Effect Of Housing On Stress-Related Parameters In NHPs

By T Rogers, V Bunker, B Darimont, R Burke, A Tenney, K Kraszewski, and S Nechev

In preclinical studies, minimizing animal stress is essential for both ethical reasons and to reduce its impact on toxicologic parameters. Stress is known to influence in-life measures such as body weight and food consumption, as well as clinical pathology markers, organ weight, and histopathology. Myostatin (MSTN), a TGF-β superfamily member and negative regulator of muscle deposition, has been linked to psychological stress in mice, where increased MSTN levels correlate with reduced muscle mass.

To explore this relationship in non-human primates, MSTN plasma levels were measured in 15 young adult male cynomolgus monkeys over two weeks in both standard four-pack housing (pairs and trios) and after transitioning to gang housing enclosures (three animals per cage) that meet or exceed EU standards. MSTN levels in standard housing ranged from approximately 3,900 to 7,100 pg/mL, whereas in gang housing, levels decreased to 1,700–5,000 pg/mL. Individual animals showed a 10–32% drop in MSTN levels, suggesting reduced stress in the gang housing setting. While the significance of this change in MSTN levels in monkeys remains unclear, potential correlations with other stress markers, including body weight, clinical pathology, and behavioral evaluations, were examined. This study aimed to assess the benefits of gang versus standard housing to better understand stress manifestations in laboratory environments and their relevance to toxicology study outcomes.