In Vivo Near-Infrared Fluorescence Imaging of Matrix Metalloproteinase Activity after Cerebral Ischemia

Abstract

Matrix metalloproteinases (MMPs) have been implicated in the pathophysiology of cerebral ischemia. In this study, we explored whether MMP activity can be visualized by noninvasive nearinfrared fluorescence (NIRF) imaging using an MMP-activatable probe in a mouse model of stroke. C57Bl6 mice were subjected to transient middle cerebral artery occlusion (MCAO) or sham operation. Noninvasive NIRF imaging was performed 24 h after probe injection, and target-tobackground ratios (TBRs) between the two hemispheres were determined. TBRs were significantly higher in MCAO mice injected with the MMP-activatable probe than in sham-operated mice and in MCAO mice that were injected with the nonactivatable probe as controls. Treatment with an MMP inhibitor resulted in significantly lower TBRs and lesion volumes compared to injection of vehicle. To test the contribution of MMP-9 to the fluorescence signal, MMP9-deficient (MMP9 À/À ) mice and wild-type controls were subjected to MCAO of different durations to attain comparable lesion volumes. TBRs were significantly lower in MMP9 À/À mice, suggesting a substantial contribution of MMP-9 activity to the signal. Our study shows that MMP activity after cerebral ischemia can be imaged noninvasively with NIRF using an MMP-activatable probe, which might be a useful tool to study MMP activity in the pathophysiology of the disease.

Noninvasive High-Speed Photoacoustic Tomography of Cerebral Hemodynamics in Awake-Moving Rats

“…For example, by leaving animal in awake-moving state, more realistic hemodynamic parameters (vasodilation, intensity, latency time, and recover time) of cerebral vasculature could be obtained in response to stimulation, such as forepaw stimulation, 44 whisker stimulation, 45 and hypoxia challenge. 46,47 Moreover, employing multi-wavelength excitation, wPAT can be used to reconstruct the oxy-saturation of the cerebral hemodynamics in an awake-moving rat as we demonstrated in this study. In addition, wPAT can be applied for cerebral metabolic research and cerebral drug delivery or targeted molecular imaging by choosing appropriate laser wavelengths and employing exogenous optical contrast agents.…”

Visualizing Cell Death in Experimental Focal Cerebral Ischemia: Promises, Problems, and Perspectives

“…The literature on the use of noninvasive fluorescence imaging (NFI) is also rare, primarily because of the depth limit of the method. Nevertheless, there have been a few papers published applying NFI in animal models of stroke (Abulrob et al, 2008;Bahmani et al, 2011;Klohs et al, 2008Klohs et al, , 2009a. The strongest advantages of these techniques when compared with MRI are that they can be orders of magnitude more sensitive, and molecules and/or proteins specifically associated with cell death can be labeled with radioactive or fluorescent compounds enabling a direct visualization of cell death after stroke.…”

Imaging gene delivery in a mouse model of congenital neuronal ceroid lipofuscinosis

“…Systemic injection of knockout mice with a higher dose of this AAV vector could potentially increase their survival even further. The advantage of CathD in this paradigm is that activity can be visualized and quantitated by NIRF imaging in cells and tissues using probes that have been shown to penetrate the brain efficiently 37,38 . These studies support the feasibility of AAV-mediated gene delivery for enzyme replacement in lysosomal storage disorders which affect the nervous system.…”