Biology subjects

Hackl, A.

Publications and source records attributed to Hackl, A..

4 recordsLinked to original sources

bioRxiv2023

Correlation of calcium multiphoton with ultrastructural STED imaging of the slit diaphragm in the same glomerulus.

In recent years functional multiphoton imaging of viable mouse tissue and STED imaging of optically cleared tissues allowed new insights into kidney biology. Here, we present a novel workflow where multiphoton imaging of calcium signals in podocytes is, in the same glomerulus, correlated with super-resolved STED imaging and analysis of the slit diaphragm (SD) morphology. Mice expressing the calcium indicator GCaMP3 exclusively in podocytes served as healthy controls and were challenged with two different doses of nephrotoxic serum (NTS). NTS-induced SD architecture damage increased in a dose-dependent manner, whereas intracellular calcium levels exhibited a wide range of variation and showed no correlation with SD damage in the same glomerulus. Our co-imaging protocol is applicable to a broad range of research questions as it is suitable for other tissues and compatible with a variety of reporters and tissue antigens. Translational statementThe combination of multiphoton and super-resolution microscopy identifies the modulation of signaling pathways and resolves the changes in ultrastructure in disease states in the same glomeruli. Using our new method, we can compare functional and morphological data to investigate the degree of correlation to reveal novel underlying pathomechanism. This knowledge can improve our ability to draw conclusions from human kidney biopsies, in which the ultrastructure will be assessed more-often by routine super-resolution microscopy in the future.

cell biology↗

bioRxiv2023

Prostaglandin E2 controls the metabolic adaptation of T cells to the intestinal microenvironment

Immune cells must adapt to different environments during the course of an immune response. We studied the adaptation of CD8+ T cells to the intestinal microenvironment and how this process shapes their residency in the gut. CD8+ T cells progressively remodel their transcriptome and surface phenotype as they acquire gut residency, and downregulate expression of mitochondrial genes. Human and mouse gut-resident CD8+ T cells have reduced mitochondrial mass, but maintain a viable energy balance to sustain their function. We found that the intestinal microenvironment is rich in prostaglandin E2 (PGE2), which drives mitochondrial depolarization in CD8+ T cells. Consequently, these cells engage autophagy to clear depolarized mitochondria, and enhance glutathione synthesis to scavenge reactive oxygen species (ROS) that result from mitochondrial depolarization. Impairing PGE2 sensing promotes CD8+ T cell accumulation in the gut, while tampering with autophagy and glutathione negatively impacts the T cell population. Thus, a PGE2-autophagy-glutathione axis defines the metabolic adaptation of CD8+ T cells to the intestinal microenvironment, to ultimately influence the T cell pool.

immunology↗

bioRxiv2023

Mechanical forces at the kidney filtration barrier govern spatial orientation of podocyte processes on capillaries

Mammalian kidneys filter enormous volumes of water and small solutes, a filtration driven by the very high hydrostatic pressure in glomerular capillaries. Interdigitating cellular processes of podocytes form the slits for fluid filtration. They are connected by the membrane-like slit diaphragm cell junction containing a mechanosensitive ion channel complex and allow filtration while counteracting hydrostatic pressure. Using high-resolution microscopy, we show that filtration-slit-generating secondary processes preferentially align along the capillaries longitudinal axis while primary processes are preferably perpendicular to the longitudinal direction. The preferential orientation requires maturation in development and is lost in disease states. We demonstrate that loss of proper orientation might contribute to impaired filtration by collapsing of the filtration slits and reducing the mechanical stability of podocyte processes. Together, these data suggest that podocytes sense mechanical strain to utilize circumferential hoop stress balancing the massive mechanical strain generated from fluid flow over the filtration slit.

cell biology↗

bioRxiv2022

Resident T cells orchestrate adipose tissue remodeling in a site peripheral to infection

Infection with helminth parasites can affect adiposity, but underlying mechanisms that regulate this process are unclear. We found that fat content of mesenteric adipose tissue (mAT) declined in mice during infection with gut-restricted parasitic worms. This was associated with the accumulation of metabolically activated, immunostimulatory cytokine- and extracellular matrix-secreting multipotent stromal cells, which had potential to differentiate into preadipocytes. Concomitantly, mAT became infiltrated with Th2 lymphocytes that took up long-term residence and responded to signals from stromal cells by producing stromal cell-stimulating cytokines, including Amphiregulin. Signals delivered by Amphiregulin to stromal cells were required for immunity to infection. Our findings reveal intricate intercellular communication between Th2 cells and adipocyte progenitors and link immunity to intestinal infection to T cell-dependent effects on the adipocyte lineage.

immunology↗