Sub-cellular In-situ Characterization of Ferritin(iron) in a Rodent Model of Spinal Cord Injury

Abstract

Iron (Fe) is an essential metal involved in a wide spectrum of physiological functions. Sub-cellular characterization of the size, composition, and distribution of ferritin(iron) can provide valuable information on iron storage and transport in health and disease. In this study we employ magnetic force microscopy (MFM), transmission electron microscopy (TEM), and electron energy loss spectroscopy (EELS) to characterize differences in ferritin(iron) distribution and composition across injured and non-injured tissues by employing a rodent model of spinal cord injury (SCI). Our biophysical and ultrastructural analyses provide novel insights into iron distribution which are not obtained by routine biochemical stains. In particular, ferritin(iron) rich lysosomes revealed increased heterogeneity in MFM signal from tissues of SCI animals. Ultrastructural analysis using TEM elucidated that both cytosolic and lysosomal ferritin(iron) density was increased in the injured (spinal cord) and non-injured (spleen) tissues of SCI as compared to naïve animals. In-situ EELs analysis revealed that ferritin(iron) was primarily in Fe3+ oxidation state in both naïve and SCI animal tissues. The insights provided by this study and the approaches utilized here can be applied broadly to other systemic problems involving iron regulation or to understand the fate of exogenously delivered iron-oxide nanoparticles.

Detection of Hemosiderin-Laden Macrophages in Bronchoalveolar Lavage Fluid of COVID-19 Patients: Is Perls Stain a Potential Indicator of Oxidative Alveolar Damage?

“…A combined Perls-hematoxylin-eosin stain was also proposed to easily check the presence of ferric iron in tissue sections [13]. Moreover, an immunohistochemical technique can be used to detect the presence of ferritin in tissue samples with results equivalent to Perls stain [14]. Therefore, Perls stain may be used to identify excess iron deposits caused by oxidative damage mechanism in COVID-19 patients.…”

Indirect magnetic force microscopy

“…Applications of MFM have also extended to evaluate biological samples 12 such as ferritin proteins, 13,14 cells labeled with magnetic particles, 15 and magnetic (iron) deposits in bacteria 16,17 and in mammalian tissues. 18,19…”

Magnetic Force Microscopy of in a Polymer Matrix Embedded Single Magnetic Nanoparticles

“…For biomedical applications the investigation of hidden nanoparticles such as SPIONs embedded in tissues and the cellular uptake of SPIONs are of increasing interest. The evaluation of iron distribution in biological tissues is important for diagnosis and treatment of a variety of diseases . Blisset et al characterized the difference in ferritin distribution across injured and non‐injured tissues .…”

“…The evaluation of iron distribution in biological tissues is important for diagnosis and treatment of a variety of diseases . Blisset et al characterized the difference in ferritin distribution across injured and non‐injured tissues . Hautot et al demonstrated that the concentrations of magnetite are found to be significantly higher in Alzheimer's disease brain tissues …”

“…MFM study of the surface of SPION nanocomposites showed that the distribution of SPIONs in a matrix can create domains in the nanocomposite . The high potential of MFM for biological and medical applications has been shown, for example, by visualization the iron core of ferritin as well as by studying the cellular uptake of SPIONs . Wang et al mapped the uptake of SPIONs into tumor cells and determined the intracellular iron content and spatial distribution of the intracellular iron .…”