Effects of frozen storage temperature on the elasticity of tendons from a small murine model

Abstract

The basic mechanism of reinforcement in tendons addresses the transfer of stress, generated by the deforming proteoglycan (PG)-rich matrix, to the collagen fibrils. Regulating this mechanism involves the interactions of PGs on the fibril with those in the surrounding matrix and between PGs on adjacent fibrils. This understanding is key to establishing new insights on the biomechanics of tendon in various research domains. However, the experimental designs in many studies often involved long sample preparation time. To minimise biological degradation the tendons are usually stored by freezing. Here, we have investigated the effects of commonly used frozen storage temperatures on the mechanical properties of tendons from the tail of a murine model (C57BL6 mouse). Fresh (unfrozen) and thawed samples, frozen at temperatures of 2208C and 2808C, respectively, were stretched to rupture. Freezing at 2208C revealed no effect on the maximum stress (s), stiffness ( E), the corresponding strain (e) at s and strain energy densities up to e (u) and from e until complete rupture (u p ). On the other hand, freezing at 2808C led to higher s, E and u; e and u p were unaffected. The results implicate changes in the long-range order of radially packed collagen molecules in fibrils, resulting in fibril rupture at higher stresses, and changes to the composition of extrafibrillar matrix, resulting in an increase in the interaction energy between fibrils via collagen-bound PGs.Keywords: frozen storage temperature, strength, stiffness, strain energy, collagen Implications Ultra-low storage temperature alters (i) the long-range order of collagen packing in fibrils, resulting in fibril rupture at higher stresses, and (ii) the composition of extra-fibrillar matrix, resulting in an increase in the interaction energy between fibrils via collagen-bound proteoglycans. Consequently, the tissue strength, stiffness and fracture toughness increase.

Age-related distensibility and histology of the ascending aorta in elderly patients with acute aortic dissection

“…However, a better control of the storage time for the specimens would suppress the effects of freezing on the distensibility (Langerak et al, 2001;Goh et al, 2010;Sugita and Matsumoto, 2013).…”

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“…Rat tails were removed and stored at -20°C until the day of the experiment, which has been shown not to affect tendon mechanics [50]. Individual rat tail tendon fascicles (RTTFs) were gently extracted from the middle region of the tail, subsequently cut into two equal parts and assigned either to the glycated group or to the non-glycated control for paired analysis.…”

Resolving the viscoelasticity and anisotropy dependence of the mechanical properties of skin from a porcine model

“…For simplicity, the nominal stress was identified with the ratio of the instantaneous force to the initial (mean) cross-sectional area of the specimen; the strain was identified with the ratio of the instantaneous change in displacement to the initial gauge length. To minimise biological degradation prior to testing (Goh et al 2010), specimens were preserved in phosphatebuffered saline (PBS) at a temperature of 4 • C until testing. All specimens were tested at room temperature within 48 h after slaughter.…”