Aqueous Origanum vulgare Extract Improves the Quality of Cryopreserved Human Spermatozoa Through Its Antioxidant Effects

Sperm Cryopreservation Today: Approaches, Efficiency, and Pitfalls

The cryopreservation of human spermatozoa has been an option for patients undergoing chemo or radiotherapies since the late 1950s. Presently, there are different techniques for the cryopreservation of spermatozoa. The most commonly used techniques are programmable slow freezing and freezing on liquid nitrogen vapors, while the use of vitrification is still not accepted as clinically relevant. Although there have been many improvements, the ideal technique for achieving better post-thaw sperm quality continues to be a mystery. A major obstacle during cryopreservation is the formation of intracellular ice crystals. Cryodamage generated by cryopreservation causes structural and molecular alterations in spermatozoa. Injuries can happen because of oxidative stress, temperature stress, and osmotic stress, which then result in changes in the plasma membrane fluidity, motility, viability, and DNA integrity of the spermatozoa. To prevent cryodamage as much as possible, cryoprotectants are added, and in some clinical trial cases, even antioxidants that may improve post-thaw sperm quality are added. This review discusses cryopreservation techniques, cryodamage on molecular and structural levels, and cryoprotectants. It provides a comparison of cryopreservation techniques and describes recent advances in those techniques.

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

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.

Sperm cryopreservation and DNA methylation: possible implications for ART success and the health of offspring

Despite the beneficial effects of sperm cryopreservation, increased reactive oxygen species (ROS) production during this process can affect spermatozoon structure and function. Moreover, ROS production is associated with elevated DNA damage and alterations in DNA methylation. There is little information about the effects of cryopreservation on epigenetic modulation in sperm and the health of children born with frozen spermatozoa. Considering the potential consequences of cryopreservation in ART-conceived children, it is necessary to assure that cryopreservation does not modify sperm DNA methylation status. This review summarizes reports on epigenetic modifications of spermatozoa during cryopreservation and the probable effects of this process on offspring health. Contradictory results have reported the influence of sperm cryopreservation on DNA methylation in imprinted genes. Multiclinical studies with larger sample sizes under the same conditions of cryopreservation and DNA methylation analysis are needed to make any definitive conclusion about the effect of the cryopreservation process on sperm DNA methylation.

The Effect of Astaxanthin on Motility, Viability, Reactive Oxygen Species, Apoptosis, and Lipid Peroxidation of Human Spermatozoa During the Freezing-Thawing Process

Cryopreservation of spermatozoa is a general procedure to preserve viable sperm for an indefinite period. Despite the efficiency of sperm cryopreservation, excessive reactive oxygen species (ROS) production during cryopreservation can induce structural and functional changes in spermatozoa. Also, cryopreservation has been shown to decrease the spermatozoa's antioxidant activity inducing them to be more sensitive to damage caused by ROS. Experimental evidence suggests that astaxanthin (AXT) has essential activities such as antioxidant, antibacterial, and antithrombotic properties. Therefore, this study aimed to evaluate the effect of AXT on the sperm quality of healthy men during freezing-thawing. In the first phase, 10 semen samples with different concentrations of AXT (0.0, 0.5, 1, and 2 μM) were cryopreserved to achieve an optimal dose of AXT. Then, motility, viability, and phosphatidylserine (PS) externalization were evaluated. In the second phase, 25 samples were collected and divided into 3 groups: fresh group, control group (untreated frozen-thawed samples), and AXT group (treated frozen-thawed with AXT). Then, samples were cryopreserved in freezing media supplemented with or without the optimal concentration of AXT (1 μM). After thawing, the levels of sperm parameters, including motility (using a computer-assisted sperm analyzer), viability (eosin-nigrosin), early apoptotic change (annexin V/propidium iodide), ROS (flow cytometry), and lipid peroxidation (LPO) (using enzyme-linked immunosorbent assay), were evaluated. Our results showed that the addition of 1 μM AXT to sperm freezing media improved all parameters of sperm motility and viability (p ≤ 0.05). Furthermore, it could reduce the levels of ROS parameters (intracellular hydrogen peroxide and superoxide) compared with the control group (p ≤ 0.05). Also, AXT significantly decreased the level of PS externalization (p ≤ 0.05) and LPO (p ≤ 0.05) after the freezing-thawing process. In conclusion, our findings demonstrated that human semen treatment with 1 μM AXT before the freezing-thawing process has protective effects against oxidative stress and could diminish the destructive effects of this process on sperm quality.

Advanced biomaterials in cell preservation: Hypothermic preservation and cryopreservation

Cell-based medicine has made great advances in clinical diagnosis and therapy for various refractory diseases, inducing a growing demand for cell preservation as support technology. However, the bottleneck problems in cell preservation include low efficiency and poor biocompatibility of traditional protectants. In this review, cell preservation technologies are categorized according to storage conditions: hypothermic preservation at 1 °C~35 °C to maintain short-term cell viability that is useful in cell diagnosis and transport, while cryopreservation at -196 °C~-80 °C to maintain long-term cell viability that provides opportunities for therapeutic cell product storage. Firstly, the background and developmental history of the protectants used in the two preservation technologies are briefly introduced. Secondly, the progress in different cellular protection mechanisms for advanced biomaterials are discussed in two preservation technologies. In hypothermic preservation, the hypothermia-induced and extracellular matrix-loss injuries to cells are comprehensively summarized, as well as the recent biomaterials dependent on regulation of cellular ATP level, stabilization of cellular membrane, balance of antioxidant defense system, and supply of mimetic ECM to prolong cell longevity are provided. In cryopreservation, cellular injuries and advanced biomaterials that can protect cells from osmotic or ice injury, and alleviate oxidative stress to allow cell survival are concluded. Last, an insight into the perspectives and challenges of this technology is provided. We envision advanced biocompatible materials for highly efficient cell preservation as critical in future developments and trends to support cell-based medicine. STATEMENT OF SIGNIFICANCE: Cell preservation technologies present a critical role in cell-based applications, and more efficient biocompatible protectants are highly required. This review categorizes cell preservation technologies into hypothermic preservation and cryopreservation according to their storage conditions, and comprehensively reviews the recently advanced biomaterials related. The background, development, and cellular protective mechanisms of these two preservation technologies are respectively introduced and summarized. Moreover, the differences, connections, individual demands of these two technologies are also provided and discussed.

Effects of hydroethanolic extracts of Terminalia chebula and Thymbra spicata on ram fresh semen under normal and oxidative stress conditions

The objective of this study was to evaluate protective effects of hydroethanolic extracts of Terminalia chebula and Thymbra spicata on viability, lipid peroxidation (LPO) and DNA integrity of ram fresh semen under normal and oxidative stress (OS) conditions. Antioxidant activities of different concentrations of Terminalia chebula and Thymbra spicata extracts were evaluated with DPPH assay. Semen samples were taken from three fertile adult rams. After diluting semen with Tris-base extender, different concentrations of Terminalia chebula and Thymbra spicata (30, 300, and 3000 μg/ml) extracts were used under normal and induced OS conditions. The group not receiving any supplements was considered as control group. A total of 50 μM hydrogen peroxide was used to induce OS. MTT solution was added to each of treatment groups which were kept in an incubator at 37°C for 2 h. After incubation, readings were obtained by ELISA reader. DNA integrity and LPO were determined with acridine orange (AO) staining and malondialdehyde (MDA) assay. Higher concentrations of Terminalia chebula and Thymbra spicata extracts preserved viability and DNA integrity while reducing MDA concentrations compared to other treatment groups. Also, under induced OS, higher concentrations of both extracts reduced detrimental effects of H₂ O₂ . In conclusion, it seems that addition of Terminalia chebula and Thymbra spicata extracts can reduce induced OS in spermatozoa.