OBJECTIVETo detect the sperm plasma membrane integrity (PMI) of varicocele (VC) patients using SYBR-14/PI fluorescent staining and flow cytometry, and investigate its clinical significance.

METHODSWe collected semen samples from 120 men, including 30 grade-1 varicocele patients (VC1), 30 grade-2 (VC2), 30 grade-3 (VC3), and 30 normal fertile volunteer controls. Conventional semen analyses were performed by computer-assisted semen analysis (CASA). All the semen samples were washed with PBS and then subjected to SYBR-14/PI staining for the detection of sperm PMI by flow cytometry. The proportion of normal sperm with PMI was indicated as the percentage of sperm emitting green fluorescence (SYBR-14+/PI- %), sperm PMI was determined and sperm fertilization capacity predicted.

RESULTSSignificant differences were detected in SYBR-14+/PI- and SYBR-14-/PI+ between the normal men and varicocele male patients (P < 0.01). The percentages of the sperm with PMI (SYBR-14+/PI- %) were remarkably lower in the VC1, VC2 and VC3 groups ([54.85 +/- 3.78]%, [45.37 +/- 4.12]% and [35.14 +/- 4.91]%) than in the normal controls ([70.79 +/- 6.71]%). SYBR-14+/PI-% was correlated positively with sperm motility (r=0.965, P < 0.01) and the percentage of grade a + b sperm (r = 0.874, P < 0.01), negatively with the percentage of grade d sperm (r = -0.965, P <0.01), but not significantly with pH, semen volume and liquefaction time (P > 0.05).

CONCLUSIONSYBR-14/PI fluorescent staining and flow cytometry can quickly and exactly detect sperm PMI. Varicocele decreases sperm PMI, which might be an important cause of male infertility.