In vivo quantification of the structural changes of collagens in a melanoma microenvironment with second and third harmonic generation microscopy.
Using in vivo second harmonic generation (SHG) and third harmonic generation (THG) microscopies, we tracked the course of collagen remodeling over time in the same melanoma microenvironment within an individual mouse. The corresponding structural and morphological changes were quantitatively analyzed without labeling using an orientation index (OI), the gray level co-occurrence matrix (GLCM) method, and the intensity ratio of THG to SHG (RTHG/SHG). In the early stage of melanoma development, we found that collagen fibers adjacent to a melanoma have increased OI values and SHG intensities. In the late stages, these collagen networks have more directionality and less homogeneity. The corresponding GLCM traces showed oscillation features and the sum of squared fluctuation VarGLCM increased with the tumor sizes. In addition, the THG intensities of the extracellular matrices increased, indicating an enhanced optical inhomogeneity. Multiplying OI, VarGLCM, and RTHG/SHG together, the combinational collagen remodeling (CR) index at 4 weeks post melanoma implantation showed a 400-times higher value than normal ones. These results validate that our quantitative indices of SHG and THG microscopies are sensitive enough to diagnose the collagen remodeling in vivo. We believe these indices have the potential to help the diagnosis of skin cancers in clinical practice.
Institute of Biomedical Engineering, National Taiwan University, Taipei 10617, Taiwan.
Pei-Chun
PC
Wu
Institute of Biomedical Engineering, National Taiwan University, Taipei 10617, Taiwan.
Tsung-Yuan
TY
Hsieh
Molecular Imaging Center, National Taiwan University, Taipei 10617, Taiwan.
Zen-Uong
ZU
Tsai
1] Institute of Biomedical Engineering, National Taiwan University, Taipei 10617, Taiwan [2] Molecular Imaging Center, National Taiwan University, Taipei 10617, Taiwan.
Tzu-Ming
TM
Liu
D000818:Animals; D045744:Cell Line, Tumor; D024022:Fibrillar Collagens / Q000378:metabolism* / Q000648:ultrastructure*; D008297:Male; D008545:Melanoma / Q000378:metabolism* / Q000648:ultrastructure*; D051379:Mice; D008810:Mice, Inbred C57BL; D008853:Microscopy / Q000379:methods; D012878:Skin Neoplasms / Q000378:metabolism / Q000648:ultrastructure*; D059016:Tumor Microenvironment / Q000502:physiology*
D024022:Fibrillar Collagens