An interdisciplinary systems approach to study sperm physiology and evolution

Applications of laser technology in the manipulation of human spermatozoa

The application of laser technology in the field of assisted reproductive technology (ART) has experienced rapid growth over the past decades owing to revolutionary techniques such as intracytoplasmic sperm injection (ICSI), preimplantation genetic testing (PGT), and in vitro manipulation of gametes and embryos. For male gametes, in vitro manipulation techniques include spermatozoa selection, sorting, immobilization, and quality assessment. A number of studies have been conducted to investigate the application of different laser technologies in the manipulation of human spermatozoa. However, there is a lack of a unified understanding of laser application in the in vitro manipulation of sperm and safety considerations in ART and, subsequently, the inability to make clear and accurate decisions on the clinical value of these laser technologies. This review summarizes the advancements and improvements of laser technologies in the manipulation of human spermatozoa, such as photobiomodulation therapy, laser trap systems for sperm analysis and sorting, laser-assisted selection of immotile sperm and laser-assisted immobilization of sperm prior to ICSI. The safety of those technologies used in ART is also discussed. This review will provide helpful and comprehensive insight into the applications of laser technology in the manipulation of human spermatozoa.

Preimplantation embryo metabolism and culture systems: experience from domestic animals and clinical implications

Despite advantages of in vitro embryo production in many species, widespread use of this technology is limited by generally lower developmental competence of in vitro derived embryos compared to in vivo counterparts. Regardless, in vivo or in vitro gametes and embryos face and must adjust to multiple microenvironments especially at preimplantation stages. Moreover, the embryo has to be able to further adapt to environmental cues in utero to result in the birth of live and healthy offspring. Enormous strides have been made in understanding and meeting stage-specific requirements of preimplantation embryos, but interpretation of the data is made difficult due to the complexity of the wide array of culture systems and the remarkable plasticity of developing embryos that seem able to develop under a variety of conditions. Nevertheless, a primary objective remains meeting, as closely as possible, the preimplantation embryo requirements as provided in vivo. In general, oocytes and embryos develop more satisfactorily when cultured in groups. However, optimization of individual culture of oocytes and embryos is an important goal and area of intensive current research for both animal and human clinical application. Successful culture of individual embryos is of primary importance in order to avoid ovarian superstimulation and the associated physiological and psychological disadvantages for patients. This review emphasizes stage specific shifts in embryo metabolism and requirements and research to optimize in vitro embryo culture conditions and supplementation, with a view to optimizing embryo culture in general, and culture of single embryos in particular.