Label-free multimodal multiphoton microscopy for monitoring of cell and tissue preservation and degradation in ex vivo whole organs (Conference Presentation)

Multiphoton microscopy uses ultrafast nonlinear light-matter interactions to generate signal contrast from biological samples. The imaging of tissue from various organs plays an important role for a better understanding of cellular processes within their microenvironment and helps to reveal mechanisms of cellular changes in tissues during disease processes. Most tissue imaging studies by the pharmaceutical industry or by pathologists have typically been performed using harvested and sectioned tissue from organs to investigate drug toxicity or disease-related changes. However, immediately following biopsy, tissues begin to degrade due to cell necrosis and apoptosis, and substantial information is lost during the process. We demonstrate tissue degradation monitoring at different time points after tissue excision by using our label-free multimodal multiphoton imaging system which integrates SHG, TPEF, FLIM, and CARS in one platform. We examined whole organs and tissues harvested from mice, including kidney, liver, pancreas, and brain, and immersed each in several different media including saline, Euro-Collins solution, UW solution, HTK, and formalin. We collected time-lapse images from each sample and compared rates of cell degradation, tissue structure changes, and variations in optical properties including the intensities of NADH and FAD, the metabolic redox ratio, and FLIM of free/bound NADH. As a result, we quantified rates of degradation and metabolic changes associated with the preservation methods based on these label-free optical properties. Therefore, these results can be used as reference values for most ex vivo tissue research that relies on tissue and cell viability.