Mineral and Skeletal Homeostasis Influence the Manner of Bone Loss in Metabolic Osteoporosis due to Calcium-Deprived Diet in Different Sites of Rat Vertebra and Femur

Abstract

Rats fed calcium-deprived diet develop osteoporosis due to enhanced bone resorption, secondary to parathyroid overactivity resulting from nutritional hypocalcemia. Therefore, rats provide a good experimental animal model for studying bone modelling alterations during biochemical osteoporosis. Three-month-old Sprague-Dawley male rats were divided into 4 groups: (1) baseline, (2) normal diet for 4 weeks, (3) calcium-deprived diet for 4 weeks, and (4) calcium-deprived diet for 4 weeks and concomitant administration of PTH (1-34) 40 µg/Kg/day. Histomorphometrical analyses were made on cortical and trabecular bone of lumbar vertebral body as well as of mid-diaphysis and distal metaphysis of femur. In all rats fed calcium-deprived diet, despite the reduction of trabecular number (due to the maintenance of mineral homeostasis), an intense activity of bone deposition occurs on the surface of the few remaining trabeculae (in answering to mechanical stresses and, consequently, to maintain the skeletal homeostasis). Different responses were detected in different sites of cortical bone, depending on their main function in answering mineral or skeletal homeostasis. This study represents the starting point for work-in-progress researches, with the aim of defining in detail timing and manners of evolution and recovery of biochemical osteoporosis.

Interplay among calcium diet content, PTH(1-34) treatment and balance of bone homeostases in rat model: the trabecular bone as keystone

“…For the exhaustive discussion of the present data it is to be underlined, as already above reported, that the observations here described must be interpreted together with those previously published [39].…”

“…As above mentioned, the results reported here, collected during diet restoration, will be compared with those concerning calcium-free diet already published [39]. Figure 1 shows the overall experimental conditions of the previous and the present studies, to understand better their meaning.…”

“…A previous study of ours, performed in rats fed calcium-free diet for one month [39], showed how, after the induction of metabolic osteopenia/osteoporosis, both the mineral and skeletal homeostasis influence the sites of bone loss: trabecular and/or cortical bone in axial and/or appendicular skeleton (i.e. lumbar vertebra and femur).…”

“…The amount of food intake by each rat was regularly checked, verifying the absence of significant differences in the feeding of each animal. Groups 1, 2, 3 and 4 have been previously analyzed and the results were reported in the paper by Ferretti and coworkers [39]. The following descriptions refer to groups 5 to 9.…”

“…The present study, concerning the normal diet restoration, is the second experimental step and all data here reported will be considered together with the previous ones [39] to fully understand the progress of recovery. The aim is to determine whether the normal diet restoration (after 1 month of calcium-free feeding), with/without PTH(1-34) administration, can influence amounts and deposition sites of the total bone mass, also depending on skeletal homeostasis.…”