Quantitative high-resolution microradiographic imaging of amyloid deposits in a novel murine model of AA amyloidosis

Abstract

The mouse model of experimentally induced systemic AA amyloidosis is long established, well validated, and closely analogous to the human form of this disease. However, the induction of amyloid by experimental inflammation is unpredictable, inconsistent, and difficult to modulate. We have previously shown that murine AA amyloid deposits can be imaged using iodine-123 labeled SAP scintigraphy and report here substantial refinements in both the imaging technology and the mouse model itself. In this regard, we have generated a novel prototype of AA amyloid in which mice expressing the human interleukin 6 gene, when given amyloid enhancing factor, develop extensive and progressive systemic AA deposition without an inflammatory stimulus, i.e., a transgenic rapidly inducible amyloid disease (TRIAD) mouse. Additionally, we have constructed high-resolution micro single photon emission computed tomography (SPECT)/computed tomography (CT) instrumentation that provides images revealing the precise anatomic location of amyloid deposits labeled by radioiodinated serum amyloid P component (SAP). Based on reconstructed microSPECT/CT images, as well as autoradiographic, isotope biodistribution, and quantitative histochemical analyses, the (125)I-labeled SAP tracer bound specifically to hepatic and splenic amyloid in the TRIAD animals. The ability to discern radiographically the extent of amyloid burden in the TRIAD model provides a unique opportunity to evaluate the therapeutic efficacy of pharmacologic compounds designed to inhibit fibril formation or effect amyloid resolution.

Dynamic PET and SPECT imaging with radioiodinated, amyloid-reactive peptide p5 in mice: A positive role for peptide dehalogenation

“…Briefly, the constitutive expression of the pro-inflammatory cytokine human interleukin 6 (IL-6) in these mice in combination with the intravenous (IV) administration of ~10 μg of amyloid enhancing factor (AEF) at 8 weeks of age caused rapid induction of amyloid deposition by 3 weeks post-AEF injection [31]. Mice used in these experiments were 6 weeks post induction.…”

“…To confirm the presence of amyloid, consecutive tissue sections from those used for microautoradiography were stained with freshly prepared alkaline Congo red [31]. The tissues were examined using a Leica DMR using epifluorescent illumination and a rhodamine filter.…”

Diagnosis of Systemic Amyloid Diseases

“…The use of radiography to discern the extent of amyloid burden was beneficial for quantitating the total-body burden of amyloid and for evaluation of the therapeutic efficacy of pharmacologic compounds [57].…”

Approximate Volumetric System Models for MicroSPECT

“…This voxel is then added to a queue. Subvoxel cone containment is tested for each voxel on the queue using (2). Voxels that fail the test are discarded.…”

“…A MICROSPECT system has been developed for the purpose of studying the progression and regression of systemic, inflammation-associated (AA) and localized, primary (AL) amyloidosis in murine models of these diseases [1], [2]. The system is equipped with two detector heads, each consisting of a crossed-wire, multi-anode photomultiplier tube coupled to a pixellated NaI(Tl) crystal array [3].…”