Use of a Synthetic Macromolecule (Hydroxypropyl Cellulose ) and Trehalose as Additives for Oocyte Vitrification

Infertility

Oocyte vitrification, survival rate, egg banking, ovum donation

This study is aimed to evaluate the use of Hydroxypropyl Cellulose (HPC) as substitute for the traditional protein supplement (Synthetic Serum Substitute; SSS) and Trehalose as substitute for the most widely used sugar (Sucrose) in the vitrification solutions employed for oocyte vitrification.

Vitrification involves the transformation of an aqueous solution into a very viscous solid avoiding ice formation. To achieve this, the vitrification protocols include high concentrations of cryoprotectants dissolved in a base medium supplemented with serum rich in protein. Traditionally available preparations contains human albumin (HSA). The most commonly used in vitrification solutions is the synthetic serum replacement (SSS) consisting of synthetic glycoporoteins and HSA. The replacement of human albumin by other fully synthetic components enables compliance with the European directives for classification of Class III medical device in accordance with the Manual for the Classification of Medical Devices in the regulatory framework of the European community, and therefore these media have the European CE conformity marking (Directive 93/42/EEC). According to European regulations, Class III medical devices are subject to special supervision and require certification exam or design type examination by a notified body. Commercial media supplied by Kitazato supplies ® (Tokyo, Japan) to be used in this study have been submitted to the whole process of evaluation and certification by the notified body BSI0086. Because of physical properties of hydroxypropyl cellulose (HPC), fully synthetic macromolecule, including the ability to form a viscous gel at low temperatures, this macromolecule has been proposed as a substitute for human origin albumin (HSA). Another necessary component of vitrification media is sucrose, which acts as an osmotic agent. Trehalose, a disaccharide present in nature is used by certain species to survive extreme conditions, being able to remain vitrified for years. This sugar has also been employed previously in cryobiology in some vitrification protocols. We have tested HPC and threhalose for oocytes vitrification in a pilot study, showing that no impairment in the survival rates, embryo development and pregnancy rates. The current study is a prospective randomized trial aimed to assess the outcome of ovum donation cycles conducted with vitrified oocytes using HPC and trehalose versus oocytes vitrified using traditional available solutions containing HAS and sucrose.

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