Effects of temperature and storage time on the motility, viability, DNA integrity and apoptosis of processed human spermatozoa

Manipulation of metabolism to improve liquid preservation of mammalian spermatozoa

Reproductive success in mammals hinges on the ability of sperm to generate sufficient energy through cellular metabolism to perform the energy-intensive processes required for fertilisation, including motility, maturation, and oocyte interactions. It is now widely accepted that sperm exhibit metabolic flexibility, utilising a combination of glycolysis and oxidative phosphorylation (supported by the Krebs cycle and other complementary pathways) to meet their energy demands. However, the preferred pathway for energy production varies significantly among species, making it challenging to map species-specific metabolic strategies, particularly in species with high metabolic flexibility, like the ram. Additionally, differences in methodologies used to measure metabolism have led to biased interpretations of species' metabolic strategies, complicating the development of liquid storage methods aimed at preserving spermatozoa by manipulating energy generation based on species-specific requirements. This review examines sperm energy requirements, current methods for assessing metabolic capacity, and the current research on species-specific metabolism. Future research should focus on establishing a standardised approach for determining metabolic preferences to accurately map species-specific strategies, a critical step before developing effective liquid preservation methods. By identifying species-specific regulatory points, strategies can be designed to temporarily inhibit metabolic pathways, conserving resources and reducing the accumulation of metabolic by-products. Alternatively, supplementation with depleted metabolites can be guided by understanding areas of excessive consumption during prolonged metabolism. Applying this knowledge to develop tailored preservation techniques will help minimise sperm damage and improve survival during in vitro processing and liquid storage, ultimately enhancing the success of artificial breeding programs.

Assessment of reproductive, genotoxic, and cytotoxic effects of leachate-contaminated water in male mice

Leachate-contaminated water (LCS) poses significant health risks due to its heavy metal content and altered physicochemical properties. This study examined the physicochemical parameters and heavy metal levels in LCS and assessed its reproductive toxicity, genotoxicity, and cytotoxic effects in exposed mice. Groups of mice (n = 5) were orally administered 100 μL of 30 % and 70 % LCS (v/v) twice daily for 35 days. Drinking water served as a negative control, and cyclophosphamide (Cyp) (20 mg/kg bw) as a positive control. On day 36, the mice were weighed, sacrificed, and their testicular weight, sperm count, sperm morphology, viability, acrosome integrity, and serum testosterone were examined. Oxidative stress in the testes, histopathological changes, and serum markers for liver and kidney function (SGOT, SGPT, and creatinine) were also assessed. Genotoxic effects were evaluated using a micronuclei (MN) assay. Analysis of the leachate showed altered physicochemical parameters and elevated heavy metal levels. Exposure to LCS led to a significant decrease in relative testis weight, sperm count, normal sperm morphology, viability, acrosome integrity, and serum testosterone levels. It also caused a notable increase in MDA levels and a decrease in catalase (CAT), superoxide dismutase (SOD), and glutathione (GSH) levels, along with histological changes in the testes of LCS-treated mice compared to controls. Additionally, there was a significant rise in MN formation in RBCs and elevated levels of liver enzymes and creatinine, indicating liver and renal toxicity. Histological alterations in the liver and kidneys were also observed in LCS-exposed mice. These findings suggest that LCS induces reproductive toxicity, genotoxicity, and cytotoxicity in male subjects.

Methodological considerations for examining the relationship between sperm morphology and motility

Sperm cells of all taxa share a common goal to reach and fertilize an ovum, yet sperm are one of the most diverse cell types in nature. While the structural diversity of these cells is well recognized, the functional significance of variation in sperm design remains elusive. An important function of spermatozoa is a need to migrate toward the ova, often over long distances in a foreign environment, which may include a complex and hostile female reproductive tract. Several comparative and experimental studies have attempted to address the link between sperm morphology and motility, yet the conclusions drawn from these studies are often inconsistent, even within the same taxa. Much of what we know about the functional significance of sperm design in internally fertilizing species has been gleaned from in vitro studies, for which experimental parameters often vary among studies. We propose that discordant results from these studies are in part due to a lack of consistency of methods, conditions that do not replicate those of the female reproductive tract, and the overuse of simple linear measures of sperm shape. Within this review, we provide a toolkit for imaging, quantifying, and analyzing sperm morphology and movement patterns for in vitro studies and discuss emerging approaches. Results from studies linking morphology to motility enhance our understanding of the evolution of adaptive sperm traits and the mechanisms that regulate fertility, thus offering new insights into methods used in assisted reproductive technologies in animal science, conservation and public health.