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NADH/FAD fluorescence spectroscopy/imaging is an extremely useful tool to probe cellular metabolism and has been applied in the clinic such as early cancer detection. Recently, the potential of using NADH/FAD fluorescence as a biomarker to detect cell death has been investigated for development of cancer treatments with higher efficacy. This review aims to provide the updated information in cell death detection using the NADH/FAD fluorescence spectroscopy and imaging based on measurement of the intensity or lifetime of NADH or FAD fluorescence. The response of NADH fluorescence lifetime to metabolic perturbation, hypoxic environment, and anaerobic glycolysis (e.g., in precancerous tissues and stem cells) is also reviewed to discuss the nature and implications of the lifetime change of NADH fluorescence. Further studies are required to understand the actual site and mechanism of NADH binding of a specific death pathway for future successful in vivo detection of cell death using the NADH fluorescence lifetime.

Blood content and tumor oxygen level are important biomarkers and prognostic indicators in patients with colorectal cancer (CRC). However, noninvasive measurements of both quantities in human colon are limited. In this study, we extracted the total hemoglobin concentration (THC) and oxygen saturation (StO(2)) of normal, premalignant, and malignant colonic tissues in 27 patients using a diffuse reflectance instrument and algorithms based on the diffusion equation. The mean+/-standard error of THC and StO(2) from all normal sites (n=26) is 93.4+/-17.1microM and 67.2+/-3.7%, respectively. THC increased to 136.9+/-23.8microM and 153.8+/-38.6microM and StO(2) decreased to 51.3+/-7.0% and 26.4+/-6.1% for premalignant and malignant tissues, respectively. The disease-to-normal THC ratios are 3.2+/-1.1 and 4.4+/-1.9 and the disease-to-normal StO(2) ratios are 0.7+/-0.1 and 0.5+/-0.1 for pr alignant and malignant tissues, respectively. These results demonstrate the feasibility of a robust optical method to assess colon THC and StO2 at all stages of carcinogenesis in vivo so that the angiogenesis and hypoxia of the disease and the therapeutic role can be studied in CRC patients.

Photodynamic therapy (PDT) is a novel cancer therapy that uses light‐activated drugs (photosensitizers) to destroy tumor tissue. Reactive oxygen species produced during PDT are thought to cause the destruction of tumor tissue. However, the precise mechanism of PDT is not completely understood. To provide insight into the in vitro mechanisms of PDT, we studied the subcellular localization of the photosensitizer HOSiPcOSi(CH3)2‐(CH2)3N(CH3)2 (Pc 4) in mouse lymphoma (LY‐R) cells using double‐label confocal fluorescence microscopy. This technique allowed us to observe the relative distributions of Pc 4 and an organelle‐specific dye within the same cell via two, spectrally distinct, fluorescence images. To quantify the localization of Pc 4 within different organelles, linear correlation coefficients from the fluorescence data of Pc 4 and the organelle‐specific dyes were calculated. Using this measurement, the subcellular spatial distributions of Pc 4 could be successfully monitored over an 18 h period. At early times (0–1 h) after introduction of Pc 4 to LY‐R cells, the dye was found in the mitochondria, lysosomes and Golgi apparatus, as well as other cytoplasmic membranes, but not in the plasma membrane or the nucleus. Over the next 2 h, there was some loss of Pc 4 from the lysosomes as shown by the correlation coefficients. After an additional incubation period of 2 h Pc 4 slowly increased its accumulation in the lysosomes. The highest correlation coefficient (0.65) was for Pc 4 and BODIPY‐FL C5 ceramide, which targets the Golgi apparatus, and also binds to other cytoplasmic membranes. The correlation coefficient was also high (0.60) for Pc 4 and a mitochondria‐targeting dye (Mitotracker Green FM). Both of these correlation coefficients were higher than that for Pc 4 with the lysosome‐targeting dye (Lysotracker Green DND‐26). The results suggest that Pc 4 binds preferentially and strongly to mitochondria and Golgi complexes.

Background Optical coherence tomography (OCT) revealed that cells lining proximal convoluted tubules of living donor kidneys (LDK) procured by laparoscopic procedures were very swollen in response to the brief period of ischemia suffered between the time of arterial vessel clamping and flushing the excised kidney with cold preservation solution. Damage to the tubules as a result of this cell swelling resulted in varying degrees of acute tubular necrosis (ATN) that slowed the recovery of the donor kidneys during the first two weeks following their transplant. Methods In order to prevent this cell damage during LDK procurement, we changed the protocol for intravenous administration of mannitol (i.e., 12.5 or 25 g) to the donor. Specifically, we reduced the time of mannitol administration from 30 to 15 minutes or less prior to clamping the renal artery. Result OCT revealed that this change in the timing of mannitol administration protected the human donor proximal tubules from normothermic induced cell swelling. An evaluation of post-transplant recovery of renal function showed that patients treated with this modified protocol returned to normal renal function significantly faster than those treated with mannitol 30 or more minutes prior to clamping the renal artery. Conclusion Since slow graft recovery in the first weeks following transplantation represents a risk factor for long-term graft function and survival, we believe that this change in pretreatment protocol will improve renal transplants in patients receiving LDK.

Chronic kidney disease (CKD) is characterized by a progressive loss of renal function over time. Histopathological analysis of the condition of glomeruli and the proximal convolutional tubules over time can provide valuable insights into the progression of CKD. Optical coherence tomography (OCT) is a technology that can analyze the microscopic structures of a kidney in a nondestructive manner. Recently, we have shown that OCT can provide real-time imaging of kidney microstructures in vivo without administering exogenous contrast agents. A murine model of CKD induced by intravenous Adriamycin (ADR) injection is evaluated by OCT. OCT images of the rat kidneys have been captured every week up to eight weeks. Tubular diameter and hypertrophic tubule population of the kidneys at multiple time points after ADR injection have been evaluated through a fully automated computer-vision system. Results revealed that mean tubular diameter and hypertrophic tubule population increase with time in post-ADR injection period. The results suggest that OCT images of the kidney contain abundant information about kidney histopathology. Fully automated computer-aided diagnosis based on OCT has the potential for clinical evaluation of CKD conditions.

Acute tubular necrosis (ATN) induced by ischemia is the most common insult to donor kidneys destined for transplantation. ATN results from swelling and subsequent damage to cells lining the kidney tubules. In this study, we demonstrate the capability of optical coherence tomography (OCT) to image the renal microstructures of living human donor kidneys and potentially provide a measure to determine the extent of ATN. We also found that Doppler-based OCT (i.e., DOCT) reveals renal blood°ow dynamics that is another major factor which could relate to posttransplant renal function. All OCT/DOCT observations were performed in a noninvasive, sterile and timely manner on intact human kidneys both prior to (ex vivo) and following (in vivo) their transplantation. Our results indicate that this imaging model provides transplant surgeons with an objective visualization of the transplant kidneys prior and immediately post transplantation.