Abstract
.Significance: The study has confirmed the feasibility of using ultraviolet (UV) excitation to visualize and quantify desmoplasia in fresh tumor tissue of pancreatic adenocarcinoma (PDAC) in an orthotopic xenograft mouse model, which provides a useful imaging platform to evaluate acute therapeutic responses.Aim: Stromal network of collagen prominent in PDAC tumors is examined by imaging fresh tissue samples stained with histological dyes. Fluorescence signals are color-transferred to mimic Masson’s trichrome staining.Approach: Murine tumor samples were stained with Hoechst, eosin, and rhodamine B and excited at 275-nm. Fluorescence signals in the visible spectrum were captured by a CMOS color camera with high contrast and resolution at whole-tumor slice field of view.Results: Fluorescence imaging using UV excitation is capable of visualizing collagen deposition in PDAC tumors. Both fluorescence and histology data showed collagen content of up to 30%. The collagen modulation effect due to photodynamic priming treatment was observed showing 13% of collagen reduction. Necrosis area is visible and perfusion imaging using Texas Red dextran is feasible.Conclusions: The study demonstrates collagen visualization in fresh PDAC tumor samples using UV excitation. This imaging platform also provides quantitative stromal information from fiber analysis and visibility of necrosis and perfusion, suitable for therapeutic response assessment of photodynamic therapy.
Highlights
The microenvironment of pancreatic adenocarcinoma (PDAC) is well recognized as a highly complex cellular-molecular-stromal milieu that hinders therapeutic response.[1,2] The hyperdense desmoplastic nature of PDAC has been associated with drug resistant[3] cancer progression,[4]Journal of Biomedical OpticsDownloaded From: https://www.spiedigitallibrary.org/journals/Journal-of-Biomedical-Optics on 08 Nov 2021 Terms of Use: https://www.spiedigitallibrary.org/terms-of-useJanuary 2021 Vol 26(1)Vincent et al.: Visualization and quantification of pancreatic tumor stroma in fresh tissue. . .prompting a major direction of targeted therapies focusing on stromal depletion.[5]
The current study examined if equivalent collagen information could be visualized and quantified directly from fresh tissue imaging as compared to traditional pathology stained fixed tissues
Fluorescence signals were focused by a long working distance objective (Mitutoyo, Kawasaki, Japan) onto a 200-mm tube lens (#TTL-200A, Thorlabs), which were captured by a commercial Electro-Optical System (EOS) color camera (EOS 60D, Canon, Japan)
Summary
Prompting a major direction of targeted therapies focusing on stromal depletion.[5] attempts to alleviate the effects of dense stroma have yielded mixed results,[6,7] and it may be that systemic molecular therapies may not be the ideal way to deal with the type of desmoplasia in PDAC. While major mechanistic efforts have elucidated the pathobiological relationship of pancreatic stellate cells with other tumor microenvironment components,[8,9] recent findings have called for more attention toward the spatial orientation of particular biomarkers such as immune cells[10] and fibroblasts.[11] The study of these components and contributors to the desmoplasia is challenging to examine because of how dynamic the microenvironment is and how hard it is to examine molecular signals and morphology in fresh tissues. A methodology to image and quantify stroma and some molecular signals in fresh PDAC is examined
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