Sperm Selection in Assisted Reproduction: A Review of Established Methods and Cutting-Edge Possibilities - Beyond the Abstract

Assisted reproduction technologies (ART) are employed in human medical practice to overcome infertility issues or in the veterinary field to increase the number and the quality of subjects in the animal breeding industry, to obtain purebred subjects or to preserve endangered animal species. ART includes methods for gametes (oocytes and sperm) processing and their subsequent use for fertilization.

During the last decades, the demand for ART is increasing due to delayed parenthood, diseases, and idiopathic or unknown causes. According to the World Health Organization guidelines, embryologists should use Swim Up and Density Gradient Centrifugation techniques for sperm selection.1 However, these techniques rely on centrifugation steps responsible for cell damage. Alternative novel techniques have been introduced but offer disadvantages that need to be overcome. In this respect, the lab-on-a-chip (LOC) is an emerging tool among ART for sperm selection, which shows different practical advantages in comparison to the other techniques.

Microfluidics deal with the manipulation of small amounts of volume within a microdevice, which offers rapid analyses, ease of use, small reagent sample volumes, high-throughput processing and wide reproducibility owing to automation and standardization. Furthermore, the presence of a closed system inside such devices may reduce potential environmental contamination. As the LOC allows gamete handling within a microenvironment that strictly mimics physiological in vivo conditions and avoids centrifugation steps and long processing time, the use of microfluidics for sperm sorting and selection have been proposed during the last fifteen years and is currently under investigation. Many studies show how these microfluidic devices are able to sort sperm cells with better or comparable quality than the sperm fraction obtained with the other employed techniques.

The high relevance of the topic is confirmed also by the presence of a commercialized microfluidic device and by the publication of the first clinical trial performed with the same device in 2018. Moreover, LOC technologies to sort, identify and analyze other kinds of cells could be transferred to sperm selection and analysis, thus opening the way to a novel approach to sperm cell selection and manipulation. Our review offers an updated description of all the techniques performed in human and animal clinical practice for sorting good-quality spermatozoa, including LOCs, and provides to the reader the positive and negative aspects of each method, as well as the comparison between different techniques when possible.

Written by: Alessandra Ferramosca, MD, University Researcher, Department of Biological and Environmental Sciences and Technologies, Università del Salento, Piazza Tancredi, Italy

Reference:

1. World Health Organization, and Stop TB Initiative (World Health Organization). Treatment of tuberculosis: guidelines. World Health Organization, 2010.

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