Chapter 4 Role of Antioxidants and Antifreeze Proteins in Cryopreservation/Vitrification

Ovarian tissue cryopreservation and transplantation: a review on reactive oxygen species generation and antioxidant therapy

Cancer is the leading cause of death worldwide. Fortunately, the survival rate of cancer continues to rise, owing to advances in cancer treatments. However, these treatments are gonadotoxic and cause infertility. Ovarian tissue cryopreservation and transplantation (OTCT) is the most flexible option to preserve fertility in women and children with cancer. However, OTCT is associated with significant follicle loss and an accompanying short lifespan of the grafts. There has been a decade of research in cryopreservation-induced oxidative stress in single cells with significant successes in mitigating this major source of loss of viability. However, despite its success elsewhere and beyond a few promising experiments, little attention has been paid to this key aspect of OTCT-induced damage. As more and more clinical practices adopt OTCT for fertility preservation, it is a critical time to review oxidative stress as a cause of damage and to outline potential ameliorative interventions. Here we give an overview of the application of OTCT for female fertility preservation and existing challenges; clarify the potential contribution of oxidative stress in ovarian follicle loss; and highlight potential ability of antioxidant treatments to mitigate the OTCT-induced injuries that might be of interest to cryobiologists and reproductive clinicians.

Ovarian tissue cryopreservation: prospective randomized study on thawed ovarian tissue viability to estimate the maximum possible delivery time of tissue samples

Ovarian tissue cryopreservation is one of the most important methods to protect female fertility, but we just recently established the first central laboratory in China, now building a network with other hospitals. The aim was to estimate the thawed ovarian tissue viability and to explore the feasibility of short-distance transportation. Fifteen samples were obtained from each of 11 patients, i.e. in total 165 samples. One fresh sample was used for follicle counts, 14 punches were cryopreserved, thawed, and randomly divided into seven groups depending on the time after thawing: 0, 20, 40, 60, 80, 100, 120 min. Follicle counts, steroid hormones, and lactate levels were assessed. No significant differences for the three parameters of tissue viability comparing the seven groups were seen. The time can last up to two hours for the delivery of tissue samples from the laboratory to the surgery room. To our knowledge, this question has been tested for the first time systematically within a prospective randomized comparative study.

Advances in the slow freezing cryopreservation of microencapsulated cells

Over the past few decades, the use of cell microencapsulation technology has been promoted for a wide range of applications as sustained drug delivery systems or as cells containing biosystems for regenerative medicine. However, difficulty in their preservation and storage has limited their availability to healthcare centers. Because the preservation in cryogenic temperatures poses many biological and biophysical challenges and that the technology has not been well understood, the slow cooling cryopreservation, which is the most used technique worldwide, has not given full measure of its full potential application yet. This review will discuss the different steps that should be understood and taken into account to preserve microencapsulated cells by slow freezing in a successful and simple manner. Moreover, it will review the slow freezing preservation of alginate-based microencapsulated cells and discuss some recommendations that the research community may pursue to optimize the preservation of microencapsulated cells, enabling the therapy translate from bench to the clinic.