.), University of Electro-Communications, Tokyo, Japan
| | - Maho Kotani
- Graduate School of Informatics and Engineering (J.M., Y.K., M.K., K.M.), University of Electro-Communications, Tokyo, Japan
| | - Iwao Kanno
- Department of Functional Brain Imaging, National Institutes for Quantum Science and Technology, Chiba, Japan (I.K.)
| | - Yoshikane Izawa
- Department of Neurology (M.U., Y.I., Y.T., J.N.), Keio University School of Medicine, Tokyo, Japan
| | - Yutaka Tomita
- Department of Neurology (M.U., Y.I., Y.T., J.N.), Keio University School of Medicine, Tokyo, Japan
- Tomita Hospital, Aichi, Japan (Y.T.)
| | - Kenji F Tanaka
- Division of Brain Sciences, Institute for Advanced Medical Research (K.F.T.), Keio University School of Medicine, Tokyo, Japan
| | - Jin Nakahara
- Department of Neurology (M.U., Y.I., Y.T., J.N.), Keio University School of Medicine, Tokyo, Japan
| | - Kazuto Masamoto
- Graduate School of Informatics and Engineering (J.M., Y.K., M.K., K.M.), University of Electro-Communications, Tokyo, Japan
- Center for Neuroscience and Biomedical Engineering (K.M.), University of Electro-Communications, Tokyo, Japan
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