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Imaging lymphatic function and inflammation response through hypoxia via endogenous biomarker.
Marien I Ochoa1, Xu Cao1,2, Matthew S Reed1,2
1University of Wisconsin-Madison, Department of Medical Physics, Madison, Wisconsin, United States.
Journal of Biomedical Optics
|December 31, 2025
Summary
We developed a new method to image lymphatic function by detecting natural hypoxia in lymphatic vessels. This technique visualizes lymphatic dynamics and inflammation in real-time without needing injected agents.
Area of Science:
- * Biomedical imaging
- * Lymphatic system research
- * Hypoxia studies
Background:
- * The lymphatic system is vital for immunity and fluid balance but challenging to study noninvasively.
- * Current lymphatic imaging often requires exogenous agents and lacks real-time capabilities.
- * Lymphatic system's natural hypoxia is linked to lymphangiogenesis and cancer metastasis.
Purpose of the Study:
- * Introduce a novel method for real-time, noninvasive imaging of lymphatic function.
- * Visualize lymphatic response to inflammation by leveraging intrinsic hypoxia.
- * Establish a new contrast mechanism for studying lymphatic dynamics.
Main Methods:
- * Utilized delayed fluorescence (DF) imaging of endogenous protoporphyrin IX (PpIX) in mice.
- * Induced PpIX with 5-aminolevulinic acid, which accumulates in inflamed areas.
- * Analyzed DF signal amplification under low oxygen conditions within lymphatic structures.
- * Characterized lymphatic kinetics in wound, inflammation, and tumor models.
- * Performed immunohistochemistry (IHC) on excised tissues for validation.
Main Results:
- * Lymphatic pumping frequency correlated with wound severity.
- * Hypoxia was detected in sentinel lymph nodes near tumors.
- * Cyclical lymphatic pumping observed at edema, wound, and tumor sites.
- * Awake mice showed localized hypoxia in lymph nodes, unlike anesthetized mice.
- * IHC confirmed PpIX and hypoxia in macrophages and T cells within nodes, tumors, and wounds.
Conclusions:
- * Delayed fluorescence hypoxia imaging offers a natural, whole-body contrast mechanism for lymphatic visualization.
- * This method bypasses the need for injection-based lymph node mapping.
- * Potential applications include surgical guidance, metastatic tumor tracking, and immune response monitoring.
