Three-dimensional visualization of intrauterine conceptus through the uterine wall by tissue clearing method.

Visualization of specific cells in the three-dimensional organ architecture is one of the key steps to develop our knowledge about pathophysiological mechanisms in various organs. In this study, we successfully obtained stereoscopic whole images of the intrauterine murine embryo and placenta through the uterus using a modified tissue clearing CUBIC method. By this procedure, we can recognize the three-dimensional relationships among various tissues within the pregnant uterus and analyze free-angle images of cross-sections with single-cell resolution using a computer system. Based on these data, we can select optimal cross-section angles and then produce the corresponding tissue slices that are adequate for further immunohistochemical examination. Furthermore, using transgenic mice, distinct images of an EGFP-positive embryo and the placenta can be obtained, confirming the precise three-dimensional location of invading trophoblasts in the feto-maternal interface in the uterus. These results indicate that this procedure will significantly contribute to analyzing pathophysiological mechanisms in reproductive organs.