Clarification and confocal imaging of the non-human primate placental micro-anatomy

Placental function is essential for the development of the fetus, and is – in part – related to the 3D arrangement of the villous and vascular geometry. Recent advances in tissue clarification techniques allow for deep high-resolution imaging with confocal microscopy without altering the spatial characteristics of the tissue. These image stacks can be analyzed quantitatively to provide insights regarding the villous and vascular micro-anatomy as well as the interrelationships between the two. However, such analyses require optimization of the tissue preparation, immuno-labeling, and clarification protocol in order to provide reliable results suitable for the detection of subtle differences in pathologic pregnancies. Placental and fetal development are similar between human and non-human primate pregnancies, with the latter serving as a reliable, validated, highly-controlled, well-characterized translational model for the former. We present a protocol for the preparation, immuno-labeling, and clarification of the non-human primate placenta optimized for confocal microscopy and subsequent quantification of the micro-anatomic structures.