Capillary-associated microglia regulate vascular structure and function through PANX1-P2RY12 coupling in mice

Kanchan Bisht,Hong-Ru Chen,Zainab Calcuttawala,Joseph O Uweru,Kenneth A Okojie,Ukpong B Eyo,Yu-Yo Sun,Dennis H Lentferink,Bria Friestad,Marie-Ève Tremblay,Lara Jabbour,Brant E Isakson,Kaushik Sharma,Jordan Benderoth,Antony Brayan Campos-Salazar,Saipranusha Amancherla,Chia-Yi Kuan,William A Mills,Bruce Corliss

doi:10.1038/s41467-021-25590-8

Abstract

Microglia are brain-resident immune cells with a repertoire of functions in the brain. However, the extent of their interactions with the vasculature and potential regulation of vascular physiology has been insufficiently explored. Here, we document interactions between ramified CX3CR1 + myeloid cell somata and brain capillaries. We confirm that these cells are bona fide microglia by molecular, morphological and ultrastructural approaches. Then, we give a detailed spatio-temporal characterization of these capillary-associated microglia (CAMs) comparing them with parenchymal microglia (PCMs) in their morphological activities including during microglial depletion and repopulation. Molecularly, we identify P2RY12 receptors as a regulator of CAM interactions under the control of released purines from pannexin 1 (PANX1) channels. Furthermore, microglial elimination triggered capillary dilation, blood flow increase, and impaired vasodilation that were recapitulated in P2RY12−/− and PANX1−/− mice suggesting purines released through PANX1 channels play important roles in activating microglial P2RY12 receptors to regulate neurovascular structure and function.

Highlights

Microglia are brain-resident immune cells with a repertoire of functions in the brain
Characterization of capillary-associated microglia (CAMs) revealed (i) that they are enriched on the vasculature than is expected at random based of the brain blood vessel density; (ii) that while microglial processes are known to make transient physical contacts with the neurovasculature, these CAM interactions occur through the more stable microglial somata; (iii) that they exhibit mostly similar features with parenchymal microglia (PCMs), suggesting that they are unlikely to be ontogenically or functionally distinct cells; and (iv) that their interactions with capillaries are at least in part regulated by purinergic P2RY12 signaling activated by purines released from pannexin 1 (PANX1) channels
Pharmacological treatment to eliminate microglia resulted in an increase in capillary diameter, cerebral blood flow (CBF), and impairment in vasodilative responses, which were recapitulated with P2RY12 and PANX1 deficiencies

Summary

Introduction

Microglia are brain-resident immune cells with a repertoire of functions in the brain. Characterization of capillary-associated microglia (CAMs) revealed (i) that they are enriched on the vasculature (about a third of the microglial population) than is expected at random based of the brain blood vessel density; (ii) that while microglial processes are known to make transient physical contacts with the neurovasculature, these CAM interactions occur through the more stable microglial somata; (iii) that they exhibit mostly similar features with parenchymal microglia (PCMs), suggesting that they are unlikely to be ontogenically or functionally distinct cells; and (iv) that their interactions with capillaries are at least in part regulated by purinergic P2RY12 signaling activated by purines released from pannexin 1 (PANX1) channels. Pharmacological treatment to eliminate microglia resulted in an increase in capillary diameter, cerebral blood flow (CBF), and impairment in vasodilative responses, which were recapitulated with P2RY12 and PANX1 deficiencies Together, these results provide evidence into the identification, characterization, interaction mechanisms, and functional significance of CAMs, highlighting microglia as bona fide components of the NVU

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Results

Conclusion