Massimo, M. | Search bioRxiv

bioRxiv2024

Unraveling Microglial Spatial Organization in the Developing Human Brain with DeepCellMap, a Deep Learning Approach Coupled to Spatial Statistics

Mapping cellular organization in the developing brain presents significant challenges due to the multidimensional nature of the data, characterized by complex spatial patterns that are difficult to interpret without high-throughput tools. We developed DeepCellMap, a deep-learning-assisted tool that integrates multi-scale image processing with advanced spatial and clustering statistics. This pipeline was designed to map microglial organization during normal and pathological brain development but can be adapted to any cell type. Using DeepCellMap, we capture the morphological diversity of microglia, identify strong coupling between proliferative and phagocytic phenotypes, and show that distinct spatial clusters rarely overlap as human brain development progresses. Additionally, we uncover a novel association between microglia and blood vessels in fetal brains exposed to maternal SARS-CoV-2. These findings offer insights into whether various microglial phenotypes form networks in the developing brain to occupy space, and in conditions involving haemorrhages, whether microglia respond to, or influence changes in blood vessel integrity. DeepCellMap is available as open-source software and is a powerful tool for extracting spatial statistics and analyzing cellular organization in large tissue sections, accommodating various imaging modalities. This platform could open new avenues for studying brain development and related pathologies.

developmental biology↗

bioRxiv2024

25-hydroxycholesterol dysregulates brain endothelial cell function and exacerbates cerebral haemorrhage

The antiviral enzyme cholesterol 25-hydroxylase (CH25H) and its metabolite 25-hydroxycholesterol (25HC), which modulates cholesterol metabolism during infection, have been previously associated with vascular pathology. Viral infections have been linked to risk of intracerebral haemorrhage (ICH) but the molecular mechanisms leading to brain vessel rupture via antiviral responses remain unknown. We hypothesised that the CH25H/25HC pathway may impact neuroendothelial integrity in the context of infection-associated ICH. Here, using a SARS-CoV-2-spike-induced zebrafish ICH model and foetal human SARS-CoV-2-associated cortical tissue containing microbleeds, we identified an upregulation of CH25H in infection-associated cerebral haemorrhage. Using zebrafish ICH models and human brain endothelial cells, we asked whether 25HC may promote neurovascular dysfunction by modulating cholesterol metabolism. We found that 25HC and pharmacological inhibition of HMGCR by atorvastatin interacted to exacerbate brain bleeding in zebrafish larvae and in vitro brain endothelial dysfunction. In vitro 25HC-induced dysfunction was also rescued by cholesterol supplementation. These results demonstrate that the antiviral factor 25HC can dysregulate brain endothelial function by remodelling cholesterol metabolism. We propose that the CH25H/25HC pathway represents an important component in the pathophysiology of brain vessel dysfunction associated with infection and cholesterol dysregulation in the context of ICH. Summary StatementThe antiviral metabolite 25-hydroxycholesterol dysregulates brain endothelial function by remodelling cholesterol metabolism, thereby providing a mechanistic link between viral infection and brain endothelial dysfunction in conditions such as intracerebral haemorrhage.

neuroscience↗