Mouse Anesthesia: The Art and Science

Cardiovascular function and autonomic regulation in urethane-anesthetized and conscious mice

Urethane is widely used for its ability to induce prolonged anesthesia. Variability in previously reported cardiovascular parameters in murine models makes it challenging to definitively evaluate the cardiovascular effects of urethane anesthesia. We aimed to address these challenges, thereby advancing our understanding of urethane's effects on cardiovascular function in mice. In this study, we investigated how urethane anesthesia, with and without supplemental oxygen, impacts heart rate, arterial oxygen saturation ([Formula: see text]), blood pressure, and heart rate variability in mice. First, we conducted a literature review and found that data in mice were both limited and lacking in reproduction. Next, we conducted a series of physiological measurements to address gaps in the literature and subjected C57BL/6J mice to three conditions: 1) conscious, 2) urethane-anesthetized, and 3) urethane-anesthetized with supplemental oxygen. Blood pressure, heart rate, [Formula: see text], and heart rate variability (via time, frequency, and M-curve analyses) were assessed. We observed an increase in heart rate with urethane anesthesia (P = 0.012) compared with the conscious state. Urethane caused a decrease in heart rate variability, which was independent of oxygen supplementation. Urethane anesthesia caused a significant reduction in arterial blood pressure (P < 0.001) with oxygen-supplemented mice remained hypotensive. Urethane decreased [Formula: see text] (P = 0.001), which was restored by oxygen supplementation (P < 0.001). We did not observe sex effects of urethane anesthesia on blood pressure, heart rate, heart rate variability, or [Formula: see text]. Taken together, these results underscore the importance of a cautious approach when using urethane in mice, as urethane significantly impacts arterial blood pressure, heart rate, oxygen saturation, and heart rate variability.NEW & NOTEWORTHY This investigation documents cardiovascular outcomes in mice receiving urethane anesthesia, emphasizing sex as a biological variable, and considering oxygen supplementation during anesthesia. This is the first report of M-curve analysis in rodents as a heart rate-independent variability analysis.

Successful repositioning of mertansine for improved chemotherapy by combining a polymer prodrug approach and PET imaging

Mertansine (DM1), a potent tumor-killing maytansinoid, requires conjugation to antibodies or incorporation into nanocarriers due to its high toxicity. However, these carriers often result in undesirable biodistribution, leading to rapid and long-term accumulation in the kidneys or liver and potentially increased toxicity. To overcome this limitation, we used the hydrophilic, biocompatible, and stealth properties of polyacrylamide (PAAm) as a scaffold to develop water-soluble PAAm-DM1 polymer prodrugs, leveraging PAAm's previous success in delivering paclitaxel via subcutaneous administration. To monitor distribution and predict efficacy, we have imparted Positron Emission Tomography (PET) imaging capabilities to well-defined PAAm-DM1 polymer prodrugs. Our studies demonstrated the same tumor accumulation and the same distribution of PAAm-DM1 in the main organs such as liver, kidneys muscle, regardless of delivery route (subcutaneous or intravenous). Interestingly, tumor accumulation of PAAm-DM1 was primarily driven by passive accumulation, as indicated by PET imaging, without significantly altering treatment efficacy. This suggests complex mechanisms, possibly involving immune system interactions by influencing notably the metabolism and clearance. To enhance therapeutic outcomes, we combined the polymer prodrug with immunotherapy, specifically anti-CTLA4. Our findings highlight the promising potential of PAAm-DM1, offering a novel formulation strategy for DM1 in cancer therapy.

Protocol for in situ and in vivo dissection of mouse lung-draining lymph nodes

Lung-draining lymph nodes (LNs) play crucial roles in infection, inflammation, and cancer, but in situ and in vivo studying models are technically challenging. Here, we present a protocol for the in situ and in vivo dissection of mouse lung-draining LNs, ensuring postoperative survival. We describe steps for lymphadenectomy including localizing lung-draining LNs, open thoracotomy, and LN dissection. We then detail procedures for surgical sample preservation and postoperative care. This protocol offers broad applications in immunological and oncological research.

Anesthetic spindles serve as EEG markers of the depth variations in anesthesia induced by multifarious general anesthetics in mouse experiments

Background

Mice play a crucial role in studying the mechanisms of general anesthesia. However, identifying reliable EEG markers for different depths of anesthesia induced by multifarious agents remains a significant challenge. Spindle activity, typically observed during NREM sleep, reflects synchronized thalamocortical activity and is characterized by a frequency range of 7-15 Hz and a duration of 0.5-3 s. Similar patterns, referred to as "anesthetic spindles," are also observed in the EEG during general anesthesia. However, the variability of anesthetic spindles across different anesthetic agents and depths is not yet fully understood.

Method

Mice were anesthetized with dexmedetomidine, propofol, ketamine, etomidate, isoflurane, or sevoflurane, and cortical EEG recordings were obtained. EEG signals were bandpass filtered between 0.1 and 60 Hz and analyzed using a custom MATLAB script for spindle detection. Anesthesia depth was assessed based on Guedel's modified stages of anesthesia and the presence of burst suppression in the EEG.

Results

Compared to sleep spindles, anesthetic spindles induced by the different agents exhibited higher amplitudes and longer durations. Isoflurane- and sevoflurane-induced spindles varied with the depth of anesthesia. Spindles associated with etomidate were prominent during induction and light anesthesia, whereas those induced by sevoflurane and isoflurane were more dominant during deep anesthesia and emergence. Post-anesthesia, spindles persisted but ceased more quickly following inhalational anesthesia.

Conclusion

Anesthesia spindle waves reflect distinct changes in anesthesia depth and persist following emergence, serving as objective EEG markers for assessing both anesthesia depth and the recovery process.

The impact of isoflurane anesthesia on brain metabolism in mice: An MRI and electroencephalography study

Isoflurane is one of the most widely used anesthetic agents in rodent imaging studies. However, the impact of isoflurane on brain metabolism has not been fully characterized to date, primarily due to a scarcity of noninvasive technologies to quantitatively measure the brain's metabolic rate in vivo. In this study, using noncontrast MRI techniques, we dynamically measured cerebral metabolic rate of oxygen (CMRO2) under varying doses of isoflurane anesthesia in mice. Concurrently, systemic parameters of heart and respiration rates were recorded alongside CMRO2. Additionally, electroencephalogram (EEG) recording was used to identify changes in neuronal activities under the same anesthetic regimen employed in the MRI experiments. We found suppression of the CMRO2 by isoflurane in a dose-dependent manner, concomitant with a diminished high-frequency EEG activity. The degree of metabolic suppression by isoflurane was strongly correlated with the respiration rate, which offers a potential approach to calibrate CMRO2 measurements. Furthermore, the metabolic level associated with neural responses of the somatosensory and motor cortices in mice was estimated as 308.2 μmol/100 g/min. These findings may facilitate the integration of metabolic parameters into future studies involving animal disease models and anesthesia usage.

Both TREM2-dependent macrophages and Kupffer cells play a protective role in APAP-induced acute liver injury

The inflammatory response is a significant factor in acetaminophen (APAP)-induced acute liver injury. And it can be mediated by macrophages of different origins. However, whether Kupffer cells and mononuclear-derived macrophages play an injury or protective role in APAP hepatotoxicity is still unclear. In this study, C57/BL6N mice were performed to establish the APAP acute liver injury model. Intervention experiments were also carried out using clodronate liposomes or TREM2 knockout. We found that APAP overdose triggered the activation of inflammatory factors and enhanced the expression of the RIPK1-MLKL pathway in mice's livers. Moreover, our study showed that inflammation-related protein expression was increased after clodronate liposome administration or TREM2 knockout. The RIPK1-MLKL-mediated necroptosis was also significantly activated after the elimination of Kupffer cells or the inhibition of mononuclear-derived macrophages. More importantly, clodronate liposomes treatment and TREM2 deficiency all worsen APAP-induced liver damage in mice. In conclusion, the results indicate that Kupffer cells and mononuclear macrophages play a protective role in APAP-induced liver injury by regulating necroptosis. Therefore, macrophages hold as a potential therapeutic target for APAP-induced liver damage.

General Anesthesia Induced by a Combination of Medetomidine/Vatinoxan with Ketamine and Buprenorphine-ER in C57BL/6J Mice (Mus musculus)

Medetomidine/vatinoxan (Zenalpha®) is a novel anesthetic combination used as a sedative and analgesic in dogs. Vatinoxan minimizes adverse cardiopulmonary effects associated with medetomidine administration while preserving sedation and analgesia. In this study, we evaluated the clinical safety and efficacy of 3 dosage combinations of Zenalpha with ketamine and buprenorphine extended release (ER) as compared with xylazine with ketamine and buprenorphine-ER for anesthesia of C57BL/6J mice. We hypothesized that anesthesia with 0.5 mg/kg of Zenalpha would more reliably provide a surgical anesthetic plane, lower mortality, and fewer adverse physiologic effects as compared with anesthesia with 8 mg/kg of xylazine. Ten-week-old male and female C57BL/6J mice were randomly administered 1 of 4 anesthetic cocktails subcutaneously: ketamine (80 mg/kg) and buprenorphine-ER (0.5 mg/kg) with 1) xylazine (8 mg/kg; XKB); 2) Zenalpha (0.25 mg/kg; ZKB/0.25); 3) Zenalpha (0.5 mg/kg; ZKB/0.5); or 4) Zenalpha (1.0 mg/kg; ZKB/1.0). Following drug administration, we assessed the anesthesia induction time by measuring the time to loss of righting reflex and loss of paw withdrawal reflex (PWR). Upon reaching a loss of righting reflex, physiologic parameters including heart rate, respiratory rate, oxygen saturation, indirect mean arterial blood pressure, body temperature, jaw tone, and skin color were monitored every 5 min. Thirty minutes after anesthetic drug administration (TA), atipamezole (1 mg/kg SC) was administered. Recovery time was determined through time until return of PWR, righting reflex, and ambulation. Mice were monitored for 3 d postanesthesia. Results included: 1) ZKB anesthesia caused loss of PWR in a dose-dependent manner; 2) physiologic parameters were similar between XKB and ZKB mice by TA in 100% O2; 3) ZKB groups took longer to recover and had a 20% to 30% mortality rate in the mid-to-high dosage groups. We conclude that anesthesia with 0.5 mg/kg of Zenalpha more reliably produced a surgical anesthetic plane but also led to decreased mean arterial pressure and increased mortality as compared with anesthesia with 8 mg/kg of xylazine. We recommend using Zenalpha (0.25 to 1.0 mg/kg) with 80 mg/kg ketamine and 0.5 mg/kg buprenorphine-ER to provide general anesthesia in C57BL/6 mice, along with supplemental 100% oxygen and atipamezole.

Evaluation of general anesthesia protocols for a highly controlled cardiac ischemia-reperfusion model in mice

BACKGROUND

The aim of our study was to test different anesthetic mixtures in order to identify the most suitable one for a surgical cardiac ischemia-reperfusion model in mice.

METHODS

1) Sixty four mice were submitted to one of the 6 combinations of ketamine or alfaxalone associated to xylazine, medetomidine or midazolam. Depth and quality of anesthesia were evaluated via 5 reflex scores. 2) Impact of analgesic (buprenorphine or butorphanol), anesthesia reversal (with atipamezole) and surgery (cardiac ischemia-reperfusion surgery) have been tested in the selected protocols. 3) infarction size has been measured with TTC (Triphenyl Tetrazolium Chloride) method in mice anesthetized with best protocols.

RESULTS

Protocol involving medetomidine induced the longest surgical anesthesia: (median = 120, {interquartile range = 100-125}) min with ketamine and 53 {25-100} min with alfaxalone. Butorphanol substitution with buprenorphine did not alter time-related anesthesia parameters. Atipamezole reversal considerably reduced both recovery and immobilization time (respectively 22 {18-30} min and 98 {88-99} min vs. 55 {40-70} min and 143 {131-149} min, in groups with no reversal, p = 0.001) with no impact on infarction size measurement.

CONCLUSION

In this study, the combination alfaxalone/medetomidine/buprenorphine (80/0,3/0,075 mg.kg-1, s.c.) associated with reversal by atipamezole was a reliable anesthetic protocol for murine surgery, particularly for the study of ischemia-reperfusion.

No negative effects of intra-abdominal bio-logger implantation under general anaesthesia on spatial cognition learning in a hibernator the edible dormouse

The effect of hibernation on cognitive capacities of individuals is not fully understood, as studies provide conflicting results. Most studies focus on behavioural observations without taking the physiological state of individuals to account. To mechanistically understand the effect of hibernation on the brain, physiological parameters need to be included. The implantation of bio-loggers can provide insights on i.e. body temperature without further manipulation of the animals. Surgeries and anaesthesia, however, can harm animals' health and cause cognitive dysfunction, potentially biasing data collected through bio-loggers. We investigated the effects of bio-logger implantation surgery on cognitive performance and learning, controlling for animal and study design characteristics. First, juvenile dormice successfully learned to solve a spatial cognition task using a vertical maze. Distance, transitions, velocity, and duration were measured as indicators for performance. After training, bio-loggers were implanted intra-abdominally under general anaesthesia. Animals were re-tested in the maze two weeks after. We found no effect of bio-logger implantation and surgery on performance. This study is the first to show spatial cognition learning in edible dormice and provides a full description of the peri-anaesthetic management and a protocol for bio-logger implantation surgery in dormice. Importantly, measures were taken to mitigate common anaesthetic complications that could lead to post-operative cognitive dysfunction and influence animal behaviour. By pairing physiological measurements through bio-logger implantation with behaviour and cognition measurements, future research will significantly advance the understanding on mechanisms of learning and behaviour.

Dynamic oxygen assessment techniques enable determination of anesthesia's impact on tissue

Tissue oxygenation is well understood to impact radiosensitivity, with reports demonstrating a significant effect of breathing condition and anesthesia type on tissue oxygenation levels and radiobiological response. However, the temporal kinetics of intracellular and extracellular oxygenation have never been quantified, on the timescale that may affect radiotherapy studies. C57BL/6 mice were anesthetized using isoflurane at various percentages or ketamine/xylazine (ket/xyl: 100/10 mg/kg) (N = 48). Skin pO2 was measured using Oxyphor PdG4 and tracked after anesthetization began. Oxyphor data was validated with relative measurements of intracellular oxygen via protoporphyrin IX (PpIX) delayed fluorescence (DF) imaging. Ex vivo localization of both PdG4 Oxyphor and PpIX were quantified. Under all isoflurane anesthesia conditions, leg skin pO2 levels significantly increased from 12-15 mmHg at the start of anesthesia induction (4-6 minutes) to 24-27 mmHg after 10 minutes (p < 0.05). Ketamine/xylazine anesthesia led to skin pO2 maintained at 15-16 mmHg throughout the 10-minute study period (p < 0.01). An increase of pO2 in mice breathing isoflurane was demonstrated with Oxyphor and PpIX DF, indicating similar intracellular and extracellular oxygenation. These findings demonstrate the importance of routine anesthesia administration, where consistency in the timing between induction and irradiation may be crucial to minimizing variability in radiation response.

Quantitative MRI of a Cerebral Cryptococcoma Mouse Model for In Vivo Distinction between Different Cryptococcal Molecular Types

The controversially discussed taxonomy of the Cryptococcus neoformans/Cryptococcus gattii species complex encompasses at least eight major molecular types. Cerebral cryptococcomas are a common manifestation of cryptococcal neurological disease. In this study, we compared neurotypical symptoms and differential neurovirulence induced by one representative isolate for each of the eight molecular types studied. We compared single focal lesions caused by the different isolates and evaluated the potential relationships between the fungal burden and properties obtained with quantitative magnetic resonance imaging (qMRI) techniques such as diffusion MRI, T2 relaxometry and magnetic resonance spectroscopy (MRS). We observed an inverse correlation between parametric data and lesion density, and we were able to monitor longitudinally biophysical properties of cryptococcomas induced by different molecular types. Because the MRI/MRS techniques are also clinically available, the same approach could be used to assess image-based biophysical properties that correlate with fungal cell density in lesions in patients to determine personalized treatments.

Quantitative proteomic analysis and replacement therapy identifies haptoglobin as a therapeutic target in a murine model of SLE-associated diffuse alveolar hemorrhage

Background

Diffuse alveolar hemorrhage (DAH) is a catastrophic clinical syndrome and one of the manifestations of pulmonary involvement in systemic lupus erythematosus (SLE), which is characterized by hemoptysis, diffuse pulmonary infiltrates, and respiratory failure. However, the treatment options for DAH remain limited, and DAH-related studies are needed to explore more effective therapeutic directions for better disease management and improved prognosis.

Methods

This study utilized the pristane-induced DAH murine model to mimic the pathological process of DAH in patients with SLE. Proteomic analysis was conducted to detect differentially expressed proteins (DEPs) in the plasma of surviving and non-surviving mice, followed by an analysis of biological functions and pathways. The most significant DEP was then confirmed in the plasma of SLE patients with or without DAH and DAH murine model with or without fatal outcomes. Finally, the therapeutic value of haptoglobin (Hp) replacement was validated in a DAH murine model through lung histopathology, RT-qPCR, and survival analysis.

Results

This study identified 178 DEPs, with 118 upregulated and 60 downregulated DEPs in the non-survival group. Within a set of notable Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways, complement and coagulation cascades emerged as the most prominent pathway associated with the process of DAH. Later, the most significant DEP, haptoglobin (Hp), was confirmed to exhibit a significant decrease in the plasma of individuals with SLE-DAH and DAH murine model with poor outcomes by the ELISA test. Finally, compared with the control group, the severity of DAH in the Hp treatment group was alleviated significantly, as manifested by the decreased levels of pro-inflammatory cytokines (IL-6 and TNF-α), increased levels of anti-inflammatory cytokines (IL-10 and TGF-β), and decreased mortality.

Conclusion

A reduction in plasma Hp levels was observed in SLE-DAH, and the replacement therapy with Hp could alleviate pulmonary hemorrhage and reduce mortality in DAH mice. This study identified Hp as a potential biomarker for its clinical diagnosis and a direction for treatment.

The structural characterization and UV-protective properties of an exopolysaccharide from a Paenibacillus isolate

Introduction

Overexposure to ultraviolet (UV) light is known to cause damage to the skin, leading to sunburn and photo-aging. Chemical sunscreen products may give rise to health risks including phototoxicity, photosensitivity, and photosensitivity. Natural polysaccharides have attracted considerable interests due to diverse biological activities.

Methods

A novel polysaccharide isolated was purified and structurally characterized using chemical methods followed by HPLC, GLC-MS, as well as 1D and 2D NMR spectroscopy. The photoprotective effect of the EPS on UVB-induced damage was assessed in vitro using cultured keratinocytes and in vivo using C57BL/6 mouse models.

Results

The average molecular weight of the EPS was 5.48 × 106 Da, composed of glucose, mannose and galactose residues at a ratio of 2:2:1. The repeating units of the EPS were →3)-β-D-Glcp (1→3) [β-D-Galp (1→2)-α-D-Glcp (1→2)]-α-D-Manp (1→3)-α-D-Manp (1→. In cultured keratinocytes, the EPS reduced cytotoxicity and excessive ROS production induced by UVB irradiation. The EPS also exhibits an inhibitory effect on oxidative stress, inflammation, and collagen degradation found in the photodamage in mice. 1H NMR-based metabolomics analysis for skin suggested that the EPS partly reversed the shifts of metabolic profiles of the skin in UVB-exposed mice.

Conclusion

The EPS exhibits skin photoprotective effects through regulating oxidative stress both in vivo and in vitro. Our findings highlight that the EPS is a potential candidate in sunscreen formulations for an efficient solution to UVB radiation.

The Acute Impact of Propofol on Blood-Brain Barrier Integrity in Mice

PURPOSE

We investigated whether short term infusion of propofol, a highly lipophilic agonist at GABAA receptors, which is in widespread clinical use as anesthetic and sedative, affects passive blood-brain barrier (BBB) permeability in vivo.

METHODS

Mice were anesthetized with an intraperitoneal injection of ketamine/xylazine followed by a continuous IV infusion of propofol in lipid emulsion through a tail vein catheter. Control groups received ketamine/xylazine anesthesia and an infusion of Intralipid, or ketamine/xylazine anesthesia only. [13C12]sucrose as a permeability marker was injected as IV bolus 15 min after start of the infusions. Brain uptake clearance, Kin, of sucrose was calculated from the brain concentrations at 30 min and the area under the plasma-concentration time curve. We also measured the plasma and brain concentration of propofol at the terminal time point.

RESULTS

The Kin value for propofol-infused mice was significantly higher, by a factor of 1.55 and 1.87, compared to the Intralipid infusion and the ketamine/xylazine groups, respectively, while the control groups were not significantly different. No difference was seen in the expression levels of tight junction proteins in brain across all groups. The propofol plasma concentration at the end of infusion (10.7 µM) matched the clinically relevant range of blood concentrations reported in humans, while concentration in brain was 2.5-fold higher than plasma.

CONCLUSIONS

Propofol at clinical plasma concentrations acutely increases BBB permeability, extending our previous results with volatile anesthetics to a lipophilic injectable agent. This prompts further exploration, potentially refining clinical practices and ensuring safety, especially during extended propofol infusion schemes.

CD47;Rag2;IL-2rγ triple knock-out mice pre-conditioning with busulfan could be a novel platform for generating hematopoietic stem cells engrafted humanized mice

Introduction

Humanized mouse models to recapitulate human biological systems still have limitations, such as the onset of lethal graft-versus-host disease (GvHD), a variable success rate, and the low accessibility of total body irradiation (TBI). Recently, mice modified with the CD47-SIRPA axis have been studied to improve humanized mouse models. However, such trials have been rarely applied in NOD mice. In this study, we created a novel mouse strain, NOD-CD47nullRag2nullIL-2rγnull (RTKO) mice, and applied it to generate humanized mice.

Methods

Four-week-old female NOD-Rag2nullIL-2rγnull (RID) and RTKO mice pre-conditioned with TBI or busulfan (BSF) injection were used for generating human CD34+ hematopoietic stem cell (HSC) engrafted humanized mice. Clinical signs were observed twice a week, and body weight was measured once a week. Flow cytometry for human leukocyte antigens was performed at intervals of four weeks or two weeks, and mice were sacrificed at 48 weeks after HSC injection.

Results

For a long period from 16 to 40 weeks post transplantation, the percentage of hCD45 was mostly maintained above 25% in all groups, and it was sustained the longest and highest in the RTKO BSF group. Reconstruction of human leukocytes, including hCD3, was also most prominent in the RTKO BSF group. Only two mice died before 40 weeks post transplantation in all groups, and there were no life-threatening GvHD lesions except in the dead mice. The occurrence of GvHD has been identified as mainly due to human T cells infiltrating tissues and their related cytokines.

Discussion

Humanized mouse models under all conditions applied in this study are considered suitable models for long-term experiments based on the improvement of human leukocytes reconstruction and the stable animal health. Especially, RTKO mice pretreated with BSF are expected to be a valuable platform not only for generating humanized mice but also for various immune research fields.

Adjusting and validating a procedure for parenteral anaesthesia in neonatal mice

For neonatal pups, parenteral anaesthesia is said to be not reliable as low doses induce no anaesthesia whereas high doses render high mortality rates. In this work we have adapted parenteral anaesthesia procedures approved for pups >7 days of age, to anaesthetize neonatal animals (postnatal days 3-4; P3-P4) for keeping them immobile for a long period. In our first experiment we analysed the behaviour of P3-P4 mouse pups for 70 min after intraperitoneal administration of low (37.5/3.75 mg/kg) or high (50/5) doses of a ketamine/xylazine anaesthetic mixture, both in the low range as compared with dosages employed in adults. Pups became immobile in ≈7 min and remained immobile for ≈45 min, irrespective of the age and dose of anaesthesia, younger pups (P3) being apparently more sensitive to the dosage. In the second experiment, we studied the response of P3 pups to mildly nociceptive stimulations, performed with a 4.0 g von Frey filament applied to the dorsal aspect of their paws. These stimuli elicited reaction in 100% of the cases in non-anaesthetized pups. The results indicate that the high dose significantly reduced responses as compared with the low dose of anaesthesia. With the low dose, <40% of the pups were unresponsive to nociceptive stimulation, whereas the high dose resulted in 50-60% of the animals not responding. Mortality was low irrespective of age or dose, suggesting that doses can be further increased if needed for invasive experimental procedures.

Validation of the anesthetic effect of a mixture of remimazolam, medetomidine, and butorphanol in three mouse strains

Proper administration of anesthesia is indispensable for the ethical treatment of lab animals in biomedical research. Therefore, selecting an effective anesthesia protocol is pivotal for the design and success of experiments. Hence, continuous development and refinement of anesthetic agents are imperative to improve research outcomes and elevate animal welfare. "Balanced anesthesia" involves using multiple drugs to optimize efficacy while minimizing side effects. The medetomidine, midazolam, and butorphanol, called MMB, and medetomidine, alfaxalone, and butorphanol, called MAB, are popular in Japan. However, the drawbacks of midazolam, including its extended recovery time, and the narrow safety margin of MAB, have prompted research for suitable alternatives. This study replaced midazolam in the MMB combination with remimazolam (RMZ), which is noted for its ultra-short half-life. The resulting combination, called MRB, was effective in providing a wider safety margin compared to MAB while maintaining an anesthesia depth equivalent level to that of MMB in mice. Notably, MRB consistently exhibited better recovery scores after antagonist administration in contrast to MMB. Furthermore, the re-sedation phenomenon observed with MMB was not observed with MRB. The rapid metabolism of RMZ enables reliable anesthesia induction, circumventing the complications linked to MAB. Overall, MRB excelled in providing extended surgical anesthesia and swift post-antagonist recovery. These results highlight the potential of RMZ for broader animal research applications.

Substance specific EEG patterns in mice undergoing slow anesthesia induction

The exact mechanisms and the neural circuits involved in anesthesia induced unconsciousness are still not fully understood. To elucidate them valid animal models are necessary. Since the most commonly used species in neuroscience are mice, we established a murine model for commonly used anesthetics/sedatives and evaluated the epidural electroencephalographic (EEG) patterns during slow anesthesia induction and emergence. Forty-four mice underwent surgery in which we inserted a central venous catheter and implanted nine intracranial electrodes above the prefrontal, motor, sensory, and visual cortex. After at least one week of recovery, mice were anesthetized either by inhalational sevoflurane or intravenous propofol, ketamine, or dexmedetomidine. We evaluated the loss and return of righting reflex (LORR/RORR) and recorded the electrocorticogram. For spectral analysis we focused on the prefrontal and visual cortex. In addition to analyzing the power spectral density at specific time points we evaluated the changes in the spectral power distribution longitudinally. The median time to LORR after start anesthesia ranged from 1080 [1st quartile: 960; 3rd quartile: 1080]s under sevoflurane anesthesia to 1541 [1455; 1890]s with ketamine. Around LORR sevoflurane as well as propofol induced a decrease in the theta/alpha band and an increase in the beta/gamma band. Dexmedetomidine infusion resulted in a shift towards lower frequencies with an increase in the delta range. Ketamine induced stronger activity in the higher frequencies. Our results showed substance-specific changes in EEG patterns during slow anesthesia induction. These patterns were partially identical to previous observations in humans, but also included significant differences, especially in the low frequencies. Our study emphasizes strengths and limitations of murine models in neuroscience and provides an important basis for future studies investigating complex neurophysiological mechanisms.

Evaluation of Thermal Support during Anesthesia Induction on Body Temperature in C57BL/6 and Nude Mice

Heat supplementation during surgery is a common practice; however, thermal support is not commonly used during anesthesia induction. Mice lose body temperature quickly, and air movement can exacerbate this, potentially putting mice at a thermal deficit before surgery. Whether the method of warming during induction affects overall heat loss during anesthesia is unknown. We hypothesized that the method of heating would affect body temperature (Tb) during anesthesia induction, maintenance, recovery, and once placed back on the rack. Mice (C57BL/6NHsd-6M/6F [C57BL/6]; Hsd:Athymic Nude-Foxn1nu [Nude]; N = 24;12M/12F) were assigned to a treatment in a factorial design: thermal chamber (TC; ambient temperature [Ta] = 28.8°C); heating pad (HP; induction chamber placed on an electric heating pad;Ta = 28.4°C); and control (Ctrl; Ta = 21.6°C). During induction, one mouse at a time was anesthetized with isoflurane over a 3min period and then maintained under anesthesia for 10min on a hot water heating pad (33 °C). Then isoflurane was stopped and time to ambulation was recorded. Tb and activity were tracked in the home cage on the rack before and after anesthesia. During induction, Ctrl mice lost significantly more heat (-2.8 °C) than did TC (+0.2 °C) and HP mice (+0.1 °C) but TC and HP were not different. During anesthesia maintenance, Ctrl mice regained 1 °C, but their Tb was still lower than that of the treated groups. Nude mice consistently had a lower Tb than C57BL/6 mice, regardless of treatment or anesthesia phase. C57BL/6 Ctrl mice took longer to ambulate than either HP or TC mice, but the method of heating did not differentially affect Nude mice. In general, C57BL/6 as compared with Nude and females as compared with males were comparatively more active and had higher Tb during certain times of day, regardless of the heating methods. Overall, our findings support the provision of heat during anesthesia induction, regardless of method, to reduce overall Tb loss during a short anesthesia event.

High-Spatial-Resolution Benchtop X-ray Fluorescence Imaging through Bragg-Diffraction-Based Focusing with Bent Mosaic Graphite Crystals: A Simulation Study

X-ray fluorescence imaging (XFI) can localize diagnostic or theranostic entities utilizing nanoparticle (NP)-based probes at high resolution in vivo, in vitro, and ex vivo. However, small-animal benchtop XFI systems demonstrating high spatial resolution (variable from sub-millimeter to millimeter range) in vivo are still limited to lighter elements (i.e., atomic number Z≤45). This study investigates the feasibility of focusing hard X-rays from solid-target tubes using ellipsoidal lens systems composed of mosaic graphite crystals with the aim of enabling high-resolution in vivo XFI applications with mid-Z (42≤Z≤64) elements. Monte Carlo simulations are performed to characterize the proposed focusing-optics concept and provide quantitative predictions of the XFI sensitivity, in silico tumor-bearing mice models loaded with palladium (Pd) and barium (Ba) NPs. Based on simulation results, the minimum detectable total mass of PdNPs per scan position is expected to be on the order of a few hundred nanograms under in vivo conform conditions. PdNP masses as low as 150 ng to 50 ng could be detectable with a resolution of 600 μm when imaging abdominal tumor lesions across a range of low-dose (0.8 μGy) to high-dose (8 μGy) exposure scenarios. The proposed focusing-optics concept presents a potential step toward realizing XFI with conventional X-ray tubes for high-resolution applications involving interesting NP formulations.

The OTX2 Gene Induces Tumor Growth and Triggers Leptomeningeal Metastasis by Regulating the mTORC2 Signaling Pathway in Group 3 Medulloblastomas

Medulloblastoma (MB) encompasses diverse subgroups, and leptomeningeal disease/metastasis (LMD) plays a substantial role in associated fatalities. Despite extensive exploration of canonical genes in MB, the molecular mechanisms underlying LMD and the involvement of the orthodenticle homeobox 2 (OTX2) gene, a key driver in aggressive MB Group 3, remain insufficiently understood. Recognizing OTX2's pivotal role, we investigated its potential as a catalyst for aggressive cellular behaviors, including migration, invasion, and metastasis. OTX2 overexpression heightened cell growth, motility, and polarization in Group 3 MB cells. Orthotopic implantation of OTX2-overexpressing cells in mice led to reduced median survival, accompanied by the development of spinal cord and brain metastases. Mechanistically, OTX2 acted as a transcriptional activator of the Mechanistic Target of Rapamycin (mTOR) gene's promoter and the mTORC2 signaling pathway, correlating with upregulated downstream genes that orchestrate cell motility and migration. Knockdown of mTOR mRNA mitigated OTX2-mediated enhancements in cell motility and polarization. Analysis of human MB tumor samples (N = 952) revealed a positive correlation between OTX2 and mTOR mRNA expression, emphasizing the clinical significance of OTX2's role in the mTORC2 pathway. Our results reveal that OTX2 governs the mTORC2 signaling pathway, instigating LMD in Group 3 MBs and offering insights into potential therapeutic avenues through mTORC2 inhibition.

Mouse Anesthesia and Analgesia

Providing anesthesia and analgesia for mouse subjects is a common and critical practice in the laboratory setting. This practice is necessary for performing invasive procedures, achieving prolonged immobility for sensitive imaging modalities (magnetic resonance imaging, for instance), and providing intra- and post-procedural pain relief. In addition to facilitating the procedures performed by the investigator, the provision of anesthesia and analgesia is crucial for the preservation of animal welfare and for humane treatment of animals used in research. Furthermore, anesthesia and analgesia are important components of animal use protocols reviewed by Institutional Animal Care and Use Committees, requiring careful consideration and planning for the particular animal model. In this article, we provide technical guidance for the investigator, covering the provision of anesthesia by two routes (injectable and inhalant), guidelines for monitoring anesthesia, current techniques for recognition of pain, considerations for administering preventative analgesia, and considerations for post-operative care. © 2024 Wiley Periodicals LLC. Basic Protocol 1: Injectable anesthesia Basic Protocol 2: Inhalant anesthesia Basic Protocol 3: Assessing pain.

Anti-Apoptotic Effects of AMPA Receptor Antagonist Perampanel in Early Brain Injury After Subarachnoid Hemorrhage in Mice

This study was aimed to investigate if acute neuronal apoptosis is induced by activation of AMPA (α-amino-3-hydroxy-5-methyl-4-isoxazole propionate) receptors (AMPARs) and inhibited by a clinically available selective AMPAR antagonist and antiepileptic drug perampanel (PER) in subarachnoid hemorrhage (SAH), and if the mechanisms include upregulation of an inflammation-related matricellular protein periostin. Sham-operated and endovascular perforation SAH mice randomly received an administration of 3 mg/kg PER or the vehicle intraperitoneally. Post-SAH neurological impairments and increased caspase-dependent neuronal apoptosis were associated with activation of AMPAR subunits GluA1 and GluA2, and upregulation of periostin and proinflammatory cytokines interleukins-1β and -6, all of which were suppressed by PER. PER also inhibited post-SAH convulsion-unrelated increases in the total spectral power on video electroencephalogram (EEG) monitoring. Intracerebroventricularly injected recombinant periostin blocked PER's anti-apoptotic effects on neurons. An intracerebroventricular injection of a selective agonist for GluA1 and GluA2 aggravated neurological impairment, neuronal apoptosis as well as periostin upregulation, but did not increase the EEG total spectral power after SAH. A higher dosage (10 mg/kg) of PER had even more anti-apoptotic effects compared with 3 mg/kg PER. Thus, this study first showed that AMPAR activation causes post-SAH neuronal apoptosis at least partly via periostin upregulation. A clinically available AMPAR antagonist PER appears to be neuroprotective against post-SAH early brain injury through the anti-inflammatory and anti-apoptotic effects, independent of the antiepileptic action, and deserves further study.

Central Artery Hemodynamics in Angiotensin II-Induced Hypertension and Effects of Anesthesia

Systemic hypertension is a strong risk factor for cardiovascular, neurovascular, and renovascular diseases. Central artery stiffness is both an initiator and indicator of hypertension, thus revealing a critical relationship between the wall mechanics and hemodynamics. Mice have emerged as a critical animal model for studying effects of hypertension and much has been learned. Regardless of the specific mouse model, data on changes in cardiac function and hemodynamics are necessarily measured under anesthesia. Here, we present a new experimental-computational workflow to estimate awake cardiovascular conditions from anesthetized data, which was then used to quantify effects of chronic angiotensin II-induced hypertension relative to normotension in wild-type mice. We found that isoflurane anesthesia had a greater impact on depressing hemodynamics in angiotensin II-infused mice than in controls, which led to unexpected results when comparing anesthetized results between the two groups of mice. Through comparison of the awake simulations, however, in vivo relevant effects of angiotensin II-infusion on global and regional vascular structure, properties, and hemodynamics were found to be qualitatively consistent with expectations. Specifically, we found an increased in vivo vascular stiffness in the descending thoracic aorta and suprarenal abdominal aorta, leading to increases in pulse pressure in the distal aorta. These insights allow characterization of the impact of regionally varying vascular remodeling on hemodynamics and mouse-to-mouse variations due to induced hypertension.

Electroencephalographic monitoring of anesthesia during surgical procedures in mice using a modified clinical monitoring system

Monitoring brain activity and associated physiology during the administration of general anesthesia (GA) in mice is pivotal to guarantee postanesthetic health. Clinically, electroencephalogram (EEG) monitoring is a well-established method to guide GA. There are no established methods available for monitoring EEG in mice (Mus musculus) during surgery. In this study, a minimally invasive rodent intraoperative EEG monitoring system was implemented using subdermal needle electrodes and a modified EEG-based commercial patient monitor. EEG recordings were acquired at three different isoflurane concentrations revealing that surgical concentrations of isoflurane anesthesia predominantly contained burst suppression patterns in mice. EEG suppression ratios and suppression durations showed strong positive correlations with the isoflurane concentrations. The electroencephalographic indices provided by the monitor did not support online monitoring of the anesthetic status. The online available suppression duration in the raw EEG signals during isoflurane anesthesia is a straight forward and reliable marker to assure safe, adequate and reproducible anesthesia protocols.

3R-Refinement principles: elevating rodent well-being and research quality

This review article delves into the details of the 3R-Refinement principles as a vital framework for ethically sound rodent research laboratory. It highlights the core objective of the refinement protocol, namely, to enhance the well-being of laboratory animals while simultaneously improving the scientific validity of research outcomes. Through an exploration of key components of the refinement principles, the article outlines how these ethics should be implemented at various stages of animal experiments. It emphasizes the significance of enriched housing environments that reduce stress and encourage natural behaviors, non-restraint methods in handling and training, refined dosing and sampling techniques that prioritize animal comfort, the critical role of optimal pain management and the importance of regular animal welfare assessment in maintaining the rodents well-being. Additionally, the advantages of collaboration with animal care and ethics committees are also mentioned. The other half of the article explains the extensive benefits of the 3R-Refinement protocol such as heightened animal welfare, enhanced research quality, reduced variability, and positive feedback from researchers and animal care staff. Furthermore, it addresses avenues for promoting the adoption of the protocol, such as disseminating best practices, conducting training programs, and engaging with regulatory bodies. Overall, this article highlights the significance of 3R-Refinement protocol in aligning scientific advancement with ethical considerations along with shaping a more compassionate and responsible future for animal research.

Development of a Mouse Experimental System for the In Vivo Characterization of Bioengineered Adipose-Derived Stromal Cells

Human adipose-derived stromal cells (ADSCs) are an important resource for cell-based therapies. However, the dynamics of ADSCs after transplantation and their mechanisms of action in recipients remain unclear. Herein, we generated genetically engineered mouse ADSCs to clarify their biodistribution and post-transplantation status and to analyze their role in recipient mesenchymal tissue modeling. Immortalized ADSCs (iADSCs) retained ADSC characteristics such as stromal marker gene expression and differentiation potential. iADSCs expressing a fluorescent reporter gene were seeded into biocompatible nonwoven fabric sheets and transplanted into the dorsal subcutaneous region of neonatal mice. Transplanted donor ADSCs were distributed as CD90-positive stromal cells on the sheets and survived 1 month after transplantation. Although accumulation of T lymphocytes or macrophages inside the sheet was not observed with or without donor cells, earlier migration and accumulation of recipient blood vascular endothelial cells (ECs) inside the sheet was observed in the presence of donor cells. Thus, our mouse model can help in studying the interplay between donor ADSCs and recipient cells over a 1-month period. This system may be of value for assessing and screening bioengineered ADSCs in vivo for optimal cell-based therapies.

Investigation of Expanded Human Adipose-derived Stem Cell Dosage and Timing for Improved Defecation Function

BACKGROUND/AIM

Although certain treatment options exist for intestinal incontinence, none are curative. Adipose-derived stem cells (ADSCs) have emerged as promising therapeutic agents, but most preclinical studies of their effectiveness for anal function have used autologous or allogeneic ADSCs. In this study, the effectiveness, timing of administration, and required dosage of human ADSCs were investigated for clinical application.

MATERIALS AND METHODS

A 10-mm balloon catheter was used to induce anal sphincter injury in immunodeficient mice in the following experimental groups (n=4 per group): ADSC (injected ADSCs after injury), PBS (injected phosphate-buffered saline after injury), and control (uninjured). The effects of different timing (immediately after injection and 30 days following injury) and number of human ADSCs administered was compared among groups based on defecation status and pathological evaluation.

RESULTS

In terms of defecation status, groups receiving ≥1×104 human ADSCs after injection showed improvement. Pathological images showed that compared to the PBS group, the thinnest part of the sphincter was thicker for animals that received ≥1×104 human ADSCs, and fibrosis of the sphincter was notable in those treated with 1×103 human ADSCs or PBS. Furthermore, defecation status was improved by administration of human ADSCs, not only immediately after injury, but also at 30 days following injury.

CONCLUSION

Human ADSC administration in a mouse model of anal sphincter injury was effective. Injection of ≥1×104 human ADSCs was the amount necessary to improve defecation status, an effect detected in both the acute and chronic phases.

Mouse and Rat Anesthesia and Analgesia

Anesthesia and analgesia play pivotal roles in ethically and humanely using animal models in research, especially concerning mice and rats. These rodent species, extensively utilized in scientific investigations due to their genetic resemblance to humans, serve as invaluable tools for studying diseases and testing treatments. Proper anesthesia and analgesia not only prioritize animal welfare but also heighten experimental validity by minimizing stress-induced physiological responses. Recent years have seen remarkable advancements in anesthesia for mice and rats. The focus has shifted away from the 'one size fits all' toward tailoring anesthesia protocols, considering factors like age, strain, and the nature of the experimental procedure. The use of inhalation agents such as isoflurane and sevoflurane is often preferred due to their rapid induction and recovery characteristics, allowing precise control over anesthesia depth. However, refinements in injectable anesthetic agents also provide researchers the flexibility to select suitable agents based on study requirements. Additionally, progress in analgesic techniques has led to effective pain management strategies for these rodents. Common analgesics such as nonsteroidal anti-inflammatory drugs (NSAIDs), opioids, and local anesthetics are administered to alleviate pain and discomfort. However, standard practice also involves continuous monitoring of animals' behavior and physiological parameters, ensuring timely adjustments in analgesic regimens for optimal pain relief without compromising experimental outcomes. By integrating tailored anesthesia and analgesia protocols into the experimental design, researchers uphold high animal welfare standards while obtaining reliable scientific data. This contributes significantly to advancing medical knowledge and therapeutic interventions with reproducible results. Published 2024. This article is a U.S. Government work and is in the public domain in the USA. Current Protocols published by Wiley Periodicals LLC. Basic Protocol 1: Injectable anesthesia for mouse and rat Basic Protocol 2: Inhalant anesthesia using isoflurane for mouse and rat Basic Protocol 3: Analgesia for mice and rats.

Effects of atipamezole on selected physiologic parameters in cynomolgus macaques (Macaca fascicularis)

BACKGROUND

Atipamezole, an α-2 adrenergic receptor antagonist, reverses the α-2 agonist anesthetic effects. There is a dearth of information on the physiological effects of these drugs in cynomolgus macaques (Macaca fascicularis). We assessed atipamezole's physiologic effects. We hypothesized atipamezole administration would alter anesthetic parameters.

METHODS

Five cynomolgus macaques were sedated with ketamine/dexmedetomidine intramuscularly, followed 45 min later with atipamezole (0.5 mg/kg). Anesthetic parameters (heart rate, blood pressure [systolic (SAP), diastolic (DAP), and mean (MAP) blood pressure], body temperature, respiratory rate, and %SpO2) were monitored prior to and every 10 min (through 60 min) post atipamezole injection.

RESULTS

While heart rate was significantly increased for 60 min; SAP, DAP, MAP, and temperature were significantly decreased at 10 min.

CONCLUSIONS

This study indicates subcutaneous atipamezole results in increased heart rate and transient blood pressure decrease. These findings are clinically important to ensure anesthetist awareness to properly support and treat patients as needed.

Autonomous animal heating and cooling system for temperature-regulated magnetic resonance experiments

Temperature is a hallmark parameter influencing almost all magnetic resonance properties (e.g., T1 , T2 , proton density, and diffusion). In the preclinical setting, temperature has a large influence on animal physiology (e.g., respiration rate, heart rate, metabolism, and oxidative stress) and needs to be carefully regulated, especially when the animal is under anesthesia and thermoregulation is disrupted. We present an open-source heating and cooling system capable of regulating the temperature of the animal. The system was designed using Peltier modules capable of heating or cooling a circulating water bath with active temperature feedback. Feedback was obtained using a commercial thermistor, placed in the animal rectum, and a proportional-integral-derivative controller was used to modulate the temperature. Its operation was demonstrated in a phantom as well as in mouse and rat animal models, where the standard deviation of the temperature of the animal upon convergence was less than a 10th of a degree. An application where brain temperature of a mouse was modulated was demonstrated using an invasive optical probe and noninvasive magnetic resonance spectroscopic thermometry measurements.

Sox9 links biliary maturation to branching morphogenesis

Branching morphogenesis couples cellular differentiation with development of tissue architecture. Intrahepatic bile duct (IHBD) morphogenesis is initiated with biliary epithelial cell (BEC) specification and eventually forms a heterogeneous network of large ducts and small ductules. Here, we show that Sox9 is required for developmental establishment of small ductules. IHBDs emerge as a webbed structure by E15.5 and undergo morphological maturation through 2 weeks of age. Developmental knockout of Sox9 leads to decreased postnatal branching morphogenesis, manifesting as loss of ductules in adult livers. In the absence of Sox9, BECs fail to mature and exhibit elevated TGF-β signaling and Activin A. Activin A induces developmental gene expression and morphological defects in BEC organoids and represses ductule formation in postnatal livers. Our data demonstrate that adult IHBD morphology and BEC maturation is regulated by the Sox9-dependent formation of precursors to ductules during development, mediated in part by downregulation of Activin A.

Inhibition of CX3CL1 by treadmill training prevents osteoclast-induced fibrocartilage complex resorption during TBI healing

Introduction

The healing of tendon-bone injuries is very difficult, often resulting in poor biomechanical performance and unsatisfactory functional recovery. The tendon-bone insertion has a complex four distinct layers structure, and previous studies have often focused on promoting the regeneration of the fibrocartilage layer, neglecting the role of its bone end repair in tendon-bone healing. This study focuses on the role of treadmill training in promoting bone regeneration at the tendon-bone insertion and its related mechanisms.

Methods

After establishing the tendon-bone insertion injury model, the effect of treadmill training on tendon-bone healing was verified by Micro CT and HE staining; then the effect of CX3CL1 on osteoclast differentiation was verified by TRAP staining and cell culture; and finally the functional recovery of the mice was verified by biomechanical testing and behavioral test.

Results

Treadmill training suppresses the secretion of CX3CL1 and inhibits the differentiation of local osteoclasts after tendon-bone injury, ultimately reducing osteolysis and promoting tendon bone healing.

Discussion

Our research has found the interaction between treadmill training and the CX3CL1-C3CR1 axis, providing a certain theoretical basis for rehabilitation training.

System of Implantable Electrodes for Neural Signal Acquisition and Stimulation for Wirelessly Connected Forearm Prosthesis

There is great interest in the development of prosthetic limbs capable of complex activities that are wirelessly connected to the patient's neural system. Although some progress has been achieved in this area, one of the main problems encountered is the selective acquisition of nerve impulses and the closing of the automation loop through the selective stimulation of the sensitive branches of the patient. Large-scale research and development have achieved so-called "cuff electrodes"; however, they present a big disadvantage: they are not selective. In this article, we present the progress made in the development of an implantable system of plug neural microelectrodes that relate to the biological nerve tissue and can be used for the selective acquisition of neuronal signals and for the stimulation of specific nerve fascicles. The developed plug electrodes are also advantageous due to their small thickness, as they do not trigger nerve inflammation. In addition, the results of the conducted tests on a sous scrofa subject are presented.

A protocol and a data-based prediction to investigate virus spillover at the wildlife interface in human-dominated and protected habitats in Thailand: The Spillover Interface project

The Spillover Interface Project aims at assessing the encounter of wildlife, domestic animals, and humans along a landscape gradient from a protected area to a residential community, through areas of reforestation and agricultural land. Here, we present the protocols of the project that combine virus screening in humans, bats, rodents and dogs with camera trapping, land-use characterization, and network analyses. The project is taking place in the sub-district of Saen Thong (Nan Province, Thailand) in collaboration with local communities, the District Public Health Office, and Nanthaburi National Park. To formulate a predictive hypothesis for the Spillover Interface Project, we assess the wildlife diversity and their viral diversity that could be observed in Saen Thong through a data science analysis approach. Potential mammalian species are estimated using data from the International Union for Conservation of Nature (IUCN) and their associated viral diversity from a published open database. A network analysis approach is used to represent and quantify the transmission of the potential viruses hosted by the mammals present in Saen Thong, according to the IUCN. A total of 57 viruses are expected to be found and shared between 43 host species, including the domestic dog and the human species. By following the protocols presented here, the Spillover Interface Project will collect the data and samples needed to test this data-driven prediction.

Acute Effects of Hypothermia and Inhalant Anesthesia on Ultrasonic Vocalizations and Neuroendocrine Markers in Neonatal Rats

Neonatal rodents undergo anesthesia for numerous procedures and for euthanasia by anesthetic overdose. However, data regarding whether neonatal anesthesia is humane are limited. Hypothermia (cryoanesthesia) is the most commonly used anesthetic protocol for neonatal rats 10 d of age or younger. However, hypothermia has recently been restricted in several countries due to perceived painful effects, including pain on rewarming. Minimizing the potential pain and distress of neonates in research is imperative, although very challenging. Traditional validated and nonvalidated behavioral and physiologic outcome measures used for adult rats undergoing anesthesia are unsuitable for evaluating neonates. Therefore, we investigated the effects of several anesthetic methods on neonatal rats by using the innovative objective approaches of noninvasive ultrasonic vocalizations and more invasive neuroendocrine responses (i. e., serum corticosterone, norepinephrine, glucose). Our results show that hypothermia leads to heightened acute distress in neonatal rats as indicated by prolonged recovery times, increased duration of vocalizations, and elevated corticosterone levels, as compared with neonates undergoing inhalational anesthesia. We demonstrate that inhalational anesthesia is preferable to cryoanesthesia for neonatal rats, and researchers using hypothermia anesthesia should consider using inhalational anesthesia as an alternative method.

Cardiovascular magnetic resonance imaging for sequential assessment of cardiac fibrosis in mice: technical advancements and reverse translation

Cardiovascular magnetic resonance (CMR) imaging has become an essential technique for the assessment of cardiac function and morphology, and is now routinely used to monitor disease progression and intervention efficacy in the clinic. Cardiac fibrosis is a common characteristic of numerous cardiovascular diseases and often precedes cardiac dysfunction and heart failure. Hence, the detection of cardiac fibrosis is important for both early diagnosis and the provision of guidance for interventions/therapies. Experimental mouse models with genetically and/or surgically induced disease have been widely used to understand mechanisms underlying cardiac fibrosis and to assess new treatment strategies. Improving the appropriate applications of CMR to mouse studies of cardiac fibrosis has the potential to generate new knowledge, and more accurately examine the safety and efficacy of antifibrotic therapies. In this review, we provide 1) a brief overview of different types of cardiac fibrosis, 2) general background on magnetic resonance imaging (MRI), 3) a summary of different CMR techniques used in mice for the assessment of cardiac fibrosis including experimental and technical considerations (contrast agents and pulse sequences), and 4) provide an overview of mouse studies that have serially monitored cardiac fibrosis during disease progression and/or therapeutic interventions. Clinically established CMR protocols have advanced mouse CMR for the detection of cardiac fibrosis, and there is hope that discovery studies in mice will identify new antifibrotic therapies for patients, highlighting the value of both reverse translation and bench-to-bedside research.

Isoflurane and Pentobarbital Anesthesia for Pulmonary Studies Requiring Prolonged Mechanical Ventilation in Mice

Mechanical ventilation can be used in mice to support high-risk anesthesia or to create clinically relevant, intensive care models. However, the choice of anesthetic and inspired oxygen concentration for prolonged procedures may affect basic physiology and lung inflammation. To characterize the effects of anesthetics and oxygen concentration in mice experiencing mechanical ventilation, mice were anesthetized with either isoflurane or pentobarbital for tracheostomy followed by mechanical ventilation with either 100% or 21% oxygen. Body temperature, oxygen saturation, and pulse rate were monitored continuously. After 6 h, mice were euthanized for collection of blood and bronchoalveolar lavage fluid for evaluation of biomarkers of inflammation and lung injury, including cell counts and cytokine levels. Overall, both isoflurane and pentobarbital provided suitable anesthesia for 6 h of mechanical ventilation with either 21% or 100% oxygen. We found no differences in lung inflammation biomarkers attributable to either oxygen concentration or the anesthetic. However, the combination of pentobarbital and 100% oxygen resulted in a significantly higher concentration of a biomarker for lung epithelial cell injury. This study demonstrates that the combination of anesthetic agent, mechanical ventilation, and inspired oxygen concentrations can alter vital signs and lung injury biomarkers during prolonged procedures. Their combined impact may influence model development and the interpretation of research results, warranting the need for preliminary evaluation to establish the baseline effects.

Commonly used anesthetics modify alcohol and (-)-trans-delta9-tetrahydrocannabinol in vivo effects on rat cerebral arterioles

BACKGROUND

Ethyl alcohol and cannabis are widely used recreational substances with distinct effects on the brain. These drugs increase accidental injuries requiring treatment under anesthesia. Moreover, alcohol and cannabis are often used in anesthetized rodents for biomedical research. Here, we compared the influence of commonly used forms of anesthesia, injectable ketamine/xylazine (KX) versus inhalant isoflurane, on alcohol- and (-)-trans-delta9-tetrahydrocannabinol (THC) effects on cerebral arteriole diameter evaluated in vivo.

METHODS

Studies were performed on male and female Sprague-Dawley rats subjected to intracarotid catheter placement for drug infusion, and cranial window surgery for monitoring pial arteriole diameter. Depth of anesthesia was monitored every 10-15 min by toe-pinch. Under KX, the number of toe-pinch responders was maximal after the first dose of anesthesia and diminished over time in both males and females. In contrast, the number of toe-pinch responders under isoflurane slowly raised over time, leading to increase in isoflurane percentage until deep anesthesia was re-established. Rectal temperature under KX remained stable in males while dropping in females. As expected for gaseous anesthesia, both males and females exhibited rectal temperature drops under isoflurane.

RESULTS

Infusion of 50 mM alcohol (ethanol, EtOH) into the cerebral circulation rendered robust constriction in males under KX anesthesia, this alcohol action being significantly smaller, but still present under isoflurane anesthesia. In females, EtOH did not cause measurable changes in pial arteriole diameter regardless of the anesthetic. These findings indicate a strong sex bias with regards to EtOH induced vasoconstriction. Infusion of 42 nM THC in males and females under isoflurane tended to constrict cerebral arterioles in both males and females when compared to isovolumic infusion of THC vehicle (dimethyl sulfoxide in saline). Moreover, THC-driven changes in arteriole diameter significantly differed in magnitude depending on the anesthetic used. Simultaneous administration of 50 mM alcohol and 42 nM THC to males constricted cerebral arterioles regardless of the anesthetic used. In females, constriction by the combined drugs was also observed, with limited influence by anesthetic presence.

CONCLUSIONS

We demonstrate that two commonly used anesthetic formulations differentially influence the level of vasoconstriction caused by alcohol and THC actions in cerebral arterioles.

Regenerated Corneal Epithelium Expresses More βIII-Tubulin After Chemical Injuries Compared to Mechanical Injuries

Purpose

Defining the regenerative response following various types of corneal chemical and mechanical injuries is important for understanding the pathophysiology of the injury and evaluating the effectiveness of the therapies. This study characterizes corneal epithelial healing in a murine chemical and mechanical injury model.

Methods

Four groups of 10 mice each received complete corneolimbal injuries by AlgerBrush, AlgerBrush/thermal, NaOH (0.5 N), or ethanol. Slit-lamp and optical coherence tomography examinations were performed daily for 14 days. Corneal opacity (CO) and neovascularization (NV) were evaluated. The origin of the regenerated epithelium was illustrated by anti-cytokeratin 12 (K12) and anti-K13. The height of regenerated corneal epithelium and intraepithelial free nerve endings (FNEs) stained with anti-βIII-tubulin were measured. The amount of fibrosis was measured by anti-α-smooth muscle actin (α-SMA) monoclonal antibody in the different groups. Statistical analysis was performed by ANOVA and t-test.

Results

Corneal opacity and neovascularization were markedly higher in the NaOH and AlgerBrush/thermal groups. Molecular studies revealed the following: Regenerated corneal epithelium thickness was less than normal in all groups, the AlgerBrush group had the shortest height of the regenerated epithelium, βIII-tubulin was expressed in the entire height of corneal epithelium in all groups except in the AlgerBrush group, and K12 was replaced by K13 in all groups.

Conclusions

Corneal wound healing is more effective following chemical injuries in terms of epithelial thickness. Inflammation may play an important role in the outcome.

Translational Relevance

Inflammation following different injuries may be redirected to be more effective in corneal regeneration and clarity.

Automated measurement of distance-walked as a "sixth vital sign" for detecting infusion reactions during preclinical testing

Infusion reactions are a major risk for advanced therapeutics (e.g., engineered proteins nanoparticles, etc.), which can trigger the complement cascade, anaphylaxis, and other life-threatening immune responses. However, during the early phases of development, it is uncommon to assess for infusion reactions, given the labor involved in measuring multiple physiological parameters in rodents. Therefore, we sought to develop an automated quantification of rodent locomotion to serve as a sensitive screening tool for infusion reactions, with minimal added labor-time for each experiment. Here we present the detailed methods for building a motion tracking cage for mice, requiring ∼$100 of materials, ∼2 h to build and set up completely, and employing freely available software (DeepLabCut). The distance-walked after injection was first shown to have the predicted effects for stimulants (caffeine), sedatives (ketamine), and toxins (lipopolysaccharide). Additionally, the distance-walked more sensitively detected the effects of these compounds than did pulse oximetry-based measurements of the classical vital signs of heart rate, respiratory rate, and blood oxygen saturation. Finally, we examined a nanomedicine formulation that has been in preclinical development, liposomes targeted to the cell adhesion molecule ICAM. While this formulation has been studied across dozens of publications, it has not previously been noted to produce an infusion reaction. However, the automated motion tracking cage showed that ICAM-liposomes markedly reduce the distance-walked, which we confirmed by measuring the other vital signs. Importantly, the motion tracking cage added < 5 min of labor time per 5-mouse condition, while pulse oximetry with a neck cuff (by far the most stable oximetry signal in mice) required ∼ 100 min of labor time. Thus, automated measurement of distance-walked can indeed serve as a "sixth vital sign" for detecting infusion reactions during preclinical testing. Additionally, the device to measure distance-walked is easy and cheap to build and requires negligible labor time for each experiment, enabling distance-walked to be recorded in nearly every infusion experiment.

Inhibition of TP signaling promotes endometriosis growth and neovascularization

Endometriosis is highly dependent on angiogenesis and lymphangiogenesis. Prostaglandin E2, an arachidonic acid metabolite, has been shown to promote the formation of new blood and lymphatic vessels. However, the role of another arachidonic acid metabolite, thromboxane A2 (TXA2) in angiogenesis and lymphangiogenesis during endometriosis remains largely unexplored. Using a murine model of ectopic endometrial transplantation, fragments from the endometrium of WT donor mice were transplanted into the peritoneal walls of recipient WT mice (WT→WT), resulting in an increase in both the area and density of blood and lymphatic vessels. Upon transplantation of endometrial tissue from thromboxane prostanoid (TP) receptor (TXA2 receptor)‑deficient (TP‑/‑) mice into TP‑/‑ mice (TP‑/‑→TP‑/‑), an increase in implant growth, angiogenesis, and lymphangiogenesis were observed along with upregulation of pro‑angiogenic and lymphangiogenic factors, including vascular endothelial growth factors (VEGFs). Similar results were obtained using a thromboxane synthase (TXS) inhibitor in WT→WT mice. Furthermore, TP‑/‑→TP‑/‑ mice had a higher number of F4/80+ cells than that of WT→WT mice, with increased expression of genes related to the anti‑inflammatory macrophage phenotype in endometrial lesions. In cultured bone marrow (BM)‑derived macrophages, the levels of VEGF‑A, VEGF‑C, and VEGF‑D decreased in a TP‑dependent manner. Furthermore, TP signaling affected the polarization of cultured BM‑derived macrophages to the anti‑inflammatory phenotype. These findings imply that inhibition of TP signaling promotes endometrial implant growth and neovascularization.

How to 19F MRI: applications, technique, and getting started

Magnetic resonance imaging (MRI) plays a significant role in the routine imaging workflow, providing both anatomical and functional information. 19F MRI is an evolving imaging modality where instead of 1H, 19F nuclei are excited. As the signal from endogenous 19F in the body is negligible, exogenous 19F signals obtained by 19F radiofrequency coils are exceptionally specific. Highly fluorinated agents targeting particular biological processes (i.e., the presence of immune cells) have been visualised using 19F MRI, highlighting its potential for non-invasive and longitudinal molecular imaging. This article aims to provide both a broad overview of the various applications of 19F MRI, with cancer imaging as a focus, as well as a practical guide to 19F imaging. We will discuss the essential elements of a 19F system and address common pitfalls during acquisition. Last but not least, we will highlight future perspectives that will enhance the role of this modality. While not an exhaustive exploration of all 19F literature, we endeavour to encapsulate the broad themes of the field and introduce the world of 19F molecular imaging to newcomers. 19F MRI bridges several domains, imaging, physics, chemistry, and biology, necessitating multidisciplinary teams to be able to harness this technology effectively. As further technical developments allow for greater sensitivity, we envision that 19F MRI can help unlock insight into biological processes non-invasively and longitudinally.

Unmasking the Adverse Impacts of Sex Bias on Science and Research Animal Welfare

Sex bias in biomedical and natural science research has been prevalent for decades. In many cases, the female estrous cycle was thought to be too complex an issue to model for, and it was thought to be simpler to only use males in studies. At times, particularly when studying efficacy and safety of new therapeutics, this sex bias has resulted in over- and under-medication with associated deleterious side effects in women. Many sex differences have been recognized that are unrelated to hormonal variation occurring during the estrous cycle. Sex bias also creates animal welfare challenges related to animal over-production and wastage, insufficient consideration of welfare (and scientific) impact related to differential housing of male vs female animals within research facilities, and a lack of understanding regarding differential requirements for pain recognition and alleviation in male versus female animals. Although many funding and government agencies require both sexes to be studied in biomedical research, many disparities remain in practice. This requires further enforcement of expectations by the Institutional Animal Care and Use Committee when reviewing protocols, research groups when writing grants, planning studies, and conducting research, and scientific journals and reviewers to ensure that sex bias policies are enforced.

Simultaneous magnetic resonance imaging of pH, perfusion and renal filtration using hyperpolarized 13C-labelled Z-OMPD

pH alterations are a hallmark of many pathologies including cancer and kidney disease. Here, we introduce [1,5-13C2]Z-OMPD as a hyperpolarized extracellular pH and perfusion sensor for MRI which allows to generate a multiparametric fingerprint of renal disease status and to detect local tumor acidification. Exceptional long T1 of two minutes at 1 T, high pH sensitivity of up to 1.9 ppm per pH unit and suitability of using the C1-label as internal frequency reference enables pH imaging in vivo of three pH compartments in healthy rat kidneys. Spectrally selective targeting of both 13C-resonances enables simultaneous imaging of perfusion and filtration in 3D and pH in 2D within one minute to quantify renal blood flow, glomerular filtration rates and renal pH in healthy and hydronephrotic kidneys with superior sensitivity compared to clinical routine methods. Imaging multiple biomarkers within a single session renders [1,5-13C2]Z-OMPD a promising new hyperpolarized agent for oncology and nephrology.

3D Optical Coherence Thermometry Using Polymeric Nanogels

In nanothermometry, the use of nanoparticles as thermal probes enables remote and minimally invasive sensing. In the biomedical context, nanothermometry has emerged as a powerful tool where traditional approaches, like infrared thermal sensing and contact thermometers, fall short. Despite the strides of this technology in preclinical settings, nanothermometry is not mature enough to be translated to the bedside. This is due to two major hurdles: the inability to perform 3D thermal imaging and the requirement for tools that are readily available in the clinics. This work simultaneously overcomes both limitations by proposing the technology of optical coherence thermometry (OCTh). This is achieved by combining thermoresponsive polymeric nanogels and optical coherence tomography (OCT)-a 3D imaging technology routinely used in clinical practice. The volume phase transition of the thermoresponsive nanogels causes marked changes in their refractive index, making them temperature-sensitive OCT contrast agents. The ability of OCTh to provide 3D thermal images is demonstrated in tissue phantoms subjected to photothermal processes, and its reliability is corroborated by comparing experimental results with numerical simulations. The results included in this work set credible foundations for the implementation of nanothermometry in the form of OCTh in clinical practice.

Universal Recommendations on Planning and Performing the Auditory Brainstem Responses (ABR) with a Focus on Mice and Rats

Translational audiology research aims to transfer basic research findings into practical clinical applications. While animal studies provide essential knowledge for translational research, there is an urgent need to improve the reproducibility of data derived from these studies. Sources of variability in animal research can be grouped into three areas: animal, equipment, and experimental. To increase standardization in animal research, we developed universal recommendations for designing and conducting studies using a standard audiological method: auditory brainstem response (ABR). The recommendations are domain-specific and are intended to guide the reader through the issues that are important when applying for ABR approval, preparing for, and conducting ABR experiments. Better experimental standardization, which is the goal of these guidelines, is expected to improve the understanding and interpretation of results, reduce the number of animals used in preclinical studies, and improve the translation of knowledge to the clinic.

Effects of isoflurane and xylazine on inducing cerebral ischemia by the model of middle cerebral artery occlusion in mice

Preclinical ischemic stroke studies extensively utilize the intraluminal suture method of middle cerebral artery occlusion (MCAo). General anesthesia administration is an essential step for MCAo, but anesthetic agents can lead to adverse effects causing death and making a considerable impact on inducing cerebral ischemia. The purpose of this study was to comparatively assess the effect of isoflurane and xylazine on transient cerebral ischemia in a mouse model of MCAo. Twenty animals were randomly divided into four groups: sham group (no MCAo), control group (MCAo under isoflurane, no agent till reperfusion), isoflurane group (MCAo under isoflurane continued till reperfusion), xylazine group (MCAo under isoflurane, and administration of xylazine till reperfusion). The survival rate, brain infarct volume, and neurologic deficits were studied to assess the effect of isoflurane and xylazine on the stroke model. Our results showed that the body weight showed statistically significant change before and 24 h after surgery in the control and Isoflurane groups, but no difference in the Xylazine group. Also, the survival rate, brain infarct volume, and neurologic deficits were slightly reduced in the isoflurane group at 24 h after reperfusion injury. However, the xylazine and control groups showed similar BIV and neurologic deficits. Interestingly, a high survival rate was observed in the xylazine group. Our results indicate that the modified method of inhalation anesthetics combined with xylazine can reduce the risk of mortality and develop a reproducible MCAo model with predictable brain ischemia. In addition, extended isoflurane anesthesia after MCAo is associated with the risk of mortality.

Standardisation and future of preclinical echocardiography

Echocardiography is a non-invasive imaging technique providing real-time information to assess the structure and function of the heart. Due to advancements in technology, ultra-high-frequency transducers have enabled the translation of ultrasound from humans to small animals due to resolutions down to 30 µm. Most studies are performed using mice and rats, with ages ranging from embryonic, to neonatal, and adult. In addition, alternative models such as zebrafish and chicken embryos are becoming more frequently used. With the achieved high temporal and spatial resolution in real-time, cardiac function can now be monitored throughout the lifespan of these small animals to investigate the origin and treatment of a range of acute and chronic pathological conditions. With the increased relevance of in vivo real-time imaging, there is still an unmet need for the standardisation of small animal echocardiography and the appropriate cardiac measurements that should be reported in preclinical cardiac models. This review focuses on the development of standardisation in preclinical echocardiography and reports appropriate cardiac measurements throughout the lifespan of rodents: embryonic, neonatal, ageing, and acute and chronic pathologies. Lastly, we will discuss the future of cardiac preclinical ultrasound.

Medetomidine/midazolam/fentanyl narcosis alters cardiac autonomic tone leading to conduction disorders and arrhythmias in mice

Arrhythmias are critical contributors to cardiovascular morbidity and mortality. Therapies are mainly symptomatic and often insufficient, emphasizing the need for basic research to unveil the mechanisms underlying arrhythmias and to enable better and ideally causal therapies. In translational approaches, mice are commonly used to study arrhythmia mechanisms in vivo. Experimental electrophysiology studies in mice are performed under anesthesia with medetomidine/midazolam/fentanyl (MMF) and isoflurane/fentanyl (IF) as commonly used regimens. Despite evidence of adverse effects of individual components on cardiac function, few data are available regarding the specific effects of these regimens on cardiac electrophysiology in mice. Here we present a study investigating the effects of MMF and IF narcosis on cardiac electrophysiology in vivo in C57BL/6N wild-type mice. Telemetry transmitters were implanted in a group of mice, which served as controls for baseline parameters without narcosis. In two other groups of mice, electrocardiogram and invasive electrophysiology studies were performed under narcosis (with either MMF or IF). Basic electrocardiogram parameters, heart rate variability parameters, sinus node and atrioventricular node function, and susceptibility to arrhythmias were assessed. Experimental data suggest a remarkable influence of MMF on cardiac electrophysiology compared with IF and awake animals. While IF only moderately reduced heart rate, MMF led to significant bradycardia, spontaneous arrhythmias, heart rate variability alterations as well as sinus and AV node dysfunction, and increased inducibility of ventricular arrhythmias. On the basis of these observed effects, we suggest avoiding MMF in mice, specifically when studying cardiac electrophysiology, but also whenever a regular heartbeat is required for reliable results, such as in heart failure or imaging research.