Biology subjects

Siegenthaler, J. A.

Publications and source records attributed to Siegenthaler, J. A..

11 recordsLinked to original sources

bioRxiv2026

Perivascular fibroblasts locally regulate the vasomotor dynamics of pial arterioles

Perivascular fibroblasts (PVFs) ensheath pial arterioles on the brain surface, yet their physiological role on the healthy cerebrovasculature remains unknown. Here, we show that PVFs display calcium dynamics that are temporally aligned with arteriolar vasomotion. Depletion of fibroblasts disrupted vasomotion whereas enhancement of PVF-Gq signaling increased vasomotor activity and accelerated fluid influx into the peri-arteriolar space. These findings identify PVFs as unrecognized regulators of cerebral vasodynamics and cerebrospinal fluid movement.

neuroscience↗

bioRxiv2026

Meningeal inflammation and arachnoid barrier breakdown in a mouse model of neonatal bacterial meningitis

Newborns are especially susceptible to bacterial meningitis, primarily caused by Group B Streptococcus (GBS), due to incomplete maturation of immune and barrier systems. While meningitis is well known to break down the blood-brain barrier (BBB), how the meningeal arachnoid barrier, a critical component of the blood-cerebrospinal fluid barrier (B-CSFB), responds to infection is poorly understood. Using a neonatal mouse model of bacterial meningitis, we demonstrate that GBS infection significantly increases arachnoid barrier permeability, coinciding with alterations in Claudin-11 tight junction distribution and elevated meningeal production of proinflammatory cytokines (IL-6, TNF-, CXCL1). CD206+/Lyve1+ border-associated macrophages (BAMs) undergo significant morphological and molecular activation post-infection, but their depletion prior to GBS infection did not attenuate arachnoid barrier leakage or inflammatory cytokine levels during infection. We show that meningeal fibroblasts are a main source of proinflammatory cytokines in response to GBS infection and that exposure to the inflammatory cytokine TNF- alone is sufficient to induce neonatal arachnoid barrier breakdown. These results support neonatal arachnoid barrier is vulnerable to cytokine-induced breakdown in bacterial infection and highlight the role of non-immune meningeal cells like fibroblasts during bacterial infection.

neuroscience↗

bioRxiv2025

PDGFRα is required for postnatal cerebral perivascular fibroblast development

Perivascular fibroblasts (PVFs) are a cell type associated with large diameter blood vessels in the brain and spinal cord parenchyma and leptomeninges. PVFs have previously defined roles in injury and neuroinflammatory diseases and predicted roles in supporting neurovascular function. The temporal dynamics of PVF development in the pre- and postnatal cerebral cortex have recently been described, however the molecular mechanisms that underly PVF development have not been identified. PVFs express both platelet derived growth factor receptors (PDGFRs), PDGFR and PDGFR{beta}. Here we investigate the role of PDGF signaling in PVF development. We use immunohistochemistry and RNA transcript detection methods to show developmental expression of PDGFRs by PVFs and examine distribution of PDGF ligand expression in the brain. We show that postnatal deletion of PDGFR in fibroblasts using the Col1a2-CreERT mouse line significantly impairs PVF coverage of cerebral vessels at postnatal day 10. Perivascular macrophages, a cell type previously shown to co-develop with PVFs, have impaired cerebral vessel coverage in conditional mutants that is similar to PVF coverage defects. This work establishes a requirement for PDGFR signaling in PVF development and may shed light upon the potential pathways that are over-activated in PVFs in injury and disease contexts.

developmental biology↗

bioRxiv2024

Meningeal-derived retinoic acid regulates neurogenesis via suppression of Notch and Sox2

The meninges act as a regulator of brain development by secreting ligands that act on neural cells to regulate neurogenesis and neuronal migration. Meningeal-derived retinoic acid (RA) promotes neocortical neural progenitor cell cycle exit; however, the underlying molecular mechanism is unknown. Here, we used spatial transcriptomics and profiling of retinoic-acid receptor- (RAR) DNA binding in Foxc1-mutant embryos that lack meninges-derived ligands to identify the neurogenic transcriptional mechanisms of RA signaling in telencephalic neural progenitors. We determined that meningeal-derived RA controls neurogenesis by suppressing progenitor self-renewal pathways Notch signaling and the transcription factor Sox2. We show that RAR binds in the Sox2ot promoter, a long non-coding RNA that regulates Sox2 expression, and RA promotes Sox2ot expression in neocortical progenitors. Our findings elucidate a previously unknown mechanism of how meningeal RA coordinates neocortical development and insight into how defects in meningeal development may cause neurodevelopmental disorders.

neuroscience↗

bioRxiv2023

Leptomeningeal Neural Organoid (LMNO) Fusions as Models to Study Meninges-Brain Signaling

Neural organoids derived from human induced pluripotent stem cells (iPSCs) provide a model to study the earliest stages of human brain development, including neurogenesis, neural differentiation, and synaptogenesis. However, neural organoids lack supportive tissues and some non-neural cell types that are key regulators of brain development. Neural organoids have instead been co-cultured with non-neural structures and cell types to promote their maturation and model interactions with neuronal cells. One structure that does not form de novo with neural organoids is the meninges, a tri-layered structure that surrounds the CNS and secretes key signaling molecules required for mammalian brain development. Most studies of meninges-brain signaling have been performed in mice or using two-dimensional (2D) cultures of human cells, the latter not recapitulating the architecture and cellular diversity of the tissue. To overcome this, we developed a co-culture system of neural organoids generated from human iPSCs fused with fetal leptomeninges from mice with fluorescently labeled meninges (Col1a1-GFP). These proof-of-concept studies test the stability of the different cell types in the leptomeninges (fibroblast and macrophage) and the fused brain organoid (progenitor and neuron), as well as the interface between the organoid and meningeal tissue. We test the longevity of the fusion pieces after 30 days and 60 days in culture, describe best practices for preparing the meninges sample prior to fusion, and examine the feasibility of single or multiple meninges pieces fused to a single organoid. We discuss potential uses of the current version of the LMNO fusion model and opportunities to improve the system.

cell biology↗

bioRxiv2023

Meningeal origins and dynamics of perivascular fibroblast development on the mouse cerebral vasculature

Perivascular fibroblasts (PVFs) are a fibroblast-like cell type that reside on large-diameter blood vessels in the adult meninges and central nervous system (CNS). PVFs drive fibrosis following injury but their homeostatic functions are not well detailed. In mice, PVFs were previously shown to be absent from most brain regions at birth and are only detected postnatally within the cerebral cortex. However, the origin, timing, and cellular mechanisms of PVF development are not known. We used Col1a1-GFP and Col1a2-CreERT transgenic mice to track PVF developmental timing and progression in postnatal mice. Using a combination of lineage tracing and in vivo imaging we show that brain PVFs originate from the meninges and are first seen on parenchymal cerebrovasculature at postnatal day (P)5. After P5, PVF coverage of the cerebrovasculature rapidly expands via mechanisms of local cell proliferation and migration from the meninges, reaching adult levels at P14. Finally, we show that PVFs and perivascular macrophages (PVMs) develop concurrently along postnatal cerebral blood vessels, where the location and depth of PVMs and PVFs highly correlate. These findings provide the first complete timeline for PVF development in the brain, enabling future work into how PVF development is coordinated with cell types and structures in and around the perivascular spaces to support normal CNS vascular function. SummaryBrain perivascular fibroblasts migrate from their origin in the meninges and proliferate locally to fully cover penetrating vessels during postnatal mouse development.

developmental biology↗

bioRxiv2022

Formation and function of the meninges arachnoid barrier around the developing brain

Barriers at the level of the brain endothelium, choroid plexus, and meninges strictly regulate movement of molecules and cells into and out of the central nervous system (CNS). In contrast to the blood-brain barrier and choroid plexus epithelial barrier, developmental timing and function of the meningeal arachnoid barrier, a layer of epithelial-like cells connected by tight and adherens junctions, is largely unknown. To begin to address this, we mined our E14.5 mouse single cell transcriptomic (scRNA-seq) meningeal fibroblast data set and identified the repression of Wnt-{beta}-catenin signaling as a key mechanism underlying the specification of epithelial-like arachnoid barrier cells from Collagen 1+ and Crabp2+ mesenchymal meningeal precursors. We show that elevating Wnt-{beta}-catenin signaling in prenatal meningeal mesenchymal cells prevented the development of arachnoid barrier cells. In the absence of dorsal arachnoid barrier cells, the prenatal meninges and brain are penetrable to biocytin-TMR and Streptococcus agalactiae (Group B Streptococcus, GBS), the leading pathogen known to drive life-threatening neonatal meningitis. We show that a layer of Claudin 11 (tight junction) and E-cadherin (adherens junction) expressing arachnoid barrier cells appear around the mouse brain from E13-E15 and the emergence of a functional barrier by E17 coincides with junctional localization of Claudin 11. Postnatal growth of the arachnoid barrier is marked initially by proliferation and later re-organization of junctional domains. This work provides fundamental knowledge on development and prenatal function of a meningeal arachnoid barrier, and novel tools for future studies on regional functions of this CNS barrier in the meninges.

developmental biology↗

bioRxiv2022

Retinoic acid signaling in mouse retina endothelial cells is required for early angiogenic growth

The development of the retinal vasculature is essential to maintain health of the tissue, but the developmental mechanisms are not completely understood. The aim of this study was to investigate the cell-autonomous role of retinoic acid signaling in endothelial cells during retina vascular development. Using a temporal and cell-specific mouse model to disrupt retinoic acid signaling in endothelial cells in the postnatal retina (Pdgfbicre/+ dnRAR403fl/fl mutants), we discovered that angiogenesis in the retina is significantly decreased with a reduction in retina vascularization, endothelial tip cell number and filipodia, and endothelial crowding of stalk cells. Interestingly, by P15, the vasculature can overcome the early angiogenic defect and fully vascularized the retina. At P60, the vasculature is intact with no evidence of retina cell death or altered blood retinal barrier integrity. Further, we identified that the angiogenic defect seen in mutants at P6 correlates with decreased Vegfr3 expression in endothelial cells. Collectively, our work identified a previously unappreciated function for endothelial retinoic acid signaling in early retinal angiogenesis.

developmental biology↗

bioRxiv2021

Techniques for visualizing fibroblast-vessel interactions in the developing and adult CNS

Fibroblasts are found associated with blood vessels in various locations across the CNS: in the meninges, the choroid plexus, and in the parenchyma within perivascular spaces. CNS fibroblasts have been characterized using transcriptional profiling and a Col1a1-GFP mouse line used to identify CNS fibroblasts in vivo. However, current methods for visualizing CNS fibroblasts are lacking and, in particular, prevent adequate assessment of fibroblast-vessel interactions. Here, we describe methods for whole mount visualization of meningeal and choroid plexus fibroblasts, and optical tissue clearing methods for visualization of parenchymal vessel-associated fibroblasts. Importantly, these techniques can be combined with immunohistochemistry methods for labeling different cell types in the meninges and blood vasculature as well as EdU-based cell proliferation assays. These methods are ideal for visualization of vessel-fibroblast interactions in these CNS structures and provide significant improvement over traditional sectioning and staining methods. We expect these methods will advance studies of CNS fibroblast development and functions in homeostasis, injury, and disease.

neuroscience↗

bioRxiv2021

A human brain vascular atlas reveals diverse cell mediators of Alzheimer's disease risk

The human brain vasculature is of vast medical importance: its dysfunction causes disability and death, and the specialized structure it forms--the blood-brain barrier--impedes treatment of nearly all brain disorders. Yet, no molecular atlas of the human brain vasculature exists. Here, we develop Vessel Isolation and Nuclei Extraction for Sequencing (VINE-seq) to profile the major human brain vascular and perivascular cell types through 143,793 single-nucleus transcriptomes from 25 hippocampus and cortex samples of 17 control and Alzheimers disease (AD) patients. We identify brain region-enriched pathways and genes divergent between humans and mice, including those involved in disease. We describe the principles of human arteriovenous organization, recapitulating a gradual endothelial and punctuated mural cell continuum; but discover that many zonation and cell-type markers differ between species. We discover two subtypes of human pericytes, marked by solute transport and extracellular matrix (ECM) organization; and define perivascular versus meningeal fibroblast specialization. In AD, we observe a selective vulnerability of ECM-maintaining pericytes and gene expression patterns implicating dysregulated blood flow. With an expanded survey of brain cell types, we find that 30 of the top 45 AD GWAS genes are expressed in the human brain vasculature, confirmed in situ. Vascular GWAS genes map to endothelial protein transport, adaptive immune, and ECM pathways. Many are microglia-specific in mice, suggesting an evolutionary transfer of AD risk to human vascular cells. Our work unravels the molecular basis of the human brain vasculature, informing our understanding of overall brain health, disease, and therapy.

neuroscience↗

bioRxiv2019

A cellular atlas of the developing meninges reveals meningeal fibroblast diversity and function

The meninges, a multilayered structure that encases the CNS, is composed mostly of fibroblasts, along with vascular and immune cells. Meningeal fibroblasts are a vital source of signals that control neuronal migration and neurogenesis yet strikingly little is known about their development. We used single cell RNA sequencing to generate a cellular atlas of embryonic meningeal fibroblasts in control and Foxc1-KO mice in which severe CNS defects arise from failed meningeal fibroblast development. We report unique transcriptional signatures for dura, arachnoid and pial fibroblasts and identify S100a6 as the first unique marker of the pial layer. We describe a new meningeal fibroblast subtype marked by {micro}-Crystallin expression and show these cell types and markers are conserved in human fetal meninges. Our analysis demonstrates layer specific production of extracellular matrix components, transporter expression, and synthesis of secreted factors. Lastly, the cellular atlas of Foxc1-KO meninges provides insight into their severe phenotype, confirming a massive loss in arachnoid and dura fibroblasts and Foxc1-KO pial fibroblasts are so altered that they cluster as a different cell type based on gene expression. These studies provide an unprecedented view of meningeal fibroblast development, highlighting unexpected fibroblast diversity and function, while providing mechanistic insights into the meninges role in CNS development.

neuroscience↗