Professor Robert Edwards and assisted reproductive technology: life from a test tube

Transcription

1 Claire Durrans University of Oxford Professor Robert Edwards and assisted reproductive technology: life from a test tube Assisted reproductive technology (ART) is a relatively young branch of science allowing infertile couples the opportunity to have a baby. Infertility is now recognised as a global disease and it is estimated that ~70 million couples are affected worldwide (Ombelet et al. 2008). In 2010, the Nobel Prize in Physiology or Medicine recognised the remarkable work of Professor Robert Edwards on the first test tube baby alongside Dr Patrick Steptoe, by in vitro fertilisation (IVF). One could say he was the founder of reproductive biology as we know it. However, Edwards achievements reach far beyond IVF. His interests also included early stem cell research, and embryonic sex determination - the precursor of pre-implantation genetic diagnosis (PGD). Much controversy surrounded Edwards work; this was highlighted by a lack of support from the public, church and government. Today, these ethical issues, and further debate on topics, such as the use of stem cells, still persist. However, it was the combination of ground-breaking science, together with clinical expertise and the ability to push the boundaries of contemporary ethical opinion, which allowed this new technique to be translated into the medical world. Here, I discuss the progression of Edwards research leading up to the birth of Louise Brown, the first IVF child, the significance of Edwards other research interests, and how reproductive biology has benefitted from the development of IVF. The development of IVF has significantly enhanced our understanding of the process of fertilisation with the ultimate goal of conceiving a child. Prior to sperm-egg fusion, both the sperm and egg have to undergo complex maturational processes. Understanding the timings and conditions of these processes in vivo was essential for creating an optimal environment for sperm-egg fusion in vitro (Bavister 1974). Sperm undergo maturation resulting in capacitation, which renders sperm capable of fertilisation. This process involves destabilisation of the acrosomal sperm head, along with increased membrane fluidity and permeabilisation, and it is via this process that sperm acquire full ability to interact with the egg. Once a sperm has passed the cumulus cell layer of the egg, a biochemical process known as the acrosome reaction 1

2 occurs. Hydrolytic enzymes are released, allowing the hydrolytic enzyme acrosin to digest the outer layer of the oocyte, the zona pellucida. Work carried out by Edwards optimised the solution, which allowed capacitation to occur as in vivo - a key step in developing IVF for clinical practice. It was this very solution which was used for the first IVF procedure (Edwards et al. 1969; Bavister 1974). Egg maturation lasts for approximately 38 hours and is indicated by extrusion of the first polar body. Eggs remain arrested in the second meiotic metaphase (MII) until fertilisation occurs. Thus, optimum conditions for IVF are for oocytes matured for 38 hours to be placed into a culture dish with capacitated sperm in optimised media. Research indicated that sperm digest and penetrate the zona pellucida and that fertilisation was only successful when one sperm entered the oocyte. Upon fusion, oocyte activation occurs, thereby activating several processes in the oocyte including cortical granule release, a mechanism that prevents polyspermy (Miyazaki 2006). Having identified optimal conditions for the in vitro maturation of both the sperm and egg, and establishing that fertilisation can occur in a culture dish (Edwards et al. 1969), the next barrier for Edwards was obtaining follicular oocytes from selected patients. To solve this clinical problem, an inspired collaboration was initiated with Patrick Steptoe, a skilled laparoscopic surgeon. Whilst laparoscopy was very successful, the procedure itself was invasive, required a general anaesthetic, and inflation of the abdomen with CO 2. Despite these issues, Steptoe s technique permitted the aspiration of human oocytes in a reproducible manner (Edwards et al. 1969). Following the publication of the first successful IVF procedure (Edwards et al. 1969), external ethical interest concerning IVF escalated significantly. However, Edwards encouraged discussion of the ethics concerned, not just with IVF, but also issues such as PGD and cloning (Edwards & Sharpe 1971). Vicious public condemnation of IVF was publicised by the Pope and Protestants, leading to further lack of public support. Although ethical consent was eventually acquired, implantation of human embryos activated by IVF could not begin immediately because the Medical Research Council refused to fund such research at that time (Edwards 2001). Edwards made sure that 2

3 sceptical public opinion and lack of support did not inhibit progress, since scientific evidence for the potential success of IVF was clear and indisputable. Louise Brown, the first IVF baby, was born on the 25 th July 1978, a milestone in medical history. However, despite this unequivocal success, Bourn Hall clinic, where IVF was subsequently practised, was not opened until 3 years after her birth, largely due to lack of funding and government support. Significant concerns about IVF still existed and in a single day, Edwards was forced to issue eight libel actions in the High Court of London, all of which he won (Edwards 2001). Nowadays, IVF is accepted by the majority of the world s population as a major step forward in reproductive medicine. The work of Professor Edwards not only focused upon IVF. His other research interests also extended the boundaries of reproductive medicine. Recognising that stem cells could have applications in regenerative medicine, Edwards encouraged his then PhD student, Richard Gardner, later to be knighted for his services to developmental biology, to follow up this fledgling area of research, leading to the world s first mouse chimaera. Another of Edwards interests was sex determination at the blastocyst stage. Today, genetic screening of the embryo is commonly used to look for inherited genetic disorders and identify embryos with genetic abnormalities (Wells et al. 2008). Before the discovery of IVF, it was impossible for infertile couples to have a baby. Today, ART is used globally and there have been over 8 million births, with approximately 1 million treatments carried out annually (ICMART 2009). Since the development of IVF, more than 12,000 births each year in the UK are due to IVF (HEFA register 2007). IVF is routinely used to overcome female factor infertility including fallopian tube problems, such as tubal blockage or ovulation disorders, where eggs are not available for fertilisation. Some forms of male infertility can be readily overcome using IVF, such as oligoasthenozoospermia (low sperm count). Soon after the successful application of IVF, another revolutionary technique was developed: intracytoplasmic sperm injection (ICSI) (Tesarik & Testart 1994). Here, the principles of IVF still apply, but the sperm is directly microinjected into the 3

4 oocyte. This technique is used to overcome severe male factor infertility issues and is commonly used, in the UK, 48% of all ART cycles involve ICSI (Nasr-Esfahani et al. 2010). However, in 2-3% of patients, ICSI fails to initiate fertilisation. Some of these patients suffer from globozoospermia, a condition affecting 0.1% of infertile men where the sperm are abnormally-shaped and acrosomeless (Dam et al. 2007). It is thought that one of the factors contributing to ICSI failure is compromised oocyte activation, a process initiated by a series of Ca 2+ oscillations in the egg which start vital cellular events leading to embryogenesis. Consequently, in some cases, egg activation can be rescued by adding Ca 2+ ionophore to the egg after ICSI, inducing Ca 2+ release in the egg artificially (Miyazaki 2006). ICSI. Removal of a single cell from the blastocyst for PGD. Images copyright of Tracey Griffiths (Oxford Fertility Unit, Oxford). Expansion of ART has lead to improved understanding of reproductive biology. In particular, our understanding of what actually happens in vitro has grown, leading to significant improvement in infertility treatments. Via PGD we know that embryos with chromosome aneuploidies do not implant, this can be used as an efficient selection method to increase pregnancy rates. When embryos were screened for aneuploidies using comparative genetic hybridisation (CGH), the probability of pregnancy from an individually transferred embryo was 66.7% compared with 27.9% for unscreened embryos (Wells et al. 2008). Other areas of improvement arise from studies of patients who fail to conceive after ICSI owing to activation failure. A vital component from the sperm, PLCζ (Saunders et al. 2002), which is microinjected into the egg was found to be non-functional, increasing research concerning PLCζ could potentially provide novel therapies for ICSI-failed patients (Kashir et al. 2010). 4

5 Our knowledge of fertility mechanisms has increased profoundly, including an improved method for oocyte retrieval and transfer embryos into the uterine cavity, trans-vaginal ultrasound, eliminating the need for invasive surgery. Following IVF, surplus embryos, sperm and oocytes can be cryopreserved to allow couples additional options for pregnancy. These methods are also used with cancer patients since oncology treatments can be particularly deleterious to both the female and male reproductive systems (Diedrich et al. 2011). Even with these new techniques, pregnancy and delivery rates using IVF and ICSI are still relatively low, at 30% and 23% respectively (de Mouzon et al. 2010). Therefore, the need to improve fertility procedures and develop new treatments remains. Furthermore, IVF and ICSI are not just clinical treatments but are indispensable research tools. Edwards research was remarkable, not just for the birth of the first IVF baby but also for his inspired interest in the origins of embryonic stem cells and PGD. The frustrations that Edwards felt regarding societal norms holding back scientific progression still remain today. Now the sex and phenotypic characteristics of an embryo can be accurately determined by PGD, the only thing preventing routine use of these procedures is public acceptance and medical ethics. What is to say that society will not one day accept the era of designer babies? The technological and scientific ability required already exists. Edwards was a remarkable scientist, teacher and personality, his influence on reproductive biology has allowed infertility treatments to expand exponentially. His work has created lives and created families, and will continue to do so for many years to come. 5

6 Bavister BD 1974 The effect of variations in culture conditions on the motility of Hamster spermatozoa. J Reprod Fertil Dam AHDM, Feenstra I, Westphal JR, Ramos L, van Golde RJT & Kremer JAM 2007 Globozoospermia revisited. Human Reproduction Update De Mouzon J, Goossens V, Bhattacharya S, Castilla JA, Ferraretti AP, Korsak V, Kupja M, Hygren KG & Nyboe Anderson A: European IVF-monitoring (EIM) Consortium, for the Eurpean Society of Human Reproduction and Embryology (ESHRE) Assisted reproductive technology in Europe, 2006: results generated from European registers by ESHRE. Human Reproduction Diedrich K, Fauser BC & Devroey 2011 Cancer and fertility: strategies to preserve fertility. Reprod Biomed Online Edwards RG 2001 The bumpy road to in vitro fertilization. Nat Med Edwards RG, Bavister BD & Steptoe PC 1969 early Stages of Fertilisation in vitro of Human Oocytes Matured in vitro. Nature Edwards RG & Sharpe DJ 1971 Social Values and Research in Human Embryology. Nature Fogle R, Steiner A, Marshall F & Sokol R 2006 Etiology of azoospermia in a large nonreferral inner-city population. Fertility and Sterility Kashir J, Heindryckx B, Jones C, De Sutter P, Parrington J & Coward K 2010 Oocyte actication, phospholipase C zeta and human infertility. Human Reproduction Update Miyazaki S 2006 Thirty years of calcium signals at fertilisation. Seminars in Cell & Development Biology Munne S & Wells D 2002 Preimplantation genetic diagnosis. Curr Opin Obstet Gynecol Nasr-Esfahani MH, Deemeh MR & Tavalaee M 2010 Artificial oocyte activation and intracytoplasmic sperm injection. Fertility and Sterility Ombelet W, Cooke I, Dyer S, Serour G & Devroey P 2008 Infertility and the provision of infertility medical services in developing countries. Human Reprductive Update Tesarik J & Mendoza C 2003 Somatic cell haploidization: an update. Reproductive Biomedicine Online Tesarik S & Testart 1994 Human oocyte activation after intracytoplasmic sperm injection. Human Reproduction

7 Wells D, Alfarawati S & Fragouli E 2008 Use of comprehensive chromosomal screening for embryo assessment: microarrays and CGH. Molecular Human Reproduction