PCR genotyping for determination of origin of silver-nitrate-stained endothelial cells. (a) Polygonal endothelial cells identified on Dacron grafts after silver nitrate staining. (b) PCR genotyping of silver nitrate-stained endothelial cells demonstrating bone marrow origin. (c) Endothelial cells stained positive for CD34 antigen. (d) Hematoxylin and eosin staining of silver nitrate-stained section.