Cells under pressure: how sublethal hydrostatic pressure stress treatment increases gametes' and embryos' performance

The principal approach in in vitro embryo culture and manipulation has been a defensive one: procedures aim to satisfy passively the supposed or real physiological needs of gametes and embryos. Similarly, during cryopreservation the aim is to cause minimal damage to cells whilst attempting to obtain the highest achievable cell survival. However, carefully chosen and precisely controlled sublethal stress treatment of cells has been described to improve embryos' and gametes' performance, and, as a consequence, subsequent morphological survival, fertilisation, in vitro development, pregnancy and farrowing rates improved considerably compared with untreated controls. This review summarises studies that open up a new approach: instead of - and besides - trying to passively reduce the harm to cells during in vitro manipulations and culture, procedures may also prepare the cells themselves to ward off or reduce the damage by turning up the cells' own, inner capacities.