Biology subjects

Schallek, J.

Publications and source records attributed to Schallek, J..

3 recordsLinked to original sources

bioRxiv2024

Photoreceptor loss does not recruit neutrophils despite strong microglial activation

In response to central nervous system (CNS) injury, tissue resident immune cells such as microglia and circulating systemic neutrophils are often first responders. The degree to which these cells interact in response to CNS damage is poorly understood, and even less so, in the neural retina which poses a challenge for high resolution imaging in vivo. In this study, we deploy fluorescence adaptive optics scanning light ophthalmoscopy (AOSLO) to study microglia and neutrophils in mice. We simultaneously track immune cell dynamics using label-free phase-contrast AOSLO at micron-level resolution. Retinal lesions were induced with 488 nm light focused onto photoreceptor (PR) outer segments. These lesions focally ablated PRs, with minimal collateral damage to cells above and below the plane of focus. We used in vivo (AOSLO, SLO and OCT) imaging to reveal the natural history of the microglial and neutrophil response from minutes-to-months after injury. While microglia showed dynamic and progressive immune response with cells migrating into the injury locus within 1-day after injury, neutrophils were not recruited despite close proximity to vessels carrying neutrophils only microns away. Post-mortem confocal microscopy confirmed in vivo findings. This work illustrates that microglial activation does not recruit neutrophils in response to acute, focal loss of PRs, a condition encountered in many retinal diseases.

immunology↗

bioRxiv2020

Label-free imaging of immune cell dynamics in the living retina using adaptive optics

Our recent work characterized the movement of single blood cells within the retinal vasculature of healthy mice (Joseph et al. 2019) using adaptive optics ophthalmoscopy. Here we apply this technique to the context of acute inflammation and discover both infiltrating and tissue-resident immune cells to be visible without any labelling in the living retina using near - infrared light alone. Intravital imaging of immune cells can be negatively impacted by surgical manipulation, exogenous dyes, transgenic manipulation and phototoxicity. These confounds are now overcome, using phase contrast and time-lapse videography to reveal the dynamic behavior of myeloid cells as they interact, extravasate and survey the retina. Cellular motility and differential vascular responses can be measured noninvasively and in vivo across hours to months at the same retinal location, from initiation to the resolution of inflammation. As comparable systems are already available for clinical research, this approach could be readily translated to human application. Impact statementImmune cell motility and vascular response are imaged in vivo and label-free in the CNS for the first time, using high-resolution phase-contrast adaptive optics retinal imaging.

immunology↗

bioRxiv2019

Imaging single-cell blood flow in the smallest to largest vessels in the living retina

Impact StatementUsing a specialized camera that corrects for eye blur, millions of single blood cells are imaged and their speed measured, as they travel through the largest-to-smallest vessels of the retina. AbstractTissue light scatter limits the visualization of the microvascular network deep inside the living mammal. The transparency of the mammalian eye provides a noninvasive view of the microvessels of the retina, a part of the central nervous system. Despite its clarity, imperfections in the optics of the eye blur microscopic retinal capillaries, and single blood cells flowing within. This limits early evaluation of microvascular diseases that originate in capillaries. To break this barrier, we use adaptive optics to noninvasively measure single-cell blood flow, in one of the most widely used research animals: the C57BL/6J mouse. Flow ranged four orders of magnitude (0.0002-1.55 {micro}L min-1) across the full spectrum of retinal vessel diameters (3.2-45.8 {micro}m), without requiring surgery or contrast dye. Here we describe the data collection approach using adaptive optics and provide an analysis pipeline that can measure millions of blood cell speeds automatically.

bioinformatics↗