Abstract TP261: Spontaneous Strokes In Sickle Cell Transgenic Mice Captured Ex Vivo With Magnetic Resonance Imaging
With 11% of children with sickle cell disease (SCD) having strokes, many as early as 1 to 5 years old, the underlying mechanisms are still unclear, and it is still unknown why this subpopulation has greater risk. More will suffer from subclinical silent strokes that cause cognitive rather than physical impairments. Sickling of red blood cells due to a point mutation in hemoglobin induces chronic inflammation and vascular remodeling in SCD. We have previously shown that powerful proteases, cathepsins, are activated in SCD to promote vascular remodeling that could lead to stroke. However, a mouse model of detectable sickle cell stroke is required to study mechanism and intervention strategies. Here, we used Townes sickle transgenic mouse, with murine hemoglobin knocked out and replaced with human, sickle hemoglobin, to test the hypothesis that sickle transgenic mice have MRI detectable strokes and increased cathepsin proteolytic activity. Three mice homozygous for sickle mutation (SS) and 6 heterozygous littermate controls (AS) were perfused at 8 weeks. Brains were isolated, embedded in gadolinium-agarose, and scanned using a Bruker 9.4 Tesla magnet with a T2-weighted protocol (TE = 13.4 ms. TR= 10,000, 512 x 512 x 70). Of the 3 SS mice, 2 had abnormalities suggestive of stroke (Figure 1, red arrows), with none noted in the AS controls. Separately, immunohistochemistry with anti-cathepsin K antibody indicated a gene dosing effect of sickle allele on cathepsin K expression (SS>AS>AA), verified in aorta homogenates by multiplex cathepsin zymography assays (n=3, p<.05). To conclude, we have identified strokes in sickle transgenic mice with T2 images. These mouse stroke scans, without occlusive or chemical intervention, will be an improved model to test spontaneous stroke interventions specific to sickle cell disease including targeting upregulated cathepsins.
- © 2012 by American Heart Association, Inc.