Understanding immune cell trafficking patterns via in vivo bioluminescence imaging

Abstract

Cell migration is a key aspect of the development of the immune system and mediating an immune response. There is extensive and continual redistribution of cells to different anatomic sites throughout the body. These trafficking patterns control immune function, tissue regeneration, and host responses to insult. The ability to monitor the fate and function of cells, therefore, is imperative to both understanding the role of specific cells in disease processes and to devising rational therapeutic strategies. Determining the fate of immune cells and understanding the functional changes associated with migration and proliferation require effective means of obtaining in vivo measurements in the context of intact organ systems. A variety of imaging methods are available to provide structural information, such as X-ray CT and MRI, but only recently new tools have been developed that reveal cellular and molecular changes as they occur within living animals. We have pioneered one of these techniques that is based on the observations that light passes through mammalian tissues, and that luciferases can serve as internal biological sources of light in the living body. This method, called in vivo bioluminescence imaging, is a rapid and noninvasive functional imaging method that employs light-emitting reporters and external photon detection to follow biological processes in living animals in real time. This imaging strategy enables the studies of trafficking patterns for a variety of cell types in live animal models of human biology and disease. Using this approach we have elucidated the spatiotemporal trafficking patterns of lymphocytes within the body. In models of autoimmune disease we have used the migration of "pathogenic" immune cells to diseased tissues as a means to locally deliver and express therapeutic proteins. Similarly, we have determined the tempo of NK-T cell migration to neoplastic lesions and measured their life span in vivo. Using bioluminescence imaging individual groups of animals can be followed over time significantly reducing the number of animals per experiment, and improving the statistical significance of a study since changes in a given population can be studied over time. Such rapid assays that reveal cell fates in vivo will increase our basic understanding of the molecular signals that control these migratory pathways and will substantially speed up the development and evaluation of therapies.

Bioluminescence imaging to monitor the in vivo distribution of administered mesenchymal stem cells in acute kidney injury

“…In contrast, in cell therapy, a single cell suspension is administered, and cells are distributed throughout the whole animal, i.e., in the normal animal without any distinct cell accumulation or engraftment site. Localization and cell engraftment in disease models depends on the type of organ injury and the studied cell type and commonly is diffuse rather than localized, making cell detection a challenge (8,30). Our data show that BLI is sensitive and specific for monitoring the distribution and numbers of injected cells over time, information that is critical in the design of cell therapies.…”

Molecular imaging perspectives

“…The sensitivity of SPECT is one to two orders of magnitude less than PET (approximately 10 K10 M; Mandl et al 2002).…”

“…PET contrast agents have a short half-life (t one-half minutes to hours) which requires PET scanners to be geographically close to a cyclotron. The sensitivity of PET is of the order of 10 K11 -10 K12 M (Mandl et al 2002), and is determined by the number of counts collected during the scan, which in turn is dependent on the dosage of administered radiopharmaceutical, the duration of the scan, the sensitivity of the detector and the count-rate capability of the scanner (Ollinger & Fessler 1997). The recent introduction of lutetium-oxyorthosilicate (LSO) crystals, which scintillate faster than BGO crystals, has alleviated count-rate limitations of earlier PET scanners and increased the SNR (Miller et al 2003).…”

Conjugated Polymer Nanoparticles for Two‐Photon Imaging of Endothelial Cells in a Tissue Model

“…[17] The observed nontoxicity of CPN and its longevity inside cells demonstrate its suitability as a long-term intracellular marker. These results indicate that CPNs could be useful for a broad range of applications, including understanding immune-cell trafficking in animal models [26] and monitoring implanted-stem-cell migration. [27] A loss in fluorescence intensity over time has been observed, and the exact causes of this decrease are not certain.…”