Biology subjects

Caron, L.

Publications and source records attributed to Caron, L..

5 recordsLinked to original sources

bioRxiv2023

Transdermal Electrophysiological Recordings of Diabetic Peripheral Neuropathy Using a Needle Electrode Array in Mice and Men

Diabetic peripheral neuropathy (DPN) is a common complication of diabetes. Proactive treatment options remain limited, which is exacerbated by a lack of sensitive and convenient diagnostics, especially early in disease progression or specifically to assess small fiber neuropathy (SFN), the loss of distal small diameter axons that innervate tissues and organs. We designed, fabricated, tested, and validated a first-of-its-kind medical diagnostic device for the functional assessment of transdermal small fiber nerve activity. This device, the Detecting Early Neuropathy (DEN), is an electrically conductive needle array designed to record nerve electrical activity in the skin and subdermal tissues. DEN recordings were validated across a time course of diet-induced DPN in mice, using statistical and computational analyses compared to other SFN measures. Based on these preclinical mouse data, the device design was adapted to obtain recordings in human with a flexible printed circuit board to mold to the leg or other skin regions. The DEN successfully recorded various types of neural activity in mouse and human, with or without stimulation, including validated action potentials and electromyography signals. New functional diagnostic tools like DEN offer a promising outlook for patients needing an earlier or more sensitive diagnosis of SFN/DPN, to allow for earlier and more effective treatment options, especially as more become available in the clinic in future years.

bioengineering↗

bioRxiv2023

Telomerase reverse transcriptase (TERT)-expressing cells mark a novel stem cell population in the adult mouse brain

Telomerase reverse transcriptase (TERT) is expressed by quiescent adult stem cells (ASC) in numerous adult murine and human tissues, but has never been explored in the adult brain. Here, we demonstrate that TERT+ cells in the adult mouse brain represent a novel population of multipotent ASCs that are localized to numerous classical neuro/gliogenic niches (including the ventricular-subventricular zone, hypothalamus, and olfactory bulb), as well as more recently described regions of adult brain plasticity such as the meninges and choroid plexus. Using a direct-reporter mouse line, we found that TERT+ cells expressed known neural stem cell markers such as Nestin and Sox2, but not markers of committed stem/progenitor cells, nor markers of mature neuronal or glial cells. TERT+ ASCs rarely expressed the proliferation marker Ki67, and in vitro TERT+ cells lost TERT expression when activated by growth factors, together indicating a quiescent phenotype similar to what has been observed in other tissues. When cultured, TERT+ cells behaved like neural stem cells by forming neurospheres, which could proliferate and become more metabolically active once stimulated by growth factors. TERT+ cells were observed in numerous brain niches, particularly near the ventricles and cerebrospinal fluid barriers, but notably, TERT+ cells were never observed in the hippocampus. Lineage tracing of TERT+ cells in adult transgenic mice (mTERTrtTA::oTET-Cre::RosamTmG) revealed large-scale expansion of TERT+ progeny and differentiation to diverse cell types in multiple brain regions. For example, lineage-traced cells expressed markers of mature neurons, oligodendrocytes, astrocytes, ependymal cells, and choroid epithelial cells, thus demonstrating the striking multipotency of this stem cell population in basal tissue turnover of the adult brain. Together, these data demonstrate that TERT+ cells represent a novel population of multipotent stem cells that contribute to basal plasticity and regeneration in the adult mouse brain. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=200 SRC="FIGDIR/small/527879v1_ufig1.gif" ALT="Figure 1"> View larger version (94K): org.highwire.dtl.DTLVardef@94c0dborg.highwire.dtl.DTLVardef@185dborg.highwire.dtl.DTLVardef@1fb1e1borg.highwire.dtl.DTLVardef@17580a7_HPS_FORMAT_FIGEXP M_FIG C_FIG

neuroscience↗

bioRxiv2022

Environmental conditions of recognition memory testing induce neurovascular changes in the hippocampus in a sex-specific manner in mice

Experiences are linked to emotions impacting memory consolidation and associated brain neuronal circuits. Posttraumatic stress disorder is an example of strong negative emotions affecting memory processes by flashbacks of past traumas. Stress-related memory deficits are also observed in major depressive disorder (MDD). We recently highlighted that sex-specific blood-brain barrier (BBB) alterations underlie stress responses in mice and human depression. However, little is known about the relationship between emotional valence, memory encoding and BBB function. Here, we investigated the effects of novel object recognition (NOR) test, an experience considered of neutral emotional valence, on BBB properties in dorsal vs ventral hippocampus in the context of various environmental conditions (arena size, handling, age). The hippocampus is a brain area central for learning and memory processes with the dorsal and ventral subregions being associated with working memory vs reference memory retrieval, respectively. Expression of genes related to BBB integrity are altered in line with learning and memory processes in a region- and sex-specific manner. We observed correlations between poor learning, anxiety, stress-induced corticosterone release and changes in BBB-associated gene expression. Comparison of BBB transcriptomes between sexes also revealed profound differences at baseline in both ventral and dorsal hippocampus. Finally, we identified circulating vascular biomarkers, such as sE-selectin and Mmp-9, altered following NOR exposure supporting that recognition memory formation has an impact on the neurovasculature. Although deemed as a neutral valence test, NOR experimental conditions impact performance, highlighting the need to minimize anxiety when performing this commonly used test in mice. Significance StatementWith this study, we aim to investigate the blood-brain barriers (BBB) role in memory acquisition and consolidation to unravel new mechanisms and decipher the involvement of non-neuronal cell types in these processes. For this purpose, male and female mice were subjected to a recognition memory test associated with a neutral emotional experience and impact on the transcriptomic profile of the BBB along with blood vascular biomarkers were evaluated under various experimental conditions. Crossing the BBB remains an important challenge to develop therapeutic drugs including in the context of memory deficits driven by psychiatric disorders or neurodegenerative diseases and thus, the possibility to directly target this barrier by better understanding its biology is attractive and innovating.

animal behavior and cognition↗

bioRxiv2022

Telomere Position Effect Over Long Distance acts as a genome-wide epigenetic regulator through a common cis- element.

Among epigenetic modifiers, telomeres, represent attractive modulators of the genome in part through position effects. Telomere Position Effect - Over Long Distances (TPE-OLD) modulates genes expression by changes in telomere-dependent long-distance loops, with a reach of 10Mb from a telomere. However, TPE-OLD remains poorly defined. To gain further insights into the genome-wide impact of telomere length on genomic and epigenomic regulation through TPE-OLD, we used cells with controlled telomere length combined to a genome wide transcriptome and methylome analysis. By integrating omics data, we identified a common cis-acting motif that behaves as an insulator or enhancer. Using reporter assays integrating this element, we uncovered the trans partners regulating this activity. Further exploiting our cellular model, we observed the depletion of one candidate factor, RBPJ, at TPE-OLD associated loci upon telomere shortening. We concluded that, at the genome-wide level, TPE-OLD is relayed by RBPJ binding Alu-like elements to telomeres that acts as enhancers. In response to external stimuli (i.e., Aging), TPE-OLD might act by coordinating telomere length to the action of Alu newly evolved enhancers in association with RBPJ.

molecular biology↗

bioRxiv2022

Anabolic Factors and Myokines Improve Differentiation of Human Embryonic Stem Cell Derived Skeletal Muscle Cells

Skeletal muscle weakness is linked to many adverse health outcomes. Current research to identify new drugs has often been inconclusive due to lack of adequate cellular models. We have previously developed a scalable monolayer system to differentiate human embryonic stem cell (hESC) into mature skeletal muscle cells (SkMC) within 26 days without cell sorting or genetic manipulation. Here, building on our previous work, we show that differentiation and fusion of myotubes can be further enhanced using the anabolic factors testosterone (T) and follistatin (F) in combination with a cocktail of myokines (C). Importantly, combined TFC treatment significantly enhanced both hESC-SkMC fusion index and expression of various skeletal muscle markers including the motor protein Myosin Heavy Chain (MyHC). Transcriptomic and proteomic analysis revealed oxidative phosphorylation as the most up-regulated pathway and a significantly higher level of ATP and increased mitochondrial mass were also observed in TFC-treated hESC-SkMCs, suggesting enhanced energy metabolism is coupled to improved muscle differentiation. This cellular model will be a powerful tool for studying in vitro myogenesis and for drug discovery to further enhance muscle development or treat muscle diseases.

cell biology↗