Promising Approach for Optimizing In Vivo Fluorescence Imaging in a Tumor Mouse Model: Precision in Cancer Research

Abstract

Background/Aim: Cancer remains a major global health concern due to its high mortality rates. Advanced diagnostic imaging, such as in vivo near-infrared (NIR) fluorescence imaging, enhances early detection by reducing autofluorescence and enabling deeper tissue penetration, addressing some limitations of conventional methods. Understanding the underlying causes of autofluorescence, even in mouse model fluorescence imaging, is crucial for accurate interpretation. This study investigated the origins of autofluorescence observed in experimental animals under NIR wavelengths, achieving successful fluorescence imaging in a clinically relevant tumor mouse model. Materials and Methods: Both fasting and non-fasting groups were evaluated to assess the dietary impact on autofluorescence, with various feeds tested. Subcutaneous and lung tumor models were established in C57BL/6 and BALB/c nude mice using LL/2-iRFP cells. Cryo-sectioning and lung tissue imaging were conducted to confirm tumor presence and assess fluorescence signals. Results: It was found that autofluorescence, notably common in the abdomen, is attributed to dietary factors. By selecting feed that lacks autofluorescence, the impact of dietary fluorescence on imaging was evaluated, leading to the establishment of optimized imaging conditions suited to the presence or absence of autofluorescence. Subsequently, utilizing lung cancer cells expressing near-infrared proteins (LL/2-iRFP), intratracheal, and subcutaneous tumor mouse models were developed, and successful in vivo imaging was achieved using the optimized imaging protocols, effectively bypassing autofluorescence. Conclusion: This study emphasizes the importance of understanding and addressing autofluorescence in fluorescence imaging, presenting valuable insights for enhancing the reliability and accuracy of diagnostic imaging techniques in cancer research and clinical practice.