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Tahimic CGT, Paul AM, Schreurs AS, Torres SM, Rubinstein L, Steczina S, Lowe M, Bhattacharya S, Alwood JS, Ronca AE, Globus RK. Influence of Social Isolation During Prolonged Simulated Weightlessness by Hindlimb Unloading. Front Physiol 2019; 10:1147. [PMID: 31572207 PMCID: PMC6753329 DOI: 10.3389/fphys.2019.01147] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2019] [Accepted: 08/22/2019] [Indexed: 12/15/2022] Open
Abstract
The hindlimb unloading (HU) model has been used extensively to simulate the cephalad fluid shift and musculoskeletal disuse observed in spaceflight with its application expanding to study immune, cardiovascular and central nervous system responses, among others. Most HU studies are performed with singly housed animals, although social isolation also can substantially impact behavior and physiology, and therefore may confound HU experimental results. Other HU variants that allow for paired housing have been developed although no systematic assessment has been made to understand the effects of social isolation on HU outcomes. Hence, we aimed to determine the contribution of social isolation to tissue responses to HU. To accomplish this, we developed a refinement to the traditional NASA Ames single housing HU system to accommodate social housing in pairs, retaining desirable features of the original design. We conducted a 30-day HU experiment with adult, female mice that were either singly or socially housed. HU animals in both single and social housing displayed expected musculoskeletal deficits versus housing matched, normally loaded (NL) controls. However, select immune and hypothalamic-pituitary-adrenal (HPA) axis responses were differentially impacted by the HU social environment relative to matched NL controls. HU led to a reduction in % CD4+ T cells in singly housed, but not in socially housed mice. Unexpectedly, HU increased adrenal gland mass in socially housed but not singly housed mice, while social isolation increased adrenal gland mass in NL controls. HU also led to elevated plasma corticosterone levels at day 30 in both singly and socially housed mice. Thus, musculoskeletal responses to simulated weightlessness are similar regardless of social environment with a few differences in adrenal and immune responses. Our findings show that combined stressors can mask, not only exacerbate, select responses to HU. These findings further expand the utility of the HU model for studying possible combined effects of spaceflight stressors.
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Affiliation(s)
- Candice G T Tahimic
- Space Biosciences Division, NASA Ames Research Center, Moffett Field, CA, United States.,KBR, Houston, TX, United States
| | - Amber M Paul
- Space Biosciences Division, NASA Ames Research Center, Moffett Field, CA, United States.,Universities Space Research Association, Columbia, MD, United States
| | - Ann-Sofie Schreurs
- Space Biosciences Division, NASA Ames Research Center, Moffett Field, CA, United States.,KBR, Houston, TX, United States
| | - Samantha M Torres
- Space Biosciences Division, NASA Ames Research Center, Moffett Field, CA, United States.,Blue Marble Space Institute of Science, Seattle, WA, United States
| | - Linda Rubinstein
- Space Biosciences Division, NASA Ames Research Center, Moffett Field, CA, United States.,Universities Space Research Association, Columbia, MD, United States
| | - Sonette Steczina
- Space Biosciences Division, NASA Ames Research Center, Moffett Field, CA, United States.,Blue Marble Space Institute of Science, Seattle, WA, United States
| | - Moniece Lowe
- Space Biosciences Division, NASA Ames Research Center, Moffett Field, CA, United States.,Blue Marble Space Institute of Science, Seattle, WA, United States
| | - Sharmila Bhattacharya
- Space Biosciences Division, NASA Ames Research Center, Moffett Field, CA, United States
| | - Joshua S Alwood
- Space Biosciences Division, NASA Ames Research Center, Moffett Field, CA, United States
| | - April E Ronca
- Space Biosciences Division, NASA Ames Research Center, Moffett Field, CA, United States.,Department of Obstetrics and Gynecology, Wake Forest School of Medicine, Winston-Salem, NC, United States
| | - Ruth K Globus
- Space Biosciences Division, NASA Ames Research Center, Moffett Field, CA, United States
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