Development of in vitro tests of human sperm function: A diagnostic tool and model system for toxicological analyses

The mammalian spermatozoon is a highly specialized cell which, during the process of evolution, has developed a unique compartmentalized structure in order to express the diverse array of biological properties (movement, cell recognition, secretion, membrane fusion) required to fertilize the egg. This paper describes an integrated battery of tests that can be used to obtain information on certain key aspects of human sperm function in vitro. These tests include computerized digital image analysis systems to record the movement characteristics of the spermatozoa, in vitro assays of sperm-zona recognition based on human ova stored in high ionic strength salt solutions, the use of fluorescein-conjugated lectins to detect the acrosome reaction and inter-species in vitro fertilization procedures to assess the ability of human spermatozoa to fuse with the vitelline membrane of the oocyte. In combination these assays provide information that is predictive of the fertilizing capacity of human spermatozoa in vitro and in vivo, and, as such, should find application in assessing the influence of xenobiotics on male fertility. In addition, such tests may be of value in developing model in vitro systems employing human spermatozoa for the analysis of toxicity at the cellular level, particularly in relation to the influence of xenobiotics on the properties of biological membranes.