Freeze Drying as a Method of Long-Term Conservation of Mammalian Semen – A Review

Iwona Rajska

doi:10.2478/aoas-2020-0122

Abstract

Abstract With the development of biotechnological methods that allow the manipulation and free exchange of genetic material, the methods for collecting and storing such material need to be improved. To date, freezing in liquid nitrogen has allowed the storage of cells and entire plant and animal tissues for practically unlimited times. However, alternatives are still being sought to eliminate the constant need to maintain samples at a low temperature. Lyophilization or freeze drying is an alternative to standard freezing procedures. The storage of samples (lyophilisates) does not require specialised equipment but only refines the preservation method itself. In the case of cells capable of movement e.g., sperm, they lose the ability to reach the oocyte in vivo and for in vitro fertilization (IVF) because of the lyophilization process. However, freeze-dried sperm may be used for in vitro fertilization by intracytoplasmic sperm injection (ICSI), based on the results obtained in cleavage, embryo development and the production of live born offspring after embryo transfer. Studies on the lyophilization of sperm have been performed on many animal species, both in the laboratory and in livestock. This conservation method is considered to create biobanks for genetically valuable and endangered species with the simultaneous application of ICSI. This review article aimed to present the issues of the freeze-drying process of mammalian semen and help find solutions that will improve this technique of the long-term preservation of biological material.

Highlights

History of freeze-drying With the development of biotechnology, more efficient and less labour- and timeconsuming methods of the long-term preservation of biological material have been sought
Freeze-drying as an alternative method of the long-term conservation of mammalian semen has been used in biobanking and can help maintain the biodiversity of many species of farm and wild animals
Postmortem, ejaculated or epididymal sperm and fresh or previously frozen semen can be used for lyophilization

Summary

Introduction

History of freeze-drying With the development of biotechnology, more efficient and less labour- and timeconsuming methods of the long-term preservation of biological material have been sought. Cryopreservation is commonly used – i.e., the storage of cells or fragments of plant or animal tissues at liquid nitrogen temperature (–196°C) (Gajda and Rajska, 2014). The process of freezing and thawing itself, associated with the transformation of water into ice and vice versa, leads to the formation of ice crystals, which can significantly damage cellular organelles, thereby leading to the sample destruction (Holt, 2000) To avoid this undesirable phenomenon, cryopreservation methods were sought in which water passes from liquid to glassy (Saragusty and Arav, 2011). Benedict in 1905 and Shackell in 1909 performed the first tests of lyophilization of biological material using the vacuum itself and the vacuum pump The improvement of this preservation method led to the first bacterial lyophilisates (Hammer, 1911), followed by animal tissues, drugs, blood serum and antibiotics (Flosdorf and Mudd, 1935). Blastocysts were obtained because of the introduction of lyophilized granulosa cells, stored at room temperature for 3 years into enucleated sheep oocytes

Objectives

Findings

Conclusion