Human embryos as boundary objects? Some reflections on the biomedical worlds of embryonic stem cells and pre-implantation genetic diagnosis

Abstract

In this paper we offer some reflections on embryos in the biomedical worlds of embryonic stem cells (ESC) and pre-implantation genetic diagnosis (PGD). We draw upon two ethnographic studies of the social practices of PGD and embryonic stem cell science to examine the notion of boundary objects as an approach for understanding the social construction of embryos. We analyze the ways in which human embryos have similar and different meanings in the related social worlds of ESC and PGD labs through a discussion of two major themes: the goals of PGD and ESC; and linking the worlds of ESC and PGD. We suggest the interface between the two cultures of PGD and ESC science can facilitate the flow of concepts, skills, materials and techniques within and between these two social worlds. In conclusion, we argue this is a salient case study of the production of biomedicine as a social and material practice in the emerging sphere of new medical technologies.

Keywords:

• human embryos
• boundary objects
• pre-implantation genetic diagnosis
• embryonic stem cells
• new medical technologies

Introduction

There is a long history of humanities and social research on the nature of the embryo (e.g. Mulkay 1997, Pinto-Correia 1997, Maienschein 2003). However, embryonic stem cells (ESC) and pre-implantation genetic diagnosis (PGD) are more recent biomedical phenomena and both fields are currently developing as productive domains for the exploration of the changing nature of science and society (e.g. Brown and Webster 2004, Jasanoff 2005). We turn first to a brief outline of stem cell research. Since 1998, when human embryonic stem (hES) cell lines were first isolated (Thompson et al. 1998), stem cell biology has become one of the most rapidly developing areas within the life sciences (Holland et al. 2001, Kiessling and Anderson 2003, Scott 2006). Proponents contend that stem cells promise a medical revolution in the treatment of degenerative diseases, such as Parkinson's disease and diabetes, as new stem cell technologies offer the prospect of “cures” for currently intractable diseases (Kitzinger and Williams 2005, Wainwright et al. 2006a). The last five years have also seen a proliferation of social science research on stem cells (e.g. Franklin 2001, Waldby 2002, Kerr 2003, Parry 2003, Williams et al. 2003, Cooper 2004, Hauskeller 2004, Franklin 2005, Hauskeller et al. 2005, Cooper 2006, Franklin 2006). All of these papers, however, draw upon analysis of documentary sources. In contrast, in this paper we draw upon interview data with lab scientists to examine their views on embryos, PGD and ESC (see also Wainwright et al., 2006c).

Compared with the field of stem cell research, there is a relative paucity of social science literature on PGD (Roberts and Franklin 2004, Watt 2004, Kalfoglou et al. 2005, Meister et al. 2005, Ehrich et al. 2006, Franklin and Roberts 2006). Moreover, with the exception of Ehrich et al. (2006), all of this literature primarily explores the perceptions of patients rather than the views of scientists and practitioners. PGD was developed in the late 1980s as an alternative to prenatal diagnosis (Harper and Delhanty 2000). The technology of PGD can be offered to women/couples at risk of having a child with a serious genetic condition, or in some cases, to women who have experienced repeated miscarriage due to chromosomal rearrangements (Braude et al. 2002). In vitro fertilization (IVF) is used to create embryos in the laboratory, from which one or two cells can be tested for specific genetic disorders. Currently in the UK, up to two unaffected embryos can then be transferred to the woman, where they may successfully implant. PGD is offered in about eight centers in the UK and must be licensed by the Human Fertilisation and Embryology Authority (HFEA).

In the social worlds of both PGD and ESC, scientists inevitably work with human embryos. In many places these two worlds do not coincide, so institutions may have labs for one or the other, or perhaps both. However, in this paper we examine the interaction between these two worlds of ESC and PGD, and we explore how embryos are talked about and used in convergent and divergent ways in these two interconnected social worlds (Franklin 2006).

Boundary objects

In this section we introduce the notion of boundary objects and outline some ways in which this may provide a useful framework for analyzing the interrelated social worlds of embryos, PGD and ESC. The concept of boundary objects was developed by Star and Griesemer (1989), in a seminal paper about the development of the Berkeley Museum of Vertebrate Zoology in California. Their central question was: “How do members of different social worlds build a museum collection despite their different viewpoints and agendas?” The term “boundary object” therefore describes the shared understandings and the collective actions which help to manage and unite related but different social worlds. They state:

Boundary objects inhabit several intersecting worlds … Boundary objects are objects that are both plastic enough to adapt to local needs … yet robust enough to maintain a common identity across sites … They have different meanings in different social worlds but their structure is common enough to more than one world to make them recognizable, a means of translation. (Star and Griesemer 1989, p. 393)

This idea of translation has led to boundary objects being widely used by social scientists as a way of framing the material and conceptual intersections of social worlds (Glasner 1998), for instance, in areas such as: the links between cancer cell biology and genetics (Fujimura 1992); the development of pain centers (Bazanger 1998) and genetic counseling (Featherstone et al. 2006). To expand a little, Bazanger (1998) employs the Gate Control Theory of pain as a boundary object that unites a multidisciplinary pain team, while Featherstone et al. (2006) enroll genetic pedigrees as boundary objects which link the social sphere of the patient with the biomedical practices of clinical geneticists and genetic scientists. These examples all illustrate the ways in which:

The study of boundary objects can be an important pathway into often complicated situations, allowing the analyst to study the different participants through their distinctive relations with and discourses about the specific boundary object in question. (Clarke 2005, p. 51)

In the substantive part of the paper we describe some of the ways in which embryos act as boundary objects that both help differentiate the worlds of PGD and ESC, and yet also allow various social and material translations between the social worlds of ESC and PGD. Hence our paper can be read as a commentary on the social construction of the embryo in two emerging worlds of contemporary biomedical science. We describe the goals of PGD and ESC, and we highlight some of the practices which also differentiate the two social worlds of PGD and embryonic stem cell science. In essence, our argument in the first section of the paper is that the embryo inevitably acts as a boundary object as it takes on different meanings and structures in the diverse worlds of PGD and ESC. In contrast, in the second section of the paper we discuss some of the ways in which these two worlds have become connected and we argue that here the embryo functions as a translational boundary object which enables the transmission of materials and practices that bind the worlds of PGD and ESC into an emerging new social world.

Methods

Our data form part of the findings from two larger projects, first mapping the scientific, medical and ethical dimensions of potential innovative stem cell therapies in the areas of liver cell and islet cell transplantation (Wainwright et al. 2006a, 2006b, 2007); and secondly, exploring professional ethics in PGD (Ehrich et al. 2006). In this paper we draw on interviews with six biomedical scientists who work in a human ESC (hESC) lab and interviews with a further six biomedical scientists who work on PGD. In addition, two further participants have been instrumental in bridging these worlds of PGD and ESC science: one is described as a PGD/ESC scientist; the other, who also has a clinical background, as a PGD clinician/scientist. These 14 scientists, whom we selected as being closest to the “interconnected worlds” of ESC and PGD science, form part of the larger pool of over 100 interviews with scientists, clinicians and other professionals in these two studies. In this paper we use the number allocated to scientists in our individual projects. Rather unusually, the hESC lab currently obtains the majority of its hESC from embryos donated by couples attending for PGD (rather than IVF).

Following ethics committee approval, interviews were conducted which lasted between one and two hours, took place within the lab offices and, with permission, were taped and transcribed. Open-ended questions and an informal interview schedule were used, in order to encourage scientists to speak in their own words about their experiences. Transcripts were analyzed by content for emergent themes (Weber 1990) which were then coded (Strauss 1987). Sections of transcripts relating to such topics as the goals of PGD and ESC research were grouped together and analyzed further to generate sub-themes. Accounts were then analyzed to discern similarities and differences.

Themes

In this substantive part of the paper we analyze the ways in which embryos have similar and different meanings in the related social worlds of ESC and PGD labs through a discussion of two major themes: first, the goals of PGD and ESC; secondly, linking the worlds of ESC and PGD.

The goals of PGD and ESC

In this section we analyze some of the meanings of embryos in the social worlds of ESC science and PGD and we illustrate the different ways in which the embryo is employed as a boundary object. We begin by exploring how the divergent goals of PGD and ESC structure the different meaning of embryos in these two social worlds.

The primary goal of PGD: maximizing making “healthy” babies

In the world of PGD, making distinctions between “normal” and “affected” embryos sends embryos along different paths. If they are normal embryos, some of these will be transferred to the woman, and these may then implant and become healthy babies, so fulfilling the main aim of PGD:

At the end of the day, what we're after is healthy babies in cots. (PGD Scientist 3)

As we saw in our brief introduction, PGD is a technique that genetically tests one or two cells from an eight cell human embryo and, remarkably, despite removing these cells this embryo can go on to develop into a normal child:

Basically our aim is to create a credible pregnancy. I know that of all the embryos I handle every single day there will be relatively few of the embryos in that dish that are capable of producing a credible pregnancy, which is one that has the potential to go on and produce a live baby. (PGD/ESC Scientist 10)

Normal embryos that are good enough to lead to a successful pregnancy are rare, and so a secondary goal of PGD is to maximize the number of normal embryos available for transfer. This approach, however, inevitably leads to the creation of spare or waste embryos, as we discuss below.

The secondary goal of PGD: minimizing creation of spare/waste embryos

In PGD, scientists invariably adopt a “low risk” approach to testing. In order to minimize the risk of misdiagnosis, which could lead to the transfer of affected embryos, only embryos which are shown to be normal, or at low risk of misdiagnosis, will be transferred. This strategy means that the number of potential births may be reduced:

There's a balance of priorities between minimizing the risk of misdiagnosis and maximizing your chance of a live birth. And there's quite a lot of argument about that. So one of the things that we do, we're very keen on single cell biopsy, whereas other groups will do two cell biopsy because that does minimize your risk of misdiagnosis, but we think it's at a cost, and that cost is that you will have fewer births at the end of the process. (PGD Scientist 3)

You're under a lot of pressure to get it right. And if it's not right, then you can't say 100% that it's normal … Only a certain number of embryos are formed and so it's really critical … I can't think of any occasions off hand where that has resulted in an embryo being transferred when it shouldn't have done, because we always err on the side of caution. But I'm sure there are instances where it has meant that there hasn't been anything to transfer when it could have been. (PGD Scientist 9)

This cautious approach effectively produces “waste normal embryos”. However, the preciousness of PGD embryos also means that scientists do their utmost to ensure that the most is made of every embryo:

I'm very conscious of waste. We try to do the very best that we can, you cannot afford not to get the very maximum from an embryo. If you don't get the result, you might as well not have the embryo in the first place, so we put enormous effort into trying to keep the quality as high as we can. And to give the couple the best chance, because we don't want to put the couple through any more anxiety than is necessary … And it's unacceptable, I think, to be sitting opposite a couple and saying, “Sorry, we didn't manage to get the results through the embryos”. (PGD Scientist 3)

These first two themes, on the primary and secondary goals of PGD as making healthy babies and minimizing creating spare/waste embryos, are very different from the way in which ESC scientists talk about embryos (see below). In both cases we suggest that the embryo is acting as a boundary object that anchors divergent meanings and practices in two separate biomedical worlds. We reiterate that this is partly because these two worlds have developed at different times and in different places. However, in the next part of the paper we begin to explore how the recent shift to creating human ESC (hESC) lines began to bring these worlds into alignment, so that both PGD and ESC scientists can now talk about the potential therapeutic value of spare PGD embryos. In the final section of the paper we discuss how this alignment brought about a shift in the way the embryo acted as a boundary object, from a boundary object to a translational boundary object, as the embryo becomes transformed from an anchor of difference into a bridge of similarity (Star and Griesemer 1989, p. 392).

The tertiary goal of PGD: supplying embryos for therapeutic research

The plan to try and create hESC lines (which we discuss as our second major theme below) and the consequent alignment and connections between PGD and ESC work enabled scientists in PGD to develop a third goal to underpin their work. This tertiary goal, of contributing embryos for use in therapeutic research, is a consequence of the new prospects for making hESC lines. Before this change in the scientific landscape, many of what would now be viewed as potential embryos for hESC research were seen as spare/waste PGD embryos which were either used to develop new PGD techniques, or destroyed:

When we first started doing PGD, I had to be comfortable with the idea of what we were doing, because I have personally destroyed many hundreds of embryos as part of the PGD process, because we test an embryo and if we get a result that it's transferable, we'll transfer it, but if it's not transferable, then we destroy the embryo and confront our thoughts about the embryo. You're fully conscious when you're doing that, of the nature of the material that you're working with. So that's always something which is at the forefront of your mind. (PGD Scientist 3)

PGD scientists thus draw a distinction between normal embryos, which would be transferred (or frozen for future transfer) and so hopefully achieve implantation, and affected embryos that, by definition, would never knowingly be transferred. However, some of these embryos can now be used in what can be seen as having a more directly therapeutic goal:

We've got some of these things [embryos] that could be used for potential future therapies. Why would you think that was wrong? (PGD Scientist 8)

Part of such an answer invariably entails arguing that if the embryos are affected then they are discarded as waste, or some may be used to develop new techniques, or they can be “rescued” for therapeutic research:

The affected ones are sort of dismissed in my line as being affected so they're certainly not going anywhere. So that's fine … If they can use these embryos, then that's better for me than chucking them in the bin. (PGD Scientist 9)

As we will see a little later, this reasoning is one that is also used by hESC scientists when they argue that spare/waste embryos can be rescued for research that has therapeutic potential.

If making healthy babies is the primary goal of PGD, then supplying embryos for therapeutic research, particularly in this case, hESC research, has emerged as a relatively new subsidiary goal. As Waldby (2002) argues, stem cell research highlights conflicting ideas about life and death. Opponents of the research perceive the life of the embryo as biographical, in contrast to advocates who view the life of the embryo as, “a form of raw biological vitality. From this point of view, the embryo is not killed. Rather, its vitality is technically diverted and reorganized” (Waldby 2002, p. 314). In this way, the humanist biography of embryos is erased, and is replaced by a material biography of embryos as a biological entity. However, the development of hESC research also raises ethical questions about the lifespan of immortal hESC lines, as Scientist 10 reveals:

It wasn't really until Thompson's now hallmark paper [1998, Science] that people did believe that maybe we should be looking at it [creating hESC lines] again … The fact is that you are going to have cells in perpetuity from an embryo which actually isn't existing any more … To actually take an embryo and take some cells out of it which might be here in 30–40 years' time or longer, it's mind-blowing. (PGD/ESC Scientist 10)

In the case of PGD, as we have already seen, the primary goal entails producing live healthy babies, while in the area of stem cell research the focus is on maintaining expectations of the promise of potential future therapies which have been derived by “rescuing” spare/waste embryos (Kitzinger and Williams 2005, Wainwright et al. 2006c). In the next part of the paper we explore some of the views of ESC scientists on the embryo.

The primary goal of ESC: using spare/waste embryos for therapeutic research

The primary therapeutic goal of hESC work is forcefully expressed by Scientist 8:

This is going to sound really pretentious and it's not meant to, but I am a scientist who has a burning desire to do something useful. I have certain skills and I have certain insights that some people don't. I feel like I am here to contribute something, and this is what we can contribute. We are taking material that's going to be destroyed and we are trying to create therapies out of that … If all we are using is really what's left over and which is going to be discarded then I would argue that if something good can come out of that then I think it's worth doing. Otherwise it's tissue that's going to be destroyed anyway and to me it's equivalent to organ donation at death. (ESC Scientist 8)

Here we see a striking difference between the primary goal of PGD (making healthy babies) and hESC work. In this instance, the embryo therefore functions as a boundary object that is the bearer of different meanings and practices in these two biomedical worlds. From this ESC perspective, these scientists are attempting to refashion “spare/waste” embryos into therapeutic hESC lines.

Human ESC research, and the concomitant destruction of human embryos, is often justified on the grounds of its therapeutic potential and of its perceived ability to rescue valuable “spare/waste material”. Indeed, this is a common claim by scientists who support hESC research (see Williams et al. 2003, Kitzinger and Williams 2005, Wainwright et al. 2006c). In this hESC lab, embryos are seen as a source of good that emerges, via their skills, from what is viewed as spare/waste material:

Is it better for us to try and cure diseases with them, or is it better just to discard them? (ESC Scientist 11)

As with the PGD scientists, much was made of the fact that if spare/waste embryos, including affected PGD embryos, were not used for scientific research, many would be discarded:

With rare exceptions, the embryos that are used in stem cell research are embryos that have no future, either because they are not implantable … or they've been screened by PGD and been shown to have, or be at high risk of having, a genetic disorder … If all we're doing is using something left over and destined to be discarded, then if some good can come out of it, it's worth doing. (ESC Scientist 8)

In their analysis of media coverage of the stem cell debate in the UK in 2000, this was one of the rhetorical strategies Williams et al. (2003) identified as used by proponents of stem cell research to assert an ethical position, that embryos would otherwise be “discarded” or “left to perish”. This meant that not only could stem cell research be presented as “less wasteful” of spare embryos, but also that stem cell research could be presented as a form of rescue (Waldby 2002). Affected PGD embryos are viewed in this setting as “biologically dysfunctional”, and this particular definition of “waste” is thus implicitly deployed as a means of drawing an ethical boundary between affected and normal PGD embryos as possible sources of stem cells. This is partly due to the fact that there is a potential tension between the need to ensure high quality normal embryos are used clinically and the need for high quality embryos as a way of maximizing the prospects of creating a hESC line:

You actually do need high quality embryos to produce a stem cell line … Obviously the high quality embryos are going to go back to the patients which I think is 100% right. The same with PGD … But if it came to a choice of discarding them or using them for research, as a scientist I would go for research, simply because otherwise they are going to go in the bin … I think, “Well, what about the benefits that are going to possibly be realized?” (ESC Scientist 9)

We explore the ways in which this led to affected PGD embryos being seen as particularly useful in our second major theme (below).

Linking the worlds of ESC and PGD

So far in this paper we have concentrated on how scientists discuss and use embryos in the two different laboratory lifeworlds of ESC and PGD. In this section of our paper we explore the connections between these worlds, and we examine some of the ways in which research on hESC has bound some of the scientists in these different worlds together. We focus on the accounts of three key scientists who describe, in vivid detail, how the embryo acted as a translational boundary object that reshaped the scientific landscape of what they hoped would become interconnected biomedical worlds. Our data and analysis illustrate the argument that boundary objects emerge through processes of work when elements of the work of groups coincides (Fujimura 1992, p. 173). In our case, key members of the ESC and PGD worlds decided to work together to strive to create what they considered to be an “ethically sound” hES cell line:

Developing human embryonic stem cells for us has just been a way of getting cells that might have some potential. I never saw it as something like “Wow, I'm going to make human embryonic stem cells” because it was always with the idea that we could turn them into something useful … We made the decision that we don't use any routine IVF material whatsoever, that all the best embryos are going to the patients, and all we are using is what's left over and that's predominantly from PGD or exclusively from PGD … [We] made a decision that from an ethical standpoint the PGD embryos really represent an ethically un-contentious pool of embryos because you would never implant those. (ESC Scientist 8)

We also argue that the coordination of work within and between the PGD and ESC labs that this requires is an example of a negotiated order which moulds the development of professional practices in these two partially interconnected scientific worlds (Strauss et al. 1985, Casper 1998). A striking theme here is the mutual advantage that accrued as key staff in these separate worlds began to work together to try to produce hES lines:

I had worked with mouse stem cells extensively and the PGD unit had access to human embryos, but I had absolutely no interest in deriving human stem cells at all myself. But [ESC Scientist 8] was so enthusiastic about the whole thing and I could see that (a) [ESC Scientist 8] probably would need some help because they hadn't got any embryology experience; (b) it's a cut-throat world out there these days and I knew that human embryonic stem cells were going to be very high profile and they'd probably enable us to get some grant money, probably some papers and do some interesting work … So I could see the potential of the work and I knew that I had all the skills to actually do the derivations for [ESC Scientist 8], and [ESC Scientist 8] wanted to use the cells, so it just seemed like one of those collaborations where both people are giving something a bit different and we could see that it actually probably would work really well. (PGD/ESC Scientist 10)

Scientist 10 went on to describe how vital it was to use high quality PGD embryos to maximize the chances of producing a human ESC line:

It's a complete waste of time getting poor quality embryos from a unit which has already got a very poor pregnancy rate as that tells you that the embryos are quite poor quality … The last thing I wanted to do is spend two whole years trying to derive stem cell lines and not be successful. That's a complete waste of anyone's time! So I think probably I had a fairly major input in deciding what we should use to start off with because I knew that in order for us to get some credibility, get some reasonable funding and to get quality papers we would need to derive lines quite quickly, and we did, we derived lines quite quickly once we started. Basically because [ESC Scientist 8] has got a lot of experience in stem cell work and he has got a good stem cell lab, we were able to produce quality media and I have got lots of embryology expertise so I was able to do the initial derivations, so I think it was that combination which made us reasonably successful. (PGD/ESC Scientist 10)

Here we see how the complementary skills and expertise of two key scientists enabled the embryo to bring two contrasting but increasingly related laboratory lifeworlds into alignment. In other words, the embryo acts as an object of translation. This alignment enabled this new grouping to achieve a set of aims that are essential for research on human cell biology, namely the triptych of funding, papers and “biological outputs” (in this case, a hESC line). Moreover, the overlap of clinical and scientific, or of applied and basic, research was also essential in forging a new translational research team across the two labs, and this role was fulfilled by the input of a clinician with a strong scientific background in embryology:

It really needed to be a teamwork thing because each person's got a different skill … Then we started, and [PGD/ESC Scientist 10] was actually fantastic. [PGD/ESC Scientist 10] can make anything grow. I'm a great believer that you actually need what is called a clinically aware scientist and a scientifically aware clinician, and you put those two together, and things happen … I've got a good understanding of embryos. And you've got [ESC Scientist 8] who is a very good biologist and stem cell person. And then you've got [PGD/ESC Scientist 10], an embryologist in the middle who is clinical and also has grown stem cells before and done a lot of work on mouse stem cells. So I think the combination together just made it happen … We wanted to be in the stem cell area. Each of us for slightly different reasons, and [all] for the purposes of therapeutic application. (PGD Clinician/Scientist 16)

The mutual benefits of working together meant that three key scientific staff could both concentrate on their particular area of expertise, and yet also draw upon the complementary expertise of their new colleagues. The transfer of skills, expertise and materials for joint endeavors is another key aspect of the translations that using some embryos for hESC research wrought between and within the social worlds of the PGD and ESC labs:

I hadn't got the manpower or the time to do all of that downstream stuff that they do, but I can do the embryology no problem because I've been doing that for years. So I set up all the protocols for handling the embryos over here [PGD lab] and getting out the inner cell masses and then doing the initial passages [dividing hESC colonies into smaller clusters]. I set up all of the stuff for making feeders [on which colonies of hES cells grow] and making all the medium and everything across at the [ESC] lab, and then his people took it over, over six months, and then those two things were able to work together and that's the only way that it could have been done. I certainly couldn't have done it on my own … I think the speed with which we did it was simply because we both had right skills. (PGD/ESC Scientist 10)

In this quotation we get a glimpse of the fine line between triumph and disaster that is a characteristic of “cutting edge” research in the biomedical sciences. The combination of different disciplines also allows differing perspectives to be focused on the objects of research. In this case, embryos mean quite different things to the three chief scientists attempting to derive human ESC lines, as Clinician/Scientist 16 explains:

We realized that this would be fantastic if we could grow them … [ESC Scientist 8] was more interested in normal stem cells as a stem cell, what happens to them, how they change and so on. But [PGD/ESC Scientist 10] and I were more interested in the embryo, in what kind of embryos made good stem cell lines, and I was quite interested to try and get the PGD lines because they could be very important … stem cells for therapy … This was a potential source to study genetic conditions, and you could actually look through the very early stages where the genes switch on, what actually happens, can you change it, could it be a pharmaceutical target? (PGD Clinician/Scientist 16)

In this quote we can see some of the ways in which embryos function as boundary objects as they enable scientists to pursue similar yet different goals, and they shape the dispositions and mould the social practices in the interrelated cultural worlds of PGD and hESC research. In brief, we see the embryo of our case study as a boundary object that set in motion “a social worlds research adventure” (Clarke 1990).

Discussion and conclusion

In this paper we have argued that the concept of boundary objects highlights the ways in which embryos and cells “federate the whole while tolerating pronounced internal differences” (Bazanger 1998, p. 139) between the communities of practice that link the interrelated worlds of PGD and ESC labs. By conceptualizing embryos as boundary objects we begin to grasp how they are de-contextualized and re-contextualized within and between the “two cultures” of ESC and PGD labs. Embryos are sometimes different things to scientists in ESC and PGD labs as: “The knowledge, skills and expertise of the respective groups are different and are brought to bear on different objects” (Featherstone et al. 2006, p. 40). We can multiply and extend these differences if we expand social worlds to include those of adult stem cell scientists, clinicians in IVF and regenerative medicine, patient groups, opponents of ESC research and so on (see Waters and Cole-Turner 2003, Lanza et al. 2004, Scott 2006). However, in this paper our goal has been more modest and we have focused on how two disconnected groups of scientists became two partially interconnected groups, to illustrate how the productive relations between these different sites allows scientists both to coexist and to collaborate. This provides a useful exemplar for the work of Fujimura (1992) who states:

Boundary objects can promote translation for the purpose of winning allies, they can also allow others to resist translation and to construct other facts … The concept is valuable for its emphasis on the coordination and management of work across worlds. Boundary objects both enables some actions and disables others. (Fujimura 1992, pp. 175–176 and 204; emphasis added)

In our case study, for instance, we saw how the development of the embryo as a boundary object “enabled” hESC research and how what were once affected spare PGD embryos became valuable “disease in a dish” hESC lines, thereby partially “disabling” the destruction of a number of these embryos as waste. Following Fujimura (1992) our paper should therefore be read as an illustration of how boundary objects can also disable particular social actions. In addition, boundary objects also enable the movement of similar and different meanings and things within and between different settings. In other words, embryos can become different things and have different meanings as they circulate within and between the worlds of PGD and ESC labs.

In the first part of the paper we argued that embryos function as boundary objects which help to maintain the differences in goals and practices in the worlds of PGD and ESC work. In contrast, in the second part of the paper we argued that embryos act as translational boundary objects which unite disparate actors in a common purpose: the creation of hESC lines. In the first part of our paper we demonstrated how “different social worlds maintained a good deal of autonomy in parallel work” (Star and Griesemer 1989, p. 399), whereas in the second part of our paper we illustrated the “flow of objects and concepts through the network of participating allies and social worlds” (Star and Griesemer 1989, p. 391). In this first sense, boundary objects act like anchors which help moor participants within different social worlds; while in the second sense, what we describe as translational boundary objects act as bridges which allow the growth of scientific trade between different and yet similar social worlds. These different worlds established protocols which went beyond the mere trading of embryos across unjoined boundaries. Rather, they began to devise a common world which made possible new kinds of enterprises, such as the creation of hESC lines (Star and Griesemer 1989).

Our paper is rooted in the social worlds approach where practices are the main elements connecting diverse actors from various social arenas (see Clarke 1990, 2005, Fujimura 1992). Social worlds are made up of groups with shared commitments to certain activities which mould individual and collective identities, such as in art worlds (Becker 1984), or in the worlds of PGD and ESC labs. In addition, Strauss (1978) argued that each social world has at least one primary activity that shapes “universes of discourse” of “people doing things together”. In our case study, we explored how different aims shape different social practices in the worlds of PGD and ESC. Individuals, of course, typically participate in a number of social worlds simultaneously and so mixed worlds are common (Clarke 1990). In our example, we analyzed how the separate worlds of PGD and ESC became, in some ways at least, a mixed mutual world with shared interests in human embryos. The labs we studied became entwined through their communal interest in human embryos and we argue that it was because the embryo acted as a boundary object that a range of organizational, intellectual and epistemological ties developed between what had previously been quite separate social worlds. Until several years ago our PGD lab focused on developing PGD as a clinical service, while our ESC lab specialized in neuroscience research using animal embryonic and fetal stem cells. In other words, the embryo only emerged as a translational boundary object relatively recently when the two social worlds of PGD and ESC became an arena of shared discourses and practices.

One example of the ways in which the stem cell–embryo interface is becoming a salient topic in the broader context of new medical technologies is the connection between PGD and translational research in the field of embryonic stem cells. As we saw earlier, using stem cell lines to study the genetics of all known “diseases in a dish” in order to develop pharmacological therapies is likely to become increasingly important (Department of Health 2005, Scott 2006). For example, in the UK, “disease in a dish” applications of hES cells have been developed through the innovative use of PGD embryos to create stem cell lines with a genetic disease (Pickering et al. 2005). Similarly, in the USA this approach is also becoming an important new “biomedical platform” (Keating and Cambrosio 2003) with the potential to move hES cell science from the bench to the bedside (Mooney 2005). We hope our paper provides a salient case study of how heterogeneity and cooperation exist in the production of the cultural practices of biomedicine in an emerging arena of new medical technologies. In conclusion, our paper outlines some of the ways in which the interface between PGD and ESC is likely to prove a fruitful area for future social science research on the interactions between science, medicine and society.

Acknowledgments

We would like to thank all those who participated in this research, and acknowledge the support of the ESRC Stem Cell Initiative (grant no: RES-340-25-0003), and The Wellcome Trust Biomedical Ethics Programme (grant no: 074935).