Abstract
The deep fascia of the vertebrate body comprises a biomechanically unique connective cell and tissue layer with integrative functions to support global and regional strain, tension, and even muscle force during motion and performance control. However, limited information is available on deep fascia in relation to bone in disuse. We used rat hindlimb unloading as a model of disuse (21 days of hindlimb unloading) to study biomechanical property as well as cell and tissue changes to deep fascia and bone unloading. Rats were randomly divided into three groups (n = 8, each): hindlimb unloading (HU), HU + vibration (HUV), and cage-control (CON). The HUV group received local vibration applied to the plantar of both hind paws. Micro-computed tomography analyzed decreased bone mineral density (BMD) of vertebra, tibia, and femur in HU vs. CON. Biomechanical parameters (elastic modulus, max stress, yield stress) of spinal and crural fascia in HU were always increased vs. CON. Vibration in HUV only counteracted HU-induced tibia bone loss and crural fascia mechanical changes but failed to show comparable changes in the vertebra and spinal fascia on lumbar back. Tissue and cell morphometry (size and cell nuclear density), immunomarker intensity levels of anti-collagen-I and III, probed on fascia cryosections well correlated with biomechanical changes suggesting crural fascia a prime target for plantar vibration mechano-stimulation in the HU rat. We conclude that the regular biomechanical characteristics as well as tissue and cell properties in crural fascia and quality of tibia bone (BMD) were preserved by local plantar vibration in disuse suggesting common mechanisms in fascia and bone adaptation to local mechanovibration stimulation following hind limb unloading in the HUV rat.
Highlights
Research from space and ground based analog studies showed that microgravity and chronic disuse induced unloading causes bone loss with muscle atrophy (Vico et al, 2000; Pavy-Le Traon et al, 2007)
A moderate loss in bone mineral density (BMD) was found in L3 vertebrae (−9.93%, non-significant), and to a larger extent in both femur (−49.95%) and tibia (−69.18%) in hindlimb unloading (HU) rats compared to CON rats (Figure 2)
Plantar vibration stimulation in the HU rat was able (i) to maintain tibial BMD not seen in vertebrae spine and (ii) to prevent increased crural fascia stiffness induced by disuse
Summary
Research from space and ground based analog studies (bed rest) showed that microgravity and chronic disuse induced unloading causes bone loss with muscle atrophy (Vico et al, 2000; Pavy-Le Traon et al, 2007). Vibration exercise as countermeasure showed promising outcome in the structural and functional preservation addressing calf muscle and bone outcome in otherwise healthy male long-term bed rest participants (Blottner et al, 2006; Rittweger et al, 2010). We tested if local vibration applied to more appropriate anatomical sites such as the plantar region of the hind paw might be an alternative strategy to more efficiently prevent loss in bone mineral density and maladaptation to the associated myofascial tissue in a rat model of disuse
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