Biology subjects

Droux, J.

Publications and source records attributed to Droux, J..

5 recordsLinked to original sources

bioRxiv2025

In Vivo Network-Level Cerebrovascular Mapping Reveals the Impact of Flow Topology on Capillary Stalls After Stroke

Cerebral microvasculature is essential for brain function, but how flow and large-scale connectivity contribute to its resilience or failure remains poorly understood. To address this, we developed OMNIMap, a framework for mesoscale in vivo mapping of functional microvascular networks, capturing flow dynamics and connectivity across thousands of capillaries. OMNIMap integrates extended-focus optical coherence microscopy and learning-based segmentation with global vessel-graph optimization to resolve artery-vein classification and branching order, linking capillary flow and stalls to broader network context. Applied to over 40,000 capillaries in the mouse cortex before and after ischemic stroke, we observe heterogeneous vulnerability patterns: while most capillaries stall or reduce flow after arterial occlusion, some experience accelerated flow. Further analysis revealed that stall-prone flow topology subtypes were less prevalent than their robust counterparts. Notably, the overall distribution of these subtypes remains largely preserved after stroke, revealing a previously unrecognized, system-level organizing principle that alleviates the impact of individual capillary stalls to maintain network-level perfusion.

neuroscience↗

bioRxiv2024

Bessel Beam Optical Coherence Microscopy Enables Multiscale Assessment of Cerebrovascular Network Morphology and Function

Understanding the morphology and function of large-scale cerebrovascular networks is crucial for studying brain health and disease. However, reconciling the demands for imaging on a broad scale with the precision of high-resolution volumetric microscopy has been a persistent challenge. In this study, we introduce Bessel beam optical coherence microscopy with an extended focus to capture the full cortical vascular hierarchy in mice over 1000 x 1000 x 360 m3 field-of-view at capillary level resolution. The post-processing pipeline leverages a supervised deep learning approach for precise 3D segmentation of high-resolution angiograms, hence permitting reliable examination of microvascular structures at multiple spatial scales. Coupled with high-sensitivity Doppler optical coherence tomography, our method enables the computation of both axial and transverse blood velocity components as well as vessel-specific blood flow direction, facilitating a detailed assessment of morpho-functional characteristics across all vessel dimensions. Through graph-based analysis, we deliver insights into vascular connectivity, all the way from individual capillaries to broader network interactions, a task traditionally challenging for in vivo studies. The new imaging and analysis framework extends the frontiers of research into cerebrovascular function and neurovascular pathologies.

bioengineering↗

bioRxiv2024

Pia-FLOW: Deciphering hemodynamic maps of the pial vascular connectome and its response to arterial occlusion

The pial vasculature is the sole source of blood supply to the neocortex. The brain is contained within the skull, a vascularized bone marrow with a unique anatomical connection to the brain. Recent developments in tissue clearing have enabled unprecedented mapping of the entire pial and calvarial vasculature. However, what are the absolute flow rates values of those vascular networks? This information cannot accurately be retrieved with the commonly used bioimaging methods. Here, we introduce Pia-FLOW, a new approach based on large-scale fluo-rescence localization microscopy, to attain hemodynamic imaging of the whole murine pial and calvarial vasculature at frame rates up to 1000 Hz and spatial resolution reaching 5.4 {micro}m. Using Pia-FLOW, we provide detailed maps of flow velocity, direction and vascular diameters which can serve as ground-truth data for further studies, advancing our understanding of brain fluid dynamics. Furthermore, Pia-FLOW revealed that the pial vascular network functions as one unit for robust allocation of blood after stroke.

neuroscience↗

bioRxiv2023

Transcranial cortex-wide imaging of murine ischemic perfusion with large-field multifocal illumination fluorescence microscopy

Ischemic stroke is a common cause of death worldwide and a main cause of morbidity. Presently, computed tomography and magnetic resonance imaging are the mainstay for stroke diagnosis and therapeutic monitoring. These modalities are often limited in terms of accessibility as well as their ability to map brain perfusion with sufficient spatial and temporal resolution, particularly in the context of preclinical studies, thus calling for development of new brain perfusion techniques featuring rapid imaging speed, cost-effectiveness, and ease of use. Herein, we report on cortex-wide perfusion imaging in murine ischemic stroke with large-field multi-focal illumination fluorescence microscopy (LMI). We attained quantitative readings of hemodynamic and structural changes in cerebral vascular network and pial vessels at capillary level resolution and 80 Hz frame rate fully transcranially. The in vivo perfusion maps accurately delineated the ischemic core and penumbra, further exhibiting strong correlation with ex vivo triphenyl tetrazolium chloride staining. Interestingly, monitoring of therapeutic effects of thrombolysis in stroke has revealed that early recanalization could effectively save the penumbra whilst reducing the infarct area. Furthermore, cross-strain comparison of perfusion dynamics affirmed that C57BL/6 mice, benefiting from more extensive pial collateral recruitment, feature a larger penumbra and smaller infarct core as compared to BALB/c mice which have few or no collaterals. Finally, we apply LMI to show that sensory stimulation-based treatment enhances blood flow and abolish perfusion deficit in the ischemic core and penumbra regions. The simple, cost-effective and minimally invasive nature of the proposed approach offers new venues for brain perfusion research under various disease conditions such as stroke, neurodegeneration or epileptic seizures.

neuroscience↗

bioRxiv2023

Acoustic trapping and navigation of microrobots in the mouse brain vasculature

Many cerebrovascular and neurodegenerative diseases are currently challenging to treat due to the complex and delicate anatomy of the brain. The use of microrobots can create new opportunities in brain research due to their ability to access hard-to-reach regions and empower various biological applications; however, little is known about the functionality of microrobots in the brain, owing to their limited imaging modalities and intravascular challenges such as high blood flow velocities, osmotic pressures, and cellular responses. Here, we present an acoustic, non-invasive, biocompatible microrobot actuation system, for in vivo navigation in the bloodstream, in which microrobots are formed by lipid-shelled microbubbles that aggregate and propel under the force of acoustic irradiation. We investigated their capacities in vitro within a microfluidic 3D setup and in vivo in a living mouse brain. We show that microrobots can self-assemble and navigate upstream in the brain vasculature. Our microrobots achieved upstream velocities of up to 1.5 m/s and overcame blood flows of ~10 mm/s. Our results prove that microbubble-based microrobots are scalable to the complex 3D living milieu. Significance StatementNumerous brain diseases, including ischemic stroke, Alzheimers disease, and glioblastoma, may benefit from local and targeted therapies. Although they show great promise, microrobots have not yet demonstrated successful in vivo navigation inside the brain, as the challenging flow conditions and the complex 3D vascular network in the brain pose fundamental limitations. Here, we apply acoustically driven microrobots with the capacity for self-assembly and real-time navigation, including navigation against blood flow up to 10 mm/s, used for the first time inside the brain vasculature of a living mouse. The ultrasound manipulation of microrobots inside animal models provides a much-needed pathway for the advancement of preclinical research.

bioengineering↗