Human Sperm as an In Vitro Model to Assess the Efficacy of Antioxidant Supplements during Sperm Handling: A Narrative Review

Abstract

Spermatozoa are highly differentiated cells that produce reactive oxygen species (ROS) due to aerobic metabolism. Below a certain threshold, ROS are important in signal transduction pathways and cellular physiological processes, whereas ROS overproduction damages spermatozoa. Sperm manipulation and preparation protocols during assisted reproductive procedures—for example, cryopreservation—can result in excessive ROS production, exposing these cells to oxidative damage. Thus, antioxidants are a relevant topic in sperm quality. This narrative review focuses on human spermatozoa as an in vitro model to study which antioxidants can be used to supplement media. The review comprises a brief presentation of the human sperm structure, a general overview of the main items of reduction–oxidation homeostasis and the ambivalent relationship between spermatozoa and ROS. The main body of the paper deals with studies in which human sperm have been used as an in vitro model to test antioxidant compounds, including natural extracts. The presence and the synergic effects of different antioxidant molecules could potentially lead to more effective products in vitro and, in the future, in vivo.

In Vitro Effects of Charged and Zwitterionic Liposomes on Human Spermatozoa and Supplementation with Liposomes and Chlorogenic Acid during Sperm Freezing

“…To accomplish the first step of this research, human spermatozoa were incubated with empty liposomes (cationic, anionic, and zwitterionic), and endpoints such as motility MMP, DNA, and acrosome integrity were evaluated. This protocol considered the investigation of the main sperm characteristics and structures, giving a general outcome of the sperm’s response to the treatments [ 20 ]. The experiments were carried out in a selected sperm population which was as homogenous as possible, where it was easier to detect the possible changes caused by the interaction with liposomes.…”

“…Many antioxidants have already been successfully used for media supplementation during cryopreservation of human semen. Freezing–thawing protocols enhance reactive oxygen species (ROS) production and, consequently, oxidative stress, which damages spermatozoa [ 20 ].…”

Effect of Zinc Supplementation to Diluent Boar Semen on Sperm Characteristics and Activity of Antioxidant Enzymes

“…Beside this, the use of spermatozoa to find out the direct influence of the substance under study on their motile function and viability is the most expedient and practically justified. Due to their high differentiation and specific function, spermatozoa depend on and are deeply influenced by the external environment, making them ideal for testing trace elements, including antioxidant compounds [44]. Therefore, in this work, boars sperm as an in vitro model, has been used to assess the efficacy of zinc.…”

Redox Homeostasis and Nrf2-Regulated Mechanisms Are Relevant to Male Infertility

“…This condition favors the oxidative damages with respect to the antioxidant defenses; subsequently, it causes damage to biomolecules through oxidative reactions [16]. As oxidants, oxygen free radicals and additional ROS are known to be involved both in physiological and pathological (oxidative damage) mechanisms [17][18][19]. In sperm, ROS play a relevant role in regulating several intracellular pathways.…”