Hagenbuchner, J. | Search bioRxiv

bioRxiv2024

Optical tomography reconstructing 3D motion and structure of multiple-scattering samples under rotational actuation

Optical Diffraction Tomography (ODT) has emerged as a powerful tool for imaging biological cells in a non-invasive and label-free manner. However, conventional approaches using ODT by varying the illumination are plagued by the missing cone problem, which introduces ambiguity and deteriorates the axial resolution in the reconstruction. Although utilizing object rotation has the potential to yield isotropic resolution, experimental control or prior retrieval of the rotational parameters is challenging. In this work, we demonstrate ODT of multiple-scattering samples undergoing variable rotational motion, unlocking the potential for isotropic resolution in non-contact systems. We introduce a comprehensive reconstruction method to jointly retrieve both sample and rotational motion in 3D. An interferometric setup enables the recording of amplitude and phase data while the object is rotated in a non-contact manner around one or more chosen axes in an acoustofluidic device. We evaluate the tomographic reconstruction performance of the method for clusters of micro-beads and highlight its suitability for biomedical application beyond single cells, demonstrating high-resolution reconstruction of dense cancer spheroids containing more than 100 cells.

bioengineering↗

bioRxiv2024

Mitochondrial cardiolipin metabolism controlled by tafazzin enables ferroptosis

Mitochondria are important producers of reactive oxygen species, which are involved in triggering ferroptosis, a lipid peroxidation driven form of cell death. Paradoxically, in the rare inherited metabolic disease Barth Syndrome, we discovered a protection from erastin-induced ferroptosis, despite intrinsically elevated mitochondrial ROS levels. The affected transacylase tafazzin, which is mutated in Barth Syndrome, is pivotal for remodeling of the dimeric phospholipid cardiolipin. They unique to mitochondria and essential for shaping their membrane functionalities. We investigated which downstream effects of the pathogenic membrane alterations are responsible for the protective effect against ferroptosis. We found that while iron metabolism, the unsaturation of membrane lipids, and the metabolic activity of the cells were modifying factors, they were not causal. However, we observed that cardiolipin abnormalities are not limited to impair only inner, but also outer mitochondrial membrane protein complexes. Specifically, they impact abundance and oligomerization of voltage-dependent anion channels (VDAC) in response to oxidative stress. We found that tafazzin deficiency via alteration of cardiolipins affects VDAC functionality, thereby modulating small molecule transport and signaling between mitochondria and the remaining cell. This is in line with a reduction of mitochondria-associated membranes (MAM) sites that are formed through VDACs and trapping ROS in mitochondria where they are unable to contribute to ferroptosis. These findings demonstrate that the mitochondrial membrane architecture impacting on subcellular small molecule distribution crucially impact on the manifestation of cell fate decisions, including ferroptosis.

molecular biology↗