Institutional Animal Care Research Articles

Abstract 5903: MASTL small-molecule inhibition to target mitosis for cancer therapy

Abstract Cell cycle/tumor repressors can be pharmacologically activated to repress uncontrollable proliferation of cancer cells. However, targeting cell cycle regulators of G2/M and mitotic checkpoints to achieve maximum therapeutic benefit remains a challenge due to a limited therapeutic index. Here, we identified highly potent and selective oral bioavailable clinical candidate inhibitors to the first-in-class oncology target Microtubule Associated Serine/Threonine Kinase-Like (MASTL) aimed at expanding therapeutic control of the cell cycle for cancer therapy. Breath of efficacy screening in multiple tumor indications in vitro followed by computational analyses identified the regulatory subunit PPP2R2A as a potential patient selection biomarker that strongly correlates to MASTL inhibitor response irrespective of cancer genetic alterations. Functional genetics studies confirmed that sensitivity to MASTL inhibition is defined by PPP2R2A expression. To identify genetic mediators of MASTL inhibitor resistance, a whole genome CRISPR knockout screen with the MASTL inhibitor was performed and further established that the MASTL inhibitor response is dependent on PPP2R2A containing PP2A complexes. Mechanistic studies (proteomics, resistance, functional genetics, and time-lapse microscopy) demonstrated that MASTL inhibition disrupts mitosis by activating the tumor suppressor PP2A, leading to a switch from CDK1 activity to CDK1 inactivity, mitotic defects, and cancer cell death. MASTL inhibition treatment in tumor models in vivo and in patient-derived organoid models results in potent tumor growth inhibition. Our results demonstrate that the first identified highly selective MASTL clinical candidate inhibitors represent a potential new cancer therapeutic strategy to target mitosis and mitotic exit by activating the tumor repressor PP2A to counter CDK1 activity. All procedures performed on animals were in accordance with regulations and established guidelines and were reviewed and approved by an Institutional Animal Care and Use Committee or through an ethical review process. Citation Format: Chad M. Toledo, Koleen J. Eisele, Dong Hyun Kim, Xinmeng Mu, Sonja Brun, Carl Davis, Eric C. Greenwald, Fion Hui, Meilan He, Yanling Yang, Ana Flores-Bojorquez, Yuxin Li, Penney L. Khamphavong, Joseph H. Lee, Jian Li, Dana J. Ramms, Greg Jones, Marin Auth, Cory L. Painter, Andrew Nager, Jon Oyer, Sergei L. Timofeevski, William E. Pierceall, Anwar Murtaza, Jonathan R. Heyen, Rebecca Gallego, Casey Quinlan, Indrawan McAlpine, Todd L. VanArsdale. MASTL small-molecule inhibition to target mitosis for cancer therapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 5903.

Correlation of cerebral microvascular circulation with vital signs in cerebral compression and the validity of three concepts: vasodilation, autoregulation, and terminal rise in arterial pressure.

Vasodilation, autoregulation, and rising arterial pressure are three common concepts in cerebral compression, believed to improve cerebral blood flow to maintain the brain's nutrition. However, these concepts are unclear, unproven, and based on assumptions. This study aimed to correlate cerebral circulation with alterations of vital signs and to evaluate the above concepts based on physics and hemodynamics. Without new animal experiments, a large amount of data: recording of vital signs, long movies of cerebral circulation, and numerous photos of histological examination and microvessels obstruction in cerebral compression in cats was studied, and only partial and preliminary results were reported in 1970. The experiments were supported by an NIH grant for head injury, done before the 1985 Institutional Animal Care and Use Committee requirement. The advent of digital technology facilitated digitizing and stepwise correlating them and evaluating the validity of the above concepts. As cerebral compression increased intracranial pressure (ICP), veins dilated, not arteries, and arterial microvessels obstructed, diminished, and stopped cerebral circulation. Simultaneously, vital signs deteriorated, and pupils became fixed and dilated. There was no evidence for what is believed as autoregulation. In cerebral compression, rising ICP obstructs cerebral arterial microvessels while simultaneously deteriorating vital signs. There is no evidence for dilatation of the arteries; only veins dilate, best-called venodilation. There is no evidence of autoregulation; what occurs is a cerebral compartmental syndrome. The terminal rise of arterial pressure is the hemodynamic result of cerebral circulation cessation, overloading the aorta. None of the concepts benefit the brain's nutrition.

Abstract 7472: Melanoma-intrinsic expression of signal-regulatory protein alpha (SIRPα) confers tumor cells resistance to anti-tumor adaptive immunity

Abstract Introduction: Melanoma patient survival rates have significantly improved recently owing to the development of both targeted therapies and immunotherapies. However, there are still around 50% of patients relapse. The limited response to immunotherapies and global rise in melanoma incidence, with around 290,000 cases newly diagnosed each year, highlight the need for identifying new biomarkers, modulatory pathways, and risk factors for melanoma development. Earlier studies have characterized that aberrant expression of CD47 (a.k.a. “don’t eat me” signal) is one of the mechanisms that tumors exploit to avoid innate immune surveillance. CD47 blockade has been demonstrated to restore myeloid effector function by reinvigorating phagocytosis of tumor cells, which further enhances anti-tumor T cell responses. However, melanoma tumors are resistant to CD47 blockade. Interestingly, we and others have discovered that human and mouse melanoma cells express high levels of SIRPα, the receptor for CD47, which is typically expressed in myeloid compartments. Experimental Procedure: To investigate the role of tumor SIRPα, we designed gRNAs to CRISPR out the SIRPα N-terminal region, where it interacts with CD47, in B16 melanoma and generated SIRPα+/+ (WT) and SIRPα-/- (KO) B16 tumors. We conducted multiple in vitro and in vivo experiments to investigate whether tumor SIRPα played a role in tumor growth and modulated anti-tumor immunity. The preclinical tumor model we used is B16-F10 melanoma and the murine strains we used are the immune-competent (C57BL/6j; B6) and the immune-deficient (RAGnull) mice. For phenotypic and functional assessments, we performed analysis using flow cytometry, immunohistochemistry (IHC) and single cell RNA-sequencing (scRNA-seq) derived from live-sorted CD45+ tumor infiltrating lymphocytes (TILs) of SIRPα-WT and SIRPα-KO B16 tumors. Summary of Unpublished Data Our preliminary data in a preclinical B16-F10 melanoma model revealed that surface SIRPα expression is necessary for optimal B16-F10 melanoma growth in immune-competent mice, but not in immune-deficient RAGnull mice, suggesting a potential crosstalk between tumor SIRPα and the host adaptive immune system. Intriguingly, we found that selective SIRPα deletion in melanoma cells results in a significant increase of immune infiltrates within melanoma tumors that further suppresses tumor growth. Concluding Remarks: SIRPα is required for optimal melanoma development by suppressing anti-tumor adaptive immunity. Ethics Approval: All mice were maintained in microisolator cages and treated in accordance with the NIH and American Association of Laboratory Animal Care regulations. All mouse procedures and experiments for this study were approved by the Weill Cornell Medicine Institutional Animal Care and Use Committee. Citation Format: Chien-Huan Weng, Chana Schochet, Linda Hamadene, Shabnam Eghbali, Sébastien Monette, Levi Mangarin, Cailian Liu, Fadi Samaan, Jedd D. Wolchok, Taha Merghoub. Melanoma-intrinsic expression of signal-regulatory protein alpha (SIRPα) confers tumor cells resistance to anti-tumor adaptive immunity [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 7472.

Double-Balloon Catheter–Mediated Transarterial Chemotherapy Delivery in a Swine Model: A Mechanism Recruiting the Vasa Vasorum for Localized Therapies

PurposeTreatment of hypovascular tumors, such as pancreatic adenocarcinoma, is challenging owing to inefficient drug delivery. This report examines the potential mechanism of localized drug delivery via transarterial microperfusion (TAMP) using a proprietary adjustable double-balloon occlusion catheter in a porcine model. Materials and MethodsAdult Yorkshire swine (N = 21) were used in the Institutional Animal Care & Use Committee–approved protocols. The RC-120 catheter (RenovoRx, Los Altos, California) was positioned into visceral, femoral, and pulmonary arteries with infusion of methylene blue dye, gemcitabine, or gold nanoparticles. Transmural delivery was compared under double-balloon occlusion with and without side-branch exclusion, single-balloon occlusion, and intravenous delivery. Intra-arterial pressure and vascular histologic changes were assessed. ResultsInfusion with double-balloon occlusion and side-branch exclusion provided increased intra-arterial pressure in the isolated segment and enhanced perivascular infusate penetration with minimal vascular injury. Infusates were predominantly found in the vasa vasorum by electron microscopy. ConclusionsTAMP enhanced transmural passage mediated by localized increase in arterial pressure via vasa vasorum.

Multispecies comparative prostate anatomy by imaging: Implications for experimental models of prostatic disease.

There is an increasing interest in using preclinical models for development and assessment of medical devices and imaging techniques for prostatic disease care. Still, a comprehensive assessment of the prostate's radiological anatomy in primary preclinical models such as dogs, rabbits, and mice utilizing human anatomy as a reference point remains necessary with no optimal model for each purpose being clearly defined in the literature. Therefore, this study compares the anatomical characteristics of different animal models to the human prostatic gland from the imaging perspective. We imaged five Beagle laboratory dogs, five New Zealand White rabbits, and five mice, all sexually mature males, under Institutional Animal Care and Use Committee (IACUC) approval. Ultrasonography (US) was performed using the Vevo® F2 for mice (57 MHz probe). Rabbits and dogs were imaged using the Siemens® Acuson S3000 (17 MHz probe) and endocavitary (8 MHz) probes, respectively. Magnetic resonance imaging (MRI) was also conducted with a 7T scanner in mice and 3T scanner in rabbits and dogs. Canine transrectal US emerged as the optimal method for US imaging, depicting a morphologically similar gland to humans but lacking echoic zonal differentiation. MRI findings in canines indicated a homogeneously structured gland similar to the human peripheral zone on T2-weighted images (T2W) and apparent diffusion coefficient (ADC). In rabbits, US imaging faced challenges due to the pubic symphysis, whereas MRI effectively visualized all structures with the prostate presenting a similar aspect to the human peripheral gland on T2W and ADC maps. Murine prostate assessment revealed poor visualization of the prostate glands in ultrasound due to its small size, while 7T MRI delineated the distinct prostates and its lobes, with the lateral and dorsal prostate resembling the peripheral zone and the anterior prostate the central zone of the human gland. Dogs stand out as superior models for advanced preclinical studies in prostatic disease research. However, mice present as a good model for early stage studies and rabbits are a cost-effective alternative and serve as valuable tools in specific research domains when canine research is not feasible.

Evaluation of taurine and carnitine concentrations in whole blood, plasma, skeletal muscle and cardiac muscle in dogs.

Little is known about how plasma and whole blood taurine and plasma carnitine correlate to concentrations in skeletal and cardiac muscle and the effects of diet in dogs. The purpose of this study was to evaluate the correlation among plasma, skeletal and cardiac muscle carnitine and taurine and whole blood taurine and determine the effect of diet. The study protocol was approved by the Pet Food Solutions Institutional Animal Care and Use Committee. Thirty-three mixed-breed hounds and 32 beagles were evaluated at Day 0 then removed from their baseline diet and randomized to a test diet: high animal protein, grain-inclusive (HA-GI), low animal protein, grain-free (LA-GF), low animal protein, grain-inclusive (LA-GI), or high animal protein, grain-free (HA-GF). Blood was drawn every 30 days and endomyocardial (mixed breeds only) and skeletal muscle biopsies were collected at Days 0 and 180. The correlations between plasma and whole blood taurine, or plasma carnitine and skeletal and cardiac muscle concentrations were weak (p < 0.01-0.05). Mixed-breed hounds had increased (p = 0.029) whole blood taurine compared to beagles. Plasma taurine was lower with diet HA-GF, (p = 0.009) however, all diets had increased taurine from Day 0 and were, on average within the laboratory reference range. Dogs fed the HA-GI diet had increased cardiac muscle carnitine esters (p = 0.014). Increased carnitine esters were also appreciated in cardiac muscle in all diets from Day 0 to 180 (p = 0.0001). On Day 180 mixed-breed hounds had increased skeletal total carnitine (p < 0.001) compared to all time points and breeds. This study observed no correlation between plasma, whole blood, skeletal and cardiac muscle taurine concentrations but noted some effects between time, breed and diet.

Silver carboxylate-TiO2/polydimethyl siloxane is a safe and effective antimicrobial with significant wound care potential.

With the rise in antibiotic resistance, new methodologies are needed to combat musculoskeletal infections. Silver is an antimicrobial that can be synthesized in different forms, but its pharmacokinetics are difficult to control. This study details the antibacterial efficacy and cellular cytotoxicity of a formulation consisting of silver carboxylate (AgCar) released through a titanium dioxide/polydimethylsiloxane matrix with a predictable release profile on Pseudomonas aeruginosa, Acinetobacterium baumannii, and human-derived primary osteoblasts. Through an Institutional Animal Care and Use Committee and IRB-approved protocol, AgCar was applied to live Yucatan porcine skin and histologically analyzed for skin penetration. Graphite Furnace Atomic Absorption Spectroscopy (GFAAS) was used to measure elution of AgCar. Dose-response curves were generated through optical density to assess potency. Finally, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay was used to quantify the cellular cytotoxicity of the novel formulation. The results were subject to statistical analysis using analysis of variance and post hoc Tukey tests. The silver carboxylate coating demonstrated deep penetration into the epithelium at the level of the deep pilosebaceous glands in animal models. GFAAS testing demonstrated the extended elution profile of silver carboxylate over 96 hours, while 100% silver with no titanium dioxide-polydimethylsiloxane matrix fully eluted within 48 hours. 10x silver carboxylate demonstrated superior antimicrobial activity to antibiotics and other silver formulations and showed minimal cytotoxicity compared with other silver formulations. Current antimicrobial therapies in wound care and surgical antisepsis, such as chlorhexidine gluconate, have pitfalls including poor skin penetration and short duration of efficacy. The broad antimicrobial activity, extended elution, and deep skin penetration of this AgCar formulation show great promise for surgical site infection and wound care treatment. Novel technology to fight the growing threat of microbial resistance should be at the forefront of orthopaedic surgical site infection prevention and treatment.

Abstract B031: Localized cytokine immunotherapy with a novel injectable hydrogel confers immune memory in murine triple negative breast cancer tumors

Abstract Introduction. Triple negative breast cancer (TNBC), representing 10-15% of all diagnosed breast cancer (BC) cases, is the most aggressive BC subtype and has higher recurrence rates and therapy resistance. It typically has an inflamed tumor microenvironment and relatively high tumor infiltrating lymphocyte levels. However, T cells are typically less activated compared to non-invasive BC. Hence, we hypothesize that local delivery of immunotherapeutics to activate and reinvigorate T cells can restore the anti-tumor immune response. To this end, we have developed an injectable delivery medium to effectively localize immune agonists to activate, expand, and reinvigorate T cells at the site of the tumor. Methods. The naturally occurring polysaccharide chitosan was crosslinked to form a novel injectable hydrogel (XCSgel). For in vivo tumor treatment, 2.5 × 105 E0771 murine breast cancer cells were implanted subcutaneously on the right flank of C57BL/6 mice. When tumors grew to be 50-100mm3, 5ug and 20ug of interleukin-12 (IL-12) co-formulated in 50uL of XCSgel was delivered intratumorally, with additional treatment groups of 5ug IL-12 in saline, XCSgel alone, and an untreated control. For re-challenge studies, 2.5 × 105 E0771 murine breast cancer cells were implanted subcutaneously on the left flank of mice, with a naïve cohort as a control. For the second tumor study to reinvigorate T cells in mice with larger tumor burdens, 5 × 105 E0771 murine breast cancer cells were implanted subcutaneously on the right flank of C57BL/6 mice. When tumors reach 100-150mm3, 5ug IL-12 in XCSgel, 20ug IL-10 in XCSgel, 5ug IL-12 + 20ug IL-10 in XCSgel, 5ug IL-12 + 20ug IL-10 in saline, and XCSgel will be delivered intratumorally, with an untreated control. Tumor sizes and Kaplan-Meier survival curves were/will be collected across all cohorts. All experiments involving laboratory animals were approved by the Institutional Animal Care and Use Committee at North Carolina State University. Results and Discussion. In the first tumor study, 5ug IL-12 in XCSgel eliminated tumors in 5/5 mice, while 20ug IL-12 in XCSgel eliminated tumors in 4/5 mice and IL-12 in saline eliminated 2/5 tumors. No tumor delay or elimination was observed in untreated and gel alone groups. Upon re-challenge, 5/5 mice in the 5ug IL-12 in XCSgel remained tumor-free over 40 days post-re-challenge, as did 3/4 of the 20ug in XCSgel and 2/2 in IL-12 saline treatment groups. The second intratumoral study is ongoing. Conclusions. A single injection of IL-12 formulated in a novel injectable hydrogel was found to eliminate tumors and stimulate immune memory in a murine triple negative breast cancer model. Results from localized IL-12 and IL-10 cytokine treatment of tumors with larger tumor burdens are ongoing. Given the ability of this localized immunotherapy to induce systemic antitumor immunity, it deserves further consideration as a neoadjuvant treatment prior to breast conserving surgery.Acknowledgements. This work is supported by the NSF Graduate Research Fellowship. Citation Format: Siena M Mantooth, David A Zaharoff. Localized cytokine immunotherapy with a novel injectable hydrogel confers immune memory in murine triple negative breast cancer tumors [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Advances in Breast Cancer Research; 2023 Oct 19-22; San Diego, California. Philadelphia (PA): AACR; Cancer Res 2024;84(3 Suppl_1):Abstract nr B031.

Plant-derived exosomes extracted from Lycium barbarum L. loaded with isoliquiritigenin to promote spinal cord injury repair based on 3D printed bionic scaffold.

Plant-derived exosomes (PEs) possess an array of therapeutic properties, including antitumor, antiviral, and anti-inflammatory capabilities. They are also implicated in defensive responses to pathogenic attacks. Spinal cord injuries (SCIs) regeneration represents a global medical challenge, with appropriate research concentration on three pivotal domains: neural regeneration promotion, inflammation inhibition, and innovation and application of regenerative scaffolds. Unfortunately, the utilization of PE in SCI therapy remains unexplored. Herein, we isolated PE from the traditional Chinese medicinal herb, Lycium barbarum L. and discovered their inflammatory inhibition and neuronal differentiation promotion capabilities. Compared with exosomes derived from ectomesenchymal stem cells (EMSCs), PE demonstrated a substantial enhancement in neural differentiation. We encapsulated isoliquiritigenin (ISL)-loaded plant-derived exosomes (ISL@PE) from L. barbarum L. within a 3D-printed bionic scaffold. The intricate construct modulated the inflammatory response following SCI, facilitating the restoration of damaged axons and culminating in ameliorated neurological function. This pioneering investigation proposes a novel potential route for insoluble drug delivery via plant exosomes, as well as SCI repair. The institutional animal care and use committee number is UJS-IACUC-2020121602.

Training ultrasound-guided percutaneous nephrostomy technique with porcine model.

There is increasing interest in the use of ultrasound for endoscopic and percutaneous procedures. Access can be achieved without radiation exposure under ultrasound guidance. Our aim was to develop a porcine-based training model for ultrasound-guided percutaneous renal access that could also be personalized to a specific patient. The Institutional Animal Care and Use Committee of Severance Hospital approved the study protocol. An anesthetized pig was placed in the dorsal lithotomy position. For the nephrostomy puncture, a Chiba biopsy needle with an echo tip was used under ultrasound guidance. Eight residents and three consultants in urology participated. Puncture time was defined as the nephrostomy time to confirm the flow of irrigation via the needle. After training, satisfaction survey results for clinical usability and procedural difficulty were evaluated. The 5-point Likert scale satisfaction survey for clinical usability and procedural difficulty found mean results of 4.64 and 4.09 points, respectively. There were no differences between residents and consultants for either variable. For all participants combined, there was a significant difference for nephrostomy time between the first and second trials (278.8±70.6 s vs. 244.5±47.0 s; p=0.007). The between-trial difference was greater for residents (291.5±71.2 s vs. 259.1±41.9 s; p=0.039). The difference for the consultant was not significant (245.0±69.4 s vs. 205.7±42.5 s; p=0.250). We developed a porcine-based ultrasound-guided nephrostomy puncture training model. Satisfaction survey results indicated high clinical usability and procedural difficulty. For nephrostomy time, the model was more effective for urology residents than for consultants.

A porcine model of thoracic aortic aneurysms created with a retrievable drug infusion stent graft mirrors human aneurysm pathophysiology

ObjectiveAneurysm pathophysiology remains poorly understood, in part from the disparity of murine models with human physiology and the requirement for invasive aortic exposure to apply agents used to create aneurysm models. A retrievable drug infusion stent graft (RDIS) was developed to isolate the aortic wall intraluminally for drug exposure. We hypothesized that an RDIS could deliver aneurysm-promoting enzymes to create a porcine model of thoracic aneurysms without major surgical exposure. MethodsRetrievable nitinol stent graft frames were designed with an isolated drug delivery chamber, covered with polytetrafluoroethylene, and connected to a delivery wire with a drug infusion catheter installed to the outer chamber. Institutional Animal Care and Use Committee-approved Yorkshire pigs (n = 5) underwent percutaneous access of the femoral artery, baseline aortogram and stent placement in the thoracic aorta followed by 30-minute exposure to a cocktail of elastase, collagenase, and trypsin. After aspiration of excess drug, stent retrieval, and femoral artery repair, animals were recovered, with angiograms at 1 and 4 weeks followed by explant. Histological analysis, in situ zymography, and multiplex cytokine assays were performed. ResultsThe RDIS isolated a segment of anterior aorta angiographically, while the center lumen preserved distal perfusion during drug treatment (baseline femoral mean arterial pressure, 70 ± 14 mm Hg; after RDIS, 75 ± 12; P = .55). Endovascular induction of thoracic aneurysms did not require prior mechanical injury and animals revealed no evidence of toxicity. Within 1 week, significant aneurysmal growth was observed in all five animals (1.4 ± 0.1 cm baseline to 2.9 ± 0.7 cm; P = .002) and only within the treated region of the aorta. Aneurysms persisted out to 4 weeks. Aneurysm histology demonstrated loss of elastin and collagen that was otherwise preserved in untreated aorta. Proinflammatory cytokines and increased matrix metalloproteinase activity were increased significantly within the aneurysm. ConclusionsAn RDIS achieves isolated drug delivery while preserving distal perfusion to achieve an endovascular porcine model of thoracic aneurysms without major surgery. This model may have value for surgical training, device testing, and to better understand aneurysm pathogenesis. Most important, although the RDIS was used to simulate aortic pathology, this tool offers intriguing horizons for focused therapeutic drug delivery directly to aneurysms and, more broadly, focused locoregional drug delivery to vessels and vascular beds.

A survey of the impact of COVID-19 on the management of animal experiments and laboratory animal facilities in Korea.

The pandemic has affected the lives of people all over the world. The effects of the pandemic on laboratory animal facilities and their operations through this unusual global event are poorly understood. Here, we have applied a methodological framework of qualitative approach including semi-structured interviews to investigate laboratory animal operations in Korea and how it has shaped the on-going management and laboratory operations of such facilities. A total of fifty-two individuals, including members and administrators of the Institutional Animal Care and Use Committee (IACUC), researchers, and animal facility managers and staff, were surveyed through purposeful sampling. Survey questions explored how the pandemic impacted the IACUC and the functioning of animal facilities, and what steps to take in preparation of a future pandemic-like crisis. Our survey found evidence of an increase in animal experiments in Korea during the pandemic that correlated with increases in research funding during that period, such as for vaccine development. Also, operational challenges due to pandemic-related health issues in personnel were resolved through overtime, rather than by reducing facility operations. Moreover, a refinement of post-approval monitoring (PAM) practices was also discussed by respondents. Taken together, our study offers insights into animal facility operations during the pandemic and outlines recommendations for safeguarding operations in such future scenarios.

A Commentary on Fasting of Nonclinical Research Animals.

This commentary discusses the implementation of fasting in nonclinical animal experimental subjects. The short-term removal of food from cages of experimental animals is in all respects innocuous. The term "stress" is ill-defined and the statutes and regulations governing animal research laboratories that exert their authority in the performance of their operations do so without substantive grounds to base compliance. The legislative and administrative history of the implementation of the Animal Welfare Act (AWA) has evolved into the development of laboratory management strategies that focus on the reduction of the biological cost of stress to the animals and the determination of when subclinical stress (eustress) becomes distress. Animal welfare is based on the tenet that in laboratories conducting animal research in compliance with Good Laboratory Practices (Title 21 USC, Chapter 13,§58), it is the study protocol and the study director that establish procedures and processes that are approved by each Institutional Animal Care and Use Committee to ensure the humane care and use of animals in research, teaching, and testing and to ensure compliance with guidelines and regulations. This approval process establishes the justification of eustress in the environment that do not rise to the threshold of distress under the AWA.

Knowledge, Attitudes, and Practices on Ethics in Biomedical Animal Research in Mexico.

The most widely accepted ethical concept for the mitigation of harm to animals used in biomedical research is known as the 3Rs, which refer to replacement, reduction, and refinement. The aim of our study was to determine the ethical and regulatory criteria that researchers in Mexico consider when developing their animal research protocols and that members of the ethics committees use when they evaluate and approve these protocols. We circulated a survey to 300 individuals from different research institutions and received responses from 179 researchers and members of ethics committees on questions related to their knowledge, attitudes, and practices toward the use of animals in research based on the 3Rs. The responses obtained indicate that the respondents were aware of the 3R concept, and they claim to apply these principles. However, the responses revealed resistance to using alternatives for research, testing, and teaching (66%). Nineteen percent of the researchers reported that their institutions do not have an integrated Institutional Animal Care and Use Committee (IACUC). Around 80% of respondents were aware of Mexican regulations. The knowledge and application of the 3Rs by researchers and members of the IACUC is a fundamental concept in animal research. Such knowledge contributes the use of ethical standards, attitudes, and practices relevant to the use of animals in research.

Cardiosphere derived cell secretome therapy after experimental myocardial infarction: effects of intracoronary administration on ventricular tachycardia inducibility and cardiac function

Abstract Background Myocardial infarction (MI) carries high risk of sudden cardiac death due to the development of ventricular tachycardia (VT) which is caused by viable myocytes located within the infarct scar tissue [1]. Cardiosphere derived cell secretome (S-CDCs) has been demonstrated to possess antiarrhythmic properties when delivered transendocardially [2]. Further, S-CDCs has been proven to reduce scar size and increase viable myocardial mass in chronic MI [3]. Purpose The objective of this study was to evaluate the effects of an intracoronary (IC) administration of S-CDCs on VT inducibility and cardiac function in a porcine MI model. Methods After obtaining the approval of the Institutional Animal Care and Use Committee, 14 Large White swine were subjected to closed chest MI induction carrying out balloon occlusion of the left anterior descending coronary artery (below the second diagonal branch) for 150 minutes. One month after MI creation, pigs received an IC administration of saline (CON; 5mL; n=7) or S-CDCs (S-CDCs; 9.16 mg of protein in 5mL of saline; n=7). VT inducibility and magnetic resonance (MR) studies were performed pre- and four months post-injection determining ejection fraction (EF), infarct size (IS) and indexed end diastolic and systolic volumes (EDVi, ESVi). Results Before injection VT was inducible in all cases and no differences were observed between groups in any MR-derived parameter (figure). IC infusion was successful in all swine. At four months VT inducibility study revealed lower inducibility rates in S-CDCs compared to CON (57% versus 100%; p=0.05). At this timepoint EF was higher in S-CDCs (35±10% versus 29±10%) although differences between groups were not statistically significant. Conversely, IS was significantly lower in S-CDCs (12±3% versus 16±2% (p=0.03)). Moreover, a trend towards lower ventricular volumes (EDVi: 83±18mL/m² versus 88±29mL/m² and ESVi: 56±20mL/m² versus 64±27mL/m²) was detected in this group. Conclusions The IC administration of S-CDCs suggests a potential reduction on post-MI VT development as well as a beneficial effect on cardiac function. This therapy seems to reduce IS in this porcine MI model.MR derived parameters

Abstract 201: 3D-Printed Automated Pressure-Cycled Resuscitator Maintains Respiratory Homeostasis in Swine With Normal to Moderately Low Lung Compliance

Background: During resuscitation, manual ventilation is commonly used. However, the effectiveness of this approach heavily relies on the skills of the individuals performing, often leading to inconsistent tidal volumes and respiratory rates. Such variations in ventilation can disrupt the removal of CO 2 resulting in altered pH. To address this problem, we leveraged advancements in fluidics and 3D printing to develop a miniature, automated, pressure-cycled resuscitator (inVent) that operates without any moving parts or settings. Hypothesis: The inVent will be able to maintain a pH of 7.2 or higher in swine with a dynamic compliance (Cdyn) of 25-50 ml/cmH 2 O. Goals/Aims: To assess the inVent’s performance in an animal model with normal to severe lung injury. Methods: Hybrid Landrace swine were studied under a protocol approved by the Institutional Animal Care and Use Committee. All swine were anesthetized, and underwent oral intubation. Breath by breath measurements were obtained using the NM3 Monitor (Phillips). All 3 inVent (fluidIQ) resuscitators pressure modules were used pre and post lung injury to fully characterize how each of the modules would react in different lung conditions. Lung injury was induced through a repeated bronchoalveolar lavage. ABG analysis was performed using the epoc system (Siemens). pH values 7.2 or less were considered acidotic while those over 7.2 were considered acceptable. Results: 8 swine with an average weight of 36 (5.8) Kg were studied. 7 swine contributed to 39,770 breaths of pulmonary mechanics and 33 ABGs recorded. Mean Cdyn was lower than anticipated at 25.8 (14.7) mL/cmH 2 O and a pH 7.32 (0.16). Figure 1 demonstrates a linear relationship with compliance and pH. Conclusions: The inVent resuscitator was able to maintain a pH of at least 7.2 in moderate compliance ranges, however struggled to maintain pH of 7.2 or higher in the severely injured. Higher lung compliance ranges are needed to explore possible hyperventilation events.

PSVIII-22 A Probiotic Blend Improves Fecal Quality and Enhances Gut Immunity in Dogs with Chronic Diarrhea

Abstract Probiotics have been fed to pets for their enhanced health benefits beyond basic nutrition, as well as to manage diarrhea. Species and strains of probiotics and the combinations may elicit different beneficial effects in dogs. Therefore, the objective of this study was to evaluate the effects of a probiotic blend (2 strains of Bacillus subtilis and 1 strain of Bacillus amyloliquefaciens) on digestibility, fecal characteristics, fecal microbiota, and fecal metabolites in healthy dogs and dogs with chronic diarrhea (CD = dogs with intermittent diarrhea persisting for more than 3 months before study start that were otherwise clinically healthy). Twenty-two adult dogs (11 healthy, 11 CD; mean BW = 14.1 kg; mean age = 8.1 yr) were enrolled in a cross-over design study, with two 3-week feeding periods and a 3-week washout between feeding periods. Protocols were approved by the facility’s Institutional Animal Care and Use Committee. Dogs were assigned to a control kibble or control kibble + probiotic blend (1.5 × 106 CFU/g) top dressed on the food. Fecal scores were evaluated daily during each period. Fecal samples were collected during days 14 to 18 for nutrient digestibility. Fresh fecal samples were collected on days 17 to 18 for dysbiosis index and fecal metabolites measurements. All data were analyzed using the Mixed Models procedure of SAS. Probiotic supplementation did not affect digestibility, dysbiosis index, or fecal volatile fatty acid concentrations in both healthy and CD dogs. Fecal scores were lower (P &amp;lt; 0.05; firmer stool) when dogs consumed the probiotic blends for both healthy and CD groups. In dogs with CD, consumption of the probiotic blend resulted in greater (P &amp;lt; 0.05) fecal IgA concentrations. These data demonstrate that the probiotic blend may elicit intestinal health benefits by improving stool quality and enhancing gut immunity, especially in dogs with CD.

PSVIII-20 A Premium Dry Cat Food Enhances Digestibility and Gut Health in Cats Compared with a Grocery Dry Cat Food

Abstract As the awareness of pet owners to the benefits of nutrition on pet health and wellness increases, pet owners are looking for foods that include high-quality ingredients and functional benefits. However, little research is available on cats comparing health measures when feeding premium foods vs basic cat foods. This study aimed to compare the effects of feeding a premium cat kibble diet (Blue Buffalo Tastefuls; BB) and a basic grocery cat kibble diet on digestibility, blood biomarkers, and fecal microbiome in healthy adult cats. Sixty cats (mean BW = 4.2 ± 0.8 kg; mean age = 4.3 ± 3.2 yr) were randomly selected to consume BB (n = 30) or grocery diet (n = 30) for 180 days. On days 0, 90, and 180, fresh fecal samples were collected for fecal microbiome and dysbiosis index analysis and blood samples were collected for measurements of complete blood count, serum chemistry, and serum biomarkers. A separate 10-day digestibility study was conducted using 14 cats (BB n = 7, grocery diet n = 7; mean BW = 3.8 ± 0.7 kg). Total fecal samples were collected from day 6 to day 10 for nutrient digestibility analysis. Protocols were approved by the facility’s Institutional Animal Care and Use Committee before the study. All data were analyzed using the Mixed Models procedure of SAS. Fecal scores were not changed (P &amp;gt; 0.05) by diet. Greater (P &amp;lt; 0.05) digestibility of protein, fat, and energy were observed in cats consuming BB. Although all blood cell count and blood chemistry values were within the reference ranges, measurements such as total protein, aspartate transaminase, alkaline phosphatase, cholesterol, and triglycerides were significantly different (P &amp;lt; 0.05) between diet groups. Greater (P &amp;lt; 0.05) insulin-like growth factor-1 was observed in cats fed BB. Cats consuming BB had a lower (P &amp;lt; 0.05) dysbiosis index (less dysbiotic microbiome) and a greater (P &amp;lt; 0.05) bacterial species richness. Relative abundances of 28 bacterial genera were altered (P &amp;lt; 0.05) by the diets, with greater abundances of Faecalibacterium, Megamonas, and Ruminococcus observed in cats fed BB. The data suggest that a premium dry cat food may elicit beneficial effects on digestibility and the GI microbiome of healthy adult cats.

PSVIII-21 A Premium Dry Dog Food Elicits Gut Health Benefits Compared with a Grocery Dry Dog Food

Abstract With the pet humanization trend, pet parents are continuously seeking approaches to improve the health of their pets. Compared with grocery dog foods produced to meet the basic needs of the dog, premium dog foods include high-quality ingredients and functional benefits that can be more appealing to consumers. However, little research is available comparing health measures in dogs fed premium foods vs. basic grocery foods. The objective of this study was to compare the effects of feeding a premium dog kibble diet (Blue Buffalo; BB) and a grocery dog kibble diet on digestibility, blood biomarkers, and fecal microbiome in healthy adult dogs. Sixty dogs (mean BW = 10.8 ± 2.0 kg; mean age = 8.2 ± 3.3 yr) were randomly selected to consume BB (n = 30) or the grocery diet (n = 30) for 180 days. On days 0, 90, and 180, fresh fecal samples were collected for fecal microbiome and dysbiosis index analysis and blood samples were collected for measurements of complete blood count, serum chemistry, and serum biomarkers. A separate 10-day digestibility study was conducted using 12 dogs (BB n = 6, grocery diet n = 6; mean BW = 12.0 ± 2.1 kg). Total fecal samples were collected from day 6 to day 10 for nutrient digestibility analysis. Protocols were approved by the facility’s Institutional Animal Care and Use Committee before the study. All data were analyzed using the Mixed Models procedure of SAS. Stool quality was not different (P &amp;gt; 0.05) between diet groups. Both diets were highly digestible without dietary effects (P &amp;gt; 0.05). All blood cell count and serum chemistry values were within the reference ranges. However, dogs fed the grocery diet had greater (P &amp;lt; 0.05) liver enzyme concentrations including alanine transaminase, alkaline phosphatase, and gamma-glutamyl transpeptidase, and greater (P &amp;lt; 0.05) monocyte counts compared with BB. Dogs had greater (P &amp;lt; 0.05) serum pancreatic polypeptide when fed BB. A lower dysbiosis index (less dysbiotic microbiome) was observed in dogs consuming BB. Relative abundances of 23 bacterial genera were altered (P &amp;lt; 0.05) by the diets, with greater abundances of Bifidobacterium and Megamonas and decreased abundance of Streptococcus observed in the BB group compared with the grocery diet group. These results suggest that premium dry dog food could potentially elicit a positive impact on blood parameters and GI health.

PSVIII-19 Saccharomyces Cerevisiae Fermentation Product Modulates Blood Cell Counts and Gut Immunity in Healthy Adult Cats

Abstract Dietary Saccharomyces cerevisiae fermentation product (SCFP) has been shown to modulate immune responses in dogs and livestock. Information about feeding SCFP to cats, however, is lacking. This study aimed to evaluate the effects of SCFP (TruMune, Cargill, Inc.) on immune indices including fecal IgA, serum oxidative stress markers, and toll-like receptor (TLR) responsiveness in healthy adult cats. Sixty-three cats (mean age = 6.3 ± 2.8 yr; mean BW = 4.4 ± 0.1 kg) were used in a randomized complete block design. All cats were fed a control kibble diet without SCFP (CON) during a 21-day adaptation period. Cats were randomly assigned to one of the three diets including CON, a dry diet containing 150 mg/kg BW SCFP (TRUL), and a dry diet containing 300 mg/kg BW SCFP (TRUH) and fed for 42 days. Fecal samples were collected on days 0, 21, and 42 for fecal IgA analysis. Serum samples were collected on days 0 and 42 for measurements of serum chemistry, complete blood count, and oxidative stress markers. Whole blood samples were collected on day 42 for TLR responsive evaluation. Protocols were approved by the facility’s Institutional Animal Care and Use committee before the study. Data were analyzed using R v.4.1.2. Differences P &amp;lt; 0.05 were considered significant and P &amp;lt; 0.10 as trends. All serum chemistry and blood cell count values were within the reference ranges, with serum chemistry not affected by SCFP. Absolute cell counts of eosinophils and neutrophils decreased linearly with SCFP dose (P &amp;lt; 0.001) while absolute cell counts of lymphocytes and monocytes increased linearly with SCFP dose (P &amp;lt; 0.01). TLR responsiveness was not altered (P &amp;gt; 0.05) by SCFP. A tendency (P = 0.08) of quadratic treatment dose response was noted for thiobarbituric acids from the thiobarbituric acid reactive substance assay, with cats fed TRUL having the greatest thiobarbituric acid values. Fecal IgA showed a quadratic treatment dose response on day 42 (P = 0.01), with cats fed TRUL having the lowest fecal IgA values. These results demonstrate that SCFP may affect immune outcomes including blood cell counts and fecal IgA in adult healthy cats.