Thermotaxis of Human Sperm Cells in Extraordinarily Shallow Temperature Gradients Over a Wide Range

Abstract

On the basis of the finding that capacitated (ready to fertilize) rabbit and human spermatozoa swim towards warmer temperatures by directing their movement along a temperature gradient, sperm thermotaxis has been proposed to be one of the processes guiding these spermatozoa to the fertilization site. Although the molecular mechanism underlying sperm thermotaxis is gradually being revealed, basic questions related to this process are still open. Here, employing human spermatozoa, we addressed the questions of how wide the temperature range of thermotaxis is, whether this range includes an optimal temperature or whether spermatozoa generally prefer swimming towards warmer temperatures, whether or not they can sense and respond to descending temperature gradients, and what the minimal temperature gradient is to which they can thermotactically respond. We found that human spermatozoa can respond thermotactically within a wide temperature range (at least 29–41°C), that within this range they preferentially accumulate in warmer temperatures rather than at a single specific, preferred temperature, that they can respond to both ascending and descending temperature gradients, and that they can sense and thermotactically respond to temperature gradients as low as <0.014°C/mm. This temperature gradient is astonishingly low because it means that as a spermatozoon swims through its entire body length (46 µm) it can sense and respond to a temperature difference of <0.0006°C. The significance of this surprisingly high temperature sensitivity is discussed.

Multi-Objective Optimization Algorithm Based on Sperm Fertilization Procedure (MOSFP)

“…The temperature of the female reproductive system plays a significant role of determining the sperms movement direction. The scientists found that the sperm head acts like a temperature sensor to search for a warmer area (the egg location) [28]. Furthermore, the sperm head can response and sense to a temperature difference of <0.0006 °C [28].…”

“…As we mentioned previously, sperm head acts like a temperature sensor, which prefers to swim towards warmer temperatures (egg location) [28]. In addition, sperm moves forward to search on the guidance (higher concentrations of molecules) that produced and released by the egg, which this guidance knew as Chemo-taxis [31].…”

The construction of an interfacial valve-based microfluidic chip for thermotaxis evaluation of human sperm

“…4 Recently, they used a Lucite tube device with a controllable temperature gradient to show that only a small fraction of human sperm, which are capacitated and ready-tofertilize, have thermotactic responses, and that portion of sperm can respond to both ascending and descending temperature gradient within a wide temperature range. 5,6 Despite these advances, a convenient and efficient observable device with precise control of temperature gradient is still need to be developed for human sperm thermotaxis screening.…”

Mechanisms of the sperm guidance, an essential aid for meeting the oocyte

“…These findings raised the hypothesis that the temperature difference might serve as a cue for guiding spermatozoa to the site of fertilization. Interestingly, Bahat et al,(10) recently has reported that human spermatozoa are thermotactically responsive over a wide temperature range (29-41 ℃), much wider than the range considered physiological.As in sperm chemotaxis, only capacitated spermatozoa are thermotactically responsive (9). Additionally, in chemotaxis and thermotaxis, spermatozoa swim up the gradient by modulating the frequency of turns and hyperactivation events, essentially in the direction of the gradient (11,12).…”

“…These findings raised the hypothesis that the temperature difference might serve as a cue for guiding spermatozoa to the site of fertilization. Interestingly, Bahat et al, (10) recently has reported that human spermatozoa are thermotactically responsive over a wide temperature range (29-41 ℃), much wider than the range considered physiological.…”