Removal of bacterial contaminants from semen for in vitro fertilization or artificial insemination by the use of buoyant density centrifugation

Automatic high-throughput and non-invasive selection of sperm at the biochemical level

BACKGROUND

Sperm selection, a key step in assisted reproductive technology (ART), has long been restrained at the preliminary physical level (morphology or motility); however, subsequent fertilization and embryogenesis are complicated biochemical processes. Such an enormous "gap" poses tough problems for couples dealing with infertility, especially patients with severe/total asthenozoospermia .

METHODS

We developed a biochemical-level, automatic-screening/separation, smart droplet-TO-hydrogel chip (BLASTO-chip) for sperm selection. The droplet can sense the pH change caused by sperm's respiration products and then transforms into a hydrogel to be selected out.

FINDINGS

The BLASTO-chip system can select biochemically active sperm with an accuracy of over 90%, and its selection efficiency can be flexibly tuned by nearly 10-fold. All the substances in the system were proven to be biosafe via evaluating mice fertilization and offspring health. Live sperm down to 1% could be enriched by over 76-fold to 76%. For clinical application to patients with severe/total asthenozoospermia, the BLASTO-chip could select live sperm from human semen samples containing 10% live but 100% immotile sperm. The rates of fertilization, cleavage, early embryos, and blastocysts were drastically elevated from 15% to 70.83%, 10% to 62.5%, 5% to 37.5%, and 0% to 16.67%, respectively.

CONCLUSIONS

The BLASTO-chip represents a real biochemical-level technology for sperm selection that is completely independent of sperm's motility. It can be a powerful tool in ART, especially for patients with severe/total asthenozoospermia.

FUNDING

This work was funded by the Ministry of Science and Technology of China, the Ministry of Education of China, and the Shenzhen-Hong Kong Hetao Cooperation Zone.

A comparison between the Felix™ electrophoretic system of sperm isolation and conventional density gradient centrifugation: a multicentre analysis

PURPOSE

Developing optimized techniques for the isolation of human spermatozoa possessing low levels of DNA damage is an important objective for the ART industry. The purpose of this study was to compare a novel electrophoretic system (Felix™) of sperm isolation with a conventional method involving density gradient centrifugation (DGC).

METHODS

Five international ART Centres in Australia, India, Sweden, the USA, and China have collaborated in order to compare the quality of the sperm populations isolated by Felix™ and DGC in terms of processing time, sperm concentration, motility, vitality, and DNA integrity as assessed by 3 methods: SCSA, Halo, and TUNEL.

RESULTS

Across all centers, 112 comparisons were performed. Although significant differences were noted between centers in terms of the quality of the semen samples subjected for analysis, overall, both methods were equally capable of isolating populations of spermatozoa exhibiting high levels of vitality and progressive motility. The absolute numbers of spermatozoa recovered were significantly (p < 0.001) lower with the Felix™ device although sperm quality was higher with 4/5 centers reporting a significant improvement in DNA integrity relative to DGC (p < 0.01-p < 0.001). In practical terms, the Felix™ device featured a standardized 6 min preparation time whereas clinical DGC protocols varied from center to center but generally took around 40 min to complete.

CONCLUSIONS

The Felix™ device is a positive technical development capable of isolating suspensions of highly motile spermatozoa exhibiting low levels of DNA damage in a fraction of the time taken by conventional procedures such as DGC.

Frequency of postinsemination infections as reported by donor semen recipients

Over an 18-year period, 47 women claimed to have acquired an infection after insemination with donor semen. This translates to an infection rate of less than 1 per 10,000 inseminations.

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).

Bacterial risk and sperm cryopreservation

Prior to sperm cryopreservation, French guidelines only recommend viral screening for serological status towards human immunodeficiency virus, hepatitis B and C viruses and Treponema palidum. The probability of semen infection by other bacterial pathogens is not taken into consideration by the current recommendations. The objective of the present study was to evaluate this risk and a strategy to reduce it prospectively. Ninety-six patients consulting for sperm cryopreservation underwent a semen culture simultaneously to cryopreservation. The patients were classified into three groups following semen culture results: negative culture (group 1, 77/96, 80.2%), positive culture with saprophytic agents (group 2, 9/96, 9.4%) and positive culture with pathogen agents (group 3, 10/96, 10.4%). For six patients of the latter group showing a genital infection with Ureaplasma urealyticum, a discontinuous gradient selection performed on the cryopreserved sample was efficient to discard bacteria. These data emphasize the usefulness to cultivate semen simultaneously to cryopreservation and demonstrate the ability to remove some microbial agents from semen before its use in assisted reproductive techniques.

In vitro fertility and motility characteristics of frozen–thawed boar epididymal spermatozoa separated by Percoll

Frozen-thawed epididymal spermatozoa from four boars were separated through a Percoll gradient, and motility characteristics and in vitro fertility were assessed. Percoll-separated spermatozoa had a significantly higher percentage of motile and progressively motile spermatozoa than those that were not separated (P < 0.0001). However, there were no clear differences in other motility parameters between Percoll-separated and un-separated spermatozoa. Furthermore, sperm agglutination was decreased by Percoll separation (P < 0.05). The effects of Percoll separation on in vitro fertility of spermatozoa differed among boars. In addition, there were large differences in fertility between sperm samples in vitro. Sperm samples, which indicate highly motile and progressively motile, did not always show high in vitro fertility. Furthermore, there was no distinct pattern between fertility in vitro and motility parameters. There was no difference in fertility in vitro between Percoll-separated and un-separated spermatozoa from two of the four boars. However, in vitro fertility of Percoll-separated spermatozoa was higher than that of un-separated spermatozoa from the other two boars.

A clinical study comparing PureSperm and SpermFilter for density gradient separation of human spermatozoa in assisted reproduction

OBJECTIVE

To compare a new density gradient medium, SpermFilter, for purifying spermatozoa in assisted reproduction with the more established medium, PureSperm.

DESIGN

Part 1, a multicenter study on 225 semen samples purified using either PureSperm (115 semen samples) or SpermFilter (110 semen samples). Part 2, a retrospective, single center study on a total of 898 assisted reproductive cycles (245 insemination cycles using husband semen, 58 insemination cycles using donor semen and 595 in vitro fertilization/intracytoplasmic sperm injection (IVF/ICSI) cycles.

SETTING

Part 1, three fertility clinics in Denmark (two university-affiliated fertility clinics and one private clinic). Part 2, one university-affiliated fertility clinic in Denmark.

MAIN OUTCOME PARAMETERS

Part 1, purity of purified spermatozoa (% motile), motility index and recovery of motile spermatozoa. Part 2, malformation and baby take-home rates (insemination cycles), fertilization, cleavage, implantation, malformation and baby take-home rates (IVF/ICSI cycles).

RESULTS

No statistical differences were observed in any of the parameters investigated.

CONCLUSION

SpermFilter is a valid alternative to PureSperm in assisted reproduction technology (ART).

[Evaluation of the interest of semen culture before cryoconservation]

OBJECTIVES

French guidelines recommend screening all patients for virus infection prior to cryopreservation of their semen. In case of viral risk, the use of specific high secure CBS straws is recommended. The objective of this work was to evaluate the microbiological risk by testing all semen samples before cryopreservation.

PATIENTS AND METHODS

Fifty one patients underwent a semen culture before cryopreservation.

RESULTS

The fifty one patients were classed into 3 groups following semen culture results: group I: negative culture (39/51, 76.47%), group II: positive culture with microbiological contamination (7/51, 13.73%) and group III: positive culture with pathogen (5/51, 9.8%). For 3 patients of the latter group, we tested a three-layer density gradient to eliminate bacteria before Assisted Reproductive Techniques.

DISCUSSION AND CONCLUSIONS

This paper discusses the risks related to microbiological contamination and the options available in this case.

Fractionation of cells and subcellular particles with Percoll

At present, centrifugation is the most common method for separation and isolation of cells and subcellular particles. The technique can be used for a wide range of applications. During latter years it has become obvious what a powerful method density gradient centrifugation is, especially when used in conjunction with sensitive assays or clinical treatments. The most active areas for use of density gradient centrifugation include purification for in vitro fertilization of sperm of both human and bovine origin, isolation of cells for cell therapy of patients receiving chemo- and radiation therapy and basic research both on cellular and subcellular levels. These treatments and investigations require homogeneous populations of cells and cell organelles, which are undamaged after the separation procedure. Percoll, once introduced to reduce convection during centrifugation, has proved to be the density gradient medium of choice since it fulfills almost all criteria of an ideal density gradient medium. Recently good results have also been obtained after silanization of colloidal silica particles, e.g. BactXtractor. The latter medium has proved to be useful in recovery of microorganisms from food samples free of inhibitors to the Polymer Chain Reaction (PCR). The separation procedures described for Percoll in this review seem to be applicable to any cells or organelles in suspension for which differences in size or bouyant density exist. Furthermore, since Percoll media are inert, they are well suited for the separation of fragile elements like enveloped viruses.

Bacterial contamination and sperm recovery after semen preparation by density gradient centrifugation using silane-coated silica particles at different g forces

The effects of density gradient centrifugation through silane-coated silica particles (PureSperm) using 100, 200, 300 and 500 g on bacterial contamination of sperm samples and recovery of motile spermatozoa from sperm samples were investigated with conventional culturing techniques and microscopic visual assessment. The recovery of motile spermatozoa was variable and was not improved using 500 g compared to the recommended 300 g. The bacterial contamination was highly decreased by gradient centrifugation through PureSperm and was almost abolished when strict aseptic techniques were used, with changes to sterile Pasteur pipettes and tubes prior to washing procedures.

Iodixanol as a density gradient medium for the isolation of motile spermatozoa

PURPOSE

The purpose of this study was to establish concentrations of Iodixanol which could be used in a similar manner to the widely used Mini-Percoll technique for the separation of motile spermatozoa.

METHODS

Various density gradient combinations of Iodixanol were compared for the isolation of motile spermatozoa from cryopreserved donor semen. The toxicity of Iodixanol was tested by its effect on the growth of two-cell mouse embryos and fresh sperm survival.

RESULTS

The best sperm recovery (32%) came from the pellet of sperm passing through a discontinuous gradient of 25% over 40% OptiPrep after 20 min of centrifugation at 400 g. There was no evidence of toxicity to mouse embryo growth or sperm survival.

CONCLUSIONS

Iodixanol (OptiPrep; Nycomed) provides a satisfactory alternative for the efficient separation of motile spermatozoa for ART procedures.

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.

Processing of semen in an antibiotic-rich culture medium to minimize microbial presence during in vitro fertilization

OBJECTIVE

To identify and determine the prevalence of microorganisms in preprocessed and postprocessed semen in an IVF-ET program.

DESIGN

Prospective study.

SETTING

University Teaching Hospital.

PATIENT(S)

Seventy-four men undergoing preprogram evaluation, each producing two semen samples.

INTERVENTION(S)

Semen processing with a wash and swim-up technique in a penicillin- and streptomycin-rich medium.

MAIN OUTCOME MEASURE(S)

The identity and prevalence of seminal microorganisms before and after processing.

RESULT(S)

Sixty-three percent of individual unprocessed semen samples grew microorganisms, the majority of which were nonpathogenic. Thirty-three men (44.6%) had microbes identified in repeat samples, four had identical organisms each time. Twenty (27%) had positive cultures in one sample, negative in the other. Twenty-one (28.4%) had consistently sterile semen. After seminal processing, the recovery rate for microbes was 5%. Microbial presence after processing did not correlate with either the sperm swim-up concentration or the initial microbial concentration.

CONCLUSION(S)

Bacteriospermia is common. The microorganisms found rarely are replicated and most likely represent contamination. Wash and swim-up semen preparation in an antibiotic rich culture medium effectively eliminates 95% of organisms.

Variation in recovery of motile sperm after preparation by a simple Percoll gradient technique

PURPOSE

Numerous techniques have been used to prepare sperm for assisted reproduction technology. Density-gradient centrifugation with Percoll is becoming a method of choice. This study reviewed the results of a simple two-layer discontinuous Percoll gradient.

METHODS

We reviewed retrospectively results obtained from 208 semen specimens prepared for in vitro fertilization by a discontinuous Percoll gradient.

RESULTS

Overall results (mean +/- SD) were a recovery of 21 +/- 16% of total sperm, recovery of 38 +/- 30% of motile sperm, and a motility in the final sperm preparation of 88 +/- 10%. Specimens with higher initial concentrations had higher motility in the final preparation. Higher total recovery and higher motility in the final preparation were found for specimens with a higher initial motility.

CONCLUSIONS

This simple two-layer Percoll technique is rapid and inexpensive and reliably produces a final sperm preparation with desirable characteristics. Even though specimens with poor initial parameters yielded final preparations with excellent characteristics, fertilization rates were still related to the initial semen parameters.

Comparison of motility characteristics and normal sperm morphology of human semen samples separated by percoll density gradient centrifugation

The aim of this study was twofold: to investigate the ability of Percoll gradient centrifugation (52, 68, 84%) to fractionate semen samples according to motility quality and percentage normal morphology and to determine whether there is an association between sperm motility quality and percentage normal morphology. Sperm motility was evaluated using a Hamilton Thorn analyzer and normal sperm morphology was manually assessed according to the strict criteria (< or = 4, 5-14, and >14%). The majority of motility parameters and the percentage normal morphology were found to be significantly improved in the 84% Percoll fraction. The greatest effect was on the < or = 4% group, shifting the mean normal morphology percentage from 2.6 to 5.2%. Curvilinear velocity (VCL) and average path velocity (VAP) were the only two motility parameters that were significantly associated with the percentage normal morphology. Using a combined VCL, VAP vector the >14% group was found to have a significantly different value as compared to the 5-14 and < or = 4% groups. Percoll (discontinuous) gradient centrifugation can therefore play a significant role in the improvement of semen samples for use in assisted reproduction procedures. The VCL, VAP vector identified may also serve as an additional tool in the prediction of the fertility potential of sperm samples.

Controlled ovarian hyperstimulation and intrauterine insemination for treatment of infertility

Empirical therapy for subfertility using assisted reproductive technologies recently has gained popularity; however, the cost-effectiveness of these therapies, compared with an untreated control group, has not been established. Similarly, there has been no comparative cost analysis of the utility of controlled ovarian hyperstimulation and IUI in the management of the same condition. Significant PRs in untreated couples with subfertility mandate the design and execution of controlled trials to ascertain the role of controlled ovarian hyperstimulation and IUI in infertility therapy. Various disorders of subfertility have been treated with controlled ovarian hyperstimulation and IUI. The rationale for this therapy is the increase in gamete density at the site of fertilization, as with GIFT and IVF when used for management of the same problems. The live birth rate per initiated cycle and risk of complications are similar to results recently reported for GIFT and IVF. The utility of controlled ovarian hyperstimulation and IUI still remains controversial. When the relatively low direct and indirect costs of controlled ovarian hyperstimulation and IUI are considered, acknowledging the lack of prospective, controlled studies, this procedure appears to be at least as cost-effective as GIFT and IVF.