In vivo visualization of skin inflammation by optical coherence tomography and two-photon microscopy

Inflammation is a non-specific immune response to injury intended to protect biological tissue from harmful stimuli such as pathogens, irritants, and damaged cells. In vivo optical tissue imaging has been used to provide spatial and dynamic characteristics of inflammation within the tissue. In this paper, we report in vivo visualization of inflammation in the skin at both cellular and physiological levels by using a combination of label-free two-photon microscopy (TPM) and optical coherence tomography (OCT). Skin inflammation was induced by topically applying lipopolysaccharide (LPS) on the mouse ear. Temporal OCT imaging visualized tissue swelling, vasodilation, and increased capillary density 30 min and 1 hour after application. TPM imaging showed immune cell migration within the inflamed skin. Combined OCT and TPM was applied to obtain complementary information from each modality in the same region of interest. The information provided by each modality were consistent with previous reports about the characteristics of inflammation. Therefore, the combination of OCT and TPM holds potential for studying inflammation of the skin.