Long-Term Exposure to Low-Dose Lead Induced Deterioration in Bone Microstructure of Male Mice.

The aim of this study was to investigate the long-term effects of low-dose lead exposure on bone microstructure in mice. Ten SPF 12-week-old male C57BL/6J mice were randomly divided into two groups: control (deionized water) and lead exposure (150 ppm of lead acetate in drinking water). After 24 weeks treatment, mice were weighed and the left femurs were collected and stored at - 80 °C. The right femurs of the mice were scanned by Micro-CT for three-dimensional reconstruction, and bone mineral density, bone volume fraction, trabeculae thickness, trabeculae number, and trabeculae separation were measured. The right tibia was collected to investigate histopathological changes in H&E-stained sections. The gene expression of osteoprotegerin (OPG), RANKL, and runt-related transcription factor 2 (Runx2) was determined using real-time PCR. The bone density of femoral cancellous bone and the number of cancellous bone trabeculae in the lead exposure group were both significantly decreased compared with the control group. Bone marrow stromal cell numbers were decreased following lead administration, and lipid droplet vacuoles were observed in the lead group. Levels of OPG were significantly decreased in the lead group, and lead also inhibited the expression of Runx2 compared with the control group. Long-term exposure to low doses of lead can cause bone damage without inducing other obvious symptoms through decreasing bone density and the number of cancellous bone trabeculae, further suppressing bone formation. It suggests that lead may exacerbate bone loss and osteoporosis, especially in the elderly.