RESUMEN
Cryopreservation of human spermatozoa is a necessity for males suffering from infertility who cannot produce fresh semen for insemination. However, current ART cryopreservation protocols are associated with losses of sperm motility, vitality and DNA integrity, which are thought to be linked to the induction of oxidative damage and the toxic properties of commercial cryoprotectants (CPAs). Preventing or mitigating these losses would be hugely beneficial to sperm survival during ART. Therefore, in this in vitro investigation, lipid peroxidation, production of reactive oxygen species, movement characteristics, antioxidant capacity, vitality, and DNA integrity were examined in semen samples both pre- and post-cryopreservation with CPA supplementation. The findings revealed a 50% reduction in antioxidant capacity with CPA addition, which was accompanied by significant increases in generation of reactive oxygen species and formation of lipid aldehydes. These changes were, in turn, correlated with reductions in sperm viability, motility and DNA integrity. Antioxidant supplementation generated bell-shaped dose-response curves with both resveratrol and vitamin C, emphasising the vulnerability of these cells to both oxidative and reductive stress. At the optimal dose, vitamin C was able to significantly enhance vitality and reduce DNA damage recorded in cryopreserved human spermatozoa. An improvement in sperm motility did not reach statistical significance, possibly because additional pathophysiological mechanisms limit the potential effectiveness of antioxidants in rescuing this aspect of sperm function. The vulnerability of human spermatozoa to reductive stress and the complex nature of sperm cryoinjury will present major challenges in creating the next generation of cryoprotective media.
RESUMEN
BACKGROUND: Infertility is defined as the failure to achieve clinical pregnancy after 12 months of regular unprotected intercourse. It could be due to male or female factors, each requiring different treatment options. ART treatment exposes couples to numerous psychological stressors. Therefore, it has been recommended by the ESHRE Psychology and Counselling Guideline Development Group recently that psychosocial support should be offered as a complementary therapy during infertility treatments. In this context, the efficiency of different psychological interventions, such as cognitive behaviour therapy (CBT), deep breathing (DB), and progressive muscle relaxation (PMR), was evaluated in several clinical trials in terms of couples' mental health and pregnancy outcomes. OBJECTIVE AND RATIONALE: The neurophysiology of CBT, DB and PMR, which are used in interventional studies, in both men and women undergoing ART, has not yet been fully elucidated. This review represents a comprehensive report, aiming to collate novel insights into the neurobiological processes and physiological mechanisms that occur during the practice of CBT, DB and PMR. SEARCH METHODS: PubMed, Google Scholar and Cochrane Library were interrogated to conduct this comprehensive literature review. The search was carried out using combinations of MeSH terms and keywords: infertility, assisted reproductive techniques, IVF, ICSI, emotions, psychological stress, cognitive behavioural therapy, mind-body therapies and relaxation. Relevant information related to the mechanism of action of stress management techniques were obtained from original articles and reviews published in English without taking into consideration the time of publication. Moreover, as it was not the major focus of the review, only recent systematic reviews (2015-2019) pinpointing the effects of psychological interventions on infertility treatment outcomes were also retrieved from the above-mentioned databases. OUTCOMES: CBT, DB and PMR may modify the activity of stress-related brain regions such as the prefrontal cortex, amygdala, hypothalamus and hippocampus, as demonstrated by functional MRI and electroencephalogram studies. Furthermore, applying these techniques was associated with mood improvements and a decline in stress biomarkers, and, hypothetically, reducing stress biomarkers attenuates the stress-induced effects on ART outcomes. WIDER IMPLICATIONS: Increasing the knowledge of fertility staff, researchers and physicians regarding the mechanisms of action of these stress management techniques has several advantages. For instance, understanding the underlying neurophysiological pathways would assist practitioners to engage ART couples in the practice of these techniques. Also, it may enhance the quality of the support programmes and psychological research. Accordingly, this will ensure that these interventions reach their full potential and therefore improve clinical outcomes.