Multimodal Skin Imaging in Mice

A combination of ex vivo and in vivo imaging of murine skin were performed. For in vivo imaging, mice were anesthetized with Ketamine/Xylazine (80/10mg/kg, i.p.) with repeated half-doses as required. The anesthetized mouse was mounted on a custom-built ear stage with its body temperature controlled as described previously (Ng et al., 2008 (link); Li et al., 2012 (link)). MPM was performed on a custom-built TriMScope (LaVision BioTec, Bielefeld, Germany) attached to an Olympus BX-51 fixed stage microscope equipped with either a 16× (Nikon LWD, NA 0.80; Nikon, Tokyo, Japan) or 20× (Olympus XLUMPlanFl IR coated, numerical aperture (NA) 0.95; Olympus, Center Valley, PA) water immersion objective. For ex vivo imaging, mice were euthanized using CO₂ asphyxiation, hair removed with Nair, and tissue harvested from the ear, dorsal back, footpad and tail skin. A wideband mode-locked Ti:sapphire femtosecond laser (Mai Tai HP/Spectra-Physics; Newport Corporation, Irvine, CA) was used to excite the skin at a wavelength of 920 nm or 940 nm for imaging of GFP and YFP respectively. Blood vessels were visualized through i.v. (tail vein) injection of Evans blue (Gurr-Searle Diagnostic) conjugated to BSA (Abtin et al., 2014 (link)).