Background: Intracytoplasmic sperm injection (ICSI) is the primary treatment for male infertility. However for this procedure, with the exception of visual morphological selection, there is no standardization for sperm selection. Recently, the hypo-osmotic swelling test (HOST) has been proposed to potentially select sperm with intact membranes. The aim of this study is to evaluate the ability of this technique to select functional sperm in terms of apoptosis and morphology, as well as nuclear integrity.
Methods: A total of 20 semen samples were randomly collected from men who attended the Andrology Unit of the Isfahan Fertility and Infertility Center. Semen samples were washed and exposed to hypotonic conditions, before being fixed and simultaneously assessed for membrane integrity as well as abnormal morphology, DNA fragmentation and protamine deficiency by using Papanicolaou, TUNEL and CMA3 staining techniques, respectively. The remaining semen samples were washed with calcium buffer and stained by Annexin V, then exposed to hypotonic conditions before being assessed for early apoptosis along with membrane integrity.
Results: HOST grade 'd', followed by grade 'c', showed the highest percentages of healthy sperm, whereas sperm of HOST grade 'g' in which anomalies in terms of apoptosis, abnormal head morphology or nuclear immaturity or membrane damage, were most frequently observed in the samples assessed.
Conclusions: Integration of HOST into the sperm selection procedure may provide a valuable tool for selection of functional sperm required for ICSI. According to this study, insemination of HOST grade 'g' sperm should be avoided during ICSI.