Laparoscopical intrauterine insemination with different doses of fresh, conserved, and frozen semen for the production of ovine zygotes

The impact of cryopreserved sperm on intrauterine insemination outcomes: is frozen as good as fresh?

Introduction

Frozen sperm utilization might negatively impact cycle outcomes in animals, implicating cryopreservation-induced sperm damage. However, in vitro fertilization and intrauterine insemination (IUI) in human studies are inconclusive.

Methods

This study is a retrospective review of 5,335 IUI [± ovarian stimulation (OS)] cycles from a large academic fertility center. Cycles were stratified based on the utilization of frozen (FROZEN, n = 1,871) instead of fresh ejaculated sperm (FRESH, n = 3,464). Main outcomes included human chorionic gonadotropin (HCG) positivity, clinical pregnancy (CP), and spontaneous abortion (SAB) rates. Secondary outcome was live birth (LB) rate. Odds ratios (OR) for all outcomes were calculated utilizing logistic regression and adjusted (adjOR) for maternal age, day-3 FSH, and OS regimen. Stratified analysis was performed based on OS subtype [gonadotropins; oral medications (OM): clomiphene citrate and letrozole; and unstimulated/natural]. Time to pregnancy and cumulative pregnancy rates were also calculated. Further subanalyses were performed limited to either the first cycle only or to the partner's sperm only, after excluding female factor infertility, and after stratification by female age (<30, 30-35, and >35 years old).

Results

Overall, HCG positivity and CP were lower in the FROZEN compared to the FRESH group (12.2% vs. 15.6%, p < 0.001; 9.4% vs. 13.0%, p < 0.001, respectively), which persisted only among OM cycles after stratification (9.9% vs. 14.2% HCG positivity, p = 0.030; 8.1% vs. 11.8% CP, p = 0.041). Among all cycles, adjOR (95% CI) for HCG positivity and CP were 0.75 (0.56-1.02) and 0.77 (0.57-1.03), respectively, ref: FRESH. In OM cycles, adjOR (95% CI) for HCG positivity [0.55 (0.30-0.99)] and CP [0.49 (0.25-0.95), ref.: FRESH] favored the FRESH group but showed no differences among gonadotropin and natural cycles. SAB odds did not differ between groups among OM and natural cycles but were lower in the FROZEN group among gonadotropin cycles [adjOR (95% CI): 0.13 (0.02-0.98), ref.: FRESH]. There were no differences in CP and SAB in the performed subanalyses (limited to first cycles or partner's sperm only, after excluding female factors, or after stratification according to female age). Nevertheless, time to conception was slightly longer in the FROZEN compared to the FRESH group (3.84 vs. 2.58 cycles, p < 0.001). No significant differences were present in LB and cumulative pregnancy results, other than in the subgroup of natural cycles, where higher LB odds [adjOR (95% CI): 1.08 (1.05-1.12)] and higher cumulative pregnancy rate (34% vs. 15%, p = 0.002) were noted in the FROZEN compared to the FRESH group.

Conclusion

Overall, clinical outcomes did not differ significantly between frozen and fresh sperm IUI cycles, although specific subgroups might benefit from fresh sperm utilization.

Cholesterol-loaded cyclodextrin improves ram sperm cryoresistance in skim milk-extender

Cholesterol-loaded cyclodextrin (CLC) is known to improve ram sperm cryosurvival. This study expands on previous research to: (1) determine the mechanism by which CLC improves ram sperm cryosurvival and (2) compare the efficiency of a novel, skim milk-based extender containing CLC to a traditional egg yolk-based extender. Hypothesis #1 was that CLC enhances membrane cholesterol content to increase the resistance of ram sperm to cold and osmotic stress, thereby improving cryosurvival. We first assessed the ability of fresh sperm treated with CLC to withstand cold shock. Second, fresh sperm were treated with CLC to evaluate their tolerance to osmotic stress. Third, to confirm that cholesterol is incorporated into the sperm using CLC, we quantified sperm cholesterol. To test Hypothesis #2 that CLC is most effective in a medium without competing cholesterol, we compared sperm cryosurvival and fertility in skim milk-based extender containing CLC versus in a traditional egg yolk-based freezing extender without CLC. Our data confirmed that CLC treatment improves ram sperm cold shock and osmotic stress resistance, and augments sperm cholesterol content. Semen in skim milk-based extender containing CLC prior to freezing, had more motile sperm with intact acrosomes after thawing compared to semen in egg yolk-based extender. In contrast, sperm plasma membrane integrity and in vivo fertility of the semen cryopreserved in the skim milk-based extender with CLC did not differ from semen that was cryopreserved in egg yolk-based extender. Further research is warranted to combine CLC with other cryoprotection strategies or to modify the insemination protocol.

Effect of dietary fish oil supplementation on ram semen freeze ability and fertility using soybean lecithin- and egg yolk-based extenders

Ram semen cryopreservation is not efficient for artificial insemination in commercial herds. Beneficial effects of dietary fish oil have been evaluated for cryopreservation of ram semen in soybean lecithin (SL) and egg yolk (EY)-based extenders. A factorial study (two diets × two extenders) was used to analyze the effects of two diets supplemented with fish oil (n-3 fatty acid) or palm oil (saturated fatty acids; [SFAs]) to freeze ram semen in two extenders containing SL or EY. Motility characteristics, membrane integrity, abnormal morphology, mitochondria activity, acrosome integrity, apoptotic status, and fertilizing ability were assessed after freeze-thawing. Although diet had significant (P ≤ 0.05) effects on the quality parameters of frozen-thawed sperm, effects of extenders on these traits were not significant (P > 0.05). The higher significant (P ≤ 0.05) percentage of total motility and progressive motility were observed in n-3/SL (44.83 ± 1.56 and 28.33 ± 1.4) and n-3/EY (43.33 ± 1.56 and 28.50 ± 1.4) than SFA/SL (32.16 ± 1.56 and 14.00 ± 1.4) and SFA/EY (31.66 ± 1.56 and 12.66 ± 1.4) groups. Moreover, n-3/SL and n-3/EY produced the higher significant (P ≤ 0.05) percentage of membrane integrity of sperm (39.83 ± 1.4 and 37.33 ± 1.4) than SFA/SL and SFA/EY (29.83 ± 1.4 and 28.5 ± 1.4). For viability results, the higher significant percentage of live sperm was observed in n-3/SL and n-3/EY (43.16 ± 1.38 and 45.66 ± 1.38) than SFA/SL and SFA/EY (28.66 ± 1.38 and 27.5 ± 1.38). For fertility trials, n-3-based diets (n-3/SL and n-3/EY) improved significantly (P ≤ 0.05) pregnancy rate (44% and 46%), parturition rate (42% and 42%), and lambing rate (46% and 44%) compared with the SFA-based diets (SFA/SL and SFA/EY). No interaction effects have been found between diets and extenders (P > 0.05). It seems that dietary fish oil can improve the semen performance after freezing-thawing process and artificial insemination aside from type of extenders.

Association of soybean-based extenders with field fertility of stored ram (Ovis aries) semen: a randomized double-blind parallel group design

Two consecutive randomized double-blind field fertility experiments were conducted over a 4-month period and aimed at evaluating the association of two commercial soybean lecithin-based extenders (AndroMed [Minitub, Tiefenbach, Germany] and BioXcell [IMV Technologies, L'Aigle, France]) with pregnancy rates of chilled-stored (CS) and frozen-thawed (FT) ram semen. Semen samples with more than 2 × 10(9) sperm per mL and 70% progressive motile spermatozoa were collected via an artificial vagina from twelve proven fertile Chios rams, split-diluted with the above mentioned extenders, packaged in 0.25 mL straws and either stored at 5 ± 1 °C for 30 to 36 hours or frozen and thawed. Non-lactating multiparous ewes were inseminated in progestagen-synchronized estrus either with CS (AndroMed: N = 212 and BioXcell: N = 206; intracervical AI) or with FT (AndroMed: N = 114 and BioXcell: N = 92; laparoscopic intrauterine AI) semen. Ovulation was confirmed in all ewes based on determination of blood plasma progesterone (>1 ng/mL) 8 days post AI. Ewes were screened for pregnancy diagnosis by transabdominal ultrasonography 65 days post AI. BioXcell was superior to AndroMed in preserving the fertilizing potential of CS (P < 0.05) and FT (P < 0.005) semen. In AndroMed-stored semen, young rams (1.5-2.5 years old, N = 8) had a pregnancy rate (59.1%; 124/210) lower than that (72.4%; 84/116) of mature rams (4.5 to 5.5 years, N = 4; P < 0.025). Compared with AndroMed extender, processing of young ram semen in BioXcell extender improved pregnancy rates of CS (66.7%; 88/132 vs. 83.9%; 94/112; P < 0.005) and FT (46.2%; 36/78 vs. 71.0%; 44/62; P < 0.01) spermatozoa. Both extenders were similarly effective in preserving pregnancy rates of mature ram semen (P > 0.05). Ram-by-extender interactions were significant for pregnancy rates of CS and FT semen. Irrespective of extenders, overall pregnancy rates after intracervical and intrauterine AI were 75.1% and 62.2%, respectively (P < 0.001). In conclusion, BioXcell is a suitable extender for short- and long-term storage of ram semen. Selection of the ewes, farms, and extenders for intracervical AI programs can contribute to satisfactory fertility rates with semen preserved more than 24 hours at 5 °C.

Use of laparoscopic intrauterine insemination associated with a simplified superovulation treatment for in vivo embryo production in sheep: a preliminary report

This study evaluated the reproductive performance of sheep that were subjected to superovulatory treatment and intrauterine insemination with two different doses of semen. The main objective was to determine whether intrauterine insemination is associated with higher rates of embryo recovery than existing procedures. In the first experiment 30 Ojalada de Soria ewes were used at the end of their productive life and nine younger ewes of the same breed were used in Experiment 2. Synchronisation of oestrus was conducted with intravaginal sponges and the superovulation treatment consisted of an intramuscular injection of 210 IU pFSH and 500 IU eCG administered 24 h before sponge removal. After 48 h of sponge withdrawal, ewes were inseminated by laparoscopy. They were divided into two groups: low dose group (LD, 25 × 106 sperm; n = 14 Expt 1 and n = 5 Expt 2) and high dose group (HD, 100 × 106 sperm; n = 14 Expt 1 and n = 4 Expt 2). Embryos were recovered 7 days after the onset of oestrus by laparotomy and uterine flushing. Two blood samples were collected in order to analyse cortisol, at sponge insertion and the day the embryos were recovered. The same protocol was repeated twice in Experiment 1, with an interval of 2 months between two consecutive treatments. Results show a significant effect of the number of recovery on ovulation rate (21.7 ± 2.2 v. 11.8 ± 1.1 corpora lutea for first and second recoveries, respectively), and number of structures recovered (11.4 ± 1.6 v. 5.2 ± 1.1, P < 0.01). Differences of embryo performance in the second recovery compared with the first one were more evident in the LD group compared with the HD group. In Experiment 2, results reflected a significant superiority of the HD group compared with the LD group, especially rate of fertilisation, which was 25% higher. Sheep producing non-fertilised embryos had higher cortisol levels at the time of flushing than those with embryos (P < 0.01). It is concluded that the use of simplified and consecutive superovulatory treatments associated with intrauterine insemination is a potential means of obtaining embryos, although the response seems to depend on donor sheep age. The use of a higher number of sperm cells per millilitre results in better outcomes in terms of embryos produced.

Improvement strategies in ovine artificial insemination

Artificial insemination in ram is scarcely widespread comparing with other domestic species. This has been due not only to fertility results being irregular and low but also because of the difficulty in the application of enhancements such as the use of frozen-thawed sperm. Although there is a lot of information on the use of different options to improve these AI results (such as transcervical application, the use of thawed sperm, etc.) commercial programmes can be classified on two general categories: those using refrigerated semen (15 degrees C) by superficial intracervical deposition (vaginal), and, more restricted, those using thawed sperm by intrauterine deposition (laparoscopy). In the present work, we have summarized our viewpoint on three general research lines for the improvement of AI results in sheep: semen preservation, AI procedures and semen assessment. Briefly, in ram it is necessary to develop a medium term methodology of sperm refrigeration (3-5 days), which would allow the distribution of sperm doses to a widespread area. Nevertheless, it is also necessary to develop an intrauterine transcervical AI technique, which allows thawed semen to be applied by vaginal insemination. Besides, the low predictive value of classic assessment techniques limits the ability to adjust the number of spermatozoa per dose according to its actual fertility.

Utilization of frozen–thawed epididymal ram semen to preserve genetic diversity in Scrapie susceptible sheep breeds

The European Union has introduced transmissible spongiform encephalopathy (TSE) resistance breeding programmes for several sheep breeds to cope with the genetic susceptibility to Scrapie infections. Due to the different allele frequencies among breeds, strong selection for ARR alleles is associated with a loss of genetic diversity in small populations and in larger populations with unfavourable ARR allele frequencies. To ensure maintenance of genetic diversity, an adhoc cryopreservation programme was initiated employing epididymal sperm from 109 rams representing 16 different breeds within one breeding season. Epididymal semen was chosen for this adhoc programme because time consuming training of rams for ejaculated semen collection via an artificial vagina was not possible. Prior to freezing, average sperm motility was 79.7% and acrosome integrity was 93.7%. After freezing, these levels were decreased to 60.5 and 72.8%, respectively. An insemination trial using frozen-thawed epididymal semen resulted in a lambing rate of 87.5%. Results show that this semen preservation method is robust and efficient and associated with high fertility. It may also be useful for other animal species.

New Preservation Method for Mouse Spermatozoa Without Freezing1

The objective of this study was to investigate the preservation of spermatozoa in a simple medium without freezing and to examine the effects of the preserved sperm on fertilization and development after injection into mature mouse oocytes. Mouse spermatozoa were collected from two caudae epididymides of mature B6D2F1 males and stored under various conditions: 1) in KSOMaa medium (potassium simplex optimized medium with amino acids) supplemented with 0, 1, or 4 mg/ml BSA and held at room temperature (RT, 27 degrees C); 2) in KSOMaa medium containing 4 mg/ml BSA (KSOM-BSA) and held at 4 degrees C, RT, or 37 degrees C (CO2 incubator); 3) in KSOM-BSA with osmolarity ranging from 271 to 2000 mOsmol, adjusted by addition of NaCl and held at 4 degrees C; and 4) a two-step preservation system consisting of storage in 800 mOsmol KSOM-BSA for 1 wk at RT followed by storage at -20 degrees C. Preservation of mouse spermatozoa at 4 degrees C in a medium with high osmolarity (700-1000 mOsmol) resulted in the highest frequency of live births after intracytoplasmic sperm injection (ICSI) into mature oocytes. The optimal conditions for preservation of mouse spermatozoa were 800 mOsmol KSOM containing 4 mg/ml BSA and a holding temperature of 4 degrees C. More than 40% of oocytes injected with sperm heads stored under these conditions for 2 mo developed to the morula/blastocyst stage in vitro and 39% of the embryos developed to term after transfer to recipient mice. Our results also indicate that mouse spermatozoa can be stored in 800 mOsmol KSOM-BSA medium at RT for 1 wk and then at -20 degrees C for up to 3 mo and retain their competence for ICSI. These new preservation methods permit extended conservation of viable spermatozoa that are capable of supporting normal embryonic development and the live birth of healthy offspring after ICSI.