Microenvironment of the male and female reproductive tracts regulate sperm fertility: Impact of viscosity, pH, and osmolality

Abstract

Background: Terminally differentiated mammalian sperm are exposed to gradients of viscosity, pH, and osmolality both in the male and female reproductive tract during their perilous journey to quest the ovum. The complex physicochemical factors play an integral role in preparing sperm for the fertilization process.Objectives: To elucidate the influence of the reproductive tract microenvironment especially viscosity, pH, and osmolality in regulating sperm functional and fertilization competence. Materials and Methods:The data used in this review were collected from the research papers and online databases focusing on the influence of viscosity, pH, and osmolality on sperm function. Discussion:The gradients of viscosity, pH, and osmolality exist across various segments of the male and female reproductive tract. The changes in the viscosity create a physical barrier, pH aid in capacitation and hyperactivation, and the osmotic stress selects a progressive sperm subpopulation for accomplishing fertilization. The sperm function tests are developed based on the concept that the male genotype is the major contributor to the reproductive outcome. However, recent studies demonstrate the significance of sperm genotype-environment interactions that are essentially contributing to reproductive success. Hence, it is imperative to assess the impact of physicochemical stresses and the adaptive ability of the terminally differentiated sperm, which in turn would improve the outcome of the assisted reproductive technologies and male fertility assessment. Conclusion:Elucidating the influence of the reproductive tract microenvironment on sperm function provides newer insights into the procedures that need to be adopted for selecting fertile males for breeding, and ejaculates for the assisted reproductive technologies.

Relevance of Aquaporins for Gamete Function and Cryopreservation

“…On the one hand, in bovines, the epididymis, uterine and oviductal environments are hyperosmotic compared to the isoosmotic seminal plasma. In humans, mice, and rats, osmolality is progressively lower from the epididymis to the seminal plasma and then to the uterus, whereas in cattle and sheep the uterus and the epididymis are relatively hyperosmotic to seminal plasma (reviewed in [ 68 ]).…”

Deletion of the Sodium Glucose Cotransporter 1 (Sglt‐1) impairs mouse sperm movement

“…These motility defects are exacerbated when the cells are exposed to a medium with higher viscosity, which mimics the female reproductive tract. This highly viscous environment is believed to act as a mechanism for the selection of those spermatozoa that are best fit for fertilization (Hunter et al, 2011; Kirkman‐Brown & Smith, 2011; Lavanya et al, 2022). Progressive motility is critical for sperm migration through the viscous fluids of the cervical mucus (Sakkas et al, 2015).…”

Iberiotoxin and clofilium regulate hyperactivation, acrosome reaction, and ion homeostasis synergistically during human sperm capacitation

“…Sperm capacitation occurs when the ejaculated sperm enters the female reproductive tract with microenvironment changes (Lavanya et al, 2022). Ion homeostasis regulation is critical for sperm capacitation (Miller et al, 2015; Shukla et al, 2012).…”

“…However, the capacitation mechanisms are intricate and elusive. This process occurs when sperm travel through the female reproductive tract and face microenvironmental changes (Lavanya et al, 2022), such as osmotic pressure, pH, and ion concentration variation, thus the ion channels are generally considered to play essential roles during sperm capacitation (Brown et al, 2019; Kirichok & Lishko, 2011; Shukla et al, 2012).…”