Sema Birler

Effects of estrous cycle stage and transport temperature of ovaries on in vitro maturation of canine oocytes

Unlike other domestic animals, in vitro maturation (IVM) of canine oocytes still has limited success. The present study investigated the effects of estrous cycle stage and transport temperature of ovaries on in vitro maturation of canine oocytes. The donor bitches were categorized into three groups based on stage of estrus cycle: follicular (proestrus or estrous), luteal (diestrus) and anestrus. One ovary of each pair collected from 39 mature bitches was transported in Phosphate Buffer Saline (PBS) at 4 degrees C while the other was transported at 37 degrees C. A total of 1138 Grade I COCs obtained from all ovaries were grouped and matured in modified synthetic oviduct fluid (mSOF) supplemented with follicle stimulating hormone (FSH), luteinizing hormone (LH), essential and non-essential amino acids at 38.5 degrees C in a humidified 5% CO(2), 5% O(2), and 90% N(2) atmosphere for 72 h. The nuclear maturation rates were evaluated by aceto-orcein staining. Oocytes harvested from follicular and luteal ovaries have a significantly higher maturation rates (MI+MII) than the oocytes from anestrual ovaries in the 37 degrees C group (p<0.05). However, oocytes harvested from anestrual ovaries transported at 4 degrees C had the highest maturation (MI+MII) rate, and the difference between anestrual and luteal ovary groups was significant (p<0.05). The oocytes from anestrual ovaries transported at 4 degrees C have significantly higher maturation rates than those transported at 37 degrees C (p<0.0001). However, the transport temperature (37 or 4 degrees C) did not significantly affect the maturation (MI+MII) rates of oocytes harvested from the luteal (p=0.61) and follicular (p=0.48) stage ovaries. It can be concluded from this study that (1) both transport temperature and transport temperaturexestrus cycle stage interaction effected the maturation rates, while estrus cycle stage alone did not, and (2) transporting canine ovaries at 4 degrees C can improve in vitro maturation rates in oocytes harvested from anestrous ovaries.

Adding hormones sequentially could be an effective approach for IVM of dog oocytes

There have not been successful and repeatable methods for in vitro embryo production in the dog. Up to date, only one blactocyst has been achieved on in vitro culture. Since reproductive physiology of the dog is different from that of other mammalian species, it seems that a suitable method for in vitro production of canine embryos is still far from being designed and routinely applied, and an effective protocol is needed. Therefore, the aim of the present study was to examine the effects of adding hormones sequentially, for mimicking the dogs in vivo endocrine milieu, on maturation of immature dog oocytes in vitro. At the end of the 96 h IVM period, nuclear maturation rates were evaluated by the aceto-orcein staining method. In comparison relating IVM rates, the sequential hormone addition was more beneficial on IVM rates (MI + MII) than the traditional hormone addition and control groups (48.1%, 38.9% and 23.0% respectively; P < 0.0001). As a result, hormone addition sequentially may be an effective approach for the IVM of the immature dog oocytes. We suggest that attempts to define the adequate conditions for IVM in the dog should extend towards this new perspective.

Kedi Oositlerinin In Vitro Olgunlaştırılması ve Kumulus Hücrelerinin Apoptoz Oranları Üzerine, Ovaryum Taşıma ve Saklama Sıcaklığının Etkisi

The objective of the present study was to examine the effects of two different transport temperature (37°C vs 4°C) and cold storage of ovaries for 24 h on cumulus cell apoptosis and maturation rates of cat oocytes in vitro. Ovaries were collected from 15 ovariohysterectomized domestic cats and maintained and transported to the laboratory in phosphate buffer saline at 37°C and 4°C. In order to determine the effects of storing time, some ovaries transported at 4°C were stored at the same temperature for 24 h. Selected cumulus oocyte complexes (COCs) were matured for 48 h at 38°C in four-well petri dishes containing 500 μL of modified oviduct medium (mSOF) under mineral oil in a 5% CO2 incubator with nearly 100% humidified. The morphological features of apoptosis were analysed in the cumulus cells at the beginning of in vitro maturation in both transporting temperature groups and after 24 h of cold stored group. The degree of apoptosis in cumulus cells were measured by terminal deoxynucleotidyltransferase-mediated dUTP nick end labeling (TUNEL). The IVM rates of oocytes were determined using Hoechst (33342) staining. Although the apoptotic morphological features were seen rarely and in similar rates in 37 and 4°C transporting groups (19.40 and 21.55%, P>0.001), it was seen more intensely in the 24 h cold stored group (34.80%, P<0.001). The IVM findings were similar (49.77, 44.55%) at 37°C and 4°C groups (P>0.05), and importantly lower at 4°C transporting and 24 h cold stored groups (18.90%, P<0.05). In conclusion, the results of this study suggest that (I) cumulus cells of cat oocytes are partially exposed to apoptosis during transportation at warm or cold temperature, (II) storing of ovaries for 24 h at 4°C causes apoptosis of the cumulus cells at much higher rates and (III) storing of ovaries for 24 h at 4°C affects negatively IVM rate of oocytes.

Kedilerde MI ve MII Oositleri Kullanilarak Somatik Klonlama

Animal production via SCNT provides a unique tool for protection of valuable individuals, conservation of vulnerable and endangered species and production of transgenic animals. A total of 167 MI and 219 MII stage oocytes were used as the material of the study. The oocytes were enucleated at 44 h after in vitro maturation by aspiration of the polar body and the MI or MII plates. Cycling granulosa cells were used for nuclear transfer. Cell fusion was induced with DC pulses of 2.0 kV/cm 60µs, 0.1s apart (2x) delivered by a BTX Electrocell Manipulator 200 (BTX, San Diego, CA, USA). After fusion, the embryos were activated by 1.0 kV/cm 20µs DC pulses 0.1s apart (2x) followed by 2 mM 6-DMAP (6-dimethylaminopurine) incubation in culture medium for 4 h in a humidified atmosphere of 5% CO2, 5% O2, and 90% N2 at 38°C. The somatic cell transferred embryos were cultured for 8 days in mSOF medium supplemented with 0.4% BSA in a humidified 5% CO2, 5% O2, and 90% N2 atmosphere at 38°C. After in vitro culture period, all embryos transferred to HSOF containing Hoechst 33342 (5 μg/mL) and the cell numbers were counted under ultraviolet light using a fluorescent microscope. The fusion (66.66 vs 21.55%) and cleavage rates (15.75 vs 11.11%) were significantly higher in MII stage oocytes than MI stage oocytes (P<0.02). While SCNT embryos were developed to morula stage in MII group (14; 9.58%), all the cleaved embryos were arrested at the 2-4 cell stage in MI group. None of the embryos was developed to blastocyst stage in both groups.