Biology subjects

Hodges, M. R.

Publications and source records attributed to Hodges, M. R..

3 recordsLinked to original sources

bioRxiv2025

Molecular Deconstruction of the Medullary Raphe Magnus in the rat: Transcriptional Responses to Repeated Seizures

Sudden Unexpected Death in Epilepsy (SUDEP) is a leading cause of death in patients with epilepsy and is thought to result from dysfunctional and/or failure of cardiorespiratory control systems. Post-mortem brainstem tissue analyses in human SUDEP cases point to reductions in markers of the brainstem serotonin (5-HT) system, which is known as a brainstem center that provides excitatory neuromodulation. We have previously shown in a knockout rat model (SSkcnj16-/- rats) that repeated seizures led to progressively greater ventilatory inhibition in the post-seizure period, seizure-associated mortality, and reduced brainstem 5-HT and tryptophan hydroxylase (Tph) particularly within the Raphe Magnus (RMg). Here, we account for the cellular constituency and local transcriptional responses to repeated seizures in male SSkcnj16-/- rats that experienced daily seizures for 3, 5, 7, or 10 consecutive days using single nuclear RNA sequencing (snRNA seq) from brainstem tissue biopsies including the RMg (-12.12 mm to -10.30 mm caudal to Bregma) two hours post-seizure. Unbiased cluster analysis identified 18 cell major clusters that were by identified by the expression of known gene markers, with most cells being oligodendrocytes. However, local RMg neurons showed the greatest numbers of differentially expressed genes with seizures compared to all other cell types. Further re-clustering of neuronal cell types yielded 14 distinct RMg neuron subpopulations, including 5 types of GABAergic neurons, 2 glutamatergic clusters, and 2 groups of 5-HT neurons which all had unique expression profiles. Nearly all DEGs across neuronal subtypes were increased following seizures, and a large fraction of which were common across seizure days and across neuron type suggesting uniformity in cellular response to seizures in this region. These studies provide foundational information regarding the cellular constituency of the RMg region in the rat, and altered neuronal function following repeated seizures in the absence of changes in other cell types in this key region of cardiorespiratory control.

neuroscience↗

bioRxiv2025

Molecular deconstruction of the pre-B&oumltzinger Complex/Nucleus Ambiguus (preB&oumltC/NA) region: cellular constituencies and transcriptional responses to repeated seizures in the rat hindbrain

Epilepsy affects millions worldwide, but a significant portion suffers from uncontrollable epilepsy. Repeated seizures have many consequences, including a high risk of post-ictal cardiorespiratory failure and Sudden Unexpected Death in Epilepsy (SUDEP). Major risk factors for SUDEP include biological sex in addition to the occurrence of generalized tonic-clonic seizures (GTCSs). How repeated seizures lead to cardiorespiratory dysfunction remains unknown. A key factor in many neurological diseases is neuroinflammation, predominantly mediated by microglia and astrocytes that become dysfunctional. Mechanistically, questions remain how they affect neuronal function in epilepsy and contribute to cardiorespiratory dysfunction and increased SUDEP risk. Previously, we have shown that repeated seizures in our novel rat model with genetic mutations in kcnj16, an inwardly rectifying K+ channel, in the Dahl salt sensitive rat (SSkcnj16-/-) led to increased neuroinflammation in key ventilatory regions at 3 and 5 days of seizures. Specifically, there was increased recruitment of various inflammatory mediators, increased recruitment of activated microglia, with improvement in post-ictal respiratory dysfunction and mortality with usage of anti-inflammatory agents. Here we tested the hypothesis that repeated seizures lead to differential neuroinflammatory activation after repeated seizures in CNS regions of ventilatory control. Male SSkcnj16-/- rats were subjected to 0 (Naive), 3, 7 or 10 days of seizure, and subsequently, the pre-Botzinger Complex/Nucleus Ambiguus (preBotC/NA) was isolated and sent for nuclei isolation and sequencing. Seurat was utilized to filter and process the data, integrate across conditions and allow for differential gene expression (DEG) analysis. Afterwards, pathways enrichment analysis was performed allowing for determination of unique pathways recruited across cell types for each seizure condition. Overall, we were able to identify 18 unique cell types based on transcriptomic signatures, with 8 different neuronal populations, grouped based on Type 1, Type 2 or a mixed Type 1 & Type 2 genetic expression, indicating rhythm generation or pattern generation, respectively. We found that majority of the neuronal clusters were Type 1 or mixed type, indicating predominantly rhythmogenic neuronal populations. Importantly, these critical neuronal populations showed significant upregulation in various metabolic and neurological disease pathways at the 3 and 7 Day timepoints. Furthermore, we identified various glial cells, including microglia and astrocytes and saw increased recruitment in various Inflammatory pathways, Metabolic pathways and Chemokine related pathways after 3 and 7Days of seizures, confirming our previous results. Consequently, our results show for the first time, transcriptomic characterization of crucial rhythmogenic neuronal populations after repeated seizures and the changes that may underlie their dysfunction in SUDEP, mediated in part through the network change in upregulated inflammatory pathways in surrounding glial cells.

neuroscience↗

bioRxiv2024

Glenn circulation causes early and progressive shunting in a surgical model of pulmonary arteriovenous malformations

BackgroundPulmonary arteriovenous malformations (PAVMs) universally develop in patients with single ventricle congenital heart disease (CHD). Single ventricle PAVMs have been recognized for over 50 years, yet they are poorly understood, and we lack any medical therapies. To improve our understanding of single ventricle PAVM initiation and progression, we developed a surgical rat model of Glenn circulation and characterized PAVM physiology over multiple time points. MethodsUsing adult rats, we performed a left thoracotomy and end-to-end anastomosis of the left superior vena cava to the left pulmonary artery (unilateral Glenn), or sham surgical control. To assess for PAVM physiology in the left lung, we quantified intrapulmonary shunting using two independent methods (bubble echocardiography and fluorescent microsphere injection) at 2 weeks, 2 months, and 6 months. Additionally, we performed arterial blood gas measurements to assess oxygenation and plethysmography to assess ventilation. ResultsWe identified pathologic intrapulmonary shunting by bubble echocardiography as early as 2 weeks post-Glenn surgery, and shunting continued chronically at 2- and 6-months post-Glenn. Shunting also progressed over time, demonstrated by increased shunting of 10{micro}m microspheres at 6 months. Shunting was accompanied by mildly decreased arterial oxygenation, but there were no differences in ventilation as quantified by plethysmography. ConclusionsOur surgical animal model of unilateral Glenn circulation re-creates the clinical condition of single ventricle PAVMs with early and progressive intrapulmonary shunting. This model is poised to characterize single ventricle PAVM pathophysiology and lead to mechanistic and therapeutic discovery. Graphic Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=78 SRC="FIGDIR/small/588015v1_ufig1.gif" ALT="Figure 1"> View larger version (32K): org.highwire.dtl.DTLVardef@b1c722org.highwire.dtl.DTLVardef@1889af9org.highwire.dtl.DTLVardef@1767519org.highwire.dtl.DTLVardef@1c230_HPS_FORMAT_FIGEXP M_FIG C_FIG

physiology↗