A comparison of two recovery methods of ovine oocytes for in vitro maturation

Effects of triton X-100 pretreatment of lyophilized and frozen-thawed ram sperm on preimplantation embryo developmental competence

In this study, it was aimed to determine the effect of destruction of lyophilized and frozen-thawed ram sperm plasma and acrosomal membrane on development of embryos produced by intracytoplasmic sperm injection (ICSI). Semen samples were divided into two groups for lyophilization (L) and freezing (F). For the removal of the plasma membrane, L and F groups were incubated with Triton X-100 (LTX-100 and FTX-100, respectively). Integrities of the plasma membrane, acrosome and chromatin structure were evaluated. Oocytes were injected with these sperm groups. Although no plasma membrane and acrosome integrities of the L (0.0%) group were detected, the plasma membrane integrity of the F group (69.4%) was significantly higher than the FTX-100 group (23.6%) (p < 0.05). The acrosome integrity of the FTX-100 group (3.80%) was significantly lower than the F group (55.6%) (p < 0.05). The chromatin integrities of L and F groups were higher than the Triton X-100 treated groups (p < 0.05). ICSIs with L, LTX-100, F and FTX-100 sperm were produced similar cleavage and blastocyst rates. In conclusion, data presented here confirm that ram spermatozoa can effectively be lyophilized and injected into oocytes for initiation of embryonic development and Triton X-100 pretreatment is not necessary while using lyophilized and frozen semen.

In vitro ovine embryo production: the study of seasonal and oocyte recovery method effects

Background:

To current knowledge, different oocyte's recovery method and various seasons have profound impact on in vitro embryo production (IVEP).

Objectives:

The aim of this study was to define an efficient recovery method for oocytes harvesting from slaughterhouse material in different seasons, and their effects on IVEP yield.

Materials and Methods:

Ovaries from slaughtered ewes in breeding season (BS) and non-breeding season (NBS) were collected from a local abattoir. The oocytes were recovered through aspiration, centrifugation (ORC), puncture and slicing, and categorized into three classes (I, oocytes with more than three layers of cumulus cells; II, less than three layers with damaged cumulus cells; III, denuded oocytes). After cultivation in TCM 199 for 24 hours, matured oocytes were subjected to in vitro fertilization (IVF) and in vitro culture (IVC). The oocyte recovery using ORC in BS and NBS was significantly higher (P < 0.05) compared with other recovery methods.

Results:

No significant dissimilarities in the proportion of oocytes reaching M-II stage were recorded when using different oocyte recovery methods in different seasons. Aspiration resulted in lower (P < 0.05) proportion of class I (BS, 60.0 ± 2.1; NBS, 51.1 ± 2.1) compared to ORC (BS, 82.0 ± 1.2; NBS, 70.0 ± 1.2), slicing (BS, 80.0 ± 2.1; NBS, 71.0 ± 1.4) and puncture (BS, 80.0 ± 1.5; NBS, 72.0 ± 2.0). Monospermy and blastocyst development rates were significantly higher using ORC than other recovery techniques in both BS and NBS. More oocytes with high quality, greater blastocyst development and oocyte recovery rates were achieved in BS.

Conclusions:

The results revealed that oocytes harvesting technique and season are effective in the rate of cleavage and blastocysts’ development, and suggest that despite same meiotic resumption rate in all treatments, it would be better to use ORC.

Endocrinological profile and follicular development in cyclic ewes subjected to repeated ovum pick-up

Blood concentrations of progesterone, FSH and oestradiol in Karagouniko ewes subjected to laparoscopic ovum pick-up (OPU) at specific stages of induced oestrous cycle, were measured. Twenty-four cyclic ewes were randomly allocated into four equal groups (A, B, C and D). Oestrus was synchronized with progestagen intravaginal sponges and detected by teaser rams (oestrus: day 0). In group A, during the induced oestrous cycle, OPU was performed on days 4, 9 and 14 (sessions A1, A2 and A3, respectively). In group B and group D, OPU was performed once, on day 9 and 14, respectively. In group C (controls), endoscopic observation of follicular population was performed three times, as in group A. Starting at sponge removal, progesterone was measured in blood samples collected on 22 daily occasions and oestradiol in samples collected on 27 occasions collected at various time-points starting 2h before to 24h after OPU. Follicular populations did not differ among A1, A2, A3 or between C1, C2, C3 and A1, A2, A3 or A1, B, D, respectively. Oocytes of better quality (category '1' or '2') were collected at A3 session compared with A1 (P<0.05). Progesterone concentration and oestrous cycle length did not differ among groups. Decreased oestradiol concentrations followed by FSH increase were recorded 3-5h after OPU. The results confirm the regulatory role of oestradiol on FSH secretion. The quality of collected oocytes was improved in subsequent pick-up sessions in the oestrous cycle. Moreover, OPU at specific stages of the luteal phase of the cycle, even when applied repeatedly, do not affect the normal oestrous cycle length of ewes.

Induction of lamb follicular development and embryo production in vitro

Effect of lamb age, transport stimulation and repeated hormone superovulation on the number of collected oocytes were determined. Effect of the culture medium containing ethylenediaminetetraacetic acid (EDTA) on the development of embryos produced in vitro from lamb oocytes was also investigated. Results indicated that the mean numbers of collected and available oocytes (oocytes with compacted cumulus cells, evenly granulated ooplasm and morphologically normal) from 6- to 8-week-old lambs were 60.8±13.9 and 58.2±12.3, respectively. These figures were higher than those obtained from 12- to 14-week-old lambs (27.3±5.1 and 26.0±4.9) (P<0.05). Stimulation by transportation didn't decrease the number of collected oocytes from the superovulated lambs (P>0.05). However, the number of collected oocytes in the repeated superovulation group was significantly reduced, compared with the control group (P<0.05). The embryonic culture medium supplemented with 10 μmol/l EDTA highly improved the development capability of the embryos from lamb oocytes (P<0.05). Healthy lambs were born following embryo transfer.

Age, FSH Dose and Follicular Aspiration Frequency Affect Oocyte Yield from Juvenile Donor Lambs

Experiments were conducted to determine the effects of lamb age, frequency of follicular aspirations, and hormone stimulation by fixed or variable FSH dose, on the number of collected oocytes and their maturational competence. In trial 1, the characteristics of follicular population (number and diameter of follicles) were studied in 40 lambs which were slaughtered at the age of 30 days (S1), 42 days (S2), 60 days (S3) and 5-6 months (S4), each n = 10. In trial 2, 27 lambs were divided into four groups. group MF lambs (n = 6) had follicular aspiration (OPU) in four monthly intervals commencing from the age of 8-9 weeks (sessions MF1, MF2, MF3 and MF4). In groups SF2, SF3 and SF4 (each n = 6), OPU was conducted once during the 12-13, 16-17 and 20-21 week of age, respectively. Ovarian stimulation was conducted with fixed FSH dose (3.52 mg/animal). In trial 3, 10 lambs (group MV) were treated as those of group MF apart from the FSH dose, which was administered according to the body weight in a dose of 0.27 mg/kg. The number and the size of follicles, the number and the quality of collected oocytes and the maturational competence of the oocytes were compared between and within groups. In trial 1, the total number and the number of small follicles were greater in groups S1 and S2 compared with those of S3 and S4 (p < 0.01). Similarly, the follicular population was greater in group MF1 than in group SF3 (p < 0.01). In sessions MF2, MF3, MV2, MV3 and MV4, more oocytes were collected in comparison with those from the respective once-aspirated age mates (groups SF2, SF3 and SF4). In total, more (p = 0.02) oocytes per donor were collected from group MV (15.2 +/- 5.5) than from group MF (9.0 +/- 3.2). An absolute maturational failure was observed in oocytes collected from groups SF2 and SF3. Maturational competence varied between 16.7% and 58.3% (p = 0.017) among sessions of group MF, but it was more uniform among sessions of group MV (range 12.5-42.9%, p > 0.05). Our results indicate that firstly, the number and the quality of harvested oocytes from juvenile lambs can be much improved if follicular stimulation regime is adjusted to the body weight. Secondly, in terms of follicular population and oocyte quality, 3 and 4-month-old lambs are naturally bad oocyte donors, but this characteristic can be reversed by a previous follicular ablation.