Endogenous iron biomineralization in the mouse spleen of metabolic diseases.

As the most abundant essential trace element in our human bodies, iron plays essential roles in multiple physiological and pathological conditions, including oxygen transport, cancer, diabetes, Alzheimer's and Parkinson's diseases. Although it has been shown that iron can form particles in some bacteria, migrating birds and fish, whether iron biomineralization can also occur in mammals is still debated. Here we demonstrate that iron metabolism abnormalities in diseased mice can directly lead to endogenous iron biomineralization and particle formation in the spleen. Excessive iron accumulation leads to endogenous particle formation with an averaged size of ∼800 nm. In the spleens of severely diabetic mice, they accumulate in the red pulp region, where the red blood cells are recycled. This directly changes the magnetic property of the spleens and results in spleen damage in a gradient high magnetic field. Therefore, our findings not only demonstrate the existence of endogenous iron biomineralization in metabolic diseases, but also set up a direct link among iron accumulation, magnetic property and magnetic responses of animal organs, which may also be applied in other iron metabolism-related diseases including cancer and Alzheimer's disease.