Different relationships between cortical bone design and bone tissue mass and quality (mineralization) in limb bones of 3 anuran species, in relation with the mechanostat control of bone structure

MIRIAM CORINA VERA; FERRETI JOSÉ LUIS; ABDALA VIRGINIA; COINTRY GUSTAVO

Congreso; ASBMR 2020 Annual Meeting; 2020

American Society for Bone and Mineral Research

Bone mechanostat is a feedback mechanism that regulates bone structural stiffness by spatially orienting bone modeling accordingly with the strains induced by mechanical usage. The mechanostat efficiency to optimize the diaphyseal design (CSMIs) can be evaluated as a function of either the availability or the vBMD of cortical tissue  in negative ?distribution/ quality? (d/q) curves, or how well bone mass (BMC) is utilized to optimize diaphyseal design (CSMI) in positive ?distribution/mass? (d/m) curves, respectively. Anurans? long bones offer a suitable model to test the efficiency of the mechanostat that way because of the wide variety of mechanical challenges derived from their different locomotion modes and habitats. We aimed to show that both d/q and d/m relationships would describe differences in the efficiency of the bone mechanostat under different mechanical loads, and the curves would show similar patterns between jumper and swimmer species and different patterns between these and walker frogs. To test it, we scanned by pQCT the femur and tibia-fibula of an arboreal-walker (Ar-W, 5 specimens), an arboreal-jumper (Ar-J, 6 specimens), and an aquatic-swimmer (Aq-S, 5 specimens) frog species at 9 sites placed at every 10% of their length.The d/q relationships showed a highly significant adjustment to common curves for Ar-J and Aq-S (r=0.85, p<0.001), with Aq-S data shifting to the upper-left zone of the graph, showing higher CSMI and lower cortical vBMD values than Ar-J. In contrast, the walking frogs plotted in a different region of the graph, especially in the case of data from mid diaphysis, both in femur and tibia-fibula. This could be explained by the slow movement of the Ar-W frogs compared to the quick and powerful movement of Ar-J and Aq-S species.The d/m associations confirmed that idea. The Ar-J and Aq-S data were significantly adjusted to common correlation curves (r=0.82, p <0.001), suggesting that both movements respond to a common pattern, although its location in different zones would indicate some habitat influence. In contrast, the Ar-W data correlated significantly (r=0.80, p <0.001) at a different height and with a different slope (ANCOVA p<0.001) with respect to those of Ar-J and Aq-S.These findings show that the movements of the jumping and swimming frogs present common patterns, involving higher mechanical demands than those followed by walker frog.