Biology subjects

Sletten, E. M.

Publications and source records attributed to Sletten, E. M..

5 recordsLinked to original sources

bioRxiv2026

NIR-II squeezed light-field microscopy enables high-speed volumetric imaging of deep-tissue dynamics in vivo

High-speed three-dimensional imaging in scattering biological tissues remains challenging because volumetric microscopy generally requires scanning, whereas snapshot light-field approaches divide limited detector pixels among multiple views. This constraint is particularly severe in the second near-infrared window (NIR-II), where InGaAs cameras have small sensor formats and high detector noise. Here we introduce NIR-II squeezed light-field microscopy (NIR-II SLIM), which optically rotates and compresses multiple perspective views before detection, allowing efficient use of camera pixels while retaining complementary spatial information for three-dimensional reconstruction. NIR-II SLIM acquires up to 600 volumes s-1 with a reconstructed lateral sampling grid of 512 x 512 pixels. We use this method for label-free imaging of cardiac dynamics in pigmented late-larval zebrafish, resolving chamber deformation and millisecond-scale atrioventricular-valve motion, and for NIR-II fluorescence imaging of vascular and lymphatic transport in mice. NIR-II SLIM provides a detector-efficient approach for high-speed volumetric imaging of rapid biological dynamics in scattering tissues.

bioengineering↗

bioRxiv2025

Tissue surface mechanics constrains proliferation-driven forces to guide mammalian body axis elongation

Mammalian embryos undergo complex morphogenetic changes after implantation in the uterus. The elongation of the body along a head-to-tail axis is a pivotal event, as it lays the foundation of the body plan. While genetic and biochemical aspects of mammalian body elongation have been uncovered, the physical mechanism of axial morphogenesis remains unknown, largely due to the inaccessibility of the implanted embryo to physical measurements and manipulations in utero. Gastruloids, a stem-cell-based embryo model of mammalian axial morphogenesis, lift such limitations. Combining live imaging, direct mechanical measurements, and chemical and mechanical perturbations, here we show that axis elongation in mouse and human gastruloids is guided by a posterior actin cap at the tissue surface that constrains the expansive forces of cell proliferation. Measurements of mechanical stresses using oil microdroplets, as well as inhibition of cell proliferation and myosin activity, show that the forces driving elongation arise from cell proliferation, and not from convergent extension movements. We find that isotropic tissue expansion is redirected into posterior elongation by the formation of a supracellular actin cap at the posterior tissue surface that restricts lateral tissue expansion. Finally, we show that posterior elongation in mouse embryos displays the key features of the physical elongation mechanism reported for mouse and human gastruloids. These findings reveal that mammalian body axis elongation, including human, occurs via a different physical mechanism from other vertebrate species.

biophysics↗

bioRxiv2023

Shortwave infrared (SWIR) fluorescence imaging of peripheral organs in awake and freely moving mice

Extracting biological information from awake and unrestrained mice is imperative to in vivo basic and pre-clinical research. Accordingly, imaging methods which preclude invasiveness, anesthesia, and/or physical restraint enable more physiologically relevant biological data extraction by eliminating these extrinsic confounders. In this article we discuss the recent development of shortwave infrared (SWIR) fluorescent imaging to visualize peripheral organs in freely-behaving mice, as well as propose potential applications of this imaging modality in the neurosciences.

bioengineering↗

bioRxiv2022

In situ quantification of osmotic pressure within living embryonic tissues

Mechanics is known to play a fundamental role in many cellular and developmental processes. Beyond active forces and material properties, osmotic pressure is believed to control essential cell and tissue characteristics. However, it remains very challenging to perform in situ and in vivo measurements of osmotic pressure. Here we introduce doubleemulsion droplet sensors that enable local measurements of osmotic pressure intra- and extra-cellularly within 3D multicellular systems, including living tissues. After generating and calibrating the sensors, we measured the osmotic pressure in blastomeres of early zebrafish embryos as well as in the interstitial fluid between the cells of the blastula by monitoring the size of droplets previously inserted in the embryo. Our results show a balance between intracellular and interstitial osmotic pressures, with values of approximately 0.7 MPa, but a large pressure imbalance between the inside and outside of the embryo. The ability to measure osmotic pressure in 3D multicellular systems (developing embryos, organoids, etc.) will help understand its role in fundamental biological processes.

biophysics↗

bioRxiv2021

Stress-driven tissue fluidization physically segments vertebrate somites

The precise and robust formation of embryonic structures is essential for the function of the organism. During somitogenesis, genetic traveling waves in the presomitic mesoderm orchestrate somite formation and the segmentation of the vertebrate body axis. While key molecular and genetic aspects of this process are known, the mechanical events required to robustly define sharp somite boundaries and physically segment the presomitic mesoderm remain unclear. Here we show that both mechanical noise in the tissue and somite boundary tension are optimized to define sharp somite boundaries and robustly segment the body axis. We find that a large, actomyosin-driven increase in boundary tension progressively straightens the nascent somite-somite boundary. While noise is typically believed to be detrimental to robustness, our results show how mechanical noise in the tissue, introduced by active tension fluctuations at cell contacts, is necessary to fully straighten somite boundaries and minimize variation across individuals. Chemical and optogenetic perturbations of both boundary tension and mechanical noise in the surrounding tissue show that zebrafish embryos optimally tune these quantities to the values necessary to ensure maximal somite boundary straightness. Altogether, these results reveal the physical mechanism of somite formation in zebrafish and uncover how optimal mechanical noise helps robustly shape embryonic structures.

biophysics↗