Rajesh Wakchaure et al Int. J. Phar. & Biomedi. Rese. 2015, 2 (5): 11-16 ISSN: 2394 – 3726 Copyright © 2015; IJPBR 11 A Review on Cryopreservation of Embryos and its Research Implications in Animal Breeding and Reproduction Rajesh Wakchaure 1 , Subha Ganguly 2 *, Subhash Sharma 3 , Praveen Kumar Praveen 4 , Maneesh Sharma 5 and Tanvi Mahajan 6 1 Dept. of Animal Genetics & Breeding, 2 Dept. of Veterinary Microbiology, 3 Dept. of Veterinary Parasitology, 4 Dept. of Veterinary Public Health & Epidemiology, 5 Dept. of Veterinary Pathology, 6 Dept. of Veterinary Anatomy & Histology, Arawali Veterinary College (Affiliated with Rajasthan University of Veterinary and Animal Sciences, Bikaner) N.H. – 11 Jaipur Road, V.P.O. Bajor, Dist. Sikar, Pin – 332001, Rajasthan, India *Corresponding Author E-mail: ganguly38@gmail.com INTRODUCTION Embryo cryopreservation has been a useful tool for embryology since the early 1970s. It has become an essential part of assisted reproductive technologies, allowing long term storage of valuable embryos from lab animals, livestock, endangered species and humans. Initially, work was done with conventional slow cooling technologies using cryoprotectants such as glycerol or ethylene glycol and sucrose. More recently, however, a greater advance has been made with vitrification, a procedure that bypasses ice crystal formation and places the embryo in a glass-like state. This technology is receiving greater attention as it is simpler, faster and less expensive, and provides the embryo with greater protection from cryoinjury. Principle of Embryo Cryopreservation For prolong Storage of embryos, one has to attain a suspended stage of animation where cleavage of embryo would be suspended and cellular activities would be practically at standstill. The safest method to achieve this goal is to expose the embryos to progressively lower temperature and finally store in liquid nitrogen (-196 o C) or liquid helium (-296 o C). There are six step storage of embryo to successful embryo cryopreservation i) exposure to cryoprotectant, ii) cooling to subzero temperatures, iii) storage, iv) thawing or warming, v) removal of cryoprotectant and vi) return to a physiological environment [1-3]. Two important parameters determine the success of all cryopreservation protocols 1) Rate of cells regaining equilibrium in response to cooling 2) Speed of freezing [1-3]. Cryoinjury can occur from formation of intracellular or extracellular ice crystals, chemical toxicity and osmotic injury [4] and is dependent upon size and shape of cells, membrane permeability, Available online at www.ijpbr.org ISSN: 2394 - 3726 Int. J. Phar. & Biomedi. Rese. 2015, 2 (5): 11-16 ABSTRACT The goal of embryo cryopreservation is long term storage and reproducible high survival rates of embryos following warming, leading to the successful establishment of pregnancy and live offspring following embryo transfer. Successful cryopreservation requires a good understanding of the proper use of cryoprotectants, sugars and macromolecules in order to allow the highest survival rates and ultimately pregnancy and live offspring following embryo transfer. The success is dependent upon many variables, including embryo stage and quality, embryo species, cooling and warming rates and culture conditions. Efforts to optimize these conditions will further enhance survival and future developmental potential of the embryo. Key words: Cryoprotectants, Embryo cryopreservation, Reproduction, Vitrification