Hypodynamia Alters Bone Quality and Trabecular Microarchitecture

Abstract

Disuse induces a rapid bone loss in humans and animals; hypodynamia/sedentarity is now recognized as a risk factor for osteoporosis. Hypodynamia also decreases bone mass but its effects are largely unknown and only few animal models have been described. Hypodynamic chicken is recognized as a suitable model of bone loss but the effects on the quality have not been fully explored. We have used ten chickens bred in a large enclosure (FREE group); ten others were confined in small cages with little space to move around (HYPO group). They were sacrificed at 53 days and femurs were evaluated by microcomputed tomography (microCT) and nanoindentation. Sections (4 µm thick) were analyzed by Fourier Transform InfraRed Microspectroscopy (FTIR) to see the effects on mineralization and collagen and quantitative backscattered electron imaging (qBEI) to image the mineral of the bone matrix. Trabecular bone volume and microarchitecture were significantly altered in the HYPO group. FTIR showed a significant reduction of the mineral-to-matrix ratio in the HYPO group associated with an increase in the carbonate content and an increase in crystallinity (calculated as the area ratio of subbands located at 1020 and 1030 cm) indicating a poor quality of the mineral. Collagen maturity (calculated as the area ratio of subbands located at 1660 and 1690 cm) was significantly reduced in the HYPO group. Reduced biomechanical properties were observed at the tissue level. Confined chicken represents a new model for the study of hypodynamia because bone changes are not created by a surgical lesion or a traumatic method. Animals have a reduced bone mass and present with an altered bone matrix quality which is less mineralized and whose collagen contains less crosslinks than in control chicken.

Influence of physical activity on tibial bone material properties in laying hens

“…Prolonged immobility in cage hens increases bone resorption whereas increased physical activity (as in aviary birds) stimulate bone formation and remodeling. These results are comparable with other studies using laying hens and broiler chickens as animal models and which show the effects immobility or physical activity restriction on bone growth/ quality (Bassey 1995;Mosekilde et al, 1994;Bell et al, 1988;Shipov et al, 2010;Aguado et al, 2015;2017). Besides changes in the amount of bone for different levels of physical activity, changes in bone material properties could have also influenced bone breaking strength.…”

Efficacy of targeting bone-specific GIP receptor in ovariectomy-induced bone loss

“…Blocks were polished to a 1 µm finish with diamond particles (Struers, France) and subjected to rehydration in saline 24 h prior to nanoindentation testing. Twelve indentations, at distance from canals, osteocyte lacunae and/or microcracks were randomly positioned in cortical bone with a NHT-TTX system (Anton Paar, Les Ulis, France) as previously detailed (Aguado et al 2017). At maximum load, a holding period of 15 s was applied to avoid creeping of the bone material.…”

A case of bone fracture with callus on the right femur of a chicken (Gallus gallus domesticus, L. 1758) from the ancient site of Dharih, Jordan

“…The bone has a trabecular aspect, almost spongy and similar to that observed in the consolidation callus. The modification of the bone microarchitecture is related to the absence of mechanical stresses (Aguado, 2015;Aguado et al, 2017;Libouban, 2015;Whitehead, 2004a;Whitehead and Fleming, 2000) induced by loss of support due to pain and a change in vascularization, the phenomenon of bone healing.…”