The effect of temperature shock on enhancing sperm motility: A new insight into molecular and cellular mechanisms through current procedures

Abstract

Asthenozoospermia, characterized by reduced progressive motility (below 32%), is a leading cause of male infertility. Intrauterine Insemination (IUI) serves as the first-line treatment in sperm-related processes, aiming to increase sperm motility. Although Density Gradient Centrifugation (DGC) and swim-up procedures have become primary treatment options, considered the gold standard for IUI, there is a need to optimize these methods with additional factors to enhance motility, particularly for Asthenozoospermia patients. We hypothesize that a brief cold shock, lasting approximately 15-20 min at 17 degrees C, followed by incubation and sperm processing, can substantially enhance motility. For the first time, the hypothesis and evaluation of postexposure incubation following a short-term cold shock, within the temperature range of 17-20 degrees C, were explored and discussed. This hypothesis appears valid and holds importance for several reasons. Firstly, there is a significant relationship between cold shock and its impact on intracellular components and the molecular organization of the cell membrane. Additionally, this process regulates various physiological cellular processes, including transbilayer distribution, acrosome reaction, and sperm motility. Moreover, lowering the temperature induces a molecular flux, facilitating calcium uptake by sperm. This process significantly impacts the quantity of calcium accessible to the sperm, particularly within the flagellum. Choosing the temperature below 20 degrees C temperature can lead to the activation of calcium-absorbing protein channels in the shortest possible time. Furthermore, a crucial reaction in IUI is sperm capacitation, which occurs when the protein tyrosine phosphorylation pathway, a key factor, is activated. Alternatively, the cold incubation of sperm reveals an increased level of tyrosine phosphorylation and a higher percentage of induced Acrosome Reaction (AR) compared to sperm incubated at normal temperatures. Hence, when sperm is cooled, it initiates a process called tyrosine phosphorylation, ultimately leading to sperm capacitation. Besides these logical reasons, there is limited empirical and incidental support in two cases that confirmed the hypothesis well.