KIT and atrial fibrillation: Moreover, considering that when detected, CD117+ cells represent only approximately 1–5% of AF cells, whereas the percentage of cells expressing pluripotent markers such as Oct4 or SSEA4 can be sensibly higher, the preferential selection of the c-kit+ subpopulation might be too restrictive to determine the possible loss of cells at the top of the stem hierarchy with high differentiation potential.