Effect of trypsin treatment of in vitro fertilized bovine embryos on their subsequent survival and development

Risk of Chlamydia abortus transmission via embryo transfer using in vitro produced early bovine embryos

The objectives of this study were to determine (i) whether Chlamydia (C.) abortus would adhere to the intact zona pellucida (ZP-intact) of early in vitro produced bovine embryos; (ii) whether the bacteria would adhere to the embryos (ZP-free) after in vitro infection; and (iii) the efficacy of the International Embryo Transfer Society (IETS) washing protocol. The experimentation was made twice. For each replicate 100 (8-16-cell) bovine embryos produced in vitro were randomly divided into 10 batches. Height batches (4 ZP-intact and 4 ZP-free) of 10 embryos were incubated in a medium containing 4 × 10⁷Chlamydia/ml of AB7 strain. After incubation for 18 h at 37 °C in an atmosphere of 5% CO₂, the embryos were washed in accordance with the IETS guidelines. In parallel, two batches (1 ZP-intact and 1 ZP-free) of 10 embryos were subjected to similar procedures but without exposure to C. abortus as a control group. The 10 washing fluids from each batch were collected and centrifuged for 1 h at 13,000×g. Each batch of washed embryos and each wash pellets were tested using PCR. C. abortus DNA was found in all ZP-intact and ZP-free batches of 10 embryos after 10 successive washes. For ZP-intact infected embryos, Chlamydia-DNA was also detected in all 10 wash baths for two batches (2/8) of embryos, whereas for ZP-free infected embryos, Chlamydia-DNA was detected in all 10 wash baths for 6/8 batches of embryos. In contrast, none of the embryos or their washing fluids in the control batches was DNA positive. The bacterial load for batches of 10 embryos after the 10 wash baths was significantly higher for batches of ZP-free embryos (20.7 ± 9 × 10³ bacteria/mL) than for batches of ZP-intact embryos (0.47 ± 0.19 × 10³ bacteria/mL). These results demonstrate that C. abortus adheres to the ZP as well as the early embryonic cells of in vitro produced bovine embryos after in vitro infection, and that the standard washing protocol recommended by the IETS fails to remove it.

Can Chlamydia abortus be transmitted by embryo transfer in goats?

The objectives of this study were to determine (i) whether Chlamydia abortus would adhere to or penetrate the intact zona pellucida (ZP-intact) of early in vivo-derived caprine embryos, after in vitro infection; and (ii) the efficacy of the International Embryo Transfer Society (IETS) washing protocol for bovine embryos. Fifty-two ZP-intact embryos (8-16 cells), obtained from 14 donors were used in this experiment. The embryos were randomly divided into 12 batches. Nine batches (ZP-intact) of five embryos were incubated in a medium containing 4 × 10(7)Chlamydia/mL of AB7 strain. After incubation for 18 hours at 37 °C in an atmosphere of 5% CO2, the embryos were washed in batches in 10 successive baths of a phosphate buffer saline and 5% fetal calf serum solution in accordance with IETS guidelines. In parallel, three batches of ZP-intact embryos were used as controls by being subjected to similar procedures but without exposure to C. abortus. The 10 wash baths were collected separately and centrifuged for 1 hour at 13,000 × g. The washed embryos and the pellets of the 10 centrifuged wash baths were frozen at -20 °C before examination for evidence of C. abortus using polymerase chain reaction. C. abortus DNA was found in all of the infected batches of ZP-intact embryos (9/9) after 10 successive washes. It was also detected in the 10th wash fluid for seven batches of embryos, whereas for the two other batches, the last positive wash bath was the eighth and the ninth, respectively. In contrast, none of the embryos or their washing fluids in the control batches were DNA positive. These results report that C. abortus adheres to and/or penetrates the ZP of in vivo caprine embryos after in vitro infection, and that the standard washing protocol recommended by the IETS for bovine embryos, failed to remove it. The persistence of these bacteria after washing makes the embryo a potential means of transmission of the bacterium during embryo transfer from infected donor goats to healthy recipients and/or their offspring. Nevertheless, the detection of C. abortus DNA by polymerase chain reaction does not prove that the bacteria found was infectious. Further studies are required to investigate whether enzymatic and/or antibiotic treatment of caprine embryos infected by C. abortus would eliminate the bacteria from the ZP.

Open pulled straw vitrification and slow freezing of sheep IVF embryos using different cryoprotectants

The aim of the present study was to evaluate the post-thaw survival and hatching rates of sheep blastocysts using different cryoprotectants. In Experiment 1, Day 6 sheep embryos were cryopreserved by a slow freezing protocol using 10% ethylene glycol (EG), 10% dimethyl sulfoxide (DMSO) or a mixture of 5% EG and 5% DMSO. Hatching rates were higher in the 10% EG group than in the 10% DMSO or EG + DMSO groups (30% vs 18% and 20%, respectively). In Experiment 2, embryos were cryopreserved by open pulled straw (OPS) vitrification using either 33% EG, 33% DMSO or a mixture of 16.5% EG + 16.5% DMSO. Re-expansion and hatching rates in the EG + DMSO group (79.16% and 52.74%, respectively) were higher than those in the EG group (64.28% and 30.02%, respectively), whereas the outcomes for the DMSO group were the lowest (45.18% and 8.6%, respectively). In Experiment 3, embryos were cryopreserved by OPS vitrification using either 40% EG, 40% DMSO or a mixture of 20% EG + 20% DMSO. Re-expansion and hatching rates were highest in the EG group than in the EG + DMSO and DMSO groups (92.16% vs 76.30% and 55.84% re-expansion, respectively; and 65.78% vs 45.55% and 14.46% hatching, respectively). In conclusion, OPS vitrification was found to be more efficient for cryopreservation of in vitro-developed sheep embryos than traditional freezing.

Disinfection procedures for controlling microorganisms in the semen and embryos of humans and farm animals

Semen and embryos generated by assisted reproductive techniques (ARTs) may be contaminated with numerous microorganisms. Contamination may arise from systemic or local reproductive tract infections in donors or the inadvertent introduction of microorganisms during ARTs, and may lead to disease transmission. This review describes sanitary procedures which have been investigated to ascertain whether they are effective in rendering semen and embryos free of pathogenic microorganisms, including internationally adopted washing procedures, which can be supplemented by antibiotics and enzymatic treatments. Other methods include treatment with antibodies or ozone, photoinactivation, acidification, and the use of novel antiviral compounds. In conclusion, despite the wide range of antimicrobial procedures available, none can be recommended as a universal disinfection method for rendering semen and embryos free from all potentially pathogenic microorganisms. However, some procedures are unsuitable, as they can compromise the viability of semen or embryos. In humans, washing by the gradient centrifugation method appears to be effective for reducing the microbial population in semen and is harmless to the spermatozoa. A useful procedure for embryos involving multiple washes in sterile medium has much to commend it for the prevention of disease transmission; furthermore, it is recommended by the International Embryo Transfer Society (IETS).

Evaluation of virus decontamination techniques for porcine embryos produced in vitro

The objective of this study was to explore approaches to decontaminate embryos either contaminated naturally or under experimental conditions with different viruses. Embryos were obtained from in vitro maturation and fertilisation of porcine oocytes. After 7 days of development, morula and blastocyst stages were exposed for 1 h to the following viruses: encephalomyocarditis virus (EMCV), porcine circovirus type 2 (PCV2), porcine parvovirus (PPV), porcine reproductive and respiratory syndrome virus (PRRSV), and bovine viral diarrhea virus (BVDV) at an infectivity of 100 TCID50/mL. Embryos samples were treated with different washing procedures, which all included the following standard washing solutions: PBS+0.4% BSA (five times for 10 s), Hank's+0.25% trypsin (two times for 60-90 or 120-150 s, or one time of 5 min), Hank's+0.1 mg/mL DNase 1+20 U/mL RNase One (one time of 30 min) and PBS+0.4% BSA again (five times for 10s). Two new approaches were used to improve trypsin treatment, 0.1% hyaluronidase (one time for 5 min) instead of trypsin and a pre-incubation with oviductal cells. Therefore, in the first experiment, oocytes received standard maturation treatments and in the second, they were also co-incubated with oviductal cells for the last 3 h of maturation. The effectiveness of the different washing techniques in removing viruses was evaluated by polymerase chain reaction (PCR) analysis. In the first experiment, trypsin treatment did not eliminate PRRSV, PPV, PCV, and EMCV from contaminated embryos. Surprisingly, treatment with hyaluronidase eliminated all tested viruses. In the second experiment, all viruses tested were removed from the oocytes following the different enzymatic treatments. In conclusion, in vitro embryo decontamination was more effective following exposure to oviductal secretions and hyaluronidase eliminated more virions than trypsin in washing techniques.

Reduction of infectious epizootic hemorrhagic disease virus associated with in vitro produced bovine embryos by non-specific protease

Infectious viruses bind more tenaciously to the zonae pellucidae of in vitro produced bovine embryos than to zonae of in vivo derived embryos. Currently, the International Embryo Transfer Society recommends that all in vivo derived embryos be subjected to a rigorous washing procedure in combination with exposure to trypsin to remove viruses adherent to the zonae. In contrast to in vivo derived embryos, this method is not effective for disinfecting in vitro produced embryos. Our hypothesis was that a more potent, non-specific protease from Streptomyces griseus (S. griseus) would provide a more effective treatment for virus removal from in vitro produced bovine embryos. Bovine oocytes were matured, fertilized, and cultured in completely defined in vitro conditions. Zygotes were washed according to the procedure outlined by the International Embryo Transfer Society, replacing trypsin with the experimental protease. Experimental incubations were with 0.1% (4 units/ml) protease for 0, 30, 45, 60 and 75s intervals. Embryos were able to withstand exposure to this enzymatic treatment for only 45s before their developmental potential was significantly reduced; 60s exposure was detrimental (P<0.05). Oocytes were exposed to epizootic hemorrhagic disease virus serotype 2 (EHDV-2, 10(6) TCID(50)/ml) during in vitro maturation. Resulting zygotes were washed according to the International Embryo Transfer Society procedure and either exposed to trypsin or protease. Exposure to EHDV-2 prevented cumulus expansion and markedly reduced embryonic development (P<0.05). There were no differences in development among virus exposed groups receiving no treatment or treatment with trypsin or protease. However, proportions of infected embryos were reduced after protease treatment versus positive controls and trypsin treated embryos.

The efficacy of trypsin for disinfection of in vitro fertilized bovine embryos exposed to bovine herpesvirus 1

Bovine cumulus-oocyte complexes (COC) or in vitro fertilized (IVF) embryos were exposed to bovine herpesvirus 1 (BHV-1) during in vitro maturation or co-culture with uterine tubal cells, respectively. Trypsin, at a concentration of 0.25%, was applied (for approximately 90 s) to disinfect either COC or cumulus-free oocytes (CFO) 18 h after insemination, or on day 7 to embryos resulting from infected oocytes. In total, virus was not detected in 71% of 93 samples containing 233 embryos exposed to BHV-1 and trypsin treatment. BHV-1 was detected in 14% and 54% of samples containing a single embryo and five embryos, respectively. In corresponding groups of embryos exposed to BHV-1, then washed but not treated with trypsin (70 samples), 85% and 96% of samples containing one embryo and pooled embryos, respectively, were positive for the virus. There was no effect of trypsin treatment on the development of IVF-embryos. It is concluded that IVF-generated embryos have a greater tendency to carry BHV-1 after experimental exposure to the virus than IVF uterine stage embryos, and that they are more difficult to disinfect by means of the standard trypsin treatment use.

A review on disease transmission studies in relationship to production of embryos by in vitro fertilization and to related new reproductive technologies

This paper addresses the circumstances of germplasm contamination and updates on transmission of pathogenic agents by embryos produced in vitro and by associated techniques. It has been shown that some pathogenic agents might have been associated with the follicular oocytes and oviductal cells, collected for in vitro fertilization (IVF), resulting in infected embryos. Experimental introduction of pathogenic agent with oocytes or infected semen into the IVF system allows, in most cases, for the fertilization of eggs and for the production of some transferable quality embryos. Rendering of oocytes and embryos free of infectious pathogens, using the standard sequential washing or enzymatic treatment, is inconsistent and more difficult in the presently used in vitro fertilization system as compared to in vivo produced embryos.