New G-lab paper: effects of dim light at night on sensorimotor and mood-related behaviors after spinal cord injury

Our new paper has been accepted for publication at Experimental Neurology! Congrats to co-first authors Dr. John Aldrich and Ashley Scheinfeld, and the rest of our team. In this manuscript, we sought to determine whether dim light-at-night (dLAN) after spinal cord injury (SCI) alters locomotor recovery, pain- or mood-related behaviors, or neuroprotection.

Our new manuscript is available at Experimental Neurology; the article is accessible on BioRxiv; and its dataset is on Open Data Commons repository.

Our prior work established that SCI disrupts the circadian system, including glucocorticoid rhythms, core temperature and activity rhythms, and rhythms of clock and inflammatory gene RNA in the spinal cord and liver. Others revealed that clinically relevant environmental circadian disruptors – such as dLAN – can exacerbate secondary damage and recovery in neurological conditions, such as global ischemia.

In our manuscript, we hypothesized that dLAN initiated after SCI would worsen functional and anatomical deficits. Adult female and male mice were subjected to SCI (or sham surgery), then placed back in light-dark (LD) cycles or newly placed in dLAN (12 h light; 12 h dim 15 lux light). This was designed to mimic the hospital setting, which often has unnaturally high nighttime light levels.

Fig. 1. Effects of dim light-at-night (dLAN) after SCI on locomotor recovery (Basso Mouse Scale; a), mechanical pain symptoms (von Frey test; b), and juvenile exploration (mood-related behavior; c). SCI-dLAN (vs. SCI-LD) mice showed improved BMS at 28 dpo, worsened mechanical hypersensitivity at 13 dpo, and worse anxiety- and/or depressive-like behavior at 21 dpo. p<0.05: red cross = sham vs. SCI; hourglass = effect of time; lightbulb = LD vs. dLAN.

Our results showed that dLAN had modest effects on behavioral outcomes. Locomotor recovery was assessed using the open-field Basso Mouse Scale (BMS). dLAN had little effect on locomotor recovery after SCI, except at the final timepoint, when SCI-dLAN mice had increased function compared to SCI-LD mice (Fig. 1a above). Lesion size and neuroprotection were not significantly different between SCI-LD compared to SCI-dLAN mice. Neuropathic pain-like behavior was assessed using the Hargreaves test (heat) and the von Frey test (mechanical). Whereas dLAN did not modulate sensitivity to heat (not shown), SCI-dLAN mice showed worsened mechanical hypersensitivity at 13 dpo only compared to SCI-LD mice (Fig. 1b). Mood-related behaviors were assessed using the sucrose preference test, open field test, and juvenile social exploration. dLAN had no significant effect on sucrose anhedonia or open field behavior (not shown). Interestingly, SCI-dLAN mice had decreased juvenile social exploration at 21 dpo compared to SCI-LD mice (Fig. 1c), suggestive of worsened anxiety- and/or depressive-like behavior.

Overall, our data suggest that dLAN has mixed effects on behavioral recovery after SCI - compared to SCI-LD mice, SCI-dLAN mice had slightly improved locomotor recovery at 28 dpo, worsened mechanical hypersensitivity at 13 dpo, and heightened anxiety-like behavior at 21 dpo. Future studies should explore whether SCI recovery is impaired by other clinically relevant circadian disruptors – e.g., LAN in a melatonin-expressing strain, sleep deprivation, or combining disruptors. Ultimately, studying circadian disruption after SCI in mice will help define whether improving circadian hygiene in acute clinical care could benefit SCI recovery.

Accumulating knowledge at Winter Brain - Gaudet and colleagues speak in spinal cord injury sessions

Science and skis - the Winter Conference for Brain Research provides an ideal venue for discussing research and integrating those thoughts afterwards on the slopes. Networking opportunities occurred during seminars - but also in the lodge, on the ski lift, or at apres-ski. The Conference occurred in late January 2024 in Breckenridge, CO. Dr. Gaudet was invited to speak at a session on Immune-Sympathetic Effects of Spinal Cord Injury and presented a talk titled, “Circadian control of neuroinflammation after spinal cord injury.”

 

The Gaudet Lab presents at Texas A&M's Annual Winter Society for Neuroscience conference

Gaudet Lab members enjoying late-afternoon sun after the Annual Winter Symposium at Texas A&M in College Station, TX.

Texas meets Texas A&M - but without the rivalry. Dr. Gaudet and his lab members were invited to present at the Annual Winter Society for Neuroscience Symposium, hosted by the Texas A&M Institute for Neuroscience! Gaudet was honored to be the keynote speaker, and presented a seminar titled, “Neuroimmune regulation of biology and behavior.” Lab members John Aldrich, Sydney Lee, Ashley Scheinfeld, and Kalina Dusenbery presented posters. It was great to see our A&M friends, meet with faculty, and discuss lab life with graduate students. We enjoyed the hospitality and innovative science in College Station!

Gaudet lab presents at the Mission Connect Annual Symposium in Houston

The Gaudet lab went on an overnight road trip to Houston to present and learn at the Mission Connect Annual Symposium. The meeting is a fantastic venue to learn about Texas spinal cord injury science and to interact with old and new friends. We enjoyed the keynote talk, the feedback from poster visitors, and the high-quality posters presented by others - as well as the breakfast tacos! We look forward to visiting again next year.

Out for a laid-back beverage with the lab and colleagues from MD Anderson after the Mission Connect Symposium in Houston.

New paper: spinal cord injury in mice amplifies anxiety-like behaviors

Our team, led by graduate student Sydney Lee, published a paper in Experimental Neurology addressing how spinal cord injury (SCI) affects the relative salience of anxiety vs. heat sensitivity (access pdf here also).

To explore the effects of SCI on mouse behaviors, we used our newly developed Thermal Increments Dark-Light (TIDAL) conflict test (Fig. 1) (for more details, see our related preprint). This test places mice in a two-chambered apparatus: one chamber remains dark but gradually heats to aversive temperatures, whereas the other chamber is illuminated and remains isothermic. If SCI caused strongly increased heat sensitivity, then mice would leave the dark, heating plate more quickly than control sham mice. Conversely, if SCI increased the salience of anxiety more than heat, then mice would persist on the dark plate longer despite increasing temperatures.

Figure 1. The Thermal Increments Dark-Light (TIDAL) conflict test is used in mice to assess anxiety- vs. heat sensitivity-related behaviors after spinal cord injury. A: The TIDAL conflict test places an anxiety-inducing stimulus (light vs. dark) in conflict with aversive heat. B: A control condition is thermal place preference, with both plates illuminated. C: Experimental conditions: for the dark plate, 5 minutes are spent at each temperature noted (i.e., 2 x 5 min at 31°C, then 5 min at each degree between 39-44°C), whereas the isothermic plate is maintained at 31°C throughout. D: TIDAL interpretations for possible behavioral shifts induced by SCI.

Our previous work showed that female mice exhibit increased preference for the dark, heating plate, suggesting that females exhibit increased salience of anxiety-related stimuli compared to males. Here, we again showed that females display increased anxiety-like behavior.

Interestingly, SCI in both females and males increased preference for the dark, heating plate compared to sham control mice (Fig. 2 below; Fig. 3 and 4 in the paper). This was not simply increased preference for warmth - SCI mice with both plates illuminated (thermal place preference, TPP) had reduced preference for the heated plate compared to mice on TIDAL. SCI increased dark-heated plate preference at all heated temperatures, from 39-44°C. Therefore, female and male mice at 7 d post-SCI displayed increased salience of anxiety.

Figure 2. After SCI, female and male mice in the TIDAL conflict test exhibit increased anxiety-like behavior. A: In the initial dark-light test with both plates at 31°C, female and male SCI mice exhibit only minor preference for the dark plate. B,C: Control condition - in the thermal place preference with both plates illuminated, uninjured and SCI mice show no significant differences in preference for the heating plate. D,E: In the TIDAL conflict test, both female and male mice with SCI show increased preference for the dark, heating plate compared to uninjured control mice.

A subset of mice were tested at 7 d post-operative (dpo) and re-tested at 21 dpo to establish whether anxiety-related differences persist, or whether differences are dampened and/or affected by learning (Fig. 5 and 6 in the paper). Our data showed differential effects in females and males. Females with SCI or sham surgery at 21 dpo both showed high initial dark plate preference, but decreased preference more quickly at higher temperatures (42-44°C). Males with SCI showed increased preference for the dark plate at 21 dpo compared to sham mice (a difference that was not apparent at 7 dpo), suggesting that male mice with SCI maintain higher anxiety-like behaviors than sham males.

Overall, we use our new TIDAL conflict test to reveal that SCI in mice drives previously underappreciated increases in anxiety-like behavior. Previous studies had suggested mice display minor anxiety-like behavior. Our data imply that placing an anxiety-driving stimulus in conflict with another stimulus - here, heat - can unmask underestimated anxiety-like behaviors. Testing using TIDAL revealed that both female and male mice with SCI exhibit increased anxiety-like behaviors at 7 dpo. Future studies could use TIDAL or other conflict tests after SCI to explore behaviors related to mood and anxiety. Ultimately, studying behaviors related to mood and anxiety after SCI could enhance our understanding of mechanisms and targets for improving mood-related therapies for humans afflicted with SCI or other neurologic conditions.

Gaudet lab publishes in J. Neurotrauma: sex differences in SCI-elicited behaviors related to pain

The Gaudet lab published an exciting new paper in Journal of Neurotrauma titled, “Sex differences in pain: Spinal cord injury in female and male mice elicits behaviors related to neuropathic pain.”

Chronic pain afflicts 65% of individuals with spinal cord injury (SCI). Women are more susceptible to pain symptoms than men. Although previous preclinical studies have explored sex differences in SCI-elicited pain-like behaviors, it remains understudied how SCI-driven pain behaviors develop over time and differ between the sexes. Here, we hypothesized that moderate force T9 contusion SCI in mice would cause neuropathic pain-like behaviors, and that these would be exacerbated in females compared to males.

First, we explored the effects of two different SCI forces on pain-like behaviors in female mice (Fig. 1). Both 60 and 75 kDyn SCI elicited mechanical allodynia (von Frey test) and heat hyperalgesia (Hargreaves test). The more severe 75 kDyn SCI caused excessive sensorimotor deficits at 7 d post-operative (dpo) that confounded sensory testing, so we used the less-severe 60 kDyn force for subsequent studies.

Figure 1. In female mice, spinal cord injury (SCI) of different forces causes graded locomotor deficits (a) and pain-like behaviors (b,c) compared to sham controls.

Next, we compared female and male mice with SCI regarding locomotor recovery and pain-like behavior (Fig. 2). Using the Basso Mouse Scale for locomotor recovery, females recovered slightly slower than males. For mechanical sensitivity, SCI caused increased hypersensitivity in mice of both sexes across all times tested (weekly from 6-27 dpo), and there was no substantial difference between females and males (Fig. 2 below; and Fig. 2-4 in the paper). However, females did show increased hypersensitivity at 27 dpo (Fig. 3 below; and Fig. 4 in the paper). For heat sensitivity, SCI again increased heat hypersensitivity at all times tested. Females with SCI exhibited increased hypersensitivity compared to males (Fig. 2 and Fig. 4 below; and Fig. 2, 3, and 5 in the paper).

Figure 2. SCI causes locomotor deficits and pain-like behaviors over 28 days post-operative (dpo) in female and male mice. (a-c) SCI in female and male mice caused locomotor deficits, which were slightly worse at acute-to-subacute times in females. (d-f) SCI elicited mechanical hypersensitivity compared to sham mice, as measured using the von Frey test. Females and males exhibited a similar extent of hypersensitivity. (g-i) SCI evoked heat pain-related behaviors in mice of both sexes; heat hypersensitivity was amplified in females.

Figure 3. A 27 dpo, SCI causes mechanical hypersensitivity. SCI-driven hypersensitivity is increased in female compared to male mice.

One strength of our study was the uniquely large size of our dataset. We have completed several experiments using age-matched mice of both sexes, so here we compiled a rigorous and comprehensive analysis of pain-like behavior in female and male mice. One limitation of our study is we assessed pain-like behaviors using only evoked tests, which may have limited relevance for chronic pain related to dull, ongoing sensations or spontaneous pain. Separately, we also created a test that attempted to unveil affective-related pain-like behaviors, though instead this revealed increased anxiety-like symptoms. Thus, it is challenging to develop effective tests for spontaneous or affective pain-like behavior in mice with SCI, particularly given the confounding combination of motor and sensory deficits. Others are also working on this challenge; e.g., Angelo Lepore’s group has used the grimace scale in mice to measure spontaneous pain-like behavior after SCI.

Figure 4. SCI elicits acute-to-chronic heat hypersensitivity, which is exacerbated in females compared to males.

Overall, our data suggest that moderate T9 contusion SCI in mice reliably causes mechanical and heat hypersensitivity, and that females with SCI exhibit increased heat hypersensitivity compared to males. Sex differences in pain-like behavior may relate to sex-specific underlying mechanisms. Future research should continue integrating sensory testing and both sexes. Ultimately, these studies will help unravel the relationship between sex/gender and neuropathic pain and to develop new therapies to benefit individuals with SCI.

New publication: review on the Neuroimmunology of healthy aging

How does brain physiology shift in response to aging?

How does the CNS interact with the neuroimmune system, and how does this change with age?

How are these changes beneficial and detrimental?

These are some of the questions addressed by Andrew and long-time collaborator Laura Fonken in their latest review paper, titled “Neuroimmunology of healthy brain aging,” published in Current Opinion in Neurobiology.

Schematic of brain, parenchyma, BBB, glymphatics, and neuroimmune cells.

Aging is associated with compensatory shifts in CNS physiology and function, which collaborate to increase neuroimmune priming and pro-inflammatory bias.

Timeline of aging in humans and mice

Timeline of aging and neuroimmunity in humans and mice.

Key points addressed in the review: Aging progressively disrupts homeostatic systems, including neuroimmunity. Neuroimmune responses in the aged brain are sensitized, and include impaired phagocytosis. With age, key neuroimmune-related cells - including microglia, astrocytes, and T cells - develop primed or pro-inflammatory phenotypes. In addition, the aged glymphatic system enables pathological accumulation of danger signals and cytokines. Age-related neuroimmune hyperreactivity has behavioral consequences - e.g., age-related neuroimmune activity predisposes to cognitive decline.



Gaudet lab posts a preprint: exploring sex differences in pain symptoms after spinal cord injury

65% of individuals with spinal cord injury (SCI) experience chronic pain. Further, chronic pain afflicts females more frequently, and can act on females vs. males via distinct cellular mechanisms. Unfortunately, we still lack effective treatments for chronic pain and do not fully understand mechanisms underlying sex differences in pain. In our new preprint, we reveal that female and male mice with SCI exhibit neuropathic pain symptoms. Further, females have amplified pain symptoms compared to males. Our thorough study illuminates an effective SCI model and pain tests for elucidating SCI pain-related mechanisms. Future studies should use complementary evoked and affective-related pain tests to gain a broad perspective on SCI-driven pain. We also had fun discussing the implications of this study, relating to sex differences and other future directions.

Sydney Lee, Emily Greenough, and Paul Oancea from the lab led the study.

The Gaudet Lab is hiring!

Are you looking to level up your research experience? Are you interested in neuroscience, and a vibrant research team and environment? Check us out!

The Gaudet lab at the University of Texas at Austin is hiring a Research Technician. Our research focus is using rodent models to improve inflammation in the central nervous system. We use molecular, cellular, and behavioral techniques. Our main model of interest is spinal cord injury, and we also study affective behaviors such as those related to anxiety, locomotion, and sensation.

Our lab’s view from the Health Discovery Building at UT-Austin: urban Austin and nature intersect along Waller Creek.

Brainstorming: teamwork can aid analysis, right?

Salary is flexible depending on experience.

If we get a new technician, we can relieve our son from some of his chores :)

Austin is a great place to live - lively neighborhoods, great music, outdoor fun, happy people. UT-Austin is a remarkable place for learning and growth. And in the Gaudet Lab, we aim to support your success by enabling you to use your own expertise and to learn more about new techniques and how to science. Let’s publish together!

All of these benefits combine in a nicely sized lab (not too big and not too small!) with a positive and productive team of researchers.

Interested in grad school? We’re accepting applications this Fall! See details on graduate school applications to UT’s Departments of Psychology or Neuroscience here.

Gaudet presented work on circadian rhythms and phagocytosis at Drexel College of Medicine.

Gaudet was delighted this week to visit Drexel College of Medicine in Philadelphia! Drexel has so many productive and interesting people - lots of interesting questions and ideas were discussed.

It was great having lunch with the trainees. It was my first time having a double-patty veggie burger, and the weather was perfect for the visit.

Thanks for the invitation, Megan Detloff!


Graduate student Sydney Lee and colleagues published a new preprint on anxiety-like behaviors

We published a new preprint: “Anxiety-like behaviors in mice unmasked: Revealing sex differences in anxiety using a novel light-heat conflict test.” We have also submitted the manuscript for publication. The study was led by graduate student Sydney Lee. Thanks also to contributors Emily Greenough, Paul Oancea, and Laura Fonken.

Anxiety is twice as prevalent in women than men - yet tests for anxiety in rodents fail to consistently reveal sex differences. New preclinical approaches are required to unmask sex differences in anxiety.

Here, we reveal a new heat-light conflict test - the Thermal Increments Dark-Light (TIDAL) conflict test. In TIDAL, female (vs. male) mice exhibit strongly amplified anxiety behavior, recapitulating gender differences in human anxiety

The TIDAL test apparatus consists of two heat-controlled plates. One plate is illuminated and maintained at a "comfy" temperature. The other plate is dark - but its temperature increases incrementally to aversive temperatures..

Rodents can move freely between the plates. We found that females persist on the heated, dark plate to higher temperatures than males.

Thus, our novel TIDAL conflict test reveals robust anxiety behavior in females. Future studies should integrate TIDAL or other conflict tests to identify mechanisms and treatments for anxiety.

The Gaudet lab has been awarded a grant!

Dr. Gaudet and his lab have been awarded a grant from Mission Connect, a program of the TIRR Foundation! Mission Connect is a group that connects and funds spinal cord injury research in Texas. The group holds monthly meetings, and organizes a top-notch research meeting in Houston every November.

Gaudet’s grant will explore the role of neuroinflammation and phagocytosis after spinal cord injury. The proposal combines complementary transgenic and pharmacologic approaches. We are excited to proceed with this study, with an aim to identify novel neuroprotective therapies that improve SCI outcomes.

Warm welcome to our new graduate student, Ashley Scheinfeld!

The Gaudet Lab is excited to welcome a new graduate student to the lab! Ashley Scheinfeld is from El Paso, TX. She has been in the Gaudet lab for 3 years as an undergraduate - she completed her Bachelor’s degree in Neuroscience at UT-Austin last year. She has been honing her technical skills by working in clinical labs prior to starting graduate school. We are delighted she’s joining the lab, and can’t wait to see what Ashley will contribute to the field of neuroscience!

Gaudet is awarded a Teaching Fellowship at the University of Texas at Austin

Gaudet was awarded a Raymond Dickson Centennial Endowed Teaching Fellowship “in recognition of exemplary performance and commitment to teaching.” This award is through the University of Texas at Austin and the College of Liberal Arts.

At UT-Austin, Gaudet teaches an upper-level undergraduate course, “Biological Clocks and Behavior,” and a graduate course titled “Neuroinflammation in Health and Pathology.” Gaudet is honoured to receive this award. He is thankful for extensive training in teaching from coursework and mentors at the University of British Columbia, and for the support of colleagues and teaching experts at UT-Austin and in the Department of Psychology.

New paper: Aging and miR-155 affect survival and neuropathic pain after spinal cord injury

We published a new paper in Brain, Behavior, and Immunity!

“Aging and miR-155 in mice influence survival and neuropathic pain after spinal cord injury.”

Fig 1 survival copy.jpg

The average age at spinal cord injury is increasing, and people are living longer with improved treatment after spinal cord injury - yet there remain important questions about how spinal cord injury affects the geriatric population. How does age at SCI affect pain symptoms? Can pain symptoms after SCI be quenched using strategies that reduce inflammation?

In this paper, we assessed spontaneous pain symptoms and evoked pain in adult and aged mice. We also sought to reduce pain symptoms by using mice lacking a key pro-inflammatory microRNA, miR-155. Aged mice showed increased spontaneous pain symptoms and death after injury, which were dampened in mice lacking miR-155.

 
Fig 2 HG - VF copy.jpg

At baseline, aged mice had increased heat hypersensitivity. After SCI, both adult and aged mice displayed pain symptoms, which were partially alleviated by miR-155 deletion.

These results highlight the importance of studying SCI and neurologic disorders across the lifespan. Identifying age-related deficits and immunomodulatory treatments after SCI could help improve clinical approaches for pain management.

For more, see our related Twitter thread.