Amelioration of Cd-induced bone deterioration by orally administered calcium phosphate

Cadmium (Cd) is a heavy metal that accumulates in the body, primarily through daily grain intake, and has a high affinity for bone, leading to skeletal diseases such as osteomalacia and fractures. Hydroxyapatite (HAp), a major bone mineral component, is highly pH-sensitive and is known to incorporate Cd, as observed in studies of Itai-itai disease. Based on these findings, we hypothesized that HAp could serve as an effective oral detoxification material for heavy metals. This study investigated the efficacy of orally administered HAp in inhibiting Cd-induced changes in bone physical and chemical properties, comparing its effects to those of activated charcoal (AC), a common detoxifying agent. Six-week-old male ICR mice were exposed to cadmium via drinking water containing CdCl2 and subsequently given diets containing either HAp or AC for four weeks. Three-point bending tests, micro-CT analysis, and histological observations of the femurs demonstrated that mice receiving HAp exhibited improved mechanical strength and enhanced bone quality protection compared to the control and other Cd-treated groups. Activated charcoal also contributed to bone quality improvement at low concentrations, but its effect diminished at high concentrations. These results suggest that the oral administration of HAp may be a promising therapeutic strategy for suppressing cadmium-induced osteomalacia.