Semi-automated Image Processing for Preclinical Bioluminescent Imaging

Similarities and differences between the Chaetopterus variopedatus polychaete luciferases depending on the type of habitat

The marine polychaete Chaetopterus variopedatus (Renier) (family Chaetopteridae) is a cosmopolitan species complex, consisting of distinct populations/ subspecies. The worms release glowing (460 nm) clouds of mucus when disturbed, and their parapodia often glow brightly. Currently, it is still unclear how exactly the bioluminescence system of these polychaetes functions. It has been previously assumed that the C. variopedatus luciferase may be used for detection of ferroptosis, the recently explored pathway of programmed cell death, resulting from accumulation of the ferrous ions. This study was aimed to extract and characterize the C. variopedatus luciferases, as well as to compare luciferases obtained from C. variopedatus of different populations. When extracting the enzyme responsible for bioluminescence from the frozen samples of Brazilian C. variopedatus using the improved method, two active luciferases, L1 and L2, were obtained. We assumed that one of the listed above luciferases was responsible for luminescence of the mucus and the other luciferase was responsible for luminescence in parapodia, and used the method for the distinct samples of mucus and parapodia of the living Far Eastern C. variopedatus. However, mucus of the latter turned out to be non-glowing. It is shown that luciferase L2 is responsible for luminescence in the parapodia of the C. variopedatus polychaete, since this luciferase has been found in the total biomass of Brazilian polychaetes and parapodia of Far Eastern polychaetes. Luminescence of the Brazilian C. variopedatus mucus is attributed to the functioning of luciferase L1, which is lacking in the mucus of the Far Eastern subspecies. The range of luciferase isoforms in polychaetes C. variopedatus depends on the place of origin.

Bioluminescence Imaging Applications in Cancer: A Comprehensive Review

Bioluminescence imaging (BLI), an optical preclinical imaging modality, is an invaluable imaging modality due to its low-cost, high throughput, fast acquisition times, and functional imaging capabilities. BLI is being extensively used in the field of cancer imaging, especially with the recent developments in genetic-engineering, stem cell, and gene therapy treatments. The purpose of this paper is to provide a comprehensive review of the principles, developments, and current status of BLI in cancer research. This paper covers the fundamental BLI concepts including BLI reporters and enzyme-substrate systems, data acquisition, and image characteristics. It reviews the studies discussing the use of BLI in cancer research such as imaging tumor-characteristic phenomena including tumorigenesis, metastasis, cancer metabolism, apoptosis, hypoxia, and angiogenesis, and response to cancer therapy treatments including chemotherapy, radiotherapy, immunotherapy, gene therapy, and stem cell therapy. The key advantages and disadvantages of BLI compared to other common imaging modalities are also discussed.

A bioluminescent system of fungi: prospects for application in medical research

Bioluminescence is chemical oxidation of a small luciferin molecule by air catalyzed by luciferase and accompanied by the emission of photons in the visible spectrum. This reaction is used in bioluminescent bioimaging, the method for the visualization of organism’s interior. Bioimaging is a popular tool used in medical research. However, it has an unfortunate drawback: it requires introduction of external luciferin to the system before every experiment. In this work we discuss a possibility of developing an autonomous luminescent system in eukaryotes based on the bioluminescent system of higher fungi.

Correlation of 360-degree Surface Mapping In Vivo Bioluminescence with Multi-Spectral Optoacoustic Tomography in Human Xenograft Tumor Models

Pre-clinical monitoring of tumor growth and identification of distal metastasis requires a balance between accuracy and expediency. Bioluminescence imaging (BLI) is often used to track tumor growth but is primarily limited to planar 2-dimensional (2D) imaging. Consistent subject placement within a standard top-mounted, single-detector small animal imager is vital to reducing variability in repeated same-animal measures over time. Here, we describe a method for tracking tumor development using a multi-angle BLI and photo-acoustic workflow. We correlate serial caliper measurements and 2D BLI to 360° BLI and photo-acoustic datasets for the same animals. Full 360° BLI showed improved correlations with both volumes obtained from caliper measurements and photo-acoustic segmentation, as compared to planar BLI. We also determined segmented tumor volumes from photo-acoustic datasets more accurately reflects true excised tumors' volumes compared to caliper measurements. Our results demonstrate the distinct advantages of both 360° surface mapping by BLI and photo-acoustic methodologies for non-invasive tracking of tumor growth in pre-clinical academic settings. Furthermore, our design is fully implementable in all top-mounted, single-detector imagers, thereby providing the opportunity to shift the paradigm away from planar BLI into rapid BLI tomography applications.

1001 lights: luciferins, luciferases, their mechanisms of action and applications in chemical analysis, biology and medicine

Bioluminescence (BL) is a spectacular phenomenon involving light emission by live organisms. It is caused by the oxidation of a small organic molecule, luciferin, with molecular oxygen, which is catalysed by the enzyme luciferase. In nature, there are approximately 30 different BL systems, of which only 9 have been studied to various degrees in terms of their reaction mechanisms. A vast range of in vitro and in vivo analytical techniques have been developed based on BL, including tests for different analytes, immunoassays, gene expression assays, drug screening, bioimaging of live organisms, cancer studies, the investigation of infectious diseases and environmental monitoring. This review aims to cover the major existing applications for bioluminescence in the context of the diversity of luciferases and their substrates, luciferins. Particularly, the properties and applications of d-luciferin, coelenterazine, bacterial, Cypridina and dinoflagellate luciferins and their analogues along with their corresponding luciferases are described. Finally, four other rarely studied bioluminescent systems (those of limpet Latia, earthworms Diplocardia and Fridericia and higher fungi), which are promising for future use, are also discussed.

Iterative Image Processing for Early Diagnostic of Beta-Amyloid Plaque Deposition in Pre-Clinical Alzheimer's Disease Studies

PURPOSE

To test and evaluate an efficient iterative image processing strategy to improve the quality of sub-optimal pre-clinical PET images. A novel iterative resolution subsets-based method to reduce noise and enhance resolution (RSEMD) has been demonstrated on examples of PET imaging studies of Alzheimer's disease (AD) plaques deposition in mice brains.

MATERIALS AND METHODS

The RSEMD method was applied to imaging studies of non-invasive detection of beta-amyloid plaque in transgenic mouse models of AD. Data acquisition utilized a Siemens Inveon® micro PET/CT device. Quantitative uptake of the tracer in control and AD mice brains was determined by counting the extent of plaque deposition by histological staining. The pre-clinical imaging software inviCRO® was used for fitting the recovery PET images to the mouse brain atlas and obtaining the time activity curves (TAC) from different brain areas.

RESULTS

In all of the AD studies the post-processed images proved to have higher resolution and lower noise as compared with images reconstructed by conventional OSEM method. In general, the values of SNR reached a plateau at around 10 iterations with an improvement factor of about 2 over sub-optimal PET brain images.

CONCLUSIONS

A rapidly converging, iterative deconvolution image processing algorithm with a resolution subsets-based approach RSEMD has been used for quantitative studies of changes in Alzheimer's pathology over time. The RSEMD method can be applied to sub-optimal clinical PET brain images to improve image quality to diagnostically acceptable levels and will be crucial in order to facilitate diagnosis of AD progression at the earliest stages.