Only a subpopulation of mouse sperm displays a rapid increase in intracellular calcium during capacitation

DALOTTO-MORENO, TOMAS; PUGA MOLINA, LIS C.; SCHIAVI-EHRENHAUS, LIZA J.; LUQUE, GUILLERMINA M.; VISCONTI, PABLO E.; RITAGLIATI, CARLA; DALOTTO-MORENO, TOMAS; BALESTRINI, PAULA A.; PUGA MOLINA, LIS C.; KRAPF, DARIO; SCHIAVI-EHRENHAUS, LIZA J.; LUQUE, GUILLERMINA M.; VISCONTI, PABLO E.; RITAGLIATI, CARLA; BALESTRINI, PAULA A.; KRAPF, DARIO; MARTÍN-HIDALGO, DAVID; ROMAROWSKI, ANA; GILIO, NICOLAS; BUFFONE, MARIANO G.; MARTÍN-HIDALGO, DAVID; ROMAROWSKI, ANA; GILIO, NICOLAS; BUFFONE, MARIANO G.

JOURNAL OF CELLULAR PHYSIOLOGY

WILEY-LISS, DIV JOHN WILEY & SONS INC

Año: 2018 vol. 233 p. 9685 - 9700

0021-9541

Mammalian sperm must undergo a functionally defined process called capacitation to be able to fertilize oocytes. They become capacitated in vivo by interacting with the female reproductive tract or in vitro in a defined capacitation medium that contains bovine serum albumin, calcium (Ca2+), and bicarbonate (HCO3 −). In this work, sperm were double stained with propidium iodide and the Ca2+ dye Fluo-4 AM and analyzed by flow cytometry to determine changes in intracellular Ca2+ concentration ([Ca2+]i) in individual live sperm. An increase in [Ca2+]i was observed in a subpopulation of capacitated live sperm when compared with noncapacitated ones. Sperm exposed to the capacitating medium displayed a rapid increase in [Ca2+]i within 1 min of incubation, which remained sustained for 90 min. These rise in [Ca2+]i after 90 min of incubation in the capacitating medium was evidenced by an increase in the normalized median fluorescence intensity. This increase was dependent on the presence of extracellular Ca2+ and, at least in part, reflected the contribution of a new subpopulation of sperm with higher [Ca2+]i. In addition, it was determined that the capacitation-associated [Ca2+]i increase was dependent of CatSper channels, as sperm derived from CatSper knockout (CatSper KO) or incubated in the presence of CatSper inhibitors failed to increase [Ca2+]i. Surprisingly, a minimum increase in [Ca2+]i was also observed in CatSper KO sperm suggesting the existence of other Ca2+ transport systems. Altogether, these results indicate that a subpopulation of sperm increases [Ca2+]i very rapidly during capacitation mainly due to a CatSper-mediated influx of extracellular Ca2+.