Comparative study of metallic biomaterials toxicity: a histochemical and immunohistochemical demonstration in mouse spleen

Metallic biomaterials available for orthopaedic purposes become essential to perform important physical activities, due to their low cost and excellent mechanical properties. In addition, they are frequently used in dentistry. However, corrosion phenomena of such devices are the main problems resulting in subsequent spreading of the elements through the whole body via lymph and blood. The spleen is the most important lymphoid organ and the only one included in the blood circulation. Thus, the aim of this study was to evaluate the short-term effects on spleen tissues of heavy metals released from stainless steel and Cr-Co-Mo alloys, as well as from titanium, at histochemical and immunohistochemical levels. For this purpose, metallic suspensions were obtained by electrochemical dissolution of the mentioned biomaterials: stainless steel (Fe 490 mg/L, Cr 224 mg/L, Ni 150 mg/L), Cr-Co-Mo (Cr 200 mg/L, Co 375 mg/L), and titanium (400 mg/L). Then 0.5 mL of each solution was subcutaneously administered to male Charles River mice each 72 hours during 30 days. Cryostat sections of the spleen from all groups were submitted to routine staining with haematoxylin/eosin, peroxidase detection by 3-3′ diaminobenzidine (DAB), and alkaline phosphatase anti-alkaline phosphatase (APAAP) for lymphocyte detection. Several pronounced alterations were found in the spleen architecture, as manifested by irregular features within the capsule and medulla, namely depletion of T4 and B cells. Altogether these results suggest toxic alterations within the spleen induced by some of the metallic elements, indicating that the immune system may be hampered and so interfering in the body mechanisms of defence.