Biology subjects

Atlan, M.

Publications and source records attributed to Atlan, M..

3 recordsLinked to original sources

bioRxiv2024

Adaptive Optics Rolling Slit Ophthalmoscope: Combining cellular-resolution, high-speed and large field-of-view in a multimodal retinal imager

Label-free optical imaging systems capable of monitoring dynamic biological processes over a large field-of-view (FOV) are essential for advancing our understanding of retinal and neurovascular health. However, existing imaging modalities often involve trade-offs between spatial resolution, contrast, FOV, and frame rate. In this study, we present the Adaptive Optics Rolling Slit Ophthalmoscope (AO-RSO), a novel imaging system that integrates the high-speed, wide-FOV capabilities of camera-based systems with the enhanced contrast and multimodal functionality of point-scanning techniques--without compromising resolution or speed. The AO-RSO utilizes line illumination synchronized with the rolling shutter of a high-speed sCMOS camera, enabling precise and dynamic spatial selection of detected photons: back-scattered photons for near-confocal bright-field imaging and forward-scattered photons for phase-contrast imaging of translucent retinal features. This system successfully visualizes diverse retinal structures, including cone and rod photoreceptors, nerve fiber bundles, red blood cells, vessel walls, and ganglion cells, across a wide retinal area (4.5{degrees}x 2.5{degrees}). With a large FOV and frame rates up to 200 Hz, the AO-RSO enables the quantification of blood flow, tracking of red blood cells within hundreds of capillaries, and evaluation of thousands of photoreceptors in the living human retina. This capability opens new opportunities for functional neuronal imaging, neurovascular coupling studies, and the early detection of retinal and neurodegenerative diseases.

bioengineering↗

bioRxiv2024

Measuring flicker induced vasodilation at a high spatial and temporal resolution in the human retina.

Neurovascular coupling (NVC) is a crucial process in which blood flow is dynamically adjusted to meet the metabolic demands of active neurons. In this study, we introduce an innovative method for in-vivo imaging of retinal blood vessel dilation in response to visible light stimulation, offering insights into the functional regulation of retinal blood flow. Using high-resolution, high-speed phase contrast imaging, we continuously monitored retinal vessel dynamics in eight healthy subjects, capturing precise temporal and spatial changes in vessel size under both stimulated and baseline conditions. We have measured a significant vessel dilation of 5.2% {+/-} 1.6% (4.4 {micro}m {+/-} 1.3 {micro}m) during flicker-stimulation compared to a dilation of 2.5% {+/-} 1% (2.1 {micro}m {+/-} 0.9 {micro}m) without stimulation. The flexibility of our method also allowed for the exploration of various acquisition and stimulation settings, broadening possibilities for investigating neurovascular coupling in the retina. This work not only enhances our understanding of neurovascular coupling but also has the potential to identify new biomarkers for vision-impairing conditions and neurodegenerative diseases. SignificanceNeurovascular coupling is a fundamental mechanism of the brain which locally regulates blood flow in response to changes in neuronal activity. Here, we present a new imaging technique that enables measuring vasodilation in response to visible light stimulation of the neurons at high spatial and temporal resolution in the living human retina. Owing to the unprecedented measurement precision of the presented technique, we provide new insights into the inner working of functional blood flow regulation in the retina. Clinically, this method holds promise for vascular dysfunction early detection, which can improve diagnosis of retinal and neurodegenerative diseases, as well as assist the development of new targeted therapies.

neuroscience↗

bioRxiv2020

Metformin alleviates aging-associated cellular senescence of human adipose stem cells and derived adipocytes

Aging is associated with central fat redistribution, and insulin resistance. To identify age-related adipose features, we evaluated the senescence and adipogenic potential of adipose-derived-stemcells (ASCs) from abdominal subcutaneous fat obtained from healthy normal-weight young (<25y) or older women (>60y). Aged-donor ASCs showed more intense features of aging (senescence, mitochondrial dysfunction, and oxidative stress) than young-donor ASCs. Oxidative stress and mitochondrial dysfunction occurred earlier in adipocytes derived from aged-donor than from young-donor ASCs, leading to insulin resistance and impaired adipogenesis. When aged-donor ASCs were treated with metformin, senescence, oxidative stress and mitochondrial dysfunction returned to the levels observed in young-donor ASCs. Furthermore, metformins prevention of senescence and dysfunction during ASC proliferation restored the cells adipogenic capacity and insulin sensitivity. This effect was mediated by the activation of AMP-activated-protein-kinase. We show here that targeting senescent ASCs from aged women with metformin may alleviate age-related dysfunction, insulin resistance, and impaired adipogenesis.

cell biology↗