Sığır embriyolarının klasik ve vitrifikasyon tekniği ile dondurulması

Son yıllarda sığır embriyoları ticari amaçlı üretilmekte ve uluslararası transferleri gerçekleşmektedir. Embriyo dondurma teknolojisi ile üretilen embriyolar ucuza mal olmakta ve genetik potansiyeli korumak amacıyla gün geçtikçe önem kazanmaktadır. Günümüzde çok sayıda sığır embriyosu in vitro maturasyon, fertilizasyon ve kültür ile yani in vitro olarak üretilmektedir. Avrupa’ da ve Amerika’ da hem in vitro üretilmiş hem de canlı hayvanlardan elde edilen dondurulmuş embriyoların ulusal ve uluslararası ticareti yapılmaktadır. Bu teknolojinin tam olarak kullanılabilmesi için in vitro üretilen embriyoların sıvı nitrojende saklanması şarttır. Farklı kimyasal yapılara sahip olan Glycerol, Dimetilsülfoksid ve Glycoller sığır embriyolarının dondurulması için yaygın olarak kullanılmaktadır. în vitro üretilen embriyolar in vivo elde edilenlere oranla düşük sıcaklıklara hassastır. Bu sorunun üstesinden gelebilmek için geliştirilen vitrifikasyon teknikleri ile in vitro üretilen embriyolarda, klasik tekniklere oranla daha yüksek canlılık oranları elde edilmektedir. Genellikle in vitro üretilen sığır embriyolarının dondurmayı takiben düşük canlılık oranları vermesi bu teknolojinin ticari uygulamasını kısıtlayan en önemli faktörlerdendir. Vitrifikasyon tekniğinin kolay uygulanabilirlik, düşük maliyet, hızlı uygulanması gibi avantajlarına rağmen, günümüzde kullanımı deneysel çalışmalarla sınırlı kalmaktadır. Bu nedenle ticari olarak embriyo transferi için geleneksel yavaş dondurma tekniği hâlâ tercih edilmektedir. Dondurma çözdürme prosedürleri, tekniklerin basitleşmesinden ötürü çiftlik koşullarına bile adapte edilebilmektedir. Bu makalede, sığır embriyolarının cryobiyolojik özellikleri, farklı dondurmaçözdürme prosedürleri ve tekniklerinin embriyoların canlılık oranlarına etkileri ortaya konmaktadır

Anahtar Kelimeler:

Dondurma, Kryoprotektanlar, Sığır embriyoları, Vitrifikasyon

Cryopreservation of bovine embryos

In the last decade, production and international transport of viable/transferable bovine embryos are getting more attention. Embryo cryopreservation technology has been used for many years as a tool to provide genetic resources at low cost. Large numbers of bovine embryos are currently produced by means of in vitro maturation, fertilization, and culture techniques. İn Europe and U.S.A., frozen embryos both produced in vitro and in vivo are sold as a commercial good both nationally and internationally. Storage of in vitro derived embryos in liquid nitrogen is essential to make full use of this technology. Glycerol, DMSO and Glycols, which have different biochemical structure, have conventionally been used for the cryopreservation of bovine embryos. However, in vitro derived embryos have been shown to be more sensitive to low temperature than their in vivo counterpaıls. To overcome this sensitivity, vitrifıcation procedures were modifıed for in vitro derived embryos to provide higher survival rate than conventional freezing technique. The poor survival of bovine in vitro produced embryos following cryopreservation is a majör factor limiting the commercial application of this technologies. Despite of the advantages of the vitrifıcation technique such as easness, low cost and quickness its use is mainly limited to experimental studies. For commercial embryo transfer purposes, the traditional slow-rate freezing has been used. Freezingthawing procedures adapted to condition of commercial farm breeding, since the technics are getting less complex. In this review, the cryobiological characteristics of bovine embryos, freezing and thavving procedures and survival rates obtained by different technics were described

Keywords:

Cryopreservation, Cryoprotectants, Bovine embryo, Vitrifıcation,

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