Optical coherence tomography for in vivo imaging of endocardial to mesenchymal transition during avian heart development.

The endocardial to mesenchymal transition (EndMT) that occurs in endocardial cushions during heart development is critical for proper heart septation and formation of the heart's valves. In EndMT, cells delaminate from the endocardium and migrate into the previously acellular endocardial cushions. Optical coherence tomography (OCT) imaging uses the optical properties of tissues for contrast, and during early development OCT can differentiate cellular versus acellular tissues. Here we show that OCT can be used to non-invasively track EndMT progression in vivo in the outflow tract cushions of chicken embryos. This enables in vivo studies to elucidate factors leading to cardiac malformations.