Testing for “Life”—how predictable?

Abstract

I read with interest the article by El-Nour and colleagues (1) depicting the outcome of ICSI when nonmotile spermatozoa are the only source available for injection as evaluated for viability by exposure to a modified hypo-osmotic swelling (HOS) test. Selection of spermatozoa identified for its membrane functional integrity may yield improvements in fertilization rates and embryo development, especially for spermatozoa from suboptimal specimens such as those employed in the study by El-Nour and colleagues (1). However, I would like to direct the authors’ attention to an aspect of the procedure that may not have been considered by making reference to other studies for illustration purposes and also by illustrating the use of HOS testing for diagnostic and clinical purposes (2, 3). In the study by El-Nour and colleagues, the authors incubated the HOS test-group immotile spermatozoa and then selected swollen spermatozoa for injection (1). By using this approach, one cannot be sure that each spermatozoon selected represents a spermatozoon undergoing “true swelling,” which is defined as that swelling induced by the exposure to the hypo-osmotic environment. By comparison, spontaneous swelling of spermatozoa, which occurs in physiologic environments, may not represent viable sperm. It must be remembered that when assessing spermatozoa after HOS incubation, both types of swelling (true swelling and spontaneous swelling) will be encountered. Thus, for diagnostic HOS testing, the sample is first assessed for the percentage of spontaneous swelling and this percentage is then subtracted from the percentage of swelling after the HOS test to determine true swelling. To overcome this limitation when performing clinical HOS for ICSI, one can expose a single spermatozoon to the HOS solution and observe its behavior while in solution. If the reaction is positive, i.e., beginning of tail swelling, then the spermatozoon is handled for injection, and if the reaction is negative, then another spermatozoon may be chosen. This protocol may be time consuming, especially if the sample is very poor in terms of availability of motile spermatozoa. However, one can be sure of the type of spermatozoa chosen for injection in terms of sperm viability. In addition, there is the possibility that the authors may have selected spontaneously swollen spermatozoa, which may have affected their results. Another approach under consideration may be the modification of HOS solutions with protein supplements (4). The protein supplementation seems to delay the onset of sperm swelling when the spermatozoa are exposed to the hypo-osmotic environment. A high proportion of the spermatozoa exposed to those solutions containing protein supplementation remain motile or undergo minimal swelling with associated motility under hypo-osmotic conditions. Thus, spermatozoa may be directly incubated in those modified hypo-osmotic solutions supplemented with protein and assessed for motility with or without associated swelling and used directly for ICSI. It is believed that this population of spermatozoa represents those that would otherwise react optimally to the conventional HOS solutions with the advantage of reducing the time involved in exposing a single spermatozoon or a sample of spermatozoa to the HOS solution and reequilibrating the spermatozoon to physiologic conditions before performance of the injection procedure.