Polarization-resolved second harmonic generation imaging of human ovarian cancer.

Kirby R Campbell ,Rajeev Chaudhary,Julia Handel ,Manish S Patankar ,Paul J Campagnola

doi:10.1117/1.jbo.23.6.066501

Kirby R Campbell , Rajeev Chaudhary + Show 3 more

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https://doi.org/10.1117/1.jbo.23.6.066501

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Abstract

.Remodeling of the extracellular matrix in human ovarian cancer can be manifested in increased collagen concentration, changes in alignment within fibrils/fibers and/or up-regulation of different collagen isoforms. We used pixel-based second harmonic generation (SHG) polarization microscopy analyses to probe these molecular changes in human ovarian tissues [normal stroma, benign tumors, and high-grade serous (HGS) tumors] by: (i) determination of the -helical pitch angle via the single-axis molecular model, (ii) collagen alignment within fibrils via SHG anisotropy, and (iii) chirality via SHG circular dichroism (SHG-CD). Pixel approaches are required due to the complex structure of the matrix that lacks a high degree of fiber alignment. The largest differences in the helical pitch angle were between normal stroma and benign tumors, consistent with gene expression showing the Col III isoform is up-regulated in the latter. The data were not consistent with up-regulation of Col III in HGS tumors as previous reports have suggested. The different tissues also displayed differing SHG anisotropies and SHG-CD responses, consistent with either Col III incorporation or randomization of Col I alignment within benign and malignant tumors. Additionally, the high-grade tumors displayed higher collagen concentration, where this desmoplasia is consistent with the higher fiber density in these tissues. These results collectively indicate that the fibril assemblies are distinct in all tissues, where these differences likely result from the synthesis of collagen rather than remodeling of existing collagen. Importantly, these analyses are label-free and interrogate subresolution collagen structure on intact tissues, without the need for conventional structural biology tools.

Highlights

In 2018, an estimated 22,240 new cases of ovarian cancer will be diagnosed and 14,070 women will die from this disease in the United States alone.[1]
Stage III and IV high-grade serous (HGS) tumor samples show long, wavy unidirectional fibers, where these overall patterns are well conserved within the patient population, they appear more highly crimped in the latter samples
We previously classified a spectrum of ovarian tumors by texture analysis[12] and second harmonic generation (SHG) physical attributes[14] but did not delineate stage III and IV tumors, nor investigate the respective collagen abundance

Summary

Introduction

In 2018, an estimated 22,240 new cases of ovarian cancer will be diagnosed and 14,070 women will die from this disease in the United States alone.[1]. Serum methods lack sufficient specificity and sensitivity for effective screening of tumor progression.[4,5,6,7,8] With the current repertoire of diagnostic modalities, only 15% of ovarian cancer cases are diagnosed while the disease is still localized to the ovary (stage I), suggesting the need for a new modality with the resolution and specificity to detect ovarian cancer before metastasis occurs This is especially important for high-grade serous (HGS) tumors as these can metastasize while still microscopic.[9]

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