Effect of cadmium on bone tissue in growing animals

Accumulation of cadmium (Cd), an extremely toxic metal, can cause renal failure, decreased vitamin D synthesis, and consequently osteoporosis. The aim of this work was to evaluate the effect of Cd on two types of bone in growing Wistar rats. Sixteen 21-day-old male Wistar rats were assigned to one of two groups. The Cd group subcutaneously received 0.5mg/kg of CdCl2 5 times weekly for 3 months. The control group similarly received bidistilled water. Following euthanasia, the mandibles and tibiae were resected, fixed, decalcified and processed histologically to obtain sections for H&E and tartrate-resistant acid phosphatase (TRAP) staining. Photomicrographs were used to determine bone volume (BV/TV%), total growth cartilage width (GPC.Wi) hypertrophic cartilage width (HpZ.Wi), percentage of yellow bone marrow (%YBM), megakaryocyte number (N.Mks/mm(2)), and TRAP+osteoclast number (N.TRAP+Ocl/mm(2)). Results were statistically analyzed using Student's t test. Cd exposed animals showed a significant decrease in subchondral bone volume and a significant increase in TRAP+ osteoclast number and percentage of yellow bone marrow in the tibia, and an increase in megakaryocyte number in mandibular interradicular bone. No significant differences were observed in the remaining parameters. The results obtained with this experimental design show that Cd would seemingly have a different effect on subchondral and interradicular bone. The decrease in bone volume and increase in tibial yellow bone marrow suggest that cadmium inhibits differentiation of mesenchymal cells to osteoblasts, favoring differentiation into adipocytes. The different effects of Cd on interradicular bone might be due to the protective effect of the mastication forces.