Microstructural Alterations and Oligodendrocyte Dysmaturation in White Matter After Cardiopulmonary Bypass in a Juvenile Porcine Model.

BACKGROUND: Newly developed white matter (WM) injury is common after cardiopulmonary bypass (CPB) in severe/complex congenital heart disease. Fractional anisotropy (FA) allows measurement of macroscopic organization of WM pathology but has rarely been applied after CPB. The aims of our animal study were to define CPB-induced FA alterations and to determine correlations between these changes and cellular events after congenital heart disease surgery. METHODS AND RESULTS: Normal porcine WM development was first assessed between 3 and 7 weeks of age: 3-week-old piglets were randomly assigned to 1 of 3 CPB-induced insults. FA was analyzed in 31 WM structures. WM oligodendrocytes, astrocytes, and microglia were assessed immunohistologically. Normal porcine WM development resembles human WM development in early infancy. We found region-specific WM vulnerability to insults associated with CPB. FA changes after CPB were also insult dependent. Within various WM areas, WM within the frontal cortex was susceptible, suggesting that FA in the frontal cortex should be a biomarker for WM injury after CPB. FA increases occur parallel to cellular processes of WM maturation during normal development; however, they are altered following surgery. CPB-induced oligodendrocyte dysmaturation, astrogliosis, and microglial expansion affect these changes. FA enabled capturing CPB-induced cellular events 4 weeks postoperatively. Regions most resilient to CPB-induced FA reduction were those that maintained mature oligodendrocytes. CONCLUSIONS: Reducing alterations of oligodendrocyte development in the frontal cortex can be both a metric and a goal to improve neurodevelopmental impairment in the congenital heart disease population. Studies using this model can provide important data needed to better interpret human imaging studies.

Glucosamine-linked near-infrared fluorescent probes for imaging of solid tumor xenografts.

PURPOSE: Near-infrared fluorescence (NIRF) imaging is an attractive technique for studying diseases at the molecular level in vivo. Glucose transporters are often used as targets for in vivo imaging of tumors. The efficiency of a tumor-seeking fluorescent probe can be enhanced by attaching one or more glucosamine (GlcN) moieties. This study was designed to evaluate the use of previously developed GlcN-linked NIRF probes for in vitro and in vivo optical imaging of cancer. PROCEDURES: Cellular uptake of the probes (1 µM) was investigated in monolayer cultures of luciferase-expressing PC3 (PC3-luc) cells. The prostate tumors were established as subcutaneous xenografts using PC3-luc cells in nude mice. The biodistributions and tumor-targeting specificities of cypate (cyp), cypate-D: -(+)-glucosamine (cyp-GlcN), and D: -(+)-gluosamine-cypate-D: -(+)-gluosamine (cyp-2GlcN) were studied. The tumor, muscle, and major organs were collected for ex vivo optical imaging. RESULTS: The tumor cell uptake of the probe containing two glucosamine residues, cyp-2GlcN, was significantly higher than the uptake of both the probe with one glucosamine residue, cyp-GlcN, and the probe without glucosamine, cyp only. Similarly, in in vivo experiments, cyp-2GlcN demonstrated higher maximum fluorescence intensity and longer residence lifetime in tumors than cyp-GlcN or cyp. The ex vivo biodistribution analysis revealed that tumor uptake of cyp-2GlcN and cyp-GlcN was four- and twofold higher than that of cyp at 24 h post-injection, respectively. CONCLUSION: Both cyp-GlcN and cyp-2GlcN NIRF probes exhibited good tumor-targeting properties in prostate cancer cell cultures and live mice. The cyp-2GlcN probe showed the highest uptake with good retention characteristics in vivo. The uptake of cyp-2GlcN and cyp-GlcN is likely mediated by glucosamine-recognizing transporters. The uptake mechanism is being explored further for developing cypate-glucosamine-based probes for in vivo imaging.