  Understanding the structural and functional development of human-induced
pluripotent stem-cell-derived cardiomyocytes is essential to engineering
cardiac tissue that enables pharmaceutical testing, modeling diseases, and
designing therapies. Here we use a method not commonly applied to biological
materials, small angle X-ray scattering, to characterize the structural
development of human-induced pluripotent stem-cell-derived cardiomyocytes
within 3D engineered tissues during their preliminary stages of maturation. An
X-ray scattering experimental method enables the reliable characterization of
the cardiomyocyte myofilament spacing with maturation time. The myofilament
lattice spacing monotonically decreases as the tissue matures from its initial
post-seeding state over the span of ten days. Visualization of the spacing at a
grid of positions in the tissue provides an approach to characterizing the
maturation and organization of cardiomyocyte myofilaments and has the potential
to help elucidate mechanisms of pathophysiology, and disease progression,
thereby stimulating new biological hypotheses in stem cell engineering.
