Should posthumously retrieved mammalian spermatozoa be evaluated via interspecific ICSI?

There are circumstances in which mammalian spermatozoa are collected and/or long-term stored under suboptimal conditions, such as during posthumous sperm retrieval. As a consequence, the sperm can exhibit lower motility, be completely immotile, or have membranes that are more or less severely damaged. With the advent of ICSI (intracytoplasmic sperm injection), either the entire sperm or only the sperm head (e.g., in the mouse) can be directly injected into a mature oocyte, thereby making motility a less critical parameter. However, if sperm were collected and stored under suboptimal conditions, blind sperm injection into oocytes seems risky, especially when oocytes are also scarce, as in the case of endangered animals. The same applies to humans, where safety and ethical considerations are primary concerns. If such sperm are intended for reproductive purposes, DNA quality and integrity should be routinely evaluated, as they are among the most important factors for embryo viability. Although there are several standard tests to assess sperm quality, they may not be sufficient when working with to a certain extent compromised samples. Here, we discuss whether, in these specialized cases, interspecific ICSI could help expand the range of tests available to assess sperm normality.