Biology subjects

Low, W. C.

Publications and source records attributed to Low, W. C..

11 recordsLinked to original sources

bioRxiv2025

Functional Neural Connectivity of the Mouse Brain using Photoacoustic Ultrasound Imaging

Brain connectomes are insightful models that describe the connectivity of different regions throughout the brain. These connectomes are traditionally generated through temporal correlation of blood oxygen level dependent (BOLD) signals detected by functional magnetic resonance imaging (fMRI). Photoacoustic ultrasound (PAU) can also detect oxygenation levels while being more accessible and cost effective than fMRI. We propose the use of PAU to generate brain connectomes as an alternative to fMRI. In this study we successfully developed a pipeline for processing PAU data from whole brain scans of mice models and found that the connectomes it produced were comparable to those generated by fMRI, particularly, in detecting connections previously documented in the literature. Our findings suggest that PAU is a promising alternative to fMRI for mapping brain connectome, offering advantages in sensitivity and accessibility, making it a valuable tool for future research on brain connectivity.

bioengineering↗

bioRxiv2025

Characterization of the intraspecies chimeric mouse brain at embryonic day 12.5

Incidence of neurodegenerative diseases such as Alzheimers, Parkinsons, Huntingtons, and amyotrophic lateral sclerosis have increased dramatically as life expectancy at birth has risen year-over-year and the population ages. Neurological changes within the central nervous system, specifically the brain, include cell loss and deterioration that impact motor function, memory, executive function, and mood. Available treatments are limited and often only address symptomatic manifestations of the disease rather than disease progression. Cell transplantation therapy has shown promise for treating neurodegenerative diseases, but a source of autologous cells is required. Blastocyst complementation provides an innovative method for generating those autologous neural cells. By injecting mouse induced pluripotent stem cells (iPSCs) into a wild type (WT) mouse blastocyst, we generated a chimeric mouse brain derived of both donor and host neuronal and non-neuronal cells. An embryonic day 12.5 (E12.5), automated image analysis of mouse-mouse chimeric brains showed the presence of GFP-labeled donor-derived dopaminergic and serotonergic neuronal precursors. GFP-labeled donor-derived cholinergic precursor neurons and non-neuronal microglia-like and macrophage-like cells were also observed using more conventional imaging analysis software. This work demonstrates that the generation of mouse-mouse chimeric neural cells is possible; and that characterization of early neuronal and non-neuronal precursors provides a first step towards utilizing these cells for cell transplantation therapies for neurodegenerative diseases.

developmental biology↗

bioRxiv2025

Exosomes derived from highly scalable and regenerative human progenitor cells promote functional improvement in a rat model of ischemic stroke

Globally, there are 15 million stroke patients each year who have significant neurological deficits. Today, there are no treatments that directly address these deficits. With demographics shifting to an older population, the problem is worsening. Therefore, it is crucial to develop feasible therapeutic treatments for stroke. In this study, we tested exosomes derived from embryonic endothelial progenitor cells (eEPC) to assess their therapeutic efficacy in a rat model of ischemic stroke. Importantly, we have developed purification methods aimed at producing robust and scalable exosomes suitable for manufacturing clinical grade therapeutic exosomes. We characterized exosome cargos including RNA-seq, miRNAs targets, and proteomic mass spectrometry analysis, and we found that eEPC-exosomes were enhanced with angiogenic miRNAs (i.e., miR-126), anti-inflammatory miRNA (i.e., miR-146), and anti-apoptotic miRNAs (i.e., miR-21). The angiogenic activity of diverse eEPC-exosomes sourced from a panel of eEPC production lines was assessed in vitro by live-cell vascular tube formation and scratch wound assays, showing that several eEPC-exosomes promoted the proliferation, tube formation, and migration in endothelial cells. We further applied the exosomes systemically in a rat middle cerebral artery occlusion (MCAO) model of stroke and tested for neurological recovery (mNSS) after injury in ischemic animals. The mNSS scores revealed that recovery of sensorimotor functioning in ischemic MCAO rats increased significantly after intravenous administration of eEPC-exosomes and outpaced recovery obtained through treatment with umbilical cord stem cells. Finally, we investigated the potential mechanism of eEPC-exosomes in mitigating ischemic stroke injury and inflammation by the expression of neuronal, endothelial, and inflammatory markers. Taken together, these data support the finding that eEPCs provide a valuable source of exosomes for developing scalable therapeutic products and therapies for stroke and other ischemic diseases.

neuroscience↗

bioRxiv2025

Novel Single-Cell Multiomics Approach to Analyze Replication Timingand Gene Expression in Mouse Preimplantation Embryos

Analysis of a cells replication timing (RT) provides insight into how genes replicate, early or late, during the S-phase of the cell cycle. RT is cell-type specific, inheritable, and has been correlated to gene expression in normal and diseased states. However, most studies have been limited to somatic cells. Very little is known about RT control in early mouse embryos, and how it correlates with the start of transcription during zygote gene activation (ZGA), at the 2-cell stage. In this study, we developed a novel in-house single-cell multiomics approach to simultaneously analyze RT and gene expression in individual cells of the mouse 1-cell, 2-cell, and 4-cell embryos. We detected that RT was established at the 1-cell stage prior to ZGA. Surprisingly, we observed that the coordinated RT and gene expression control was different in early totipotent embryos, compared to previously published studies in somatic cells. Late replicating regions correlated with higher gene expression and open chromatin in the early developing embryos. Lastly, we performed an integrated pseudo time trajectory analysis combining RT and gene expression information per cell.

developmental biology↗

bioRxiv2025

Development of a Novel Single Cell Multiomics Approach for Simultaneous Analysis of Replication Timing and Gene Expression

Replication timing (RT) allows us to analyze temporal patterns of genome-wide replication, i.e., if genes replicate early or late during the S-phase of the cell cycle. RT has been linked to gene expression in normal and diseased acute and chronic states such as cancer. However, studies done to date focused on bulk cell populations that required tens of thousands of cells for RT analysis. Here, we developed an affordable novel single cell (sc)-multiomics approach to simultaneously analyze RT and gene expression from cells or nuclei. We used this approach to generate sc-RT profiles and sc-gene expression data from the well-established human liver cancer cell line, HepG2. We demonstrated that as few as 17 mid S-phase cells were sufficient to produce cell-type specific pseudo bulk RT profiles that had a high correlation to previously published HepG2 bulk RT profiles. The sc-RT profiles allowed us to visualize how individual cells progressed through genome replication. We were also able to demonstrate high-resolution correlations between RT and gene expression within each individual cell, which to our knowledge, has not been reported. We observed trends that were conserved between individual cells, as well as cell-to-cell variations, which were not possible to detect with the bulk RT studies.

genomics↗

bioRxiv2023

Impact of age and sex on neuroinflammation following SARS-CoV-2 infection in a murine model

Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), the etiological agent for the worldwide COVID-19 pandemic, is known to infect people of all ages and both sexes. Senior populations have the greatest risk of severe disease, and sexual dimorphism in clinical outcomes has been reported in COVID-19. SARS-CoV-2 infection in humans can cause damage to multiple organ systems, including the brain. Neurological symptoms are widely observed in patients with COVID-19, with many survivors suffering from persistent neurological and cognitive impairment, potentially accelerating Alzheimers disease. The present study aims to investigate the impact of age and sex on the neuroinflammatory response to SARS-CoV-2 infection using a mouse model. Wild-type C57BL/6 mice were inoculated, by intranasal route, with SARS-CoV-2 lineage B.1.351 variant known to infect mice. Older animals and in particular males exhibited a significantly greater weight loss starting at 4 dpi. In addition, male animals exhibited higher viral RNA loads and higher titers of infectious virus in the lung, which was particularly evident in males at 16 months of age. Notably, no viral RNA was detected in the brains of infected mice, regardless of age or sex. Nevertheless, expression of IL-6, TNF-, and CCL-2 in the lung and brain was increased with viral infection. An unbiased brain RNA-seq/transcriptomic analysis showed that SARS-CoV-2 infection caused significant changes in gene expression profiles in the brain, with innate immunity, defense response to virus, cerebravascular and neuronal functions, as the major molecular networks affected. The data presented in this study show that SARS-CoV-2 infection triggers a neuroinflammatory response despite the lack of detectable virus in the brain. Age and sex have a modifying effect on this pathogenic process. Aberrant activation of innate immune response, disruption of blood-brain barrier and endothelial cell integrity, and supression of neuronal activity and axonogenesis underlie the impact of SARS-CoV-2 infection on the brain. Understanding the role of these affected pathways in SARS-CoV-2 pathogenesis helps identify appropriate points of therapeutic interventions to alleviate neurological dysfunction observed during COVID-19.

microbiology↗

bioRxiv2023

Portable Arbitrary Pulse Generator for Driving μCoils for Micromagnetic Neurostimulation

Micromagnetic stimulation (MS) is a promising branch of neurostimulation technologies. Microcoil (coil) based magnetic stimulation uses micrometer sized coils that generate a time-varying magnetic field which as per Faradays Laws of Electromagnetic Induction induces an electric field on a conductive surface. This method of stimulation has the advantage of not requiring electrical contact with tissue, however these coils are not easy to operate. Large currents are required to generate the required magnetic field. These currents are too large for standard test equipment to provide, and additional power amplifiers are needed. To aid in the development and application of micromagnetic stimulation devices, we have created a compact single unit test setup for driving these devices called the Coil Driver. This unit is designed to drive small inductive loads up to {+/-}8 V at 5 A and 10 kHz.

neuroscience↗

bioRxiv2023

Micromagnetic Stimulation (μMS) Controls Dopamine Release: An in vivo Study Using WINCS Harmoni

ObjectiveResearch into the role of neurotransmitters in regulating normal and pathologic brain functions has made significant progress. Yet, clinical trials that aim to improve therapeutic interventions do not take advantage of the in vivo changes in the neurochemistry that occur in real time during disease progression, drug interactions or response to pharmacological, cognitive, behavioral, and neuromodulation therapies. In this work, we used the WINCS Harmoni tool to study the real time in vivo changes in dopamine release in rodent brains for the micromagnetic neuromodulation therapy. ApproachAlthough still in its infancy, micromagnetic stimulation (MS) using micro-meter sized coils or microcoils (coils) has shown incredible promise in spatially selective, galvanic contact free and highly focal neuromodulation. These coils are powered by a time-varying current which generates a magnetic field. As per Faradays Laws of Electromagnetic Induction, this magnetic field induces an electric field in a conducting medium (here, the brain tissues). We used a solenoidal-shaped coil to stimulate the medial forebrain bundle (MFB) of the rodent brain in vivo. The evoked in vivo dopamine releases in the striatum were tracked in real time by carbon fiber microelectrodes (CFM) using fast scan cyclic voltammetry (FSCV). ResultsOur experiments report that coils can successfully activate the MFB in rodent brains, triggering dopamine release in vivo. We further show that the successful release of dopamine upon micromagnetic stimulation is dependent on the orientation of the coil. Furthermore, varied intensities of MS can control the concentration of dopamine releases in the striatum. SignificanceThis work helps us better understand the brain and its conditions arising from a new therapeutic intervention, like MS, at the level of neurotransmitter release. Despite its early stage, this study potentially paves the path for MS to enter the clinical world as a precisely controlled and optimized neuromodulation therapy.

neuroscience↗

bioRxiv2022

Micromagnetic Stimulation (μMS) Dose-Response of the Rat Sciatic Nerve

ObjectiveThe objective of this study was to investigate the effects of micromagnetic stimuli strength and frequency from the Magnetic Pen (MagPen) on the rat right sciatic nerve. The nerves response would be measured by recording muscle activity and movement of the right hind limb. ApproachThe MagPen was custom-built such that it can be held over the sciatic nerve in a stable manner. Rat leg muscle twitches were captured on video and movements were extracted using image processing algorithms. EMG recordings were also used to measure muscle activity. Main resultsThe MagPen prototype when driven by alternating current, generates time-varying magnetic field which as per Faradays Law of Electromagnetic Induction, induces an electric field for neuromodulation. The orientation dependent spatial contour maps for the induced electric field from the MagPen prototype has been numerically simulated. Furthermore, in this in vivo work on MS, a dose-response relationship has been reported by experimentally studying how the varying amplitude (Range: 25 mVp-p through 6 Vp-p) and frequency (Range: 100 Hz through 5 kHz) of the MagPen stimuli alters the hind limb movement. The primary highlight of this dose-response relationship is that at a higher frequency of the MS stimuli, significantly smaller amplitudes can trigger hind limb muscle twitch. This frequency-dependent activation can be justified following directly from the Faradays Law as the magnitude of the induced electric field is directly proportional to frequency. SignificanceThis work reports that MS can successfully activate the sciatic nerve in a dose-dependent manner. The MagPen probe, unlike electrodes, does not have a direct electrochemical interface with tissues rendering it much safer than an electrode. Magnetic fields create more precise activation than electrodes because they induce smaller volumes of activation. Finally, unique features of MS such as orientation dependence, directionality and spatial selectivity have been demonstrated.

bioengineering↗

bioRxiv2021

Strength-frequency curve for micromagnetic neurostimulation through EPSPs on rat hippocampal neurons and numerical modeling of magnetic microcoil (μcoil)

ObjectiveThe objective of this study was to measure the effect of micromagnetic stimulation (MS) on hippocampal neurons, by using single microcoil (coil) prototype, Magnetic Pen (MagPen). MagPen will be used to stimulate the CA3 region magnetically and excitatory post synaptic potential (EPSP) response measurements will be made from the CA1 region. The threshold for micromagnetic neurostimulation as a function of stimulation frequency of the current driving the coil will be demonstrated. Finally, the optimal stimulation frequency of the current driving the coil to minimize power will be estimated. ApproachA biocompatible, watertight, non-corrosive prototype, MagPen was built, and customized such that it is easy to adjust the orientation of the coil and its distance over the hippocampal tissue in an in vitro recording setting. Finite element modeling (FEM) of the coil design was performed to estimate the spatial profiles of the magnetic flux density (in T) and the induced electric fields (in V/m). The induced electric field profiles generated at different values of current applied to the coil can elicit a neuron response, which was validated by numerical modeling. The modeling settings for the coil were replicated in experiments on rat hippocampal neurons. Main resultsThe preferred orientation of MagPen over the Schaffer Collateral fibers was demonstrated such that they elicit a neuron response. The recorded EPSPs from CA1 region due to MS at CA3 region were validated by applying tetrodotoxin (TTX). Application of TTX to the hippocampal slice blocked the EPSPs from MS while after prolonged TTX washout, a partial recovery of the EPSP from MS was observed. Finally, it was interpreted through numerical analysis that increasing frequency of the current driving the coil, led to a decrease in the current amplitude threshold for micromagnetic neurostimulation. SignificanceThis work reports that micromagnetic neurostimulation can be used to evoke population EPSP responses in the CA1 region of the hippocampus. It demonstrates the strengthfrequency curve for MS and its unique features related to orientation dependence of the coils, spatial selectivity and stimulation threshold related to distance dependence. Finally, the challenges related to MS experiments were studied including ways to overcome them.

bioengineering↗

bioRxiv2020

Zika virus-based immunotherapy enhances long-term survival of rodents with brain tumors through upregulation of memory T-cells

Zika virus (ZIKV) exhibits a tropism for brain tumor cells and has been used as an oncolytic virus to target brain tumors in mice with modest effects on extending median survival. Recent studies have highlighted the potential for combining virotherapy and immunotherapy to target cancer. We postulated that ZIKV could be used as an adjuvant to enhance the long-term survival of mice with malignant glioblastoma and generate memory T-cells capable of providing long-term immunity against cancer remission. To test this hypothesis mice bearing malignant intracranial GL261 tumors were subcutaneously vaccinated with irradiated GL261 cells previously infected with the ZIKV. Mice also received intracranial injections of live ZIKV, irradiated ZIKV, or irradiated GL261 cells previously infected with ZIKV. Long-term survivors were rechallenged with a second intracranial tumor to examine their immune response and look for the establishment of protective memory T-cells. Mice with subcutaneous vaccination plus intracranial irradiated ZIKV or intracranial irradiated GL261 cells previously infected with ZIKV exhibited the greatest extensions to overall survival. Flow cytometry analysis of immune cells within the brains of long-term surviving mice after tumor rechallenge revealed an upregulation in the levels of T-cells, including CD4+ and tissue-resident memory CD4+ T-cells, in comparison to long-term survivors that were mock-rechallenged, and in comparison to naive untreated mice challenged with intracranial gliomas. These results suggest that ZIKV can serve as an adjuvant to subcutaneous tumor vaccines that enhance long-term survival and generate protective tissue-resident memory CD4+ T-cells.

cancer biology↗