A brief assisted reproduction techniques revision without forgetting the moral difficulties of in-vitro fertilisation, especially as regards the loss of human embryos and the eugenic nature of preimplantation genetic diagnosis (PGD).
There is no question of the great social impact of assisted reproduction and its huge acceptance among married and other couples with infertility problems. Thus, we consider it of great interest to comment on a superb review published in Reproductive Biomedicine Online Journal (25; 108-117, 2012), in which the authors evaluate some positive and also negative aspects of assisted reproduction, which in our opinion allows us to approach the current situation of this medical practice with reasonable impartiality.
The article mentions how technology in this medical area has grown rapidly since the birth of the first child by assisted reproduction, Louise Brown. Nevertheless, despite this impressive development, “new technology has rarely been robustly validated before clinical use”, since following the usual regulations for biomedical research, these techniques, like all others, “should be first evaluated in a suitable animal model, and only when safety has been confirmed should it be applied to humans”, which has not occurred in many of them. Furthermore, the “newly introduced techniques should only be used routinely after randomized controlled trials (RCT) have confirmed that the technique is of benefit and that all safety issues have been addressed”.
Major medical and ethical problem
That is, the fundamental question is raised of whether the new techniques being introduced in the field of assisted reproduction have been properly assessed prior to their clinical use, something which, in the authors’ opinion, does not always happen, thus constituting a major medical and ethical problem.
Assisted reproduction techniques revision
In this report, we will briefly review some of the latest techniques used in the field of assisted reproduction, focusing particularly on whether they have been properly evaluated for use in human medicine.
Among the techniques discussed by the authors of this review, Rachel Brown and Joyce Harper, are sperm DNA-damage tests, since it clearly the results of in-vitro fertilisation “can be improved if the most suitable gametes are involved in fertilisation”.
Male fertility test
Male fertility is usually assessed by examining the morphology and concentration of sperm cells in the seminal fluid. Now, however, it is known that these parameters “provide only a limited diagnostic and prognostic value and an improved marker of sperm quality is desirable”. Among these is a proposal to evaluate the genome, since it seems obvious that “genomic integrity of the spermatozoa is important for its cellular functions, including the ability to promote embryonic development and health after fertilization, and therefore methods to assess genomic integrity could have important clinical applications”.
In this respect, as far back as 1980, it was reported that sperm DNA integrity could be a useful indicator of male fertility. However, “to what degree such DNA fragmentation tests are currently beneficial has now been called into question”. In order to shed light on this problem, new techniques have been developed, among them the sperm chromatin structure assay (SCSA), although there appear to be technical difficulties “for the correct interpretation of assay results”. To overcome this difficulty, new methods have been developed, such as the sperm chromatin dispersion test (SCD), but the validation and standardisation of the assays performed using these new tests has been very limited, so that when the results obtained using different techniques are compared, it is not easy to obtain comparable data; thus “thresholds to distinguish fertile from infertile men on the basis of several assays have not been developed, and concerns over the high intra-individual variation of results, at least with the SCSA, have been raised”.
Furthermore, it seems inappropriate to give undue credibility to the results of a technique that has scarcely been evaluated, so relating DNA damage in sperm, using SCSA, with the health of children born does not seem correct. Therefore, the authors conclude that “more evidence is required before such a routine use could be supported” in human medicine.
It does not seem reasonable to claim that DNA damage in spermatozoa is a risk indicator of health problems for children conceived by in-vitro fertilisation.
In conclusion, it does not seem reasonable to claim that DNA damage in spermatozoa is a risk indicator of health problems for children conceived by in-vitro fertilisation, so the use of these genetic tests should be limited until there is better knowledge of what they mean and their clinical importance has been evaluated.
Intracytoplasmic sperm injection (ICSI)
Another assisted procreation technique that is becoming increasingly used is intracytoplasmic sperm injection (ICSI), which consists of selecting a sperm cell for direct injection into the oocyte to be fertilised. As only a single sperm cell is selected, the barrier that nature has always used in order that only the most suitable, the best sperm, can fertilise the oocyte is removed. That is, the system that nature uses to guarantee the quality of the sperm that fertilises the oocyte and thus maintains, and even improve, the quality of the species is eliminated.
To overcome this drawback, it has been proposed that the best sperm cell be selected, depending on its motility and morphology, since other quality parameters, especially genetic integrity, cannot be used for obvious technical reasons. Therefore, it is evident that setting up new techniques for determining the quality of the sperm used in ICSI is extremely important.
Intracytoplasmic morphologically selected sperm injection (IMSI) utility
To this end, a new method called intracytoplasmic morphologically selected sperm injection (IMSI) has recently been developed, which magnifies the resolution power of techniques currently used to evaluate sperm morphology at least 6600 times, allowing visualisation of their intracellular structures and thereby increasing the possibility of selecting the best quality spermatozoa more reliably than with currently used techniques. However, although it has not been possible to improve fertilisation rates using this technique so far, it has improved embryo implantation and pregnancy rates, and decreased the number of miscarriages and aneuploid embryos produced.
Unresolved issue of this technique
However, one unresolved issue related with IMSI is that studies conducted to date have used small sample sizes, so that new studies must be conducted with larger samples “to establish whether IMSI will become a routine technique or be restricted to patients with severe infertility and/or repeated ICSI failure”. Furthermore, the “time-consuming nature of IMSI may well limit its clinical applicability”, so developing other more simple methods to select the best spermatozoa is a target object at present.
Embryonic metabolomics procedure for determining embryos’ quality
Lately, a technique known as embryonic metabolomics has been gaining a foothold as a useful procedure for determining the quality of embryos for transfer. It aims to quantify small molecules used by the embryo in its metabolic processes, allowing its life profile to be determined. Using embryo metabolomics, the functionality of the embryo can be better determined, using a non-invasive technique which is therefore safe for the embryo itself, enabling its “viability index” to be established more rigorously and with fewer technical problems. This is important since it is known that embryos with greater viability are those which implant best. According to recent studies, the sensitivity of the method may be close to 86%. For these reasons, embryo metabolomics could be a promising technique for improving the efficiency of in-vitro fertilisation.
Nevertheless, it must be taken into account that everything known about embryo metabolomics has been through retrospective studies, which limits its validity, so optimising the quality of the assays performed with prospective studies is necessary.
Preimplantation genetic diagnosis (PGD)
Preimplantation genetic diagnosis (PGD) is a method that enables chromosomal diseases (the most common is Down’s syndrome) or monogenic diseases (those caused by the alteration of a single gene) to be identified in preimplantation embryos. The most common indication for PGD is in the detection of aneuploid embryos (those with more or less than 23 chromosomes; the most common diseases are monosomies or trisomies), which in addition to causing severe diseases, can increase spontaneous miscarriages.
Morphological observation of embryos is not usually sufficient for detecting aneuploidies, so the use of PGD may be useful. The use of PGD may also be indicated in the case of women of advanced maternal age who turn to in-vitro fertilisation, when IVF repeatedly does not achieve the objectives pursued, or when there is repeated embryo implantation failure and in cases of severe male factor infertility, since it seems to be accepted that transferring only euploid embryos (those with 23 chromosomes) in in-vitro fertilisation favours implantation. As a result, it has been proposed that PGD be used in all cases of in-vitro fertilisation, to thus try to increase its efficacy.
However, recently conducted large studies indicate that using PGD in assisted fertilisation does not increase implantation rates, which means that, in the opinion of the authors of the review discussed here, this practice should not be used regularly in in-vitro fertilisation, as it is “incapable of improving clinical outcomes”.
Assisted reproduction techniques review of the recent improvements
However, improvements in the technique have recently been introduced, especially with the use of microarrays, which could improve its efficiency in the detection of chromosomal abnormalities in embryos prior to implantation, thus improving the possibility that the implantation is consolidated.
In the event that genetic studies cannot be performed in embryos to be transferred, we can attempt to select the best, as previously discussed, using morphological criteria. Historically, methods that have allowed the embryos to be visualised at specific time points in their development have been used. This technique has the disadvantage that the incubation of the embryos must be interrupted in order to observe them, which may harm their development. In order to circumvent this technical difficulty, methods have recently been set up that allow embryo development to be continually monitored, which makes it possible to determine some parameters which indicate that embryo development is normal.
This technique also has the advantage of being non-invasive, which avoids disorders in the embryos studied. According to the authors who advocate it, good specificity has been obtained for selecting the best quality embryos. However, others object that the experiments conducted to date to refine the technique are insufficient, so that “a single case report is certainly insufficient to suggest a clinical benefit of the technique”, since “although the potential benefits of time-lapse imaging are clear and current data promising, on balance there is still a paucity of efficiency and safety data into this technique. Large-scale, multicentre trials are needed to ensure the accuracy and benefit of this method”.
Gene therapy could also be another option for restoring fertility in some cases, as the genes that may be involved in reproductive processes are becoming increasingly better known, so specific causes of infertility could be prevented with this therapy, although naturally, prior animal experimentation to determine that it achieves positive results and does not have negative side effects is required.
Current techniques do not ‘cure’ infertility, they just overcome it
In general, however, it can be stated that “current techniques do not ‘cure’ infertility, they just overcome it” so the objectives in this field should be directed at developing techniques that permanently restore fertility.
Likewise, according to the authors of this article, it seems clear that “although the same could be said for all areas of medicine, assisted reproductive technology, in particular, has developed a very strong commercial backing. It is therefore particularly important to ensure that all new technologies are adequately and rigorously tested for both safety and efficiency, ideally before being used clinically”.
In conclusion, it can be stated that, although not all the aforementioned techniques should be commonly used in in-vitro fertilisation, they could be used in those cases in which in-vitro fertilisation has failed repeatedly.
Finally, we feel it is necessary to mention the ethical judgement that these techniques merit, regardless of the above, as the moral difficulties of in-vitro fertilisation should be remembered, especially as regards the loss of human embryos (Medicina e Morale 4; 603-616, 2012) and the eugenic nature of preimplantation genetic diagnosis, in which human embryos are selected to be transferred or discarded based on their biological health.
Justo Aznar MD PhD