RESUMEN
BACKGROUND: Reducing the percentage of sperm anomalies in insemination samples remains a goal to be achieved in the intra-cytoplasmic sperm insemination (ICSI) procedure. The aim of this study was to evaluate the efficiency of density gradient centrifugation (DGC) and Zeta methods to recover sperm with intact chromatin, and to evaluate whether the combined DGC/Zeta procedure improved ICSI outcome. METHODS: In Experiment 1, DGC and Zeta methods were carried out on 60 unprocessed semen samples. The samples were then assessed by chromomycin A3 staining, acridine orange test, terminal deoxynucleotidyl transferase dUTP nick end labeling assay and the sperm chromatin dispersion test for protamine deficiency and DNA fragmentation. In Experiment 2, sibling oocytes from 30 ICSI candidates were divided into two groups; one group was inseminated with sperm processed by DGC and the second with sperm processed by DGC/Zeta. The outcomes of 30 ICSI cycles were compared between the two groups and also with 34 ICSI candidates whose oocytes were inseminated by DGC-processed sperm. RESULTS: Both procedures were efficient for the recovery of sperm with normal protamine content and low DNA fragmentation. However, the Zeta method yielded a greater number of sperm with less DNA fragmentation. Fertilization and pregnancy rates were improved following the combined DGC/Zeta procedure. Compared with DGC alone, the pregnancy rate appeared improved but this was not statistically significant (P = 0.091). CONCLUSIONS: Combining DGC and Zeta procedures improves the quality of semen samples which may increase fertilization rates and possibly pregnancy rates.