Behavioral Assessment of Stress Compensation in Minipigs Transgenic for the Huntington Gene Using Cortisol Levels: A Proof-of-Concept Study.

BACKGROUND: Huntington's disease (HD) is an autosomal-dominant, progressive neurodegenerative disorder with motor, cognitive, behavioral and metabolic symptoms. HD patients exhibit an altered response to stress which is reflected in changes of cortisol levels. Large animal models of HD such as the Libechov minipig are currently explored in preclinical studies to improve translational reliability and assessing behavior is of interest. OBJECTIVE: This study aimed to investigate whether cortisol metabolism and response to stress are changed in minipigs transgenic for the Huntington gene (tgHD) compared to wildtype (wt) animals suggesting that cortisol may be used as a marker for stress in minipigs. METHODS: Thirty-two Libechov minipigs (14 tgHD and 18 wt) were tested before, during and after a stressor, i.e., a hoof trimming procedure, was applied at baseline and after one year. A total of six saliva samples were collected at each assessment and cortisol was measured. In addition, body temperature and respiratory rate were assessed at three pre-determined points during each hoof trimming procedure. RESULTS: All minipigs showed a rise of cortisol in response to the hoof trimming stressor similarly to cortisol changes induced by stress observed in humans. No relevant differences were detected between tgHD and wt minipigs. CONCLUSION: Cortisol testing for the assessment of stress compensation, e.g., during hoof trimming, is feasible and well tolerated in wt and tgHD minipigs. To elucidate the time profile of cortisol responses to stressors further studies with assessments at multiple time points and exploration of the diurnal profiles of cortisol in minipigs are recommended.

Behavioral testing of minipigs transgenic for the Huntington gene-A three-year observational study.

BACKGROUND: Large animal models of Huntington's disease (HD) may increase the reliability of translating preclinical findings to humans. Long live expectancy offers opportunities particularly for disease modifying approaches, but also challenges. The transgenic (tg) HD minipig model assessed in this study exhibits a high genetic homology with humans, similar body weight, and comparable brain structures. To test long-term safety, tolerability, and efficacy of novel therapeutic approaches in this model reliable assessments applicable longitudinally for several years are warranted for all phenotypical domains relevant in HD. OBJECTIVE: To investigate whether the tests proposed assessing motor, cognitive and behavioral domains can be applied repetitively over a 3-year period in minipigs with acceptable variability or learning effects and whether tgHD minipigs reveal changes in these domains compared to wildtype (wt) minipigs suggesting the development of an HD phenotype. METHODS: A cohort of 14 tgHD and 18 wt minipigs was followed for three years. Tests applied every six months included a tongue coordination and hurdle test for the motor domain, a color discrimination test for cognition, and a dominance test for assessing behavior. Statistical analyses were performed using repeated ANOVA for longitudinal group comparisons and Wilcoxon-tests for intra-visit differences between tgHD and wt minipigs. RESULTS: All tests applied demonstrated feasibility, acceptable variance and good consistency during the three-year period. No significant differences between tgHD and wt minipigs were detected suggesting lack of a phenotype before the age of four years. CONCLUSIONS: The assessment battery presented offers measures in all domains relevant for HD and can be applied in long-term phenotyping studies with tgHD minipigs. The observation of this cohort should be continued to explore the timeline of phenotype development and provide information for future interventional studies.