Evaluation of morphological parameters of bone formation in Sprague–Dawley rats of different ages by in vivo fluorochrome labeling

Abstract

Abstract: Our study focuses on the morphological parameters of bone growth and bone formation in Sprague–Dawley (SD) rats of different ages, using fluorochrome labeling in vivo. We concluded that bone longitudinal growth rate (LGR) and bone mineral apposition rate (MAR) were significantly increased in both the 1- and 3-month-old rats compared with the 6- and 14-month-old rats, and that of the parameters were significantly decreased in both the 6- and 14-month-old rats. Meanwhile, bone formation rate (BFR) and percent labeled perimeter (%L.Pm) peaked in 3-month-old rats, and were followed by remarkable decrease with aging. In the present study, static parameters including percent trabecular area (%Tb.Ar), trabecular thickness (Tb.Th) and trabecular number (Tb.N), contrary to previous reports, progressively increased, whereas trabecular separation (Tb.Sp) reduced with increasing age. Furthermore, bone mass increased for 14-month-old rats due to the significantly decreased bone turnover rate.