Ciccarelli, A. | bioRxiv Science

bioRxiv2024

Mycobacterium tuberculosis ESX-T7SS impacts the 3D architecture of tuberculous lesion in susceptible mice

Tuberculosis (TB) is characterized by the formation of heterogenous, immune-rich granulomas present in various forms in the lungs. Both host and pathogen contribute to this heterogeneity however the molecular and cellular drivers of within-host granuloma heterogeneity remain to be fully elucidated. This knowledge gap is due to a lack of experimental approaches that can fully capture the complex dynamics of the lung architecture, dynamics of host-pathogen interplay and pathogenesis. Here, we developed an approach that combines PACT-based clearing with light sheet fluorescent microscopy for visualizing lesion architecture development and lung involvement in M. tuberculosis-infected C3HeB/FeJ susceptible mice. This 3D modelling of whole lung lobes approach revealed critical architectural features in lesion development and lung involvement that were not apparent using traditional thin section imaging. Wild type M. tuberculosis infection triggered a clear and well-organized granulomatous-like organization with substantial growth throughout the infection period that invaded a high percentage of the total lung volume. In contrast, infection with the avirulent ESX-1 deletion mutant strain Mtb {Delta}RD1 showed an altered growth pattern with diffuse and sparsely organized CD11b recruitment to sites of infection. Moreover, most of the Mtb {Delta}RD1-triggered lesions were present in the periphery of the lungs and did not display any formal organization. We further provide a novel way of interrogating PACT-cleared tissue for high ultrastructural content using volumetric correlative light and electron microscopy, allowing individual immune cell populations to be tracked and their fate within the granuloma captured. Ultimately, the combination of both modalities allowed an unprecedented view of the architectural distribution of M. tuberculosis in the lungs and the progression of lesion development over time. Our data highlight that ESX-1 from M. tuberculosis is required for lesion architecture progression in a susceptible mouse model of TB.

microbiology↗

bioRxiv2024

Sympathetic neuron-derived NPY protects from obesity by sustaining the mural progenitors of thermogenic adipocytes.

Neuropeptide Y (NPY) is secreted by sympathetic nerves1,2, but its direct impact on thermogenic adipocytes is unknown. Here we uncover the mechanism by which peripheral NPY protects from obesity. Our imaging of cleared murine brown and white adipose tissue (BAT and WAT) established that NPY+ sympathetic axons are only a minority that mostly maps to the peri-vasculature; our analysis of single-cell RNA-sequencing datasets identifies mural cells as the main NPY-responsive cells in adipose tissues. We show that NPY sustains mural cells, which are known to be a source of beige cells in both BAT and WAT3-5 and that NPY facilitates the differentiation to thermogenic adipocytes. We found that diet-induced-obesity leads to neuropathy of NPY+ axons and concomitant depletion of the mural cell pool of beige fat progenitors. This defect is replicated in conditional knockout (cKO) mice with NPY specifically abrogated from sympathetic neurons. These cKO mice have whitened BAT with reduced thermogenic ability and lower energy expenditure even before the onset of obesity; they develop adult-onset obesity on a regular chow diet and are more susceptible to diet induced obesity without increasing food consumption. Our results indicate that, relative to central NPY, peripheral NPY produced by the sympathetic nerves has the opposite effect on body weight homeostasis by sustaining the proliferation of the mural cell progenitors of thermogenic adipocytes.

physiology↗