Flow cytometry TUNEL standardization for assaying sperm DNA fragmentation.

摘要

We read with great interest Muratori's paper (Muratori et al, 2010), because we believe that terminal deoxynu-cleotidyl transferase-mediated dUTP nick end labeling (TUNEL) assay standardization is a matter of great concern and that there are certain steps that must be followed to achieve accurate results.We agree with the authors of the paper but feel the need to stress several important considerations. As the authors mention in their introduction, the labeling of DNA breaks should be carried out by nuclear staining with propidium iodide (PI; Muratori et al, 2008). We have noted in oligozoospermia samples a clear increase in the percentage of Pi-negative events with forward scatter/side scatter similar to sperm, yielding lower results. The upper sperm count limit that could be considered a threshold for this phenomenon is difficult to establish; thus, TUNEL/PI should be applied to all samples, and reference values should be recalculated for future clinical use.