Cardiac applications of second harmonic generation (SHG) microscopy

Human induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs) are an unlimited ex vivo supply of heart cells for cardiac applications. The establishment of pure iPSC-CMs populations is crucial for downstream medical applications such as human disease modeling, patient-specific stem cell therapy, human transplantation, and drug development. However, a significant challenge is the lack of an established purification method to isolate populations of iPSC-CMs by their phenotype, maturity, and subtype due to the lack of specific iPSC-CM markers. The ability to remove potentially teratoma forming pluripotent stem cells, arrhythmia inducing immature and pacemaking cells, and other non-CMs is extremely important for engineering tissues with desired cell compositions that are both safe for human transplantation and that can accurately replicate cardiac functions. Contemporary purification techniques have either low specificity or require genetic modification. We have proposed that second harmonic generation (SHG) signals, which are known to originate from the sarcomeric myosin filaments in cardiomyocytes, can be a highly specific, labelfree marker for identifying iPSC-CMs. Here, we demonstrate the use of SHG microscopy for characterizing iPSC-CMs and their subtypes.