Most patients with rectal cancer have a better prognosis after receiving neoadjuvant therapy because of its remarkable curative effect. However, no device delivers real-time histopathologic information on treatment response to help clinicians tailor individual therapeutic strategies. We assessed the potential of multimodal nonlinear optical microscopy to monitor therapeutic responses, including tumoral and stromal responses. We found that two-photon excited fluorescence imaging can, without labeling, identify colloid response, inflammatory cell infiltration, vascular proliferation, and tumor regression. It can also directly detect rare residual tumor cells, which may be helpful for distinguishing tumor shrinkage from tumor fragmentation. In addition, second harmonic generation imaging shows the ability to monitor three types of fibrotic responses: mature, intermediate, and immature. We also determined nonlinear spectra, collagen density, and collagen orientation indexes to quantitatively analyze the histopathologic changes induced by neoadjuvant therapy in rectal cancer. Our work demonstrates that nonlinear optical microscopy has the potential to become a label-free, real-time, in vivo medical imaging technique and provides the groundwork for further exploration into the application of nonlinear optical microscopy in a clinical setting.
Multiphoton microscopy (MPM) based on two-photon excited fluorescence (TPEF) and second harmonic generation (SHG) as a potential diagnostic tool is attractive. MPM can effectively provide information about morphological and biochemical changes in biological tissues at the molecular level. In this paper, we attempt to identify normal and cancerous human colorectal muscularis propria by multiphoton microscopy in different sections (both in transverse and longitudinal sections). The results show that MPM can display different microstructure changes in the transverse and longitudinal sections of colorectal muscularis propria. MPM also can quantitatively describe the alteration of collagen content between normal and cancerous muscle layers. These are important pathological findings that MPM images can bring more detailed complementary information about tissue architecture and cell morphology through observing the transverse and longitudinal sections of colorectal muscularis propria. This work demonstrates that MPM can be better for identifying the microstructural characteristics of normal and cancerous human colorectal muscularis propria in different sections.
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