Teamer, J. | Search bioRxiv

bioRxiv2023

Three-dimensional spatial quantitative analysis of cardiac lymphatics in the mouse heart

Objective3D microscopy and image data analysis are necessary for studying the morphology of cardiac lymphatic vessels (LyVs) and association with other cell types. We aimed to develop a methodology for 3D multiplexed lightsheet microscopy and highly sensitive and quantitative image analysis to identify pathological remodeling in the 3D morphology of LyVs in young adult mouse hearts with familial hypertrophic cardiomyopathy (HCM). MethodsWe developed a 3D lightsheet microscopy workflow providing a quick turn-around (as few as 5-6 days), multiplex fluorescence detection, and preservation of LyV structure and epitope markers. Hearts from non-transgenic (NTG) and transgenic (TG) HCM mice were arrested in diastole, retrograde perfused, immunolabeled, optically cleared, and imaged. We built an image processing pipeline to quantify LyV morphological parameters at the chamber and branch levels. ResultsChamber-specific pathological alterations of LyVs were identified, but most significantly in the right atrium (RA). TG hearts had a higher volume fraction of ER-TR7+ fibroblasts and reticular fibers. In the RA, we found associations between ER-TR7+ volume fraction and both LyV segment density and median diameter. ConclusionsThis workflow and study enabled multi-scale analysis of pathological changes in cardiac LyVs of young adult mice, inviting ideas for research on LyVs in cardiac disease.

pathology↗

bioRxiv2019

Toxoplasma induces stripping of perisomatic inhibitory synapses

Infection and inflammation within the brain induces changes in neuronal connectivity and function. The intracellular protozoan parasite, Toxoplasma gondii, is one pathogen that infects the brain and can cause encephalitis and seizures. Persistent infection by this parasite is also associated with behavioral alterations and an increased risk for developing psychiatric illness, including schizophrenia. Current evidence from studies in humans and mouse models suggest that both seizures and schizophrenia result from a loss or dysfunction of inhibitory synapses. In line with this, we recently reported that persistent Toxoplasma gondii infection alters the distribution of glutamic acid decarboxylase 67 (GAD67), an enzyme that catalyzes GABA synthesis in inhibitory synapses. These changes could reflect a redistribution of presynaptic machinery in inhibitory neurons or a loss of inhibitory nerve terminals. To directly assess the latter possibility, we employed serial block face scanning electron microscopy (SBFSEM) and quantified inhibitory perisomatic synapses in neocortex and hippocampus following parasitic infection. Not only did persistent infection lead to a significant loss of perisomatic synapses, it induced the ensheathment of neuronal somata by phagocytic cells. Immunohistochemical, genetic, and ultrastructural analyses revealed that these phagocytic cells included reactive microglia. Finally, ultrastructural analysis identified phagocytic cells enveloping perisomatic nerve terminals, suggesting they may participate in synaptic stripping. Thus, these results suggest that microglia contribute to perisomatic inhibitory synapse loss following parasitic infection and offer a novel mechanism as to how persistent Toxoplasma gondii infection may contribute to both seizures and psychiatric illness.\n\nMAIN POINTSO_LIToxoplasma-infection leads the loss of perisomatic inhibitory synapses\nC_LIO_LIPhagocytic microglia ensheath neuronal somata following Toxoplasma-infection\nC_LIO_LIMicroglia contact and envelop perisomatic nerve terminals, suggesting that Toxoplasma induces synaptic stripping\nC_LI

neuroscience↗