Pair Housing Research Articles

Positive reinforcement-based magnet training permits social housing in catheterized squirrel monkeys

BackgroundNon-human primates play a critical role in neuroscience research. Though they are social animals, laboratory study requirements can sometimes require single housing and thereby prevent social housing. New MethodTo eliminate single housing and promote well-being within our squirrel monkey colony, we used positive reinforcement training in combination with magnetic/mechanical clasps and custom jackets to permit pair housing of catheterized squirrel monkeys used in behavioral studies. ResultsAdult Saimiri boliviensis boliviensis monkeys (n = 7) readily progressed through a six-stage training procedure for cooperative handling and transport from the home cage to the experimental testing rooms.Comparison with existing methods and conclusions: Given the evidence of isolation induced stress and neurobiological consequences in multiple species, and consistent with an increased regulatory emphasis on social housing of non-human primates, the methods presented herein provide a method for handling squirrel monkeys in behavioral studies that is compatible with social housing.

Effects of Nesting Material and Housing Parameters on Feed Wastage Behavior in Female Swiss Webster Mice.

Feed wastage in laboratory mice, also known as chewing or grinding behavior, is problematic for program management and animal welfare. The destruction of pelleted feed without consumption produces a powder accumulation on the cage floor called orts. Ort accumulation disrupts the cage microenvironment and can clog Lixits resulting in flooding. Moreover, added labor adds cost, and cage disruption increases animal stress. Published studies examining the behavior and ways to mitigate it have had inconsistent results, and the cause or causes have not yet been fully identified. The purpose of this study was to identify methods to reduce the development of chewing behavior in laboratory mice. Female Swiss Webster (Tac:SW) mice (n = 144) were randomly assigned to one of 8 groups (12 cages per group) with 2 housing densities (single and pair) and 4 nesting material paradigms. Mice were housed on clean bedding for 8 wk and then soiled bedding for the next 8 wk. Chewing behavior was evaluated by feed weight, cage weight, and feed scores. The addition of a Diamond Twist significantly increased ort production, while nest transfer decreased it but not significantly. Pair housing increased overall orts but not when adjusted for animal number. These results identified potential contributing factors to chewing behavior. However, further research is needed to elucidate the exact causes and solutions.

Association of Good Dairy Farming Practices, Welfare and Performance: A Review

This review underscores the critical role of good dairy farming practices in enhancing both animal welfare and dairy performance. International organizations like the World Organization for Animal Health (WOAH) and country-specific protocols emphasize the need for tailored Standard Operating Procedures (SOPs) to ensure effective and contextually appropriate practices. Advanced housing systems for calves, such as pair and group housing, have shown significant benefits in improving social interaction, cognitive development, and overall health. Effective pain management, particularly during procedures like disbudding, and optimized feeding strategies, including appropriate feed delivery timing and frequency, are crucial for enhancing health and productivity. Proper flooring, such as rubber mats, significantly improves cow comfort by providing a softer surface that reduces the risk of lameness and injuries associated with concrete floors. Effective pen management helps to mitigate dominance issues and minimize stress, leading to better welfare and productivity. Gentle handling practices, involving positive interactions like patting and stroking, significantly enhance animal welfare and milk production compared to aversive methods. Addressing issues such as mold and mycotoxins in feed is also essential for maintaining animal health and avoiding adverse effects on growth and milk production. Overall, adopting comprehensive dairy farming practices that prioritize animal welfare not only improves health and reduces stress but also leads to increased dairy productivity and sustainability, highlighting the interdependence of welfare and performance in the dairy industry.

Foxq1 activates CB2R with oleamide to alleviate POCD.

Postoperative cognitive dysfunction (POCD) is a major concern, particularly among older adults. This study used social isolation (ISO) and multiomics analyses in aged mice to investigate potential mechanisms underlying POCD development. Aged mice were divided into two groups: ISO and paired housing (PH). Oleamide and the cannabinoid receptor type 2 (CB2R) antagonist AM630 were administered intraperitoneally, while Foxq1 adeno-associated viral (AAV) vector was injected directly into the hippocampus. Intramedullary tibial surgeries were subsequently performed to establish the POCD models. Behavioral tests comprising the Y-maze, open field test, and novel object recognition were conducted 2 days after surgery. Hippocampal and serum inflammatory cytokines were assessed. Following surgery, ISO mice demonstrated intensified cognitive impairments and escalated inflammatory markers. Integrative transcriptomic and metabolomic analysis revealed elevated oleamide concentrations in the hippocampus and serum of PH mice, with associative investigations indicating a close relationship between the Foxq1 gene and oleamide levels. While oleamide administration and Foxq1 gene overexpression substantially ameliorated postoperative cognitive performance and systemic inflammation in mice, CB2R antagonist AM630 impeded these enhancements. The Foxq1 gene and oleamide may be crucial in alleviating POCD. While potentially acting through CB2R-mediated pathways, these factors may modulate neuroinflammation and attenuate proinflammatory cytokine levels within the hippocampus, substantially improving cognitive performance postsurgery. This study lays the groundwork for future research into therapeutic approaches targeting the Foxq1-oleamide-CB2R axis, with the ultimate goal of preventing or mitigating POCD.

Pairing laboratory-housed adult male rhesus macaques (Macaca mulatta): Success rates in relation to behavioral response and duration of visual contact

While the benefits of pair housing have been well documented, less is known about increasing success in adult male macaque pair introductions. In this retrospective study, 95 unfamiliar adult male macaque (Macaca mulatta) pairs were examined to determine whether duration of visual contact, behavior, age, and weight were associated with success rate, with “success” defined as two weeks in full tactile contact without excessive behavioral indicators of incompatibility or injury requiring clinical treatment or care. Overall, the unfamiliar adult male pairs achieved a success rate of 72 % and wounding requiring medical attention was rare (2 %). A significant negative relationship between pair success and time in visual contact for pairs was found. Pairs who moved into tactile contact within 48-hours showed more positive social behaviors in protected and full contact and had a high rate of success (91 %), while those who exhibited negative social behaviors were maintained in visual contact for longer. Nevertheless, rapid signs of compatibility were not necessary for the formation of successful pairs. While social introduction success rates steadily declined with increased periods of maintained visual contact, longer durations of 3 days to 1 week (70 %), and 8+ days (58 %), were still accompanied by high to moderate success, respectively. These results indicate that when negative social behavior is present early in visual contact success may be expected to decrease, but it is not necessarily indicative of incompatibility. Providing extra time in visual contact can reduce overall incidences of single housing.

Per- and polyfluoroalkyl substances (PFAS) in paired tap water and house dust from United States homes

Most people in the United States have been exposed to per- and polyfluoroalkyl substances (PFAS) which have been linked to a wide array of adverse health conditions in adults and children. The consumption of contaminated drinking water is an important human exposure pathway to PFAS. Residential sources also contribute to PFAS exposure through dermal contact and ingestion of house dust, which acts as an aggregate of chemicals from sources like furnishing materials and consumer products. The U.S. Department of Housing and Urban Development (HUD) conducted the first nationwide survey of residential hazards called the American Healthy Homes Survey (AHHS) in 2005, followed by a second survey (AHHS II) in 2017. The U.S. Environmental Protection Agency (EPA) collaborated with HUD on both efforts and subsequently analyzed PFAS in household tap water and house dust collected from the same homes during the AHHS II study. This study leverages these paired samples to investigate potentially important exposure sources and pathways in the residential environment. Here we report results for paired household tap water and house dust samples from 241 homes for 13 and 16 PFAS chemicals, respectively. All 13 targeted chemicals were detected in the household tap water samples with detections ranging from 100 % for PFBS to 1 % for PFNS, and all 16 targeted chemicals were detected in the house dust samples with detections ranging from 97 % for PFOA to 9 % for PFNS. Four chemicals (PFOA, PFOS, PFHxS, and PFHpA) were measured above the limit of detection in at least 50 % of the samples in both media. All households had at least one of the targeted PFAS detected in both their tap water and house dust. Results provided evidence that geographical factors, such as proximity to ambient contamination sources, were main drivers of PFAS contamination in tap water, while PFAS contamination in house dust was driven mainly by within-home sources. Exposure estimates calculated from the measured PFAS concentrations highlight the importance of addressing potential sources of exposure to PFAS within homes in addition to ambient sources affecting communities’ drinking water, particularly to reduce children’s exposure to these chemicals.

Calf Management: Individual or Paired Housing Affects Dairy Calf Health and Welfare.

Previous research has indicated that preweaned dairy calves reared in pairs compared with individually have improved performance and indicators of animal welfare. One hundred and thirty Holstein female calves completed the trial, with eighty-five being allocated to paired housing and forty-five calves being allocated to individual housing. Daily live weight gain (DLWG), treatments and mortality were recorded throughout the preweaning period. Salivary cortisol, latency to feed and latency to approach a novel object were assessed at batching. There were no significant differences in DLWG, mortality and disease treatments between the average of the pair and the individually housed calves, although the pair-reared calves were quicker to approach the milk feed after batching and interacted more quickly with a novel object. The heaviest born calves within the pair had the highest DLWG from birth to weaning, with a higher percentage of calves approaching the novel object, compared with the lightest born calf within the pair. This study shows that calves within a pair may have significantly different performance and welfare during the preweaning period, with the heavier calf outperforming and displaying less fear and more exploratory behaviour than the lighter calf within a pair.

Gut microbiota is necessary for pair-housing to protect against post-stroke depression in mice

The goal of this study is to investigate the role of microbiota-gut-brain axis involved in the protective effect of pair-housing on post-stroke depression (PSD). PSD model was induced by occluding the middle cerebral artery (MCAO) plus restraint stress for four weeks. At three days after MCAO, the mice were restrained 2 h per day. For pair-housing (PH), each mouse was pair housed with a healthy isosexual cohabitor for four weeks. While in the other PH group, their drinking water was replaced with antibiotic water. On day 35 to day 40, anxiety- and depression-like behaviors (sucrose consumption, open field test, forced swim test, and tail-suspension test) were conducted. Results showed pair-housed mice had better performance on anxiety- and depression-like behaviors than the PSD mice, and the richness and diversity of intestinal flora were also improved. However, drinking antibiotic water reversed the effects of pair-housing. Furthermore, pair-housing had an obvious improvement in gut barrier disorder and inflammation caused by PSD. Particularly, they showed significant decreases in CD8 lymphocytes and mRNA levels of pro-inflammatory cytokines (TNF-a, IL-1β and IL-6), while IL-10 mRNA was upregulated. In addition, pair-housing significantly reduced activated microglia and increased Nissl's body in the hippocampus of PSD mice. However, all these improvements were worse in the pair-housed mice administrated with antibiotic water. We conclude that pair-housing significantly improves PSD in association with enhanced functions of microbiota-gut-brain axis, and homeostasis of gut microbiota is indispensable for the protective effect of pair-housing on PSD.

Linking exposure to per- and polyfluoroalkyl substances (PFAS) in house dust and biomonitoring data in eight impacted communities

Per- and polyfluoroalkyl substances (PFAS) are widely used in industry and have been linked to various adverse health effects. Communities adjacent to sites where PFAS are manufactured, stored, or used may be at elevated risk. In these impacted communities, significant exposure often occurs through contaminated drinking water, yet less is known about the role of other pathways such as residential exposure through house dust. We analyzed a paired serum and house dust dataset from the Agency for Toxic Substances and Disease Registry’s PFAS Exposure Assessments, which sampled eight United States communities with a history of drinking water contamination due to aqueous film forming foam (AFFF) use at nearby military bases. We found that serum PFAS levels of residents were significantly positively associated with the dust PFAS levels in their homes, for three of seven PFAS analyzed, when accounting for site and participant age. We also found that increased dust PFAS levels were associated with a shift in the relative abundance of PFAS in serum towards those chemicals not strongly linked to AFFF contamination, which may suggest household sources. Additionally, we analyzed participant responses to exposure questionnaires to identify factors associated with dust PFAS levels. Dust PFAS levels for some analytes were significantly elevated in households where participants were older and had lived at the home longer, cleaned less frequently, used stain resistant products, and had carpeted living rooms. Our results suggest that residential exposure to PFAS via dust or other indoor pathways may contribute to overall exposure and body burden, even in communities impacted by AFFF contamination of drinking water, and the magnitude of this exposure may also be influenced by demographic, behavioral, and housing factors.

Lead Speciation, Bioaccessibility, and Sources for a Contaminated Subset of House Dust and Soils Collected from Similar United States Residences.

Residential lead (Pb) exposure is of critical concern to families globally as Pb promotes severe neurological effects in children, especially those less than 5 years old, and no blood lead level is deemed safe by the US Center for Disease Control. House dust and soils are commonly thought to be important sources of Pb exposure. Probing the relationship between house dust and soil Pb is critical to understanding residential exposure, as Pb bioavailability is highly influenced by Pb sources and/or species. We investigated paired house dust and soil collected from homes built before 1978 to determine Pb speciation, source, and bioaccessibility with the primary goal of assessing chemical factors driving Pb exposure in residential media. House dust was predominately found to contain (hydro)cerussite (i.e., Pb (hydroxy)carbonate) phases commonly used in Pb-based paint that, in-turn, promoted elevated bioaccessibility (>60%). Pb X-ray absorption spectroscopy, μ-XRF mapping, and Pb isotope ratio analysis for house dust and soils support house dust Pb as chemically unique compared to exterior soils, although paint Pb is expected to be a major source for both. Soil pedogenesis and increased protection from environmental conditions (e.g., weathering) in households is expected to greatly impact Pb phase differences between house dust and soils, subsequently dictating differences in Pb exposure.

A novel antibody that neutralizes corticotropin-releasing factor attenuates the cardiovascular effects of chronic social defeat stress in mice

According to the World Health Organization, cardiovascular disease (CVD) continues to be the leading cause of death worldwide. While a myriad of genetic and environmental factors influence the development of CVD, there are several lines of evidence suggesting that psychological stress contributes to health disparities in CVD observed amongst different populations. Our lab seeks to understand the effects of psychosocial stress on cardiovascular health using a model of chronic social defeat stress (CSDS) in mice. In this paradigm, male C57BL/6 mice undergo brief daily defeat sessions and are housed in the same cage as the larger, more aggressive CD1 defeater mouse, separated by a polycarbonate divider that allows for continuous visual, auditory, and olfactory contact while preventing physical contact. We have previously demonstrated that this paradigm causes robust and persistent elevations in blood pressure, indices of chronic inflammation, elevations in plasma corticosterone and cardiac and adrenal hypertrophy. Social defeat also leads to robust activation of corticotropin releasing factor (CRF) neurons within the paraventricular nucleus of the hypothalamus (PVN). In the present studies, we investigate whether we can alleviate some of the adverse effects of CSDS through targeting the HPA axis using CTRND05, a novel anti-CRF antibody. Adult male C57BL/6 mice were assigned to either CSDS or control (paired) housing. Following 14 days of CSDS or control housing, mice were treated with one injection of CTRND05 (25 mg/kg, i.p.) or vehicle (IgG), followed by 14 more days of CSDS or control housing. A booster administration of CTRND05 (12.5 mg/kg, i.p.) was given 7 days after the initial dose. Adrenal weights were significantly reduced in pair housed mice treated with CTRND05 compared to pair housed mice treated with IgG, and there was a trend towards a reduction in adrenal weight of CSDS mice treated with CTRND05 in comparison with CSDS mice treated with IgG. There was also a trend for reduced basal corticosterone in CSDS mice treated with CTRND05. Importantly, while IgG treatment had no effect on the systolic blood pressure (SBP) of CSDS mice, treatment with CTRND05 significantly lowered the SBP of CSDS mice when compared with pre-treatment. These data suggest that targeting CRF may serve as a therapeutic tactic for treatment of stress-related hypertension. R35HL150750, R01HL136595. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

The oxytocin receptor is essential for the protective effect of pair housing on post-stroke depression in mice

The beneficial effect of social interaction in mitigating the incidence of post-stroke depression (PSD) and ameliorating depressive symptoms has been consistently demonstrated through preclinical and clinical studies. However, the underlying relationship with oxytocin requires further investigation. In light of this, the present study aimed to explore the protective effect of pair housing on the development of PSD and the potential relationship with oxytocin receptors. The PSD model was induced by middle cerebral artery occlusion (MCAO) for 50 min, followed by 4-week isolated housing and restrained stress. Subsequently, each mouse in the pair-housing group (PH) was pair-housed with an isosexual healthy partner. Another group was continuously administrated fluoxetine (10 mg/Kg, i.p, once a day) for 3 weeks. To elucidate the potential role of oxytocin, we subjected pair-housed PSD mice to treatment with an oxytocin receptor (OXTR) antagonist (L368,889) (5 mg/Kg, i.p, once a day) for 3 weeks. At 31 to 32 days after MCAO, anxiety- and depressive-like behaviors were assessed using sucrose consumption, forced swim test, and tail-suspension test. The results showed that pair housing significantly improved post-stroke depression to an extent comparable to that of fluoxetine treatment. Furthermore, pair housing significantly decreased corticosterone in serum, increasing OXT mRNA expression in the hypothalamus. Treatment with L368,889 essentially reversed the effect of pair housing, with no discernible sex differences apart from changes in body weight. Pair housing increased hippocampal serotonin (5-HT), but treatment with L368,889 had no significant impact. Additionally, pair housing effectively reduced the number of reactive astrocytes and increased Nissl's body in the cortex and hippocampal CA3 regions. Correspondingly, treatment with L368,889 significantly reversed the changes in the Nissl's body and reactive astrocytes. Moreover, pair housing downregulated mRNA levels of TNF-α, IL-1β, and IL-6 in the cortex caused by PSD, which was also reversed by treatment with L368,889. In conclusion, pair housing protects against the development of PSD depending on OXT and OXTR in the brain, with no significant divergence based on sex. These findings provide valuable insights into the potential of social interaction and oxytocin as therapeutic targets for PSD. Further research into the underlying mechanisms of these effects may contribute to the development of novel treatments for PSD.

Differential effects of voluntary exercise and housing density on anxiety-like behavior in C57Bl/6 mice

The interaction of voluntary exercise and housing density on a) anxiety-like behavior and b) the stimulant effects of methamphetamine in C57Bl/6 mice were evaluated. Upon arrival, mice were housed singly or in pairs, and permitted access to home-cage running wheels or not for 4 weeks. Testing for anxiety-like behavior occurred over the next 3 weeks, one test per week [Elevated-Plus Maze (EPM) → Hyponeophagia (HNP) task → Open-Field (OF) task]. The final, OF task involved an 8-hour session in which mice were permitted to explore the chamber (drug free) during Hours 1–3; given an injection (s.c.) of methamphetamine (1.0 mg/kg) after Hour 3; followed by continued behavioral sampling during Hours 4–8. Several tasks (HNP and OF, but not EPM) consistently showed voluntary exercise induced anxiety-like behavior. In addition, two measures (time in center and time resting in the perimeter) in the OF task revealed that exercise mice compared to controls were more responsive to the anxiogenic effects of methamphetamine. Although pair housing was anxiolytic, it did not ameliorate the anxiogenic effects of voluntary exercise. Taken together, these results, when viewed in tandem with previous studies that utilized a less anxious mouse strain (Swiss Webster), may suggest that voluntary exercise is anxiogenic in an anxiety-prone mouse strain such as C57Bl/6 and highlight the importance of considering mouse strain when evaluating the impact of environmental manipulations on anxiety-like behavior in animal models.

Early-life nasal microbiota dynamics relate to longitudinal respiratory phenotypes in urban children

Five distinct respiratory phenotypes based on latent classes of longitudinal patterns of wheezing, allergic sensitization. and pulmonary function measured in urban children from ages from 0 to 7 years have previously been described. Our aim was to determine whether distinct respiratory phenotypes are associated with early-life upper respiratory microbiota development and environmental microbial exposures. Microbiota profiling was performed using 16S ribosomal RNA-based sequencing of nasal samples collected at age 12 months (n= 120) or age 36 months (n= 142) and paired house dust samples collected at 3 months (12-month, n= 73; 36-month, n= 90) from all 4 centers in the Urban Environment and Childhood Asthma (URECA) cohort. In these high-risk urban children, nasal microbiota increased in diversity between ages 12 and 36 months (ß= 2.04; P= .006). Age-related changes in microbiota evenness differed significantly by respiratory phenotypes (interaction P= .0007), increasing most in the transient wheeze group. At age 12 months, respiratory illness (R2= 0.055; P= .0001) and dominant bacterial genus (R2= 0.59; P= .0001) explained variance in nasal microbiota composition, and enrichment of Moraxella and Haemophilus members was associated with both transient and high-wheeze respiratory phenotypes. By age 36months, nasal microbiota was significantly associated with respiratory phenotypes (R2= 0.019; P= .0376), and Moraxella-dominated microbiota was associated specifically with atopy-associated phenotypes. Analysis of paired house dust and nasal samples indicated that 12 month olds with low wheeze and atopy incidence exhibited the largest number of shared bacterial taxa with their environment. Nasal microbiota development over the course of early childhood and composition at age 3 years are associated with longitudinal respiratory phenotypes. These data provide evidence supporting an early-life window of airway microbiota development that is influenced by environmental microbial exposures in infancy and associates with wheeze- and atopy-associated respiratory phenotypes through age 7 years.

Long-Term Effects of Pre-Weaning Individual or Pair Housing of Dairy Heifer Calves on Subsequent Growth and Feed Efficiency.

Our objective in this exploratory study was to evaluate the long-term impacts of pre-weaning social isolation vs. contact on subsequent growth and feed efficiency of Holstein heifers. As pre-weaned calves, 41 heifers were housed individually (n = 15 heifers) or in pairs (n = 13 pairs; 26 heifers). At 18 months of age, heifers were blocked by body weight and randomly assigned to one of three pens within a block (six to eight heifers per pen; six pens total), with original pairs maintained. Body weight (BW), hip height and width, and chest girth were measured at the start and end of the study. Each pen was given 3 days of access to a GreenFeed greenhouse gas emissions monitor to assess potential physiological differences between treatments in enteric methane emissions or behavioral differences in propensity to approach a novel object. During the 9-week study, heifers were fed a common diet containing 62.3% male-sterile corn silage, 36.0% haylage, 0.7% urea, and 1.0% mineral (DM basis). To calculate daily feed intake, as-fed weights and refusals were recorded for individual heifers using Calan gates. Feed samples were collected daily, composited by week, and dried to calculate dry matter intake (DMI). Feed refusal and fecal samples were collected on 3 consecutive days at 3 timepoints, composited by heifer, dried, and analyzed to calculate neutral detergent fiber (NDF), organic matter (OM), and DM digestibility. Feed efficiency was calculated as feed conversion efficiency (FCE; DMI/average daily gain [ADG]) and residual feed intake (RFI; observed DMI-predicted DMI). Paired and individually housed heifers did not differ in DMI, ADG, FCE, or RFI. Although no differences were found in initial or final hip height, hip width, or chest girth, heifers which had been pair-housed maintained a greater BW than individually housed heifers during the trial. Methane production, intensity, and yield were similar between treatments. Pre-weaning paired or individual housing did not impact the number of visits or latency to approach the GreenFeed; approximately 50% of heifers in each treatment visited the GreenFeed within 8 h of exposure. Digestibility of OM, DM, and NDF were also similar between housing treatments. In conclusion, pre-weaning pair housing had no adverse effects on growth, feed efficiency, or methane emissions at 18 to 20 months of age.

Abstract TP161: Social Isolation Increases Liver Inflammation and Alters Hepatocyte Morphology in Cerebral Amyloid Angiopathy

Introduction: Social isolation (SI) is a growing yet understudied public health concern. Accumulating evidence suggests that SI has critical psychological implications and can also lead to considerable negative physiological outcomes, as in the case of cerebral amyloid angiopathy (CAA). CAA is characterized by the accumulation of amyloid-beta (Aβ) in the leptomeningeal vessels, which compromises the integrity of cerebral vasculature, thus increasing risk of intracerebral hemorrhages. Our preliminary data suggests SI induces metabolic changes including average weight gain in CAA mice compared to pair-housed (PH) counterparts (30g vs 25g, respectively; p<0.01). Hence, it is imperative to investigate the effects of social isolation on liver physiology and energy metabolism in the context of CAA. Hypothesis: We hypothesize that SI leads to decreased Aβ clearance by the liver, and increased immune cell infiltration into the liver. Methods: 3-month-old C57BL/6 (WT, n=21) and TgSwDI mice (n=21) were either pair-housed (PH) or socially-isolated (SI) for 9 months. We assessed Aβ deposition, hepatocyte morphology, vascular structure, and liver immune cell composition through immunohistochemistry. We additionally quantified ALT/AST levels and LRP-1 levels as a measure of liver dysfunction and Aβ clearance, respectively. Neurobehavioral performance was measured by nesting and tail-suspension test. Results: Our findings show that socially isolated CAA mice exhibit sustained affective and cognitive impairments when compared to the PH group. Average nesting scores are significantly lower for male CAA SI mice compared to PH mice (1.67 vs 3.5, respectively; p<0.01). SI CAA mice have larger hepatocytes and increased immune cell infiltration when compared to the PH counterparts and WT controls. Furthermore, Aβ signals were found to colocalize with liver-resident macrophages, implying a role of amyloid clearance by these cells. Discussion: Together we show that SI increases body weight and inflammation, and exacerbates cognitive and behavioral deficits. These changes may affect AB clearance, thereby potentially worsening CAA pathology. Further investigation into liver energy metabolism and macrophage-mediated inflammation is warranted.

Abstract TP28: The Effects of Social Isolation on Cerebral Amyloid Angiopathy

Introduction: Cerebral amyloid angiopathy (CAA) is characterized by amyloid β (Aβ) deposition in the cortical and leptomeningeal vessels, and it is a largely untreatable cause of intracerebral hemorrhage and dementia. Studies estimate a 10-50% prevalence of CAA in the general elderly population, positioning it as one of the strongest vascular contributors to age-related cognitive impairment. With aging, the prevalence of social isolation (SI) also increases. Isolated individuals have an increased risk of Aβ-related cognitive decline and heightened inflammatory response to stress. Yet, whether and how SI exacerbates CAA-induced cognitive decline is unknown. Methods: TgSwDI mice harboring Swedish, Dutch, and Iowa mutations of human amyloid precursor protein were used as a mouse model of CAA. Male and female C57BL6 wildtype (WT) and CAA mice were randomly assigned to paired housing (PH) or SI at 3 months. Neurobehaviors were measured at baseline and every 3 months using the novel object recognition test (NORT), tail suspension test (TST), and fear conditioning (FC). At 12 months, microglia phenotype, vascular structure, and Aβ burden were assessed using flow cytometry and immunostaining. Results: Both WT and CAA isolated animals displayed significantly greater immobility in TST at 9 months post-SI, suggesting a depression-like behavior (n=10-15/grp, p<0.0001). Isolated CAA mice displayed exacerbated cognitive deficits in NORT and FC while WT mice showed intact cognition (n=10-15/grp, p<0.05). Specifically, SI-induced cognitive deficits were more prominent in the female CAA mice compared to males (n=5-8/grp, p<0.01). Sex differences were also observed in CAA mice in frequencies of Aβ-containing endothelial cells (CD31 + ) and vessel-associated microglia (VAM, CD45 int CD11b + CD31 + ) as well as in microglial phagocytosis of Aβ (n=3/grp, p<0.05). SI increased the frequency of Aβ-containing microglia in isolated CAA mice compared to their PH littermates. Conclusion: SI induced behavioral deficits in both WT and CAA mice but exacerbated cognitive decline only in the CAA SI mice. SI also influences microglial phagocytosis of Aβ. Further research is needed to determine the cellular and molecular mechanism underlying SI-induced changes in CAA.

Abstract WMP120: MicroRNAs as a Therapeutic Target to Reduce Microglial Activation After Post-Stroke Social Isolation

Introduction: Loneliness and social isolation (SI) are associated with increased risk of stroke and other vascular disorders, along with all-cause mortality. However, it is unknown what mechanisms mediate how social factors affect stroke recovery. Methods: To investigate the negative effects of post-stroke SI on brain miRNA profiles, aged (18-20 months) C57BL/6 male mice were utilized. Three days following a 60-minute transient right middle cerebral artery occlusion (MCAO), mice were randomly assigned to pair housing (PH) or single housing (SI). At post-stroke timepoints (specifically day 3 after the stroke), the infarct was equal between groups, reducing the possibility of differential effects resulting from different infarct sizes. At two-time intervals (post-stroke SI D4 and D27), temporal miRNA profiling of the ipsilateral hemisphere was performed. Results: Distinct miRNA candidates were significantly altered in post-stroke SI, within the brain across both acute and chronic time points (n=4/grp, FDR adjusted *p<0.05). MiR-10a-5p and miR-10b-5p were observed to have crucial nodes in the pool of miRNAs that interacted with the largest group of miRNAs for post-stroke at SI D4 and D27, respectively. KEGG pathway analysis showed 4 days of isolation resulted in the enrichment of pathways related to microglial activation and 27 days of isolation lead to the activation of neuronal-specific pathways that regulate cognition and motivation (FDR adjusted *p<0.05). At post-stroke SI D4, significant microglial activation was observed in independent validation cohorts as assessed by the median fluorescence intensity (MFI) of purinergic receptor P2Y12 (P2RY12), in CD45 int CD11b + P2RY12 + cells in the brain. MFI of P2RY12 was significantly downregulated in post-stroke SI mice at D4 (n=7-8/grp, *p<0.05) compared to PH mice. Conclusions: These findings validate our hypothesis that post-stroke SI exacerbates microglia activation and leads to differential expression of miRNAs involved in regulating microglial pathways. Taken together, utilizing miRNA-based therapies to restore miRNA-profiles in the brain may be able to alleviate the detrimental impact of post-stroke SI on chronic depressive-like phenotypes.

Changes in enclosure use and basking behaviour associated with pair housing in Tokay geckos (Gekko gecko)

Due to often insufficient information, reptiles suffer welfare issues and increased mortality in captivity. In particular, the impact of the social environment remains poorly understood, despite evidence suggesting its’ importance for welfare in a wide range of social animals. The current study investigated how pair housing changes enclosure use, basking and hiding behaviour in tokay geckos (Gekko gecko). While the captive conditions and husbandry procedures employed in this study align with existing literature recommendations, they have not been previously evaluated for their suitability for this particular species. The results show that, when socially deprived, lizards were more likely to move and hide before feeding. Furthermore, males were more likely to be found at the front than females during pair housing but not during single housing. Finally, contrary to single housing, enclosure temperature had no effect on the probability to move and hide behind a shelter during pair housing. Consistently, lizards were more likely to bask after feeding across housing conditions, and females were more likely to bask before their first clutch. Together, pair housing decreases movement and hiding in relation to human presence (feeding), which might indicate that pair housing improves tokay gecko welfare and suggest that the presence of a conspecific should be considered to improve welfare policies in social reptiles. This study serves as a baseline for future research into how enclosure furnishings, husbandry techniques, and enrichment practices impact the welfare of tokay geckos which will be crucial for refining our understanding of and improving on the welfare of reptiles in captivity.

Less activity means improved welfare? How pair housing influences pinyon jay (Gymnorhinus cyanocephalus) behaviour

Abstract The activity level and specific behaviours exhibited by captive animals are crucial indicators of welfare. Stereotypies, or repetitive behaviours that have no apparent function or goal, are performed by animals experiencing poor conditions in their environment and indicate welfare concerns. Changes in the housing environment in particular may have critical influences on behaviour and welfare. Here, we measured behavioural changes in a captive pinyon jay (Gymnorhinus cyanocephalus) population (n = 10) associated with a shift from single to pair housing. Using automated video processing, we show that pair housing greatly reduced overall activity levels in these birds. The stark reduction in activity was surprising, as we expected that social housing would increase interactions between birds, thus increasing activity levels. Upon further analysis, however, we found that stereotypic behaviours, such as beak scraping, jumping, pecking, and route tracing decreased after pair housing, whereas the positive welfare behaviours of perching and preening increased. Our results indicate that pair housing may reduce overall activity in pinyon jays; however, this reduction is primarily in stereotypic behaviours.