REVIEW Cryopreservation and oxidative stress in reproductive cells CARLA TATONE 1 , GIOVANNA DI EMIDIO 1 , MARILENA VENTO 2 , ROSANNA CIRIMINNA 3 , & PAOLO GIOVANNI ARTINI 4 1 Department of Health Sciences, University of L’Aquila, L’Aquila, Italy, 2 Servizio di PMA/Azienda Ospedaliera Cannizzaro, Catania, Italy, 3 A.M.B.R.A., Associazione Medici e Biologi per la Riproduzione Assistita, Palermo, Italy, and 4 Division of Obstetrics and Gynecology, Department of Reproductive Medicine and Child Development, University of Pisa, Pisa, Italy (Received 11 November 2009; accepted 1 February 2010) Abstract In spite of the optimisation of cryopreservation protocols, post-thawing trauma to mammalian gametes cannot be completely avoided. Based on recent literature, cellular cryodamage in reproductive cells has been extensively characterised in terms of changes in the cell structure, whereas biochemical alterations have been poorly investigated. The present paper reviews the current knowledge about the involvement of oxidative stress in frozen-thawed cells by considering the most relevant studies in sperm and oocytes. Recognising that spermatozoa are highly susceptible to oxidative damage induced by cryopreservation, the need for further research is highlighted in order to understand whether changes in the redox state have a role in the reduced developmental potential of cryopreserved human reproductive cells. Keywords: Oxidative stress, reactive oxygen species, cryopreservation, oocyte, sperm, cryodamage, redox state Introduction Recent advances in assisted reproduction and embry- ology have made cryopreservation a suitable method for long-term storage of human reproductive cells, embryos and gonadal tissues to maintain and protect fertility in various occasions such as infertility and malignancy treatments [1]. However, although highly optimised protocols improve cell viability, the ex- treme stress of freezing and thawing treatments can negatively affect the original functions of the cell. In this context, it is well established that the most vulnerable cells are the oocytes probably as a consequence of peculiar membrane permeability to water and physiology [2]. Although at a reduced extent, frozen thawed spermatozoa of many species are known to be less fertile than fresh semen, for reasons not yet completely understood [3]. It is well established that injury caused by freezing and thawing in eukaryotic cells is the result of several factors such as ice nucleation and dehydration [4], which are responsible for osmotic stress and damage to membrane structures observed by electron microscopy [5]. Biological and clinical studies per- formed so far have led to an extensive characterisation of cellular damage in female and male reproductive cells [6] and to valuable analysis of the clinical impact of the cryopreservation procedures [7]. Less well understood is the relationship of these damages with the metabolic and bioenergetic status of the cells. In this context a relevant hypothesis is that the process of freezing and thawing increases production of reactive oxygen species (ROS) which, in turn, can affect original cell functions. Oxidative metabolic perturba- tions are encountered by all aerobic organisms and will completely alter the redox state of the cells, eventually leading to generic stress responses [8]. For this reason oxidative stress is an important factor in subzero cryogenic injury. Increased ROS generation is associated with osmotic stress in a variety of somatic cells as well as in sperm, and may serve as a signalling mechanism responsible for the cell adaptive response [9,10]. It has also been proposed that the repair of cell structures requires energy generation with subsequent increase in ROS production [11,12]. The involvement of oxidative Correspondence: Carla Tatone, Department of Health Sciences, University of L’Aquila, Via Vetoio, 67100 L’Aquila, Italy. E-mail: carla.tatone@univaq.it Gynecological Endocrinology, August 2010; 26(8): 563–567 ISSN 0951-3590 print/ISSN 1473-0766 online ª 2010 Informa UK Ltd. DOI: 10.3109/09513591003686395 Gynecol Endocrinol Downloaded from informahealthcare.com by UNIVERSITA DEGLI STUDI DI PISA on 11/06/12 For personal use only.