Different approaches for assessing sperm function

Abstract

Different approaches can be used to assess sperm function in different conditions, i.e. sperm storage, freezing-thawing or activation by induction of capacitation and acrosome reaction. In this review we will focus on the assays routinely performed in our laboratories, giving a literature support to critically analyse different approaches. In fact, researchers usually tend to look for the "one shot" parameter that could explain itself a specific process; it is our conviction that a multiparametric approach is still more valid, as some changes in sperm function are very complex and could be explained only by operating in different ways. Sperm motility, the most evident sperm characteristic, should be assessed by computer-aided sperm analysers that permit an objective evaluation of the motility and its kinematic parameters. Commercial and open source instruments are available and could be profitably used together with specific statistical approaches. The use of microscopy, and particularly fluorescent microscopy, could be a very useful tool to assess different parameters in sperm cells both by fluorophores that give indication of a determined function, and by immunolocalization of proteins, that permits the discover of new features or to explain particular sperm functions. The same substrates could be used also in flow cytometry: the difference is that it permits to study wider sperm populations (and their subpopulation distribution). Flow cytometry is undergoing a very wide use in spermatology and technical and experimental rigor is needed to obtain reliable results. Metabolic assessment of sperm features, particularly energetic supply, ATP formation and other enzyme activities, could represent a very important challenge to acquire new information and complete/integrate those derived from other techniques. Finally, functional assays such as oocyte binding and in vitro fertilization, represent a very strong tool to assess sperm function in vitro, as they could evidence the functional intactness of some pathways.

Diagnostic tests in canine andrology - What do they really tell us about fertility?

“…Regarding the possibilities of systems such as CASA, further research is required to determine which measurements are of clinical importance in canine andrology [91]. It is likely that there are not many single spermatological "on-off" parameters, but a multiparametric approach may help to reliably predict fertility [87].…”

“…It has been shown, for example, that in human medicine, sperm number and morphology are associated with time to natural pregnancy, whereas sperm motility is less predictive [73] and its significance is sometimes misestimated [87]. Spermatozoa are mainly passively transported in the female genital tract [88], while their motility is, however, required for reaching the oocytes and during zona pellucida penetration [89,90].…”

Biomarker-based human and animal sperm phenotyping: the good, the bad and the ugly

“…The introduction of computer-assisted sperm analysis (CASA) was the first step toward the computerization of sperm phenotyping [ 217 ]. Naturally, fluorescent probes lend themselves to flow cytometric analysis, benefiting from high-speed, high-throughput fluorometry [ 218 , 219 ]. Vital stains and probes for sperm analysis have been reviewed in detail including live/dead, mitopotential, acrosomal integrity, and ROS indicators [ 220 , 221 ].…”

Sperm chromatin stability and their relationship with fertilization rate in Sheep of the Junín race

“…Membrane integrity is important for sperm metabolism, training, acrosomal reaction, and sperm binding to the surface of the oocyte [4]. In contrast, damage to membrane integrity can cause loss of normal sperm function, such as motility, viability, and fertilizing capacity.…”