Biology subjects

Bretheau, F.

Publications and source records attributed to Bretheau, F..

3 recordsLinked to original sources

bioRxiv2026

Blood-brain barrier model architecture shapes peripheral immune cell trafficking in Parkinson's disease

Parkinsons disease (PD) is a neurodegenerative disorder traditionally characterized by dopaminergic neuron loss in the substantial nigra pars compacta, but peripheral immune dysregulation and blood-brain barrier (BBB) dysfunction have been increasingly implicated in disease etiology. However, how circulating immune cells interact with the human BBB and how these interactions are captured across experimental models remains poorly understood. In particular, human BBB models offer multiple platforms to interrogate these biological questions, with organ-on-chip approaches attracting significant interest. In this context, it is essential to determine whether model architecture influences the assessment of immune-endothelial interactions in PD, and if it may lead to fundamentally different interpretations of immune cell trafficking at the human BBB. Here, we compared peripheral blood mononuclear cells (PBMCs) from control donors or individuals with PD in human induced pluripotent stem cell (iPSC)-derived BBB models to determine how static and dynamic BBB systems influence immune cell behavior. To do so, we leveraged our brain chip platform to establish a model based on expression of the PD-associated SNCA triplication mutation. Using a two-dimensional transwell system and a three-dimensional (3D) microfluidic BBB chip, we evaluated PBMC attachment and transmigration under conditions of PBMC disease status, endothelial genotype associated with SNCA triplication, and exposure to -synuclein (-Syn) monomers or preformed fibrils (PFFs). PBMCs from PD donors showed increased baseline reactivity and altered endothelial interactions compared with controls. In transwell models, SNCA triplication increased PBMC attachment and selectively enhanced PD PBMC transmigration, while PFF increased attachment without affecting transmigration. In contrast, in the microfluidic BBB chip, attachment was largely unchanged by endothelial genotype or -Syn exposure, whereas transmigration increased following -Syn monomer pre-treatment. Together, PBMC-BBB interactions in PD appear to be shaped by immune cell status, endothelial genotype, and -Syn exposure, but are strongly influenced by BBB model dimensionality and flow. This study underscores the importance of physiologically relevant multicellular and flow-based BBB systems and provides a human-focused framework for studying peripheral immune cell trafficking across the diseased BBB. These findings also emphasize that biological insights into BBB function are inherently shaped by the experimental model used, underscoring the need for complementary human BBB platforms.

neuroscience↗

bioRxiv2025

Parkinson's disease risk factors are expressed at brain barriers.

Parkinsons disease (PD) is characterized by the selective loss of dopaminergic neurons in the substantia nigra pars compacta, but whether its etiology is cell autonomous remains unclear. Increasing evidence implicates the blood-central nervous system (CNS) barriers in disease development, highlighting the importance of identifying genetic risk factors linked to cells forming the cerebrovasculature to advance this emerging area of research. The objective of this study is to identify PD genetic risk factors associated with blood-brain (BBB) and blood-cerebrospinal fluid (BCSFB) barriers, and to validate protein localization in human tissue and experimental models. To do so, we integrated genome-wide association studies and single nuclei RNA-sequencing datasets from the human postmortem substantia nigra (SN), midbrain, or cortical samples from control and PD donors. An in-depth bioinformatics analysis identified genes enriched in cell types that form the multicellular architecture of brain barriers, including CAVIN2, ANXA1, ANO2, and LRP1B. We further validated whether corresponding proteins were present in cell types associated with the blood-CNS barriers in human and mouse post-mortem tissues, as well as in iPSC-differentiated cells and choroid plexus organoids. Results showed that quantifying the proportion of endothelial cells expressing PD-related genes was under-evaluated at the transcript level compared to immunofluorescence analyses. In addition, we observed that CAVIN2 and ANXA1 proteins were more abundant at the vasculature of the substantia nigra vs. cortex, and CAVIN2 protein levels were reduced in PD vs. control human postmortem tissues. In contrast, the investigation of mouse postmortem samples demonstrated that the CAVIN2 protein is only present in a subset of mouse blood vessels, compared to nearly all vessels in human tissue. Similarly, mouse ANXA1 protein localizes to dopaminergic neurons of the substantia nigra and not at the vasculature, as seen in human tissue. The primary outcome of this study is the identification of PD-relevant risk genes specifically expressed at brain barriers and enriched in PD-relevant brain regions. The secondary outcome is the demonstration of poor transcript-protein correlation in - at least - a subset of PD risk factors, and a low interspecies conservation of protein localization for the selected candidates. In conclusion, the BBB and BCSFB may represent understudied contributors to PD, endothelial-specific proteins appear differentially regulated compared to transcripts, and experimental models require comprehensive validation to ensure relevance to the human condition.

neuroscience↗

bioRxiv2025

Comparative spatial transcriptomics of hair follicle-T cell interactions in mouse, dog and human reveals conserved drivers of primary cicatricial alopecia

Primary cicatricial alopecias (PCA) encompass several autoimmune disorders characterized by scarring hair loss. Many of these conditions are lymphocytic and are thought to be driven by T cell populations. Here, we sought to characterize potential T cell-hair follicle communication pathways in the microanatomical niche using spatial transcriptomics across 3 mammalian species including a novel mouse model, spontaneous disease in companion dogs and human archival diagnostic biopsies. Flow cytometry of mouse model skin confirmed loss of CD34+ bulge cells and keratinocytes, and bulk microarray and histology revealed expression of collagens and development of fibrosis. In vivo ear imaging in mice engrafted with Kikume photoconvertible OT1 CD8+ T cells confirmed long-lived RFP+ T cells in skin arrest near hair follicles and recruit other GFP+ T cells. OT1 T cells expressed CD69, CD103, CD122 and CD62L, which is a binding partner of CD34. Digital spatial profiling using CD3, CD8 and CD45 cell masking identified CXCR3 ligands and IFN response genes in hair follicles, and "metabolic" pathways in T cells, which were also recapitulated in dog and human biopsies. Bulk human RNA as well as spatial analysis of perifollicular T cells confirmed enrichment of CD69 and SELL/CD62L. Different pathways predominated in other CD3+ regions of interest in CD4+ driven conditions including mucocutaneous lupus erythematosus and subacute cutaneous lupus erythematosus. Last, we identify novel drug-targetable pathways, namely CFD and S100A8/9, that could be further explored to disrupt processes in these conditions through veterinary and human trials.

immunology↗