Comparison of two cannulation methods for assessment of intracavernosal pressure in a rat model

RNA-seq revealed the protective effect of Huangqi Guizhi Wuwu Decoction against cisplatin induced PC12 cell injury

BACKGROUND

Chemotherapy-induced peripheral neuropathy not only affects the tolerability of chemotherapy, but also causes intolerable and prolonged neuropathic pain in cancer patients. Currently, duloxetine is the only drug used to treat chemotherapy-induced peripheral neuropathy. However, the clinical use of this drug still faces several challenges. Therefore, we focused on traditional Chinese medicine to find an effective and safe alternative medicine. Huangqi Guizhi Wuwu Decoction is a traditional Chinese medicine that has been clinically used for treating nerve pain for thousands of years. This study aimed to investigate the neuroprotective effect of Huangqi Guizhi Wuwu Decoction on cisplatin-induced nerve injury in PC12 cells and to elucidate its potential mechanism of action.

METHODS

Huangqi Guizhi Wuwu Decoction-containing serum and blank serum were prepared from a rat model. The protective effects of Huangqi Guizhi Wuwu Decoction on cisplatin (10 µmol/L)-induced PC12 cell injury were assessed by a Cell Counting Kit-8 assay. RNA expression in Huangqi Guizhi Wuwu Decoction-protected PC12 cells was analyzed using RNA-seq, and subsequently, differentially expressed genes were further analyzed using Gene Ontology and Gene Set Enrichment Analysis.

RESULTS

The Cell Counting Kit-8 results showed that pretreatment of PC12 cells with Huangqi Guizhi Wuwu Decoction-containing serum (5%, 10%, 15%) significantly increased cells' viability to 10 µmol/L cisplatin-induced cell death. RNA-seq analysis revealed 843 differentially expressed genes in the chemotherapy-induced peripheral neuropathy group and 249 in the Huangqi Guizhi Wuwu Decoction group. The gene set enrichment analysis results in this study suggest that Huangqi Guizhi Wuwu Decoction may treat chemotherapy-induced peripheral neuropathy by enhancing axon guidance.

CONCLUSIONS

This study provides valuable evidence for using Huangqi Guizhi Wuwu Decoction in treating chemotherapy-induced peripheral neuropathy, partially achieved by improving axon guidance pathways.

Therapeutic Potential of Fucoidan in Alleviating Histamine-Induced Liver Injury: Insights from Mice Studies

Histamine, a bioactive component in certain foods such as Huangjiu has been associated with liver injury and disrupted intestinal balance. This study explored the potential therapeutic effects of fucoidan (FCD) in mitigating histamine-induced imbalances in mice. We found that FCD mitigated liver injury, reducing transaminases, oxidative stress, and inflammation. Histological improvements included decreased cell infiltration and necrosis. FCD restored tight junction proteins and suppressed inflammation-related genes. Western blot analysis revealed FCD's impact on TGF-β1, p-AKT, AKT, CYP2E1, Grp78, NLRP3, Cas-1, and GSDMD. Gut LPS levels decreased with FCD. Gut microbiota analysis showed FCD's modulation effect, reducing Firmicutes and increasing Bacteroides. FCD demonstrates potential in alleviating histamine-induced liver injury, regulating inflammation, and influencing gut microbiota. Further research exploring higher dosages and additional parameters is warranted.

Sufficiently activated mature natural killer cells derived from peripheral blood mononuclear cells substantially enhance antitumor activity

BACKGROUND

Peripheral blood-derived natural killer (NK) cells spontaneously lyse tumor cells without prior sensitization. However, NK cells in peripheral blood (PBNK cells) are in a resting state and exhibit inhibitory phenotypes and impaired cytotoxicity. Thus, strengthening the cytotoxic effector function of PBNK cells and improving NK cell expansion in vitro for a convenient allogeneic therapy are essential.

MATERIALS AND METHODS

Pure cytokine activation and expansion of NK cells (super NK [SNK]) from peripheral blood mononuclear cells were studied. Markers of activated and inhibited NK cells and cytokine secretion by NK cells were examined using flow cytometry. NK cell antitumor activity in vitro was assessed using lactate dehydrogenase (LDH) cytotoxicity assay and an Incucyte real-time imaging system. Additionally, the function of SNK cells against ascites caused by ovarian cancer in NOD-Prkdc(em26Cd52)il2rg(em26Cd22)/Nju (NCG) mice was determined. In a further investigation of the differences between PBNK and SNK, the mRNA of both cells was sequenced and analyzed.

RESULTS

Human peripheral blood mononuclear cells showed selective NK cell expansion upon cytokine activation and culture. Both SNK and PBNK cells expressed activation markers, but at different levels, and SNK cells secreted more cytokines related to cytotoxicity than PBNK cells did. Accordingly, SNK cells exhibited strong antitumor activity ex vivo and improved NCG mice survival after intraperitoneal ovarian cancer transplantation. Mechanistically, SNK cells expressed more genes associated with nucleotide metabolism, fatty acid, and ATP metabolism than PBNK cells.

CONCLUSION

SNK cells derived from peripheral blood mononuclear cells have sufficiently activated mature characteristics and high antitumor activity, rendering them a highly promising and essential therapeutic approach for cancer treatment.

Buyang Huanwu Decoction Ameliorates Damage of Erectile Tissue and Function Following Bilateral Cavernous Nerve Injury

OBJECTIVE

To verify the effect of Buyang Huanwu Decoction (BHD) in ameliorating erectile dysfunction (ED) after radical prostatectomy (RP).

METHODS

The composition of BHD was verified by ultra-performance liquid chromatography quadrupole time-of-flight mass spectrometry (UPLC-QTOF-MS/MS) analysis. Bilateral cavernous nerve crush injury (BCNI) in rats was used to mimic the neurovascular injury occurring after RP. By the envelope method, forty rats were randomly divided into 4 groups as follows: sham (cavernous nerves exposed only), model (BCNI), low-dosage BHD [LBHD, 12.8 g/(kg·d)], and high-dosage BHD [HBHD, 51.2 g/(kg·d)] groups, 10 rats in each group, feeding for 3 weeks respectively. Erectile function was evaluated by measuring intracavernosal pressure (ICP). Changes in the histopathology of corpus cavernosum (CC) were examined by hematoxylin-eosin staining. Meanwhile, the fibrosis of CC was measured by Masson's trichrome staining and Western blot was used to detect the expressions of collagen I, transforming growth factor beta 1 (TGF- β 1) and α-smooth muscle actin (α-SMA). Apoptosis index was detected by terminal-deoxynucleoitidyl transferase mediated nick end labeling (TUNEL) and Western blot for determining the expressions of B-cell lymphoma 2 (Bcl-2) and Bcl-2-associated X (Bax). The oxidative stress in the CC were assessed by the superoxide dismutase (SOD), malondialdehyde (MDA) and reactive oxygen species (ROS) levels. The proteins expression of c-Jun N-terminal kinase (JNK) and c-Jun were detected by Western blot. In addition, the expression of α-SMA and p-c-Jun in the CC was observed by double immunofluorescence staining.

RESULTS

The UPLC-QTOF-MS/MS analysis showed that BHD contained calycosin-7-O- β -D-glucoside, ononin, calycosin and formononetin. Compared with the model group, LBHD and HBHD treatment improved the ICP and the circumference, area, and weight of CC (P<0.05 or P<0.01). Furthermore, LBHD and HBHD treatments increased CC smooth muscle content and decreased apoptosis index (P<0.05 or P<0.01). LBHD and HBHD also elevated SOD and expression level of α -SMA and Bcl-2, and reduced MDA and ROS levels, as well as expression of TGF- β 1, collagen I, Bax, p-c-JNK, p-JNK in the CC compared with the model group (P<0.05 or P<0.01). The double immunofluorescence staining showed that the fluorescence degree of p-c-Jun in both LBHD and HBHD treatment groups was significantly reduced, whereas the α -SMA expression increased (P<0.05 or P<0.01).

CONCLUSIONS

BHD can improve ED of rats with BCNI, which is related to inhibiting fibrosis, apoptosis, and oxidative stress of CC. The ROS/JNK/c-Jun signaling pathway may play an important role in the process.

A review of experimental techniques for erectile function researches and development of medical technology using animal erectile dysfunction models in sexual and reproductive medicine

Background

Erectile dysfunction (ED) is one of the causes of male infertility and is a disease that requires treatment. The first‐line drugs for ED are phosphodiesterase 5 (PDE‐5) inhibitors, and further treatment options are currently limited. Medical technologies, such as genetic control and regenerative medicine, are developing rapidly. Research on erectile function is progressing rapidly, coupled with technological innovations in other areas.

Methods

A PubMed search using the keywords “animal (rat, mouse, rabbit, dog, and monkey)” and “erectile” was conducted, and all relevant peer‐reviewed English results were evaluated.

Main findings

The methods for evaluating erectile function include intracavernous pressure (ICP) measurements, isometric tension studies, and dynamic infusion cavernosometry. Papers also reported various disease model animals for the study of diabetes mellitus, cavernous nerve injury, and drug‐induced ED.

Conclusion

Basic research on ED treatment has progressed rapidly over the past 20 years. In particular, research on the mechanism of ED has been accelerated by the publication of a study on the evaluation of erectile function using ICP measurements in rats. In addition, molecular biological experimental methods such as polymerase chain reaction (PCR) and western blotting have become relatively easy to perform due to technological progress, thus advancing research development.

The polarization of microglia and infiltrated macrophages in the injured mice spinal cords: a dynamic analysis

Background

Following spinal cord injury (SCI), a large number of peripheral monocytes infiltrate into the lesion area and differentiate into macrophages (Mø). These monocyte-derived Mø are very difficult to distinguish from the local activated microglia (MG). Therefore, the term Mø/MG are often used to define the infiltrated Mø and/or activated MG. It has been recognized that pro-inflammatory M1-type Mø/MG play "bad" roles in the SCI pathology. Our recent research showed that local M1 cells are mainly CD45^-/lowCD68⁺CD11b⁺ in the subacute stage of SCI. Thus, we speculated that the M1 cells in injured spinal cords mainly derived from MG rather than infiltrating Mø. So far, their dynamics following SCI are not yet entirely clear.

Methods

Female C57BL/6 mice were used to establish SCI model, using an Infinite Horizon impactor with a 1.3 mm diameter rod and a 50 Kdynes force. Sham-operated (sham) mice only underwent laminectomy without contusion. Flow cytometry and immunohistofluorescence were combined to analyze the dynamic changes of polarized Mø and MG in the acute (1 day), subacute (3, 7 and 14 days) and chronic (21 and 28 days) phases of SCI.

Results

The total Mø/MG gradually increased and peaked at 7 days post-injury (dpi), and maintained at high levels 14, 21 and 28 dpi. Most of the Mø/MG were activated, and the Mø increased significantly at 1 and 3 dpi. However, with the pathological process, activated MG increased nearly to 90% at 7, 14, 21 and 28 dpi. Both M1 and M2 Mø were increased significantly at 1 and 3 dpi. However, they decreased to very low levels from 7 to 28 dpi. On the contrary, the M2-type MG decreased significantly following SCI and maintained at a low level during the pathological process.

Novel weight loss diet attenuates dietary-induced obesity in mice and might correlate with altered gut microbiota and metabolite profiles

Although many dietary patterns have been studied for weight loss, various limitations still exist. Therefore, we designed a novel weight loss diet (NWLD) with carbohydrate, protein, and fat (energy) contents of 45%, 20%, and 35%, respectively. The saturated fatty acids: monounsaturated fatty acids:polyunsaturated fatty acids ratio was 1:2:1, and the insoluble: soluble dietary fiber ratio was 2:1. We aimed to observe the effect of NWLD on weight loss and understand the underlying metabolic mechanisms. Twenty-nine male C57BL/6J mice were selected. Nine mice were fed ordinary feed in a blank control group, and the rest were fed a high-fat diet (HFD) to establish obese mouse models. Twelve weeks later, obesity models were established, and 10 obese mice were switched to NWLD feeding. Six weeks after switching the diet, the serum, intestinal feces, and kidneys of mice were collected. Obesity-related indicators, gut microbial composition, and fecal metabolite profiles of all the mice were determined, and the correlations among these indicators were analyzed. Kidney function indicators were also assessed. The results showed that the NWLD attenuated HFD-induced weight gain, serum triglycerides (TG), and inflammatory factors, optimized the body composition without kidney function impairment. Amino acid metabolism pathways and metabolites might play key roles in this process. The findings of this research imply that NWLD could be an effective nutritional remedy for managing dietary-induced obesity.

PCSK9 inhibitor inclisiran for treating atherosclerosis via regulation of endothelial cell pyroptosis

Background

Proprotein convertase subtilisin/kexin type 9 (PCSK9) belongs to an intracellular invertase or decarboxylase and is an independent risk factor for atherosclerosis (AS). This study aimed to investigate the therapeutic potential of the PCSK9 inhibitor, inclisiran, and its underlying mechanism in AS.

Methods

ApoE^-/- mice were fed with a high-fat diet (HFD) and intraperitoneally injected with 1, 5, or 10 mg/kg inclisiran. Low-density lipoprotein cholesterol (LDL-C), total cholesterol (TC), triglyceride (TG), and high-density lipoprotein cholesterol (HDL-C) levels were determined using commercially available kits. Oil Red O staining was applied to detect the aortic plaque area and oil formation. Human umbilical vein endothelial cells (HUVECs) were treated with oxidized low-density lipoprotein (ox-LDL) to induce cell injuries. Cell death was determined using a Hoechst 33342/propidium iodide (PI) dual-staining assay. Cytotoxicity was measured by lactate dehydrogenase (LDH) activity analysis. Quantitative real-time polymerase chain reaction (qRT-PCR) and western blot analyses were performed to examine the pyroptosis-related factors.

Results

Inclisiran inhibited the levels of LDL-C, TC, and TG, but increased the HDL-C level in the AS animal model. It also significantly inhibited plaque and oil droplet formation in a dose-dependent manner. Moreover, inclisiran markedly inhibited pyroptosis, as evidenced by the decreased levels of cleaved-caspase-1, NOD-like receptor family pyrin domain containing 3 (NLRP3), apoptosis-associated speck-like protein containing a caspase-1 recruitment domain (ASC), gasdermin-D (GSDMD)-N, interleukin (IL)-1β, and IL-18. Furthermore, inclisiran substantially inhibited cell death and cytotoxicity induced by ox-LDL in HUVECs.

Conclusions

Inclisiran exerted an anti-atherosclerotic effect by inhibiting pyroptosis. This study provides a theoretical basis for the therapeutic potential of inclisiran in AS.

NLRP3 inflammasome up-regulates major histocompatibility complex class I expression and promotes inflammatory infiltration in polymyositis

Objective

This study was designed to investigate the role of the nucleotide-binding-domain -and leucine-rich repeat -containing (NLR) family, pyrin-domain-containing 3 (NLRP3) inflammasome in the pathogenesis of polymyositis (PM).

Methods

Immunochemistry was performed to analyze the NLRP3, caspase-1 and interleukin-1 beta (IL-1β) expression in the muscle tissue of PM patients. Rat model of PM and C2C12 cell were used to investigate the potential role of NLRP3 inflammasome in PM.

Results

The percentage of CD 68+ macrophages, and the expression levels of NLRP3, caspase-1 and IL-1β in the muscle tissue were elevated in 27 PM patients. LPS/ATP treatment resulted in activation of NLRP3 inflammasome and secretion of IL-1β as well as interferons (IFNs) and monocyte chemotactic protein-1 (MCP-1) in the Raw 264.7 macrophages. Meanwhile, LPS/ATP challenged activation of NLRP3 inflammasome induced overexpression of major histocompatibility complex class I (MHC-I), a key molecular of PM in the co-cultured C2C12 cells. The effect was decreased by treatment of NLRP3 inflammasome inhibitor MCC950 or siRNA of NLRP3 inflammasome. These findings suggested certain levels of IL-1β rather than IFNs up-regulated MHC-I expression in C2C12 cells. IL-1β blockade using neutralizing IL-1β monoclonal antibody or siRNA of IL-1β suppressed MHC-I overexpression. In vivo, NLRP3 inflammasome inhibition by MCC950 reduced the expression of NLRP3, IL-1β and MHC-I in the muscle tissue of PM modal rats. Also, it attenuated the intensity of muscle inflammation as well as the CRP, CK, and LDH levels in the serum.

Conclusion

NLRP3/caspase-1/IL-1β axis may play an important role in the development of PM. Inhibition of NLRP3 activation may hold promise in the treatment of PM.

Effects of unilateral/bilateral amputation of the ischiocavernosus muscle in male rats on erectile function and conception

Background

The ischiocavernosus muscle (ICM) encompasses a pair of short pinnate muscles attached to the pelvic ring. The ICM begins at the ischial tuberosity and ends at the crus of the penis while covering the surface of the crus. According to the traditional view, the contraction of the ICM plays an auxiliary role in penile erection. However, we have previously shown that the ICM plays an important role in penile erection through an indirect method of diagnosing erectile dysfunction (ED) caused by ICM injury by observing the infertility of paired female rats. Since intracavernosal pressure (ICP) is the current gold standard for diagnosing ED, this study aimed to amputate unilaterally/bilaterally the ICM to establish an ED model by detecting the ICP, recording the infertility of matching female rats, and comparing the two methods.

Results

Forty sexually mature adult male rats were selected and randomly divided into the following groups: the control group (n = 10), sham operation group (n = 10), unilateral ischiocavernosus muscle (Uni-ICM) amputation group (n = 10), and bilateral ischiocavernosus muscle (Bi-ICM) amputation group (n = 10). Eighty female reproductive rats were randomly assigned to the above groups at a ratio of 2:1. We evaluated the time to conception for the paired female rats and the effects of unilateral/bilateral severing of the ICM on erectile function. The results showed that the baseline and maximum intracavernosal pressure (ICP) in the control group, sham operation group, Uni-ICM amputation group, and Bi-ICM amputation group were 17.44±2.50 mmHg and 93.51±10.78 mmHg, 17.81±2.81 mmHg and 95.07±10.40 mmHg, 16.73±2.11 mmHg and 83.49±12.38 mmHg, and 14.78±2.78 mmHg and 33.57±6.72 mmHg, respectively, immediately postsurgery. The max ICP in the Bi-ICM amputation group was lower than that in the remaining three groups (all P<0.05). The pregnancy rates were 100, 100, 90, and 0% in the control group, sham operation group, Uni-ICM amputation group, and the Bi-ICM amputation group, respectively. The pregnancy rate in the Bi-ICM amputation group was significantly lower than that in the remaining groups (all P<0.05). The time to conception was approximately 7–10 days later in the Uni-ICM amputation group than in the control and sham groups (all P<0.05).

Conclusions

Male rats undergoing Bi-ICM amputation may develop permanent ED, which affects their fertility. In contrast, rats undergoing Uni-ICM amputation may experience transient ED.

Myeloid lineage contributes to pathological choroidal neovascularization formation via SOCS3

Background

Pathological neovascularization in neovascular age-related macular degeneration (nAMD) is the leading cause of vision loss in the elderly. Increasing evidence shows that cells of myeloid lineage play important roles in controlling pathological endothelium formation. Suppressor of cytokine signaling 3 (SOCS3) pathway has been linked to neovascularization.

Methods

We utilised a laser-induced choroidal neovascularization (CNV) mouse model to investigate the neovascular aspect of human AMD. In several cell lineage reporter mice, bone marrow chimeric mice and Socs3 loss-of-function (knockout) and gain-of-function (overexpression) mice, immunohistochemistry, confocal, and choroidal explant co-culture with bone marrow-derived macrophage medium were used to study the mechanisms underlying pathological CNV formation via myeloid SOCS3.

Findings

SOCS3 was significantly induced in myeloid lineage cells, which were recruited into the CNV lesion area. Myeloid Socs3 overexpression inhibited laser-induced CNV, reduced myeloid lineage-derived macrophage/microglia recruitment onsite, and attenuated pro-inflammatory factor expression. Moreover, SOCS3 in myeloid regulated vascular sprouting ex vivo in choroid explants and SOCS3 agonist reduced in vivo CNV.

Interpretation

These findings suggest that myeloid lineage cells contributed to pathological CNV formation regulated by SOCS3.

Funding

This project was funded by NIH/NEI (R01EY030140, R01EY029238), BrightFocus Foundation, American Health Assistance Foundation (AHAF), and Boston Children's Hospital Ophthalmology Foundation for YS and the National Institutes of Health/National Heart, Lung and Blood Institute (U01HL098166) for PZ.

Application of laser speckle blood perfusion imaging in the evaluation of erectile function in rats

Intracavernosal pressure measurement is the gold standard for evaluating erectile function in experimental animals, but it has the shortcoming of being invasive. This study aimed to explore the application of laser speckle perfusion imaging in evaluating erectile function in rats. Sixty Sprague Dawley rats were randomly divided into the sham operation and model groups (n = 30 each). A rat model of neuroinjury erectile dysfunction was established by surgically damaging the bilateral cavernous nerves in the model group. Simulated surgery was performed in the sham operation group; the nerves were not damaged. Erectile function was evaluated by comparing the changes in intracavernosal pressure and blood flow fluctuations when the cavernous nerve was stimulated using the same voltage parameters. Intracavernosal pressure in the model group was significantly lower than that in the other group when using 2.5 V. No significant difference was found in cavernous blood flow fluctuation between the two groups when using 0.5 V. Cavernous blood flow fluctuation in the model group after 2.5 V, 5 V and 7.5 V stimulations was significantly lower than that in the sham operation group. Evaluating erectile function in rats is feasible by measuring the cavernous blood flow using laser speckle perfusion imaging.

Prolonged isoflurane anesthesia-induced acidosis decreases penile intracavernous pressure in rats

BACKGROUND

Intracavernous pressure measurement following cavernous nerve electrostimulation has been extensively adopted for the evaluation of erectile function in animals. However, the effect of measurement time and acidosis during anesthesia is still lacking.

OBJECTIVE

To explore the effect of measurement time and acidosis during anesthesia.

MATERIALS AND METHODS

Fifty-six male Sprague-Dawley rats were used and anesthetized by a spontaneous inhalation of isoflurane. In the first step, rats were randomly divided into four groups: a control group and three time-delayed measurement groups (intracavernous pressure measurement beginning at 15, 30, and 45 min after cavernous nerve exposure). In the second step, rats were randomly divided into three groups: a control group and two time-delayed measurement groups. Two intravenous fluid support strategies were used in time-delayed measurement groups: a normal saline solution and an isotonic Na₂ CO₃ solution.

RESULTS

Isoflurane-anesthetized rats developed systemic acidosis that worsens with time during intracavernous pressure measurement, which results in a significant decrease in the maximum intracavernous pressure value, intracavernous pressure/mean arterial pressure ratio, and total intracavernous pressure measured. The Na₂ CO₃ infusion could effectively correct acidosis. The decrease in intracavernous pressure was related to the reduced nitric oxide synthase activity, decreased cyclic guanosine monophosphate concentration, and reactive oxygen species activation in rat penis under acidosis conditions.

DISCUSSION AND CONCLUSION

Prolonged isoflurane anesthesia-induced acidosis markedly depresses the erectile response to cavernous nerve electrostimulation in rats. In this situation, it is recommended to supplement with a Na₂ CO₃ infusion to maintain a normal acid-base balance.

Exertional heat stroke on fertility, erectile function, and testicular morphology in male rats

The association of exertional heat stroke (EHS) and testicular morphological changes affecting sperm quality, as well as the association of EHS and hypothalamic changes affecting sexual behavior, has yet to be elucidated. This study aimed to elucidate the effects of EHS on fertility, erectile function, and testicular morphology in male rats. Animals were exercised at higher room temperature (36 ℃ relative humidity 50%) to induce EHS, characterized by excessive hyperthermia, neurobehavioral deficits, hypothalamic cell damage, systemic inflammation, coagulopathy, and multiple organ injury. In particular, EHS animals had erectile dysfunction (as determined by measuring the changes of intracavernosal pressure and mean arterial pressure in response to electrical stimulation of cavernous nerves). Rats also displayed testicular temperature disruption, poorly differentiated seminiferous tubules, impaired sperm quality, and atrophy of interstitial Leydig cells, Sertoli cells, and peri-tubular cells in the testicular tissues accompanied by no spermatozoa and broken cells with pyknosis in their seminal vesicle and prostatitis. These EHS effects were still observed after 3 days following EHS onset, at least. Our findings provide a greater understanding of the effect of experimentally induced EHS on masculine sexual behavior, fertility, stress hormones, and morphology of both testis and prostate.

Reporting animal research: Explanation and elaboration for the ARRIVE guidelines 2.0

Improving the reproducibility of biomedical research is a major challenge. Transparent and accurate reporting is vital to this process; it allows readers to assess the reliability of the findings and repeat or build upon the work of other researchers. The ARRIVE guidelines (Animal Research: Reporting In Vivo Experiments) were developed in 2010 to help authors and journals identify the minimum information necessary to report in publications describing in vivo experiments. Despite widespread endorsement by the scientific community, the impact of ARRIVE on the transparency of reporting in animal research publications has been limited. We have revised the ARRIVE guidelines to update them and facilitate their use in practice. The revised guidelines are published alongside this paper. This explanation and elaboration document was developed as part of the revision. It provides further information about each of the 21 items in ARRIVE 2.0, including the rationale and supporting evidence for their inclusion in the guidelines, elaboration of details to report, and examples of good reporting from the published literature. This document also covers advice and best practice in the design and conduct of animal studies to support researchers in improving standards from the start of the experimental design process through to publication.