Animal model of simulated microgravity: a comparative study of hindlimb unloading via tail versus pelvic suspension.

Parimal Chowdhury,Gabrielle Harris,Michael E Soulsby,Ashley Long,Maxim Dobretsov

doi:10.1002/phy2.12

Parimal Chowdhury, Gabrielle Harris + Show 3 more

Open Access

https://doi.org/10.1002/phy2.12

Copy DOI

Abstract

The aim of this study was to compare physiological effects of hindlimb suspension (HLS) in tail- and pelvic-HLS rat models to determine if severe stretch in the tail-HLS rats lumbosacral skeleton may contribute to the changes traditionally attributed to simulated microgravity and musculoskeletal disuse in the tail-HLS model. Adult male Sprague-Dawley rats divided into suspended and control-nonsuspended groups were subjected to two separate methods of suspension and maintained with regular food and water for 2 weeks. Body weights, food and water consumption, soleus muscle weight, tibial bone mineral density, random plasma insulin, and hindlimb pain on pressure threshold (PPT) were measured. X-ray analysis demonstrated severe lordosis in tail- but not pelvic-HLS animals. However, growth retardation, food consumption, and soleus muscle weight and tibial bone density (decreased relative to control) did not differ between two HLS models. Furthermore, HLS rats developed similar levels of insulinopenia and mechanical hyperalgesia (decreased PPT) in both tail- and pelvic-HLS groups. In the rat-to-rat comparisons, the growth retardation and the decreased PPT observed in HLS-rats was most associated with insulinopenia. In conclusion, these data suggest that HLS results in mild prediabetic state with some signs of pressure hyperalgesia, but lumbosacral skeleton stretch plays little role, if any, in these pathological changes.

Highlights

Hindlimb suspension (HLS) of rodents by the tail is a well-established approach to create a ground-based model of microgravity and musculoskeletal disuse that mimics many of the physiological changes associated with space flight, as well as with prolonged bed rest (Morey-Holton and Globus 2002; Morey-Holton et al 2005; Carpenter et al 2010)
Physiological Reports published by John Wiley & Sons Ltd on behalf of the American Physiological Society and The Physiological Society
We provided the evidence of pressure hyperalgesia developing in tail-hindlimb suspension (HLS) rats, as well as an indication that this could be associated with insulinopenia (Chowdhury et al 2011)

Summary

Introduction

Hindlimb suspension (HLS) of rodents by the tail is a well-established approach to create a ground-based model of microgravity and musculoskeletal disuse that mimics many of the physiological changes associated with space flight, as well as with prolonged bed rest (Morey-Holton and Globus 2002; Morey-Holton et al 2005; Carpenter et al 2010). Within 1–2 weeks of tail-HLS, rats have been shown to develop insulinopenia (Nichols et al 2008), insulin resistance and compensatory hyperinsulinemia (Stuart et al 1993), or an increase in skeletal muscle insulin sensitivity (Henriksen et al 1986; O’keefe et al 2004) Controversial, these observations warrant further exploration, as they may be critical for explaining limb disuse associated with bone loss as well as muscle atrophy

Objectives

Methods

Results

Conclusion