In vivo high-resolution structural imaging of large arteries in small rodents using two-photon laser scanning microscopy

In vivo molecular imaging of the vessel wall of large arteries at subcellular resolution is crucial for unrav- eling vascular pathophysiology. We previously showed the applicability of two-photon laser scanning microscopy TPLSM in mounted arteries ex vivo. However, in vivo TPLSM has thus far suffered from in-frame and between- frame motion artifacts due to arterial movement with car- diac and respiratory activity. Now, motion artifacts are suppressed by accelerated image acquisition triggered on cardiac and respiratory activity. In vivo TPLSM is per- formed on rat renal and mouse carotid arteries, both sur- gically exposed and labeled fluorescently cell nuclei, elastin, and collagen. The use of short acquisition times consistently limit in-frame motion artifacts. Additionally, triggered imaging reduces between-frame artifacts. In- deed, structures in the vessel wall cell nuclei, elastic laminae can be imaged at subcellular resolution. In me- chanically damaged carotid arteries, even the subendothe- lial collagen sheet 1 m is visualized using collagen- targeted quantum dots. We demonstrate stable in vivo imaging of large arteries at subcellular resolution using TPLSM triggered on cardiac and respiratory cycles. This creates great opportunities for studying diseased arteries in vivo or immediate validation of in vivo molecular im- aging techniques such as magnetic resonance imaging MRI, ultrasound, and positron emission tomography PET. © 2010 Society of Photo-Optical Instrumentation Engineers.