Nonlinear optical microscopy of the bronchus.

Because of frequent exposure to carcinogens, the bronchus is prone to early pathologic alterations. The assessment of these early changes is of key significance in physiological studies and disease diagnosis of the bronchus. We utilize nonlinear optical microscopy (NLOM) to image mouse bronchial tissue based on intrinsic nonlinear optical contrast. Our results show that NLOM is effective for imaging the bronchial intact microstructural components, providing quantitative information about the biomorphology and biochemistry of tissue. Our findings also display that NLOM can provide a two-photon ratiometric redox fluorometry, based on mitochondrial signals and reduced pyridine nucleotide (NADH and NADPH) and oxidized flavoproteins (Fp) signals, to assess the metabolic state of the epithelial cells and chondrocytes. It was found that NLOM can offer a sensitive tool, based on the second-harmonic signal depth-dependent decay, to obtain quantitative information on the optical property of the stroma associated with normal and diseased tissue states. Our results suggest that with the advent of the clinical portability of typical nonlinear optical endoscopy, the NLOM technique has the potential to be applied in vivo to the clinical diagnosis and monitoring of bronchial disease.