The development of inter-strain variation in cortical and trabecular traits during growth of the mouse lumbar vertebral body.

Abstract

Age-related changes in cortical and trabecular traits have been well studied; however, very little is known about how these bone tissues co-develop from day 1 of postnatal growth to establish functional structures by adulthood. In this study, we aimed to establish how cortical and trabecular tissues within the lumbar vertebral body change during growth for three inbred mouse strains that express wide variation in adult bone structure and function. Bone traits were quantified for lumbar vertebral bodies of female A/J, C57BL/6J (B6), and C3H/HeJ (C3H) inbred mouse strains from 1 to 105days of age (n = 6-10 mice/age/strain). Inter-strain differences in external bone size were observed as early as 1day of age. Reciprocal and rapid changes in the trabecular bone volume fraction and alignment in the direction of axial compression were observed by 7days of age. Importantly, the inter-strain difference in adult trabecular bone volume fraction was established by 7days of age. Early variation in external bone size and trabecular architecture was followed by progressive increases in cortical area between 28 and 105days of age, with the greatest increases in cortical area seen in the mouse strain with the lowest trabecular mass. Establishing the temporal changes in bone morphology for three inbred mouse strains revealed that genetic variation in adult trabecular traits were established early in postnatal development. Early variation in trabecular architecture preceded strain-specific increases in cortical area and changes in cortical thickness. This study established the sequence of how cortical and trabecular traits co-develop during growth, which is important for identifying critical early ages to further focus on intervention studies that optimize adult bone strength.