[Frontiers in Bioscience 11, 2565-2573, September 1, 2006] 2565 Up date of in vitro production of porcine embryos Takashi Nagai 1 , Hiroaki Funahashi 2 , Koji Yoshioka 3 and Kazuhiro Kikuchi 4 1 National Institute of Livestock and Grassland Science, 2 Ikenodai, Tsukuba, Ibaraki, 305-0901, Japan, 2 The Graduate School of Natural Science and Technology, Okayama University, Tsushima-Naka, Okayama 700-8530, Japan, 3 National Institute of Animal Health, 3-1-5 Kannondai, Tsukuba, Ibaraki 305-0856, Japan, 4 National Institute of Agrobiological Sciences, Kannondai 2-1-2, Tsukuba, Ibaraki 305-8602, Japan TABLE OF CONTENTS 1. Abstract 2. Introduction 3. Improvement of IVM oocyte quality 3.1. Control of anti-oxidant content in IVM oocytes 3.2. IVM of oocytes under a low oxygen tension 3.3. Importance of cumulus cells during IVM of oocytes 3.4. Step-wise IVM systems 4. Prevention of abnormal fertilization 4.1. Control of polyspermic fertilization from sperm side by changing IVF procedure 4.2. Control of polyspermic fertilization from oocyte and oviduct sides 4.3. Sperm penetration into immature oocytes 5. IVC of IVM-IVF oocytes 6. Perspective 7. Acknowledgements 8. References 1. ABSTRACT There have been intensive attempts to establish reliable in vitro maturation (IVM) and fertilization (IVF) methods in pigs. Although a great deal of progress has been made, current IVM-IVF systems still suffer from a low rate and poor quality of in vitro produced embryos . In this review, we will review the recent studies about IVM -IVF of porcine oocytes and the in vitro culture (IVC) system, especially modified in vitro production (IVP) system that produces high quality of porcine blastocysts. We then try to suggest practical ways to solve the problems mentioned above in the pigs. 2. INTRODUCTION Pigs have been playing an important role in meat production in many countries, especially in Asia. They produced over 25% of the energy and 5% of the protein that human obtained from animal sources in the world in early 1990s (1), and the percentages may be getting higher now because Bovine Spongiform Encephalopathy (BSE) in cattle and the bird influenza have the potential to ignite a human pandemic, which may reduce beef and chicken consume. Moreover, new applications of pigs outside animal industry are drawing attention in the field of human medicine. It is hoped that pig organs can be used as human organ replacement in the face of the serious shortage of human organs for transplantation (2). The use of pigs as experimental animals is also gaining ground; for example, they are useful models for studying arteriosclerosis (3). Thus, their application in fields other than traditional animal industry is expanding. The new technologies to produce transgenic and cloned pigs also provide us with the potential of very rapid genetic manipulation and dissemination. Furthermore, somatic cell cloning is expected to be a valuable method for conserving genetic resources in pigs. All such technologies involve manipulating oocytes and/or embryos in vitro. Thus the concept of in-vitro maturation (IVM) and in vitro fertilization (IVF) of oocytes in pigs has a particular importance now. Since Mukherjee (4) reported that mouse oocytes could be matured and fertilized in vitro and developed to term in 1972, there have been intensive attempts in pigs. Mattioli et al. (5) succeeded in getting piglets from IVM-IVF embryos in 1989. Although a great deal of progress has been made, our current IVM -IVF systems still suffer from two major problems: 1) a high rate of polyspermy, i.e. the penetration of porcine oocyte by more than one spermatozoon in vitro, and 2) a low rate of