Individual variability in tail tendon fiber break time in three age cohorts of different strains of mice.

Individual variability in mouse tail tendon fiber denaturation in urea was investigated. Differences in break time between fibers within tendons and between tendon groups were examined. Mean break times for each strain increased with age with the shorter-lived DBA/2 mice exhibiting higher break times within age cohorts than the C57BL/6 animals. Fibers from the two ventral tendon groups had consistently higher break times than those from the two dorsal groups, implying differential rates of collagen maturation between these two areas within the tail. Histological examination revealed conspicuous morphological dorsal/ventral differences in tendon number, proximity to a major blood vessel, and the amount of surrounding muscle tissue. These findings have methodological and experimental design implications for the use of tail tendon break time (TTBT) as a biomarker of aging. Furthermore, they suggest possible physiological mechanisms for differential rates of collagen aging.