Electron microscopy in the investigation of asthenozoospermia

Abstract

Asthenozoospermia, defined as low sperm motility, is a significant cause of subfertility in men. Its origins are diverse and in some instances cannot be ascertained. However, severely reduced motility can often be associated with abnormalities in the structure of the sperm tails, which can only be detected by transmission electron microscopy (TEM). In this respect, TEM is an important adjunct to the traditional methods of semen analysis. This review examines the development of the current state of knowledge of sperm tail abnormalities. These may be genetic in origin, or they may be acquired as a result of extrinsic factors. At present, consistent molecular markers are not available to characterise many of the genetic defects. However, TEM can distinguish specific defects of genetic origin and the non-specific structural anomalies that are typical of an acquired condition. It can also differentiate sperm structural anomalies from necrospermia, or sperm death, which is another significant cause of asthenozoospermia. In this modern era of assisted reproduction, it is possible in some instances to circumvent the problems of sperm immotility and to achieve fertilisation and pregnancy using intracytoplasmic sperm injection (ICSI). However, because of the possible genetic origin of asthenozoospermia, many scientists working in the field of infertility believe that it is of the utmost importance to investigate the causes of asthenozoospermia. This review considers the continuing relevance of TEM to the evaluation of sperm tail abnormalities in the context of current reproductive techniques.

The application of scanning near field optical imaging to the study of human sperm morphology

“…This technique allows the analysis of living unmodified spermatozoa that are immobilized in narrow chambers and examined by negative contrast phase microscopy [21]. In the last decades, other fundamental studies have been carried out by transmission and scanning electron microscopies (TEM and SEM), which have enabled to detect ultrastructural details and have provided a huge amount of information concerning morphological organization of spermatozoa [22][23][24][25]. However, SEM imaging usually needs harsh sample preparation as drying at critical point, metal coating and vacuum environment (during coating procedure and measurements) that may modify some structural features of cells.…”

The application of scanning near field optical imaging to the study of human sperm morphology

“…This technique allows the analysis of living unmodified spermatozoa that are immobilized in narrow chambers and examined by negative contrast phase microscopy [ 21 ]. In the last decades, other fundamental studies have been carried out by transmission and scanning electron microscopies (TEM and SEM), which have enabled to detect ultrastructural details and have provided a huge amount of information concerning morphological organization of spermatozoa [ 22 - 25 ]. However, SEM imaging usually needs harsh sample preparation as drying at critical point, metal coating and vacuum environment (during coating procedure and measurements) that may modify some structural features of cells.…”

Male factor infertility and ART

“…In the former category, electron microscopy is the gold standard to diagnose specific sperm defects. 49 Correction should be carried out when possible (e.g., transurethral resection of the ejaculatory ducts in partial ejaculatory duct obstruction). Injection of uncharacterized immotile sperm makes fertilization after ICSI unpredictable and decreases both fertilization and pregnancy rates.…”