cerebral blood flow; pericytes; optical imaging; microvascluar sytsem; two-photon imaging; capillaries
Lücker Adrien, Secomb Timothy W., Barrett Matthew J. P., Weber Bruno, Jenny Patrick (2018), The Relation Between Capillary Transit Times and Hemoglobin Saturation Heterogeneity. Part 2: Capillary Networks, in Frontiers in Physiology
, 9, 1296.
Barros L. Felipe, Bolaños Juan P., Bonvento Gilles, Bouzier-Sore Anne-Karine, Brown Angus, Hirrlinger Johannes, Kasparov Sergey, Kirchhoff Frank, Murphy Anne N., Pellerin Luc, Robinson Michael B., Weber Bruno (2018), Current technical approaches to brain energy metabolism, in Glia
, 66(6), 1138-1159.
Stobart Jillian L., Ferrari Kim David, Barrett Matthew J.P., Glück Chaim, Stobart Michael J., Zuend Marc, Weber Bruno (2018), Cortical Circuit Activity Evokes Rapid Astrocyte Calcium Signals on a Similar Timescale to Neurons, in Neuron
, 98(4), 726-735.e4.
Lücker Adrien, Secomb Timothy W., Weber Bruno, Jenny Patrick (2018), The Relation Between Capillary Transit Times and Hemoglobin Saturation Heterogeneity. Part 1: Theoretical Models, in Frontiers in Physiology
, 9, 420.
Schlegel Felix, Sych Yaroslav, Schroeter Aileen, Stobart Jillian, Weber Bruno, Helmchen Fritjof, Rudin Markus (2018), Fiber-optic implant for simultaneous fluorescence-based calcium recordings and BOLD fMRI in mice, in Nature Protocols
, 13(5), 840-855.
Barros L. F., Weber B. (2018), CrossTalk proposal: an important astrocyte-to-neuron lactate shuttle couples neuronal activity to glucose utilisation in the brainCrossTalk, in The Journal of Physiology
, 596(3), 347-350.
Barros L. F., Weber B. (2018), Rebuttal from L. F. Barros and B. WeberCrossTalk, in The Journal of Physiology
, 596(3), 355-356.
Barrett Matthew J. P., Ferrari Kim David, Stobart Jillian L., Holub Martin, Weber Bruno (2018), CHIPS: an Extensible Toolbox for Cellular and Hemodynamic Two-Photon Image Analysis, in Neuroinformatics
, 16(1), 145-147.
Stobart Jillian L, Ferrari Kim David, Barrett Matthew J P, Stobart Michael J, Looser Zoe J, Saab Aiman S, Weber Bruno (2018), Long-term In Vivo Calcium Imaging of Astrocytes Reveals Distinct Cellular Compartment Responses to Sensory Stimulation, in Cerebral Cortex
, 28(1), 184-198.
Schmid Franca, Barrett Matthew J.P., Jenny Patrick, Weber Bruno (2017), Vascular density and distribution in neocortex, in NeuroImage
Lücker Adrien, Secomb Timothy W., Weber Bruno, Jenny Patrick (2017), The relative influence of hematocrit and red blood cell velocity on oxygen transport from capillaries to tissue, in Microcirculation
, 24(3), e12337-e12337.
Schmid Franca, Tsai Philbert S., Kleinfeld David, Jenny Patrick, Weber Bruno (2017), Depth-dependent flow and pressure characteristics in cortical microvascular networks, in PLOS Computational Biology
, 13(2), e1005392-e1005392.
EsipovaTatiana V., BarrettMatthew J. P., ErlebachEva, MasunovArtem E., WeberBruno, VinogradovSergei A., Longitudinal Oxygen Imaging with New High-Performance Phosphorescent Probe, in Cell metabolism
The brain requires constant blood flow to ensure adequate oxygen and energy supply. Therefore, an endogenous regulatory process exists (known as functional hyperemia or neurovascular coupling), linking elevated neuronal energy demand with increased local blood flow (1). Much of the work to date has focused on blood flow changes within arterioles and arteries, but recent evidence suggests local blood flow can be regulated at the capillary level by a specific mural cell population: pericytes (2, 3). Pericytes are able to constrict brain capillaries, but there is conflicting evidence about their contribution in neurovascular coupling.Currently, only two studies have examined pericyte-mediated functional hyperemia in vivo, and they reported contradictory results: one study did not observe capillary events (4), while the other revealed fast capillary dilations that occurred before arteriole responses (2). These opposing outcomes could be attributed to differences in experimental design, data analysis, stimulation protocols, anesthesia, and vascular classification. Furthermore, neither of these studies considered intracellular signaling mechanisms regulating pericyte tone (2, 4).Our group has extensive experience with cellular imaging and blood flow measurements in vivo, and we plan to use a multi-modal approach to gain novel insights into unknown pericyte structure, intracellular signaling mechanisms and their contribution to hemodynamic responses. More specifically, we plan to work on the following three aims: Aim 1: Characterize intracellular signaling regulating brain pericyte tone in vitro and in vivo. We will investigate calcium signaling, membrane potential changes, and the activity of ATP-sensitive potassium channels in both cultured cortical pericytes and cortical pericytes in vivo. To date, visualization of intracellular signals within cortical pericytes has proven to be problematic due to the non-specificity of chemical indicators (5), so we will apply new genetic indicator tools (e.g. Ca2+, membrane potential and ATP/ADP sensors) which will selectively target pericyte cellular signaling. In addition, we will investigate the relevance of selected pathways in regulating pericyte tone in vivo by targeted gene knockout specifically in pericytes. Aim 2: Investigate the contribution of pericytes to functional hyperemia and hemodynamics in vivo. To study this, we will examine neurovascular coupling in adult pericyte-deficient animals in vivo, and also selectively alter pericyte tone by optogenetic stimulation to explore pericyte-induced changes in local blood flow. This will involve a precise analysis of hemodynamics, including capillary diameter and erythrocyte velocity and density measurements with two-photon microscopy. We plan to focus on imaging awake animals to limit the effects of anesthesia and specifically examine blood flow at capillary branch points that are surrounded by pericytes. Aim 3: High resolution imaging of neurovascular unit with special focus on pericyte contacts with endothelium and astrocytes. We will conduct high-resolution imaging of pericytes in situ to precisely elucidate their structure and connections to neighbouring cells. Using correlative light electron microscopy, we will collect functional information (i.e. changes in pericyte tone and hemodynamics) by two-photon microscopy before detailed structural analysis of the same tissue and cells by electron microscopy.A detailed functional and structural analysis of pericyte-mediated tone in vivo is currently lacking. This work has the potential to clarify the three-dimensional structure, the cellular mechanisms and the impact of pericyte tone in functional hyperemia. Our proposed research is also relevant to multiple diseases since pericytes have been shown to contract during ischemia (2, 6), and functional hyperemia is reportedly abnormal in other neurological disorders such as Alzheimer’s disease and vascular dementia.1.Roy CS & Sherrington CS (1890) On the Regulation of the Blood-supply of the Brain. The Journal of physiology 11(1-2):85-158 117.2.Hall CN, et al. (2014) Capillary pericytes regulate cerebral blood flow in health and disease. Nature.3.Peppiatt CM, Howarth C, Mobbs P, & Attwell D (2006) Bidirectional control of CNS capillary diameter by pericytes. Nature 443(7112):700-704.4.Fernandez-Klett F, Offenhauser N, Dirnagl U, Priller J, & Lindauer U (2010) Pericytes in capillaries are contractile in vivo, but arterioles mediate functional hyperemia in the mouse brain. Proc Natl Acad Sci U S A 107(51):22290-22295.5.Hirase H, Creso J, Singleton M, Bartho P, & Buzsaki G (2004) Two-photon imaging of brain pericytes in vivo using dextran-conjugated dyes. Glia 46(1):95-100.6.Yemisci M, et al. (2009) Pericyte contraction induced by oxidative-nitrative stress impairs capillary reflow despite successful opening of an occluded cerebral artery. Nat Med 15(9):1031-1037.