Development and successful clinical application of preimplantation genetic haplotyping for Herlitz junctional epidermolysis bullosa

BACKGROUND

Herlitz junctional epidermolysis bullosa (HJEB) is a severe, life-threatening, autosomal recessive blistering skin disease for which no cure is currently available. Prenatal diagnosis for couples at risk is feasible through fetal skin biopsy or analysis of DNA extracted from chorionic villi, but these methods can be applied only after pregnancy has been established. An alternative approach, which involves the analysis of single cells from embryos prior to establishment of pregnancy, is preimplantation genetic diagnosis (PGD). Until now, its clinical uptake has been hindered by lengthy delays in establishing mutation-specific protocols, and by the small amount of template DNA that can be obtained from a single cell. A new method that addresses these problems, preimplantation genetic haplotyping (PGH), relies on whole genome amplification followed by haplotyping of multiple polymorphic markers using standard DNA-based polymerase chain reaction (PCR) assays.

OBJECTIVES

To design and validate a generic PGH assay for HJEB and to transfer this into clinical practice.

MATERIALS AND METHODS

We established a multiplex PCR-based PGH assay involving 16 markers within and flanking the LAMB3 gene (the most frequently mutated gene in HJEB). The assay was then validated in 10 families with at least one previously affected offspring. After licensing by the Human Fertilisation and Embryology Authority (HFEA), the new test was used for PGD in a couple at risk of HJEB.

RESULTS

The chromosome 1 LAMB3 markers within the assay were shown to be of sufficient heterogeneity to have widespread application for preimplantation testing of HJEB. In one couple that were heterozygous carriers of nonsense mutations in LAMB3, we used the new assay to identify unaffected embryos in a series of PGD cycles. Pregnancy was established in the third PGD cycle and a healthy, unaffected child was born. DNA analysis of cord blood confirmed the predicted single-cell mutation status of wild-type LAMB3 alleles.

CONCLUSIONS

PGH represents a major step forward in widening the scope and availability of preimplantation testing for serious mapped single-gene disorders. We have established a generic test that is suitable for the majority of couples at risk of HJEB.

Preimplantation genetic diagnosis as a source of human embryonic stem cells for disease research and drug discovery

Embryos surplus to therapeutic requirements following preimplantation genetic diagnosis can be used to derive human embryonic stem cell (hESC) lines carrying mutations significant to human disease. These cells provide a powerful in vitro tool for modelling disease progression in a number of cell types as well as having the potential to revolutionise drug discovery. Robust and reproducible directed differentiation protocols are needed to maximise the potential of these cells. In this review, we explore the current use of hESC and induced pluripotent stem cells in disease-specific research and discuss the use of stem cell technology in drug discovery and toxicity testing.

Preimplantation genetic diagnosis of skin fragility-ectodermal dysplasia syndrome

Skin fragility-ectodermal dysplasia syndrome is an autosomal recessive disorder caused by loss-of-function mutations in the desmosomal protein, plakophilin 1. Clinically, there may be considerable morbidity from extensive skin erosions and painful fissures on the palms and soles. In the absence of any specific treatment, prenatal diagnosis is an option for couples at reproductive risk of recurrence. In 2000, we developed and applied a single cell nested polymerase chain reaction protocol to test one couple for compound heterozygous plakophilin 1 gene mutations by preimplantation genetic diagnosis (PGD). Although pregnancy was established, an unrelated trisomy 22 led to a spontaneous abortion. However, eight embryos of known genetic status were cryopreserved at that stage, and we planned to undertake subsequent frozen embryo replacement cycles that might lead to the birth of an unaffected child in this family. Embryo cryopreservation was carried out in June 2000 using standard protocols in a three-step freezing procedure. Four embryos were thawed in March 2003, one of which was viable and was used in a frozen embryo replacement cycle, but pregnancy did not occur. The remaining four embryos were thawed in February 2004, two of which were viable (both carriers of the paternal mutation) and these were used in a second frozen embryo replacement cycle, and a singleton pregnancy was established. The child's plakophilin 1 genotype was assessed by direct nucleotide sequencing across the site of both potential mutations. Following two frozen embryo replacement cycles, and almost 4 years after the initial embryo biopsy and mutation analysis, a pregnancy was achieved that progressed to term with the birth of a healthy baby girl. Nucleotide sequencing of cord blood DNA, taken immediately after delivery, showed that the child was a heterozygous carrier of the paternal mutation but not of the maternal mutation. This case demonstrates the value of embryo cryopreservation, which can increase the number of embryo replacement procedures and hence the cumulative pregnancy rate per retrieval cycle. Moreover, this is the first report of successful full-term pregnancy and birth of a healthy baby following exclusion of a severe genodermatosis by PGD. The successful outcome of PGD in this case illustrates what is technically possible for couples at risk of recurrence of a severe inherited skin disease.

Robertsonian translocations--reproductive risks and indications for preimplantation genetic diagnosis

BACKGROUND

Robertsonian translocations carry reproductive risks that are dependent on the chromosomes involved and the sex of the carrier. We describe five couples that presented for preimplantation genetic diagnosis (PGD).

METHODS

PGD was carried out using cleavage-stage (day 3) embryo biopsy, fluorescence in-situ hybridization (FISH) with locus-specific probes, and day 4 embryo transfer.

RESULTS

Couple A (45,XX,der(14;21)(q10;q10)) had two previous pregnancies, one with translocation trisomy 21. A successful singleton pregnancy followed two cycles of PGD. Couple B (45,XX,der(13;14)(q10;q10)) had four miscarriages, two with translocation trisomy 14. One cycle of PGD resulted in triplets. Couple C (45,XX,der(13;14)(q10;q10)) had four years of infertility; two cycles were unsuccessful. Couple D (45,XY,der(13;14)(q10;q10)) presented with oligozoospermia. A singleton pregnancy followed two cycles of PGD. Couple E (45,XY,der(13;14)(q10;q10)) had a sperm count within the normal range and low levels of aneuploid spermatozoa. PGD was therefore not recommended. No evidence for a high incidence of embryos with chaotic or mosaic chromosome complements was found.

CONCLUSIONS

For fertile couples, careful risk assessment and genetic counselling should precede consideration for PGD. Where translocation couples need assisted conception for subfertility, PGD is a valuable screen for imbalance, even when the risk of viable chromosome abnormality is low.

A comparison of different lysis buffers to assess allele dropout from single cells for preimplantation genetic diagnosis

Single cell polymerase chain reaction (PCR) for preimplantation genetic diagnosis (PGD) requires high efficiency and accuracy. Allele dropout (ADO), the random amplification failure of one of the two parental alleles, remains the most significant problem in PCR-based PGD testing since it can result in serious misdiagnosis for compound heterozygous or autosomal dominant conditions. A number of different strategies (including the use of lysis buffers to break down the cell and make the DNA accessible) have been employed to combat ADO with varying degrees of success, yet there is still no consensus among PGD centres over which lysis buffer should be used (ESHRE PGD Consortium, 1999). To address this issue, PCR amplification of three genes (CFTR, LAMA3 and PKP1) at different chromosomal loci was investigated. Single lymphocytes from individuals heterozygous for mutations within each of the three genes were collected and lysed in either alkaline lysis buffer (ALB) or proteinase K/SDS lysis buffer (PK). PCR amplification efficiencies were comparable between alkaline lysis and proteinase K lysis for PCR products spanning each of the three mutated loci (DeltaF508 in CFTR 90% vs 88%; R650X in LAMA3 82% vs 78%; and Y71X in PKP1 91% vs 87%). While there was no appreciable difference between ADO rates between the two lysis buffers for the LAMA3 PCR product (25% vs 26%), there were significant differences in ADO rates between ALB and PK for the CFTR PCR product (0% vs 23%) and the PKP1 PCR product (8% vs 56%). Based on these results, we are currently using ALB in preference to PK/SDS buffer for the lysis of cells in clinical PGD.

Preimplantation genetic diagnosis of compound heterozygous mutations leading to ablation of plakophilin-1 (PKP1) and resulting in skin fragility ectodermal dysplasia syndrome: a case report

A new form of genodermatosis resulting from mutations in the gene plakophilin 1 (PKP1) has recently been identified. The clinical features of a functional knockout of PKP1 are a combination of skin fragility and a form of hypohydrotic ectodermal dysplasia. We have developed a single cell polymerase chain reaction (PCR) assay suitable for preimplantation genetic diagnosis (PGD) and here we report on the clinical application of this assay.

Recurrent cholestasis following ovarian hyperstimulation syndrome: case report

This is a case report illustrating a patient who developed recurrent cholestasis during a twin pregnancy following in-vitro fertilization (IVF) treatment. On the first occasion cholestasis developed unusually in the first trimester, and on the second occasion, it presented in the way that obstetric cholestasis (OC) is commonly seen in the third trimester.

Non-disclosure preimplantation genetic diagnosis for Huntington's disease: practical and ethical dilemmas

Prenatal diagnosis of Huntington's Disease (HD) is controversial. Selective abortion is considered unacceptable by some, since, being a late-onset disorder, any child born carrying the HD mutation might still expect many years of disease-free life. The test result itself has implications for the parents and other members of the family who may have decided not to be tested but who know that they may be at risk because a family member is affected. For this reason some potential carriers do not want to know their carrier status and may prefer prenatal exclusion testing. However, since half the fetuses carrying the affected grandparental allele may be normal, aborting these fetuses is also controversial. Preimplantation genetic diagnosis (PGD) has been suggested as an alternative by which asymptomatic individuals who are at high risk of carrying HD can avail themselves of antenatal genetic testing without incurring the emotional, social and financial burdens that might result from the presymptomatic disclosure of their own carrier status. However, non-disclosure testing of embryos in vitro presents specific practical difficulties. Assurance of absolute secrecy is difficult in the large team required for in vitro fertilization biopsy and diagnosis, and changes in practice which may be required to maintain the deception may be unethical.

Assisted conception in HIV discordant couples: evaluation of semen processing techniques in reducing HIV viral load

Artificial insemination with motile spermatozoa prepared from HIV-infected men using standard procedures has been employed with many HIV-discordant couples. We have demonstrated that processing semen from HIV positive men can reduce HIV levels, measured as HIV1 RNA copies/ml using nucleic acid based sequence amplification (NASBA), to undetectable levels (less than 400 copies/ml) but not in all samples. We believe that all processed samples should be tested prior to insemination.

Transcatheter uterine artery embolisation to treat large uterine fibroids

Bilateral uterine artery embolisation was performed to treat eight women with symptomatic large fibroids requiring treatment. Uterine volume was quantitatively assessed by magnetic resonance imaging. Both uterine arteries were occluded effectively in all women, and the procedure was well tolerated, with a 24-36 hour admission for pain relief. The level of pain experienced was variable, but well controlled. Some women experienced intermittent vaginal discharge and pain following the procedure. Improvement of symptoms occurred in six of the seven women and the eighth woman conceived. There were no significant complications. At three months four women had a uterine volume of < 350 cm3. Embolisation appears to be a good alternative to surgery, but longer follow up is required to evaluate the long term effects and to determine those patients for whom the procedure is suitable.

The distribution of alpha- and gamma-tubulin in fresh and aged human and mouse oocytes exposed to cryoprotectant

The distribution of alpha- and gamma-tubulin in human and mouse oocytes has been investigated immunocytochemically. Comparisons have been made between freshly recovered and aged oocytes (both human and mouse), and also between human oocytes before and after exposure to cryoprotectant. Control fresh human oocytes had compact anastral spindles oriented orthogonal to the oolemma, with the pole adjacent to the oolemma being smaller than that directed towards the centre of the oocyte. Each pole was associated with a ring of particulate gamma-tubulin staining that extended a short distance into the body of the spindle. No alpha- and gamma-tubulin staining was found elsewhere in the ooplasm. Human oocytes which had failed to fertilize after an 18 h incubation with spermatozoa and had spent a further 6-8 h in culture showed an increased incidence of spindle abnormalities and of the proliferation of ooplasmic microtubules, which became more pronounced with age post-ovulation. The gamma-tubulin staining pattern of these aged human oocytes revealed greater staining over the whole of the spindle than in fresh oocytes. Examination of mouse oocytes aged in vitro or in vivo showed similar evidence of microtubule proliferation and disorganization, and the gamma-tubulin staining pattern was a sensitive indicator of ageing. The spindles of most fresh human oocytes exposed to 1.5 M dimethyl sulphoxide (DMSO) at 4 degrees C differed from controls in being slightly reduced in size or in having more pointed spindle poles with smaller diameters, both indications that some dismantling of the microtubules had occurred. The distribution of gamma-tubulin in these oocytes extended over more of the spindle. Restoration of DMSO-exposed oocytes to control medium at 37 degrees C for an extended period restored spindle structure to a state closely resembling that in controls. However, recovery of an exclusively polar gamma-tubulin staining did not occur. In both controls and DMSO-exposed human oocytes, chromosomes were arranged on the metaphase equatorial plate. In contrast, exposure of oocytes to 4 degrees C in the absence of DMSO caused dismantling of the spindle. It is concluded that (i) changes in microtubule organization with ageing of oocytes makes them unsuitable for use therapeutically after re-insemination or intracytoplasmic sperm injection, (ii) conditions of cryoprotectant addition previously found optimal for the stabilization of the spindle in the mouse oocyte also appear to be effective in stabilizing the spindle of the human oocyte, and (iii) the distribution of gamma-tubulin in relation to the spindle of the human oocyte appears to be sensitive to age and conditions.

The timing of pronuclear formation, DNA synthesis and cleavage in the human 1-cell embryo

The timing of pronuclear formation and breakdown, DNA synthesis and cleavage during the first cell cycle of human embryogenesis are described. Pronuclei formed between 3 and 10 h post-insemination (hpi; median 8 hpi). S-phase commenced between 8 and 14 hpi, and was completed between 10 and 18 hpi. M-phase was observed between 22 and 31 hpi (median duration 3 h), and cleavage to the 2-cell stage took place between 25 and 33 hpi. The timing of the same events was determined in 1-cell embryos derived from re-inseminated human oocytes that had failed to fertilize during therapeutic in-vitro fertilization (IVF). In these embryos, pronuclei formed between 3 and 8 h post-re-insemination (hpr-i), coinciding with the beginning of S-phase. While S-phase was completed as early as 10 hpr-i in some embryos, it extended until at least 16 hpr-i in others. Pronuclear breakdown and cleavage occurred from 23 and 26 hpr-i respectively; however, they did not occur in some embryos until after 46 hpr-i. The results demonstrate a markedly greater degree of variation in the timing of these events in embryos derived from re-inseminated oocytes compared with embryos derived from conventional IVF, and thus throw into question the validity of using the former as models for studies of the first cell cycle of human embryogenesis.

An analysis of multinucleated blastomere formation in human embryos

Human embryos were disaggregated into component blastomeres 42-72 h after insemination. The blastomeres were scored for the number of nuclei present and blastomeres of known nuclear morphology were returned to individual culture drops for 16-20 h, after which they were scored for cleavage and nuclear morphology. In all, 48% of mononucleated blastomeres cleaved during this period, but only 76% of these produced two mononucleated daughter blastomeres; in the remainder, one or more of the blastomeres was abnormally nucleated. During overnight culture, 30% of multinucleated blastomeres and 30% of anucleate blastomeres cleaved, the majority producing abnormally nucleated daughter blastomeres. The majority of blastomeres which showed no sign of cleavage after overnight culture retained the same nuclear morphology as when originally disaggregated. However, a small number of mononucleated blastomeres contained two nuclei after culture, indicating that karyokinesis may have taken place in the absence of cytokinesis. Overall, approximately 30% of blastomeres with more than one nucleus seemed to arise by this mechanism, the remainder probably arising by errors of chromosome segregation and/or packaging at mitosis. In addition, 25/111 mononucleated daughter cells arose either after abnormal division of mononucleated parent cells or after division of multinucleated cells, suggesting that approximately 23% of newly formed mononucleated cells might be chromosomally abnormal. The results of DNA quantitation indicated that very few (12/131, 9.2%) blastomeres (whether uni- or multinucleated) had a DNA content outside the 2-4C range. The embryos used for these studies had been cultured in one of three commonly used in-vitro fertilization (IVF) media: modified T6, Earle's balanced salts or Universal IVF medium (a commercial medium from Medi-Cult). A retrospective analysis was carried out of the number of embryos containing multinucleated blastomeres at disaggregation and of the total proportion of isolated blastomeres which were multinucleated in three groups of embryos, each of which had been cultured in one of the IVF media. Both these parameters were found to vary between cohorts of embryos cultured in the different media. The mechanism(s) by which culture medium composition might affect multinucleation of human blastomeres is discussed, as is the significance of these data for reliable preimplantation diagnosis of genetic status.

Evaluation of a simple method for measuring the cellular DNA content of mouse oocytes and embryos, human fibroblasts and parthenogenetically activated human oocytes using a computerised image analysis system (Seescan)

We report the use of a simple, reproducible, photocytometric method for measuring nuclear DNA content of DAPI-stained cells, using a computerised image analysis system: Seescan. As this technique is non-destructive and uses very short exposure to ultraviolet light, it can be used for either fixed or vital material. After correcting for any background cytoplasmic staining, the intensity of nuclear stain was measured by the Seescan and compared with that of control cells of known ploidy. Fixed material was found to stain more intensely than live material initially, but demonstrated a rapid loss of nuclear intensity over the first 90 min following removal from DAPI, after which the level plateaued. In contrast, live cells showed no change in nuclear intensity with time. The system was validated by measuring the DNA content of carefully timed mouse blastomeres, human fetal lung fibroblasts and parthenogenetically activated human oocytes. The results obtained were appropriate for the developmental stage or phenotypic appearance of each of the cell types measured.

The early development and DNA content of activated human oocytes and parthenogenetic human embryos

A total of 297 human oocytes that had failed to fertilize during in-vitro fertilization (IVF) cycles were exposed to the calcium ionophore A23187 to induce parthenogenetic activation. Of these oocytes, 192 (65%) activated, the majority (63%) exhibiting a single pronucleus and extruding a second polar body. The appearance of two pronuclei (18%) was generally associated with a failure to extrude the second polar body. Oocytes obtained from patients who were > or = 35 years had a significantly reduced activation rate (53%). The timing of developmental events, such as extrusion of the second polar body, appearance and disappearance of pronuclei and the first two cleavage divisions, is broadly similar to that seen in fertilized oocytes. However, the developmental potential of human parthenogenetic embryos was reduced, as the majority of those allowed to continue in culture arrested between the 2-cell and 8-cell stages. Measurements of cellular DNA content using a computerized image analysis system showed that activated oocytes with one pronucleus had a DNA content compatible with a haploid number of chromosomes, while those with two pronuclei were diploid. The ability of parthenogenetically activated oocytes to replicate their DNA was also demonstrated.

Use of a polymorphic dinucleotide repeat sequence to detect non-blastomeric contamination of the polymerase chain reaction in biopsy samples for preimplantation diagnosis

Using the polymerase chain reaction (PCR), amplification of two different target DNA sequences has been achieved with high frequency using single human blastomeres as template for the duplex reaction. One sequence is located within the beta-globin gene and contains the sickle cell locus, the other is a polymorphic dinucleotide repeat, which, as well as acting as a positive control for amplification, was used to check the origin of the amplified DNA. A comparison of the sequences amplified from the blastomere with sequences amplified from parental samples confirmed that amplification of blastomeric sequences, but not extraneous contaminating DNA, had taken place in most cases. The efficacy of this system for detecting extraneous DNA was checked by deliberately contaminating single blastomeres with foreign cells. The presence of contamination was detected by the amplification of sequences not present in blastomeric DNA and which therefore must have been amplified from extraneous contaminating DNA.

Preimplantation diagnosis of genetic disease

Preimplantation diagnosis offers couples at high risk of transmitting a genetic disease the opportunity of prenatal diagnosis before the establishment of pregnancy. The successful application of embryo biopsy techniques, and of the polymerase chain reaction for the amplification of DNA, as well as fluorescent in-situ hybridization methods have allowed a small number of IVF units to identify the sex and/or genetic defect in human preimplantation embryos. The development of current methods being applied are reviewed. We suggest that there is a need for constant evaluation of the technique and for improvement of the present methods to ensure reproducibility and accuracy of the diagnostic procedures.

Vaginal squamous cells in follicular aspirates following transvaginal puncture

Squamous cells are common findings on cytological examination of fluid obtained following transvaginal aspiration of simple ovarian cysts. This prospective study confirms the hypothesis that these cells are commonly introduced as contaminants during puncture of the vaginal wall. The occasional finding of bacteria also suggests a possible mechanism for post-operative pelvic infection.

Assessment of the cellular DNA content of whole mounted mouse and human oocytes and of blastomeres containing single or multiple nuclei

The nuclear DNA content of intact, live or fixed, human and mouse oocytes and blastomeres has been measured rapidly and reliably. Chromosomal DNA has been stained with DAPI, the fluorescent emission from which has been measured photocytometrically. In vitro fertilised mouse oocytes and embryos at various stages of development were assessed for their DNA content. The mean values of 1C, 2C and 4C DNA content were clearly different, and it was possible to assign correctly individual values for DNA content to each class with 92%, 61% and 81% confidence respectively. Maintaining the cells as whole mounts allowed other morphological and structural features to be examined. When formation of multiple micronuclei was induced in mouse oocytes by their insemination in the presence of nocodazole, the additive signal from all the micronuclei in one zygote was equivalent to the expected DNA content. Application to early human blastomeres of this photocytometric technique for measurement of the total cellular DNA content revealed that multinucleated blastomeres contained 2C to 4C DNA levels, consistent with a diploid DNA content.

Beta-N-acetylhexosaminidase activity in human oocytes and preimplantation embryos

beta-N-acetylhexosaminidase is a lysosomal enzyme, which has two isoenzymes: beta-Hex A, a trimer consisting of one alpha-chain and two beta-chains (alpha beta 2) and beta-Hex B, a tetramer formed of four beta-chains (beta 2 beta 2). Genetic defects in the alpha-chain lead to Tay-Sachs disease, whereas mutations in the beta-chain gene lead to Sandhoff disease. In a previous study we developed a microassay for total beta-N-acetylhexosaminidase and used this for measuring activities in mouse oocytes and preimplantation embryos. In this study, to assess the feasibility of transferring this technique to the human for the purposes of preimplantation diagnosis for Tay-Sachs and Sandhoff disease, beta-Hex activity was assayed in human oocytes and embryos and in the medium in which they had been cultured. We showed that although the activity of beta-N-acetylhexosaminidase in human oocytes and embryos was > 500 times higher than in the mouse, it was not detectable in the culture medium and the activity in oocytes and embryos remained virtually constant throughout human preimplantation development, making it difficult to distinguish embryonic from maternal enzyme activity. In the absence of this distinction it would be inappropriate to use beta-N-acetylhexosaminidase activity for the purposes of preimplantation diagnosis of Sandhoff or Tay-Sachs disease. These experiments demonstrate that measuring the beta-N-acetylhexosaminidase activity in human embryos cannot be used at present for preimplantation diagnosis.

Gene activity and cleavage arrest in human pre-embryos

There is a high rate of spontaneous cleavage arrest around the four- to eight-cell stage of human development in vitro. Since this coincides with the time of activation of the embryonic genome it has been suggested that cleavage arrest may occur as a consequence of failure of gene activation. Gene expression in human pre-embryos is associated with an alpha-amanitin sensitive, qualitative change in protein synthesis. In order to ascertain the role of gene expression in cleavage arrest, we have examined the protein synthetic patterns of human pre-embryos which have undergone spontaneous cleavage arrest in vitro. Of 54 cleavage-arrested embryos, 27 demonstrated evidence of synthesis of proteins sensitive to alpha-amanitin, suggesting that cleavage arrest is not always accompanied by failure of activation of the genome. Our results would also suggest that activation of gene expression is simply related to neither cell number nor time spent in culture since fertilization, but may be related to continuing karyokinesis.

Reliability of detection by polymerase chain reaction of the sickle cell-containing region of the beta-globin gene in single human blastomeres

Human preimplantation embryos at various stages of development have been analysed using the polymerase chain reaction to amplify a 680 base pair fragment of the beta-globin gene. Successful amplification was achieved more frequently with DNA from intact embryos containing between one and 11 cells, single cumulus cells, oocytes which had failed to fertilize and polar bodies than from single blastomeres disaggregated from intact embryos and treated in an identical manner. The distribution of nuclei demonstrated using the nuclear chromophore diamino-phenyl-indole showed considerable inter-blastomere variation; however, no clear correlation between staining pattern and successful amplification was observed. The reason for the unreliable amplification of DNA from single blastomeres is unclear but this finding has important implications for preimplantation diagnosis of genetic disease.

Amnifiltration in the first trimester: feasibility, technical aspects and cytological outcome

An amnifiltration system has been developed which allows collection of cells from the amniotic sac in the first trimester of pregnancy whilst only removing 1 ml of amniotic fluid in total. The cells can be cultured and harvested, using the same methods as early amniocentesis, to enable prenatal diagnosis of fetal karyotype. A range of filters constructed from different materials and of differing pore sizes were examined for their ability to trap and subsequently release a maximum number of amniotic fluid cells. The best filter membrane was found to be a cellulose acetate filter of 0.8 micro m pore size. To achieve the same cytogenetic outcome as a 10 ml amniocentesis, a minimum of 20 ml amniotic fluid must be filtered and recirculated through the system.

A prospective study of the incidence, time of appearance and significance of anti-paternal lymphocytotoxic antibodies in human pregnancy

The incidence and natural history of serum anti-paternal cytotoxic antibody (APCA) in normal pregnancy and spontaneous abortion was investigated prospectively in 306 women (64 primigravidae and 242 multigravidae), in order to establish whether serum APCA is a useful screening test in the diagnosis, treatment and prognosis for patients with recurrent pregnancy loss. Pre-pregnancy, serial pregnancy and post delivery serum samples were tested against partner's lymphocytes, using a microdroplet lymphocytotoxicity assay. The incidence of serum APCA in the 256 pregnancies successfully completed was 32%, compared with 10% amongst the 50 pregnancies ending in spontaneous abortion. The lower incidence of positive APCA tests in unsuccessful pregnancies was explained by our finding that positive APCA tests are related to the gestational age of the pregnancy and are rarely demonstrable before 28 weeks gestation. Since APCA usually disappears between pregnancies, its usefulness as a diagnostic test for immunotherapy against recurrent abortion should be questioned.

Cryoprotection of human oocytes: inappropriate exposure to DMSO reduces fertilization rates

Human oocytes were exposed to the cryoprotectant dimethyl-sulphoxide (DMSO) at either 4 or 37 degrees C. Subsequent fertilization of these oocytes showed that exposure to DMSO at 37 degrees C was associated with a greatly reduced fertilization rate when compared to untreated control oocytes, whereas no such reduction was seen in oocytes exposed to DMSO at 4 degrees C. The significance of these results for the potential cryopreservation of human oocytes is discussed.

The incidence of abnormal morphology and nucleocytoplasmic ratios in 2-, 3- and 5-day human pre-embryos

Human cleaving pre-embryos at 2 and 3 days and cavitated pre-embryos at 5 days post-insemination have been examined for cell number and the incidence of mononucleated cells. At least 60% of polynucleate or anucleate cells have been detected at all these stages and regardless of morphological grading at day 2. It is concluded that even by the time at which pre-embryo replacement would occur therapeutically, the majority of pre-embryos are unlikely to have full developmental potential. The possible origins of the abnormalities of nucleocytoplasmic ratios are discussed.

Transient cooling to room temperature can cause irreversible disruption of the meiotic spindle in the human oocyte

The effect on the microtubule system of human oocytes of cooling to room temperature for either 10 or 30 minutes has been investigated. Changes in spindle organization were found in all oocytes cooled for 30 minutes compared with control oocytes kept at 37 degrees C throughout. These changes included reduction in spindle size, disorganization of microtubules within the spindle itself, and sometimes a complete lack of microtubules. In some oocytes, chromosome dispersal from the metaphase plate was associated with these changes. Cooling the oocyte to room temperature for only 10 minutes produced a similar pattern of disruption to spindle structure in many cases. The spindles in oocytes that were cooled for either 10 or 30 minutes and then allowed to recover at 37 degrees C for either 1 or 4 hours were found to resemble those in noncooled control oocytes in less than one half of the cases examined, although in only a few cases did the chromosomes remain dispersed. The significance of these findings for the handling of oocytes during gamete intrafallopian transfer and in vitro fertilization procedures is discussed in relation to the levels of aneuploidy detected in early human embryos.

Acid Tyrode's solution can stimulate parthenogenetic activation of human and mouse oocytes

Fresh and aged (24 hours after ovulation) human oocytes and recently ovulated mouse oocytes may be activated by exposure to acidified Tyrode's solution. No activation of either type of human oocyte was observed after exposure to hyaluronidase or pronase, but significant numbers of fresh mouse oocytes were activated after exposure to pronase but not to chymotrypsin. The implications of these results for the manipulation of human and mouse eggs in vitro are discussed.

Ectopic ovaries associated with absent uterus and pelvic kidney: CT findings

A patient with a congenitally absent uterus and a single pelvic kidney presented with recurrent pain in the left iliac fossa. This proved to be due to a prolapsed left ovary.

Measurement of HPRT activity in the human unfertilized oocyte and pre-embryo

The hypoxanthine phosphoribosyl transferase (HPRT) and adenine phosphoribosyl transferase (APRT) activities in individual non-fertilized human eggs and in human pre-embryos (4-cell to blastocyst stage) have been analysed. A wide spread of activities was observed, the mean values of which decline with time post-ovulation for both eggs and advancing pre-embryonic stages. The variation in activities was less in groups of eggs or pre-embryos recovered from a single ovulatory cycle. The activity of HPRT, but not of APRT, was readily detectable in single 4-cell and 8-cell blastomeres. When pre-embryos at various preimplantation stages were exposed to alpha-amanitin, to block transcription of mRNA from the pre-embryonic genome, no clear effect on HPRT activity was observed. It is concluded that the HPRT and APRT activities measured in the pre-embryos studied here are likely to be maternally inherited, and that use of a direct assay for HPRT activity for the pre-implantation diagnosis of Lesch-Nyhan disease would be premature.

Quality control in the IVF laboratory: in-vitro and in-vivo development of mouse embryos is unaffected by the quality of water used in culture media

We have examined the effect of media made with tap water or with various purified waters on the fertilization of mouse oocytes, their development to blastocysts, their rate of hatching in vitro and their survival after transfer to recipients. Zona-intact and zona-free embryos, as well as cell clusters from 8-cell stage embryos, were also used. The macromolecular composition of the media was varied. We were unable to find any adverse effect of tap water under any condition examined. The implications of these findings for quality control in IVF units are discussed.

Influence of past reproductive performance on risk of spontaneous abortion

OBJECTIVE

To investigate the incidence of spontaneous abortion in a population of women in order to establish their risk of spontaneous abortion and the obstetric factors predisposing to it.

DESIGN

Prospective study of women recruited by radio and poster appeal and from hospital outpatient clinics.

SETTING

English provincial community.

PATIENTS

630 Women from the general population intending to become pregnant.

INTERVENTIONS

The viability of the pregnancy was assessed by abdominal ultrasonography before completion of the eighth week, and the assessment was repeated if vaginal bleeding occurred.

MAIN OUTCOME MEASURE

Spontaneous abortion or live births in women with or without a previous history of spontaneous abortion.

RESULTS

The overall incidence of clinically recognisable spontaneous abortion before 20 weeks of gestation was 12% (50/407 pregnancies). The risk of spontaneous abortion in each category of patient was classified with respect to the patient's past reproductive performance and found to be influenced greatly by her previous obstetric history. In primigravidas and women with a history of consistently successful pregnancies the incidences of abortion were low (5% (4/87) and 4% (3/73) respectively), whereas women with only unsuccessful histories had a much greater risk of aborting the study pregnancy (24% (24/98)), even when their sole pregnancy had ended in abortion (20% (12/59)). The outcome of the last pregnancy also influenced the outcome of the study pregnancy; only 5% of women (5/95) whose previous pregnancy had been successful aborted, whereas the incidence of loss of pregnancy among women whose last pregnancy had aborted was 19% (40/214).

CONCLUSIONS

A knowledge of the patient's reproductive history is essential for the clinical assessment of her risk of spontaneous abortion. As the most important predictive factor for spontaneous abortion is a previous abortion, the outcome of a woman's first pregnancy has profound consequences for all subsequent pregnancies.

An evaluation of semen analysis and in-vitro tests of sperm function in the prediction of the outcome of intrauterine AIH

Twenty-nine couples with an average of 5 years of infertility were selected for treatment by intrauterine insemination of washed semen (AIH). The criteria for selection were (i) the female partner showed no detectable fertility disorders by routine screening; (ii) the male partner showed subnormal semen quality on conventional semen analysis. Ovulation was stimulated uniformly with clomiphene citrate and precipitated with human chorionic gonadotrophin (HCG). Inseminations were performed 31-32 h post-HCG, with the day of HCG determined by ultrasound monitoring of follicular development. The fertilizing capacity of the male partners' spermatozoa was tested in vitro using donated human oocytes and/or the zona-free hamster oocyte penetration assay. Up to eight cycles of AIH were alternated with cycles of natural intercourse. While no pregnancies occurred in the group during normal coital cycles, the AIH pregnancy rate was 17% per couple, but only 3% per insemination cycle. Four further pregnancies were achieved spontaneously in couples from the study group within 3 years of completion of the AIH therapy and four patients became pregnant following subsequent GIFT or IVF treatments. Neither of the in-vitro tests was helpful in predicting the outcome of AIH, spontaneous pregnancy nor of subsequent assisted conception procedures.

Are human spermatozoa separated on a Percoll density gradient safe for therapeutic use?

Motile morphologically normal human spermatozoa can be separated from semen by buoyant density centrifugation on Percoll (Pharmacia Fine Chemicals AB, Uppsala, Sweden) gradients. In this study, the authors have examined (1) the efficiency of washing procedures to remove contaminating Percoll particles from the separated spermatozoa, and (2) the potential of Percoll particles, which contain silica, to cause an inflammatory response when used for intrauterine insemination, or when introduced into the fallopian tube during gamete intrafallopian transfer (GIFT) procedures, as assessed by an intraperitoneal injection into mice. Although Percoll was phagocytosed at the injection site, and therefore cannot be presumed to be totally inert, no generalized inflammatory response was detected. A double spin and wash technique was found to remove most residual Percoll from the spermatozoa, as assessed by scanning electron microscopy. These results suggest that procedures involving the use of Percoll for the separation of human spermatozoa for in vitro fertilization, GIFT, or intrauterine insemination should include stringent washing protocols that will remove most, if not all, contaminating Percoll from the sample.

Cytoskeletal organization in fresh, aged and spontaneously activated human oocytes

The cytoskeleton of the human oocyte (microtubules and actin filaments) has been examined using fluorescence microscopy. In unfertilized oocytes in metaphase of the second meiotic division, microtubules were found exclusively within the spindle which was located at the periphery of the cell and oriented radially, with its long axis perpendicular to the surface membrane. The spindle was anastral and slightly pointed at each pole, the chromosomes being arranged on a metaphase plate at the equator. When treated with taxol, the oocyte spindle became astral and microtubules appeared in the cortex of the oocyte in the form of small strands or bundles. Polymerized actin was found to be present in a dense filamentous layer throughout the cortex of the unfertilized oocyte. Aged unfertilized oocytes displayed an increased incidence of disrupted or abnormal cytoskeletal organization. In parthenogenetically activated oocytes in anaphase and telophase, microtubules were again found predominantly in the spindle but in addition, cortical strands or bundles of microtubules were often present. Oocytes in late telophase sometimes showed the presence of a concentrated ring of actin in the cleavage furrow between the oocyte and the second polar body. Activated oocytes in early interphase contained a dense cortical mesh of microtubules and a midbody remnant between the oocyte and the polar body. The cytoskeletal organizations of mouse and human oocytes are compared.

The effect of morphology on the ability of human spermatozoa to penetrate zona-free hamster oocytes

The effect of morphology on the ability of human spermatozoa to penetrate zona-free hamster oocytes was investigated using fractions of individual semen samples enriched for morphologically normal or abnormal spermatozoa, after separation by buoyant density centrifugation on self-generating Percoll gradients. Using this separation technique, the percentage of spermatozoa of normal morphology is greater in the lowermost 1 ml of the Percoll column (layer 1) than in the fraction recovered from higher up the column. Thus it was possible to compare two populations of spermatozoa from each semen sample in their ability to penetrate hamster oocytes. After normalizing the concentration of motile spermatozoa the mean hamster oocyte penetration rate was significantly higher with spermatozoa recovered from layer 1 (39 +/- 4%) compared with those recovered from layer 7 (21 +/- 4%), which suggests that morphologically abnormal spermatozoa do not have the same fertilizing capacity as those with normal morphology.

The use of mouse preimplantation embryos for quality control of culture reagents in human in vitro fertilization programs: a cautionary note

Mouse embryos with their zonae pellucidae intact are more resistant to suboptimal culture conditions than are zona-free embryos. This observation questions the general practice of using zona-intact preimplantation mouse embryos to monitor the quality of media and reagents used in human IVF programs.

Retrograde ejaculation: a systematic approach to non-invasive recovery of spermatozoa from post-ejaculatory urine for artificial insemination

Retrograde ejaculation is an uncommon but treatable form of male infertility. Successful recovery of live spermatozoa from the post-ejaculatory urine for artificial insemination is dependent on careful regulation of pH and osmolarity of the urine into which ejaculation takes place, and separation of the motile spermatozoa from the debris and cells which are found in these samples. Three pregnancies established by artificial insemination of spermatozoa recovered by noninvasive means from the bladders of men suffering from retrograde ejaculation are described. The techniques for preparing the urine for spermatozoal survival, and for removal of cells and debris by sedimentation or buoyant density centrifugation are discussed.

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

Buoyant density centrifugation of semen produces the accumulation of populations of highly motile, morphologically normal spermatozoa in the lowermost 1 ml of Percoll (Pharmacia Fine Chemicals AB, Uppsala, Sweden) density gradients. In addition, the majority of bacteria present in semen are retained in the seminal plasma at the top of the gradients. Of 40 semen samples examined, 37 contained detectable bacteria, but after buoyant density centrifugation, the spermatozoal populations collected from the lowermost 1 ml of the Percoll columns were found to contain few or no bacteria. When preparations were collected using sterile technique (by boring a hole through the bottom of the centrifuge tube), 14 of the 20 preparations were found to be bacteria-free. When preparations were collected by passing a spinal needle from the surface through the seminal plasma to the bottom of the centrifuge tube, the sterility of the final spermatozoa preparations was not maintained, with only 5 of the 20 samples completely free of bacteria. The residual bacterial contamination of the remaining 15 samples was, however, very low (less than 5 colonies after a 48-hour culture period).

A regimen for obtaining mature human oocytes from donors for research into human fertilization in vitro

Patients awaiting laparoscopic sterilization were canvassed to allow oocytes to be aspirated from their ovaries at the time of operation for the purpose of testing the fertilizing capacity of spermatozoa from clinically infertile men. Because these patients were volunteers, the standard techniques for stimulation, ovulation prediction, operation, and oocyte recovery had to be modified for maximum safety and for convenience to both patient and staff. Superovulation was induced with 100 mg or 150 mg clomiphene citrate on days 2 to 6 or 5 to 9 of the menstrual cycle. Final maturation of oocytes was stimulated with 5000 IU of human chorionic gonadotropin administered between days 11 and 15 of the cycle, and the operation was performed 34 to 36 hours later on the routine gynecology operation lists. Of the 157 patients canvassed , 47% were willing to donate oocytes to the project. Despite the variability of the stimulation regimens, the simplified operative technique, and the fact that more than half the patients were on oral contraceptives in the previous cycle, one or more oocytes were retrieved in 75% of the patients. At the initial assessment, 83% of these were considered suitable for in vitro fertilization.

Preparation of human spermatozoa for in vitro fertilization by isopycnic centrifugation on self-generating density gradients

A simple and rapid method is described for the retrieval of highly motile, morphologically normal spermatozoa from human semen. This method is a modification of a technique described previously and employs the process of isopycnic centrifugation of semen on self-generating Percoll density gradients. The procedure is carried out under sterile conditions and has no detectable deleterious effects on the fertilizing capacity of spermatozoa. Spermatozoa may be recovered from semen samples of widely differing quality and can be used successfully for in vitro fertilization (IVF). This technique may be useful not only for the preparation of spermatozoa for IVF and possibly for artificial insemination by husband (AIH) but also for the investigation and analysis of the causes of infertility associated with oligozoospermia.

The transition from maternal to embryonic control in the 2-cell mouse embryo

The development of the early 2-cell mouse embryo to the late 2-cell stage is marked by the appearance between 23 and 26 h post-insemination of a complex of polypeptides of mol. wt. approximately 67 K. Addition of alpha-amanitin between 18 and 21 h post-insemination prevents or reduces the subsequent appearance of these polypeptides. Addition of alpha-amanitin after 21 h does not obviously affect the appearance of the approximately 67 K polypeptides. A major change in synthetic profile occurs between 29 and 32 h post-insemination involving many polypeptides. Addition of alpha-amanitin to 2-cell embryos prior to 29 h post-insemination prevents the appearance of the new polypeptides observed during this major change but does not prevent the disappearance of the old polypeptides. In contrast, addition of alpha-amanitin after this time does not affect the appearance of the new polypeptides. This result, together with other evidence presented, suggests that during the 2-cell stage the embryonic genome shows transcriptional activity in two phases at 18-21 and 26-29 h post-insemination, that these transcripts are utilized soon after their synthesis, and that most maternal transcripts used before the second phase of embryonic transcription become ineffective soon afterwards.

Time-dependent effects of α-amanitin on blastocyst formation in the mouse

Early compacting mouse morulae were placed in α-amanitin at various times after HCG and the effect of this transcriptional inhibitor during formation of the blastocyst was noted. No cavitation was observed in those embryos transferred into α-amanitin before 77 h after HCG but the percentage of cavitation increased dramatically in those embryos transferred after 80 h post HCG. The large increase in amino acid incorporation which normally occurs during formation of the blastocyst was blocked in those embryos placed in the inhibitor before 80 h post HCG. Two-dimensional polyacrylamide gel electrophoresis of radiolabelled embryos showed that the changes in synthesis of certain polypeptides normally associated with blastocyst formation did not occur in those embryos placed in α-amanitin before 80 h after HCG. Only one cleavage division appears to occur in the presence of α-amanitin. However, groups of embryos which had completed their fifth division before exposure to the drug subsequently were able to form blastocysts and showed the quantitative and qualitative changes associated with blastocyst formation despite the continued presence of the inhibitor. These results suggest that a critical transcriptional event concerned with blastocyst formation occurs around 80 h after HCG and may be associated with the fifth cleavage division.