C-kit^pos cells in the human left atrial appendage

Subpopulations of myocardial c-kit^pos cells have the ability to stimulate regeneration in ischemic heart disease by paracrine effects. The left atrial appendage (LAA), which is easy accessible during cardiac surgery, may represent a perfect source for c-kit^pos cell extraction for autologous cell therapies in the living human. So far, frequency and distribution of c-kit^pos cells in LAA are unknown.

LAAs of patients who underwent cardiac surgery due to coronary artery disease (coronary artery bypass graft, CABG), valvular heart disease or both and of two body donors were examined. Tissue was fixed in 4 % paraformaldehyde, embedded in paraffin, dissected in consecutive sections and stained for c-kit^pos cells. In parallel, grade of fibrosis, amount of fat per section and cells positive for mast cell tryptase were examined.

We collected 27 LAAs (37.0 % female, mean left ventricular ejection fraction 50.4 %, 63.0 % persistent atrial fibrillation (AF)). Most of the patients underwent combined CABG and valve surgery (51.9 %). C-kit^pos cells were detected in 3 different regions: A) Attached to the epicardial fat layer, B) close to vascular structures and C) between cardiomyocytes. C-kit^pos cells ranged from 0.05 c-kit^pos cells per mm² to 67.5 c-kit^pos cells per mm². We found no association between number of c-kit^pos cells and type of AF, amount of fibrosis or amount of fat. Up to 72 % of c-kit^pos cells also showed a positive staining for mast cell tryptase.

C-kit^pos cells are frequent in LAAs of cardiovascular patients with a rather homogenous distribution throughout the LAA. The LAA can therefore be considered as a source for extraction of a reasonable quantity of autologous cardiac progenitor cells in the living human patient.