ROCKETS - a novel one-for-all toolbox for light sheet microscopy in drug discovery

First application of three-dimensional light sheet fluorescence microscopy to human testicular tumors: New perspectives in histopathology

BACKGROUND

Testicular tumors are among the most frequently diagnosed cancers in young men. The consequences of this diagnosis are orchiectomies, severely restricting fertility. For these young patients, a comprehensive diagnostics would be desirable, achieving a refined diagnosis and improved therapeutic patient stratification.

OBJECTIVE

The aim of this study was to use three-dimensional (3D) light sheet fluorescence microscopy (LSFM) to analyze a complete testicular tumor punch at subcellular resolution-allowing a detailed diagnostic assessment of the entire punch.

MATERIALS AND METHODS

Tissue punches (3  and 5 mm diameter) were taken from paraffin blocks of four miscellaneous testicular tumors. After deparaffinization and clearing using benzoic acid/benzyl benzoate, a label-free LSFM autofluorescence imaging was performed. In addition, TO-PRO-3 nuclear stain was applied to several punches. After the scan, the samples were embedded in paraffin again and physically sectioned for conventional planar histology.

RESULTS

Based on the specific autofluorescence, not only the general morphology of the tumor tissue was identified in LSFM datasets, but also diagnostic features like infiltrations, papillary and pagetoid tumor cell formations, germ cell neoplasia in situ and azoospermia. Subcellular characteristics such as vacuolated cytoplasm and pleomorphic nuclei could be detected at maximum magnification. After nuclear staining, virtual H&E sections were reconstructed from the LSFM data and tomographically visualized across the entire punch. Subsequent histology and immunohistochemistry after LSFM analyses is possible.

DISCUSSION

LSFM analysis of testicular tumors enables the detailed 2D/3D analysis of an entire tumor punch for assessment of relevant tumor characteristics due to its intrinsic fluorescence or with specific nuclear staining.

CONCLUSION

LSFM provides the technical basis for the analyses of complete testicular tumor biopsies, thus maximizing the spatial morphological and anatomical information. The subcellular 3D imaging of the tumor has the potential to identify new cancer imaging biomarkers that have additional diagnostic and prognostic value for patients.

Biodistribution of Polyaldehydedextran Nanoparticle-Encapsulated Epirubicin in Ovarian Tumor-Bearing Mice via Optical Imaging

This study investigates the biodistribution of polysaccharide-based nanoparticles loaded with epirubicin (POLEPI) compared to epirubicin hydrochloride (EPI) in naïve female nude mice following a single intravenous dose. The inherent fluorescence of epirubicin was tracked using Newton 7 animal imager and Varioskan. Initial whole-animal optical imaging failed to reliably detect epirubicin distribution, necessitating ex vivo imaging of key tissues harvested at intervals between 10 min and 48 h post-injection. Optimal imaging conditions were established using a 5 s exposure time with excitation (Ex)/emission (Em) at 480 nm/550 nm. The biodistribution of POLEPI was further evaluated in both naïve mice and immunocompromised mice bearing patient-derived ovarian tumors. Unlike epirubicin, POLEPI exhibited notable tissue distribution within 3 h post-injection. By 48 h, fluorescence signals were undetectable in both models, although non-tumored animals exhibited persistent signals. In both models, the liver was the primary organ for POLEPI accumulation, with lower levels in tumored mice. Interestingly, brain fluorescence was higher in POLEPI-treated mice compared to those receiving epirubicin. Neither POLEPI nor epirubicin accumulated in the spleen or bone marrow. In tumors, POLEPI fluorescence peaked at 24 h, with levels 2.1 times higher than in the epirubicin-treated group over a 48 h period. Furthermore, POLEPI uptake in tumors exceeded that in healthy ovaries, with the most significant tumor-to-healthy-ovary ratio observed between 6 and 24 h post-injection. These findings demonstrate that POLEPI, a novel polyaldehydedextran nanoparticle formulation, exhibits enhanced accumulation and retention in tumor tissue compared to epirubicin, with preferential distribution to the orthotopic tumor-bearing ovary over healthy ovarian tissue. The inherent fluorescence of epirubicin provided a rapid and cost-effective means of estimating biodistribution, although the limitations of this method-particularly, the inability to differentiate between the parent drug and its metabolites-were acknowledged.

3D light-sheet fluorescence microscopy in preclinical and clinical drug discovery

Light-sheet fluorescence microscopy (LSFM) combined with tissue clearing has emerged as a powerful technology in drug discovery. LSFM is applicable to a variety of samples, from rodent organs to clinical tissue biopsies, and has been used for characterizing drug targets in tissues, demonstrating the biodistribution of pharmaceuticals and determining their efficacy and mode of action. LSFM is scalable to high-throughput analysis and provides resolution down to the single cell level. In this review, we describe the advantages of implementing LSFM into the drug discovery pipeline and highlight recent advances in this field.

Current and future applications of light-sheet imaging for identifying molecular and developmental processes in autism spectrum disorders

Autism spectrum disorder (ASD) is identified by a set of neurodevelopmental divergences that typically affect the social communication domain. ASD is also characterized by heterogeneous cognitive impairments and is associated with cooccurring physical and medical conditions. As behaviors emerge as the brain matures, it is particularly essential to identify any gaps in neurodevelopmental trajectories during early perinatal life. Here, we introduce the potential of light-sheet imaging for studying developmental biology and cross-scale interactions among genetic, cellular, molecular and macroscale levels of circuitry and connectivity. We first report the core principles of light-sheet imaging and the recent progress in studying brain development in preclinical animal models and human organoids. We also present studies using light-sheet imaging to understand the development and function of other organs, such as the skin and gastrointestinal tract. We also provide information on the potential of light-sheet imaging in preclinical drug development. Finally, we speculate on the translational benefits of light-sheet imaging for studying individual brain-body interactions in advancing ASD research and creating personalized interventions.

Silicon-Rhodamine Functionalized Evocalcet Probes Potently and Selectively Label Calcium Sensing Receptors In Vitro, In Vivo, and Ex Vivo

The calcium sensing receptor (CaSR) is a ubiquitously expressed G-protein coupled receptor (GPCR) that regulates extracellular calcium signals via the parathyroid glands. CaSR has recently also been implicated in noncalcitropic pathophysiologies like asthma, gut inflammation, and cancer. To date, molecular tools that enable the bioimaging of CaSR in tissues are lacking. Based on in silico analyses of available structure-activity relationship data on CaSR ligands, we designed and prepared silicon-rhodamine (SiR) conjugates of the clinically approved drug evocalcet. The new probes EvoSiR4 and EvoSiR6, with differing linker lengths at the evocalcet carboxyl end, both showed a 6-fold and 3-fold increase in potency toward CaSR (EC50 < 45 nM) compared to evocalcet and the evocalcet-linker conjugate, respectively, in an FLIPR-based cellular functional assay. The specificity of the EvoSiR probes toward CaSR binding and the impact of albumin was evaluated in live cell experiments. Both probes showed strong albumin binding, which facilitated the clearance of nonspecific binding interactions. Accordingly, in zebrafish embryos, EvoSiR4 specifically labeled the high CaSR expressing neuromasts of the lateral line in vivo. EvoSiR4 was also assessed in human parathyroid tissues ex vivo, showing a specific absolute CaSR-associated fluorescence compared to that of parathyroid autofluorescence. In summary, functionalization of evocalcet by SiR led to the preparation of potent and specific fluorescent CaSR probes. EvoSiR4 is a versatile small-molecular probe that can be employed in CaSR-related biomedical analyses where antibodies are not applicable.