Stem Cell-Based Interventions and Research

Any exploration of issues in bioethics needs to be informed by the facts. Many readers likely have seen circular conversations or situations in which substantive misunderstandings or miscommunications derail discussion because there is no shared starting point grounded in medical or scientific information. A greatly simplified overview of stem cell types should help readers who are less familiar with the terminology and foster a shared basis for engaging the ethical issues that recent developments in SCBIs and SCBR raise.

The terms SCBR and SCBIs refer to a wide range of practices involving different types of stem cells. Stem cells often are defined as “cells with the potential to develop into many different types of cells in the body” (Agency for Healthcare Quality and Research–Effective Health Care Program, n.d.). Unlike most cells in our bodies, stem cells “can divide and renew themselves over a long time, . . . are unspecialized, so they cannot do specific functions in the body, and . . . have the potential to become specialized cells, such as muscle cells, blood cells, and brain cells” (National Library of Medicine, n.d.). Adult stem cells can “give rise to a limited number of mature cell types that build the tissue in which they reside. Their progeny replaces cells that are lost owing to tissue turnover or injury” (Nature, n.d.). Examples include hematopoietic stem cells (HSCs) found in the bone marrow that give rise to blood cells, muscle stem cells found in skeletal muscle tissue, and adipose tissue-derived stem cells, which are found in adipose tissue or fat. Perinatal stem cells are multipotent cells that can be become several different types of cells and are found in tissues that support pregnancy, such as amniotic fluid and parts of the umbilical cord (Abbaspanah et al. 2018).

Embryonic stem cells (ESCs) are pluripotent cells that can differentiate into almost all cells of the human body. They were first retrieved from human embryos in the late 1990s (Thomson et al. 1998). Typically, ESCs are extracted from a blastocyst—an embryo that is three to five days old. This process destroys the embryo. Some research has explored the possibility of extracting a single cell from an embryo as is done for pre-implantation genetic diagnosis, avoiding embryo destruction (Klimanskaya et al. 2006). ESCs can come from embryos created for IVF that are donated or embryos created specifically for research. Induced pluripotent stem cells (iPSCs) are pluripotent cells that have been “reverse engineered” in the sense that they started out as somatic (body) cells or as adult stem cells and are stimulated to become pluripotent cells (Yoshida and Yamanaka 2010).

Stem-Cell Based Interventions and Research and the Orthodox Christian Tradition

SCBIs and SCBR utilizing various types of stem cells raise different types of ethical questions from an Orthodox Christian perspective. In assessing the use of stem cells, it is worth remembering that for Orthodox Christians there is no inherent objection to advances in science and medicine. St. Basil the Great (AD 329–79) stated that

Each of the arts is God’s gift to us, remedying the deficiencies of nature . . . And, when we were commanded to return to the earth whence we had been taken and were united with the pain-ridden flesh doomed to destruction because of sin and, for the same reason, also subject to disease, the medical art was given to us to relieve the sick, in some degree at least. (St. Basil the Great 2000, 330–31)

More recently, in his work on Orthodox theology and bioethics, Metropolitan Hierotheos of Nafpaktos and St. Vlassios (n.d., Section 2.c) reminds readers that “Orthodox theology has never wished to place obstacles in the way of scientific research that aims to benefit humankind. All the scientific successes that have contributed to the health of human beings began with many years of research.” We are not to reject any and all medical attention or advances in medicine as if seeking treatment necessarily reflects a lack of faith. Jean-Claude Larchet (2002, 103) points to the many saints and bishops who also were physicians and notes also “the interest of several Church Fathers and the esteem in which they held the medical arts. Among them were Gregory of Nyssa, St. Gregory of Nazianzu, and St. Basil who began to learn medicine in the course of their studies, Nemesius, bishop of Emessa, St Isidore of Pelusia, St. Theodore of Sykon, St. Photius, the Patriarch, and Meletios the Monk.” In short, an Orthodox Christian assessment of SCBIs and SCBR should not begin with the assumption that there is something wrong with advancing science and medicine or seeking medical help.

Stem cells are of great interest to biomedical researchers and physicians because of their potential for advancing science as well as treating a wide range of diseases and repairing or regenerating damaged tissues and organs. A wide range of potential applications have been and continue to be investigated, including regenerating damaged organs and tissues such as bladders, hearts, and blood vessels; treating injuries such as spinal cord injuries, bone injuries, and burns; treating diseases such as diabetes mellitus, multiple sclerosis, arthritis, Crohn’s disease, and graft-versus-host disease; and improving outcomes for people with neurodegenerative diseases such as Parkinson disease (Poliwoda et al. 2022; Atala 2024).

Despite those potential benefits, various aspects of SCBIs and SCBR raise concerns from an Orthodox Christian perspective. The first of these relates to safety and efficacy. Some SCBIs are long-established treatments that are relatively safe and effective, most notably peripheral stem cell transplants, which have largely replaced bone marrow transplants to treat patients with a variety of cancers. These transplants are done either using one’s own cells (autologous) or donor cells (heterologous) (Keys et al. 2013). There is a great deal of interest in the possibility that SCBIs might be used to treat a wide range of conditions, and there have been significant advances through rigorous research. On the other hand, there are many SCBIs for which safety and efficacy evidence is limited or unavailable. In many cases, these interventions are offered in jurisdictions with little regulation or oversight (Bauer et al. 2018). They pose risks to patients, both in terms of the possibility of being harmed by those interventions and in terms of lost opportunity to pursue more effective treatments, as well as wasted time and money (Matthews and Iltis 2015). Some of these interventions have resulted in significant harm (The Pew Charitable Trusts 2021). For example, a young man who was injured on a trampoline at the age of twenty had gone through surgeries and rehabilitation and still had some paralysis in his arms and significant paralysis in his legs and torso. Feeling as though there were no other options, he went to Portugal and had nasal cells injected into his spinal cord at the injury site in hopes of alleviating pain and relieving some of the paralysis. He did not experience the hoped-for improvement. He ended up in more pain, and twelve years later, he noticed decreased function and more pain. Doctors found a mass on his spine; the cells in the mass were the same kinds of cells that had been transplanted into his spinal cord. They removed part of the tumor but could not remove all of it, and it might grow back (Woodworth et al. 2019). Other patients have developed serious infections, lost their eyesight, or died as a result of experimental SCBIs (Begley 2017). The COVID-19 pandemic ushered in additional “opportunities” for experimental stem cell-based interventions unbacked by careful research, many of which exposed people to risk of serious harm (Turner et al. 2021).

To be sure, all medical interventions carry risks, and experimental or innovative interventions that have not been well studied may expose patients to unknown risks of harm. Patients who receive experimental interventions in the context of well-run clinical trials face unknown risks of harm, but they also typically have the advantage of rigorous safety plans and oversight procedures meant to minimize risk. Such studies gather data on safety and efficacy, which generates knowledge necessary to improve the care of patients in the future. Receiving experimental SCBIs outside of such trials leaves patients particularly vulnerable to harm. Many clinics in the United States and around the world currently offer unproven SCBIs to patients, and there is a lack of transparency about the evidence behind the interventions offered or their results (Master, Matthews, and Abou-el-Enein 2021).

The Orthodox Christian tradition recognizes the importance of caring for the body. One way of doing this is avoiding unsafe experimentation, such as using unproven and higher risk interventions offered by providers who are operating at the margins. The “I’m willing to try anything” attitude that sometimes leads people to clinics that offer unproven interventions is understandable but can be at odds with the duty to care for our bodies. From an Orthodox Christian perspective, the pursuit of healing should not lead to taking unreasonable risks with our lives and bodies.

This is related to a second concern for Orthodox Christians, which is that the pursuit of healing or extending life must not become an obsession or all-consuming endeavor that subordinates spiritual health and the struggle toward eternal salvation. This is why St. Basil the Great (2000, 330–31) forbids “whatever requires an undue amount of thought or trouble or involves a large expenditure of effort and causes our whole life to revolve, as it were, around solicitude for the flesh.” Nor must our appreciation for the promise science and medicine offer become so great that we are more confident in them than in God, for as St. Basil the Great (2000, 331) warned, “To place that hope of one’s health in the hands of the doctor is the act of an irrational animal.” In other words, medicine is a good to be used in the context of a life of repentance and eternal salvation.

A third concern is that medicine must not be used for sinful purposes or involve sinful choices and actions. Some SCBIs and SCBR involve ESCs and thus involve the destruction of human embryos. Some SCBIs and some areas of SCBR, such as those using adult stem cells or perinatal stem cells, do not involve embryo destruction. This distinction is of vital importance for Orthodox Christians. Numerous Orthodox theologians and scholars have noted that, as Bishop Thomas (2013, 60) articulated, “from the standpoint of traditional Christianity, the destruction of human embryos is expressly forbidden regardless of any potential positive outcomes.” The Holy Synod of the Church of Greece (2000), issued a press release in 2000, stating: “Our Church expresses its categorical opposition to performing experiments on human embryonic cells. Such experimentation entails the destruction, not of embryonic cells, but of human embryos.” The Liturgy of St. Basil the Great, for example, recognizes each person’s existence as a person in the mother’s womb: “O God, who knowest the age and the name of each, and knowest every man even from his mother’s womb” (Hapgood 1996, 109). In other words, each of us exists as a person with a name, and each is known to God and thus ought to be treated as such.

Scripture, Orthodox hymnography, and Orthodox iconography recognize the unborn as living among us. Three major church feasts celebrate conception: the Feast of the Annunciation (March 25), the Feast of the Conception of the Theotokos (December 9), and the Feast of the Conception of St. John the Forerunner (September 23). The Orthodox tradition rejects the claim that because ESCs are taken from very early embryos, sometimes called “clumps of cells,” their destruction is permissible or less problematic than the destruction of older embryos and fetuses. St. Basil was clear on this point in voiding the distinction between formed and unformed pre-born life. In one of his letters, he specifies that there is no difference between an early and a late abortion: “The woman who purposely destroys her unborn child is guilty of murder. With us there is no nice enquiry as its being formed or unformed” (St. Basil the Great 1889, 652). In rejecting the significance of any difference between formed and unformed pre-born life, St. Basil, along with many others, rejects the idea that an early abortion or the destruction of a “mere embryo” is permissible. That is, he rejects the Old Testament distinction found in Exodus 21:22–25: “If two men fight and hurt a woman with child, and her child is born imperfectly formed, he shall surely be punished accordingly as the woman’s husband imposes on him; and he shall pay as the judges determine. But if the child is perfectly formed, he shall give life for life, eye for eye, tooth for tooth, hand for hand, foot for foot, burn for burn, wound for wound, stripe for stripe.” Other Orthodox scholars and theologians similarly reject the distinction between formed and unformed embryos. Metropolitan Hierotheos of Nafpaktos and St. Vlassios (n.d., Section 2.c) notes that “because, according to Orthodox theology, the soul exists from the beginning of conception—the doctrine of ‘the existence of an autotelic human entity from the first moment of conception’—as the embryo ‘receives a soul immediately upon conception,’ according to Christological teaching. The Orthodox Church does not accept the theory about ‘the process of receiving a soul’.”

The view that humans possess a soul from the time of conception may lead to questions about the implications for monozygotic (identical) twins, who develop from a single fertilized egg sometime during the first fourteen days post-fertilization. Questions that might arise include: Is there one soul that becomes divided? Does the fertilized egg contain two souls in one body for a period of time? Is a second soul delivered upon division? If monozygotic twins form and then one absorbs the other such that there is only one child gestated and born, what happened to the soul of the twin who was absorbed? The possibility of twinning, among other reasons, has led some authors, including some Orthodox Christian authors, to challenge the position that human life begins at conception (see, e.g., Woloschak 2017). Others have responded to twinning differently. Rather than see the monozygotic twins as a challenge to the notion that humans have a soul from the moment of conception, they have suggested that the problem is our attempt to see the soul quantitatively: “The soul does not represent a material essence that can be measured or counted, or an abstract hypostasis (essence of being) that differs from embryo to embryo . . . The division of an embryo, which yields two identical embryos, is not equivalent to the division of the soul since the soul, as a spiritual reality, no matter how many times it is split, does not divide, and no matter how many times it is combined, does not multiply or increase” (Griniezakis and Symeonides 2009, 34).

In short, where SCBIs and SCBR involve the destruction of human embryos, these practices generally are deeply problematic for Orthodox Christians. This is particularly true where they involve ongoing creation and destruction of embryos rather than relying on existing ESC lines or fetal cell lines derived from embryos or fetuses that were destroyed some time ago, where the harm already has been done (Engelhardt 2000, 261). Such cell lines remain in use today, but physicians, scientists, and patients were not party to that destruction. Some ESC research ultimately is aimed at developing customizable interventions that rely on a patient’s own cells and thus eliminate the possibility of immune rejection. These may involve ongoing creation and destruction of embryos through somatic cell nuclear transfer (SCNT) or cloning, to which I now turn.

Somatic Cell Nuclear Transfer (Cloning) and the Orthodox Tradition

Many people associate the term “cloning” with stem cells, yet not all STBIs or SCBR involve cloning. Cloning involves SCNT, which begins with an unfertilized egg (oocyte) from which the nucleus is removed and replaced with the nucleus of a cell from a different source. The egg is stimulated to divide, as a fertilized egg, i.e., embryo, would divide. This creates an embryo that is a clone, an exact genetic replica, of the individual whose nucleus was placed into the enucleated egg. The next step depends on the purpose of SCNT, or cloning. If the purpose is reproduction, as in the familiar case of Dolly the sheep, the dividing embryo is transferred to a uterus for continued gestation, much as is done in IVF. Human reproductive cloning currently is banned in many countries and jurisdictions and prohibited by the International Society for Stem Cell Research’s guidelines (Lovell-Badge et al. 2021). Recent developments in in vitro gametogenesis, the creation of sperm and egg in a lab, may raise questions similar to those associated with reproductive cloning and could challenge the moratorium (Segers et al. 2019a, 2019b). If instead the purpose of SCNT is to extract ESCs, then, after a series of divisions, stem cells are extracted from the developing egg (cloned embryo), destroying it. The difference here is that the ESCs obtained are genetically identical to the source of the replacement nuclear material. There are several goals motivating such research. First, those extracted ESCs would be a perfect genetic match for a patient, possibly enabling scientists to create cell lines to study specific diseases. The long-term goal is not merely to understand diseases but to treat them by generating and using genetically matched tissues or organs for an individual without risking rejection. This research is still early stages in humans but there are reports dating back to 2013 of labs making progress (Tachibana et al. 2013; Ogura et al. 2013).

Claims of success in using SCNT in humans made in 2004 turned out to be mired in controversy. Woo Suk Hwang, from Seoul National University in South Korea, and colleagues published a paper in 2004 in Science claiming to have obtained stem cells from a cloned human embryo (Hwang et al. 2004). A variety of ethical questions emerged, including concerns about the egg donors (Baylis 2009). Subsequently, questions emerged about Hwang’s data when mismatches between the allegedly patient-specific cell lines produced and the tissue samples were found not to match, which suggested either that the cells had been contaminated or that the ESC lines had not come from the allegedly cloned embryos. Further investigation revealed fabrication (Gottweis and Triendl 2006).

Sometimes, the use of SCNT for reproductive purposes is called “reproductive cloning,” while SCNT aimed at scientific discoveries and, ultimately, treatment is called “therapeutic cloning.” Both involve the same technology, i.e., in both cases, an embryo is created that is an exact genetic replica of the nuclear material donor source. What differs is the intent or goal. For some people, this distinction matters greatly, as they do not object to the destruction of embryos but are concerned about the risks to a person born from cloning. Many scientists, scholars, and others have defended so-called therapeutic cloning while categorically rejecting reproductive cloning (Tannert 2006). From within the Orthodox tradition, whether the aim is reproduction, research, or eventually treatment, all applications of SCNT raise concerns. All involve destroying human embryos, which the Orthodox tradition condemns.

Reproductive cloning raises additional concerns in the Orthodox tradition. Cloning introduces questions about status of the clone, especially concerning the relationship between the body and the soul. With respect to this issue, Metropolitan Hierotheos of Mafpaktos and St. Vlassios (n.d., Section 2.c) states that “[I] do not know whether God will allow the production by human cloning in a laboratory of a being with a human body, but without a soul. This does not happen now because man’s life is linked in a mysterious way with his soul. However, the soul and body owe their existence to God’s creative energy with the synergy of the parents (Fr. John Romanides); and according to St Maximus the Confessor, the body and the soul come into being in different ways—although this happens simultaneously at the moment of conception—since the soul is formed ineffably from the divine and life-giving inbreathing, and the body consists of existing bodily matter. For these reasons, the possible case in which God, for our chastening, allows a separation between the soul and life, and the creation of a chimera or hybrid seems tragic.” While I would not want to speculate about whether a clone would or could have a soul, such questions generate significant concerns about the possibility of creating entities that look human but cannot have a soul or whose soul and body are separated. Such a scenario would seem to deprive these beings who are made to be almost human of the gift of a soul and would create entities whom we create solely to use for our own purposes.

Despite differences regarding the origin of the soul in the early church (see, e.g., Jones 2004, chapter 7), there has long been clarity on the importance of the unity of body and soul in the Orthodox Christian tradition (Harakas 1982; Woloschak 2003). We find in the writing of St. Irenaeus of Lyon (1885) this comment on the importance of unity of body and soul:

Now God shall be glorified in His handiwork, fitting it so as to be conformable to, and modelled after, His own Son. For by the hands of the Father, that is, by the Son and the Holy Spirit, man, and not [merely] a part of man, was made in the likeness of God. Now the soul and the spirit are certainly a part of the man, but certainly not the man; for the perfect man consists in the commingling and the union of the soul receiving the spirit of the Father, and the admixture of that fleshly nature which was moulded after the image of God.

Similarly, in On the Making of Man, St. Gregory of Nyssa (1893) writes:

For our purpose was to show that the seminal cause of our constitute is neither soul without body, nor a body without a soul, but that, from animated and living bodies, it is generated at the first as a living and animate being, and that our humanity takes it and cherishes it like a nursling with the resources she herself possesses, and it thus grown on both sides and makes its grown manifest correspondingly in either part.

Finally, in his analysis of Maximus the Confessor’s understanding of the soul and body, Vladimir Cvetkovíc (2021, 264) observes that

Maximus argues that God created the human being planting his image in the soul. On the one hand the role of the soul was to cling to God by its intellectual and rational capacities in order to gain divinization. On the other hand, the role of the soul was to care for and to prudently use the body by subjecting it to the mind through virtues. By creating the soul, God endowed it with a mediatory role between God and the body. The twofold union, the necessary and reciprocal union of the soul with the body, and free and willing union of the soul with the divine should provide, according to the divine plan, both he immutability of the soul and the immortality of the body. Thus, God, created human beings as body–soul compounds in order to give them a foretaste of the future union with the divine, which although is supernatural will be felt as natural as natural is the union of the body and the soul. Moreover, the supernatural union with God, the soul and the body will be inextricably united one to another, with a bond much stronger than the natural bond.

Cloning threatens, or at least possibly threatens, the unity of body and soul, a relationship that is of great significance for Orthodox Christians.

The investigation into the soul–body relationship helps to further explain the categorical rejection of abortion and embryo destruction in the Orthodox tradition. In her careful discussion of theories of ensoulment, Anna Usacheva (2021) distinguishes early Christian accounts of the relationship between soul and body with Aristotle’s views, which informed later Western Christian accounts of the soul–body relationship. Aristotle, she demonstrates, held that “the soul cannot be alive without the body. This is why, according to Aristotle, the process of ensoulment is gradual,” rendering an early abortion “a totally decent measure” (Usacheva 2021, 153). Early Christian authors, on the other hand, “differentiated between the principles of physical formation, transmitted by the seed, and the soul provided by God” (Usacheva 2021, 153). Therefore, early Christian writers “affirmed that the bodily principles are contained in the seed, while God ensouls the embryo from the moment of conception” (Usacheva 2021, 153). It is this “conviction that ensoulment is simultaneous to conception [that] rendered every abortion as murder in the eyes of Christians” (Usacheva 2021, 154).

In light of this consistent emphasis on the unity of soul and body, and the idea that God implants, imparts, or somehow gives the soul such that it is present from conception, the possibility of asexual reproduction, including through cloning, raises concerns from within the Orthodox Christian tradition. Anything I could say about whether a clone would have a soul or whether cloning separates the body and soul would be speculative. At the same time, these possibilities generate an obligation for Orthodox Christians to humbly consider these matters and not dismiss them prematurely so as to guard against evil.

An additional concern for Orthodox Christians is that reproductive cloning would involve reproduction outside of the context of marriage of husband and wife, which the Orthodox tradition holds is the only appropriate context for procreation (Engelhardt 2000, 260). Moreover, it would involve reproduction without needing both male and female. In St. John Chrysostom’s (2000, 44) homily on Ephesians, he observes that God “did not, on the one hand, fashion woman independently from man; otherwise man would think of her as essentially different from himself. Nor did He enable woman to bear children without man; if this were the case she would be self-sufficient. Instead, just as the branches of a tree proceed from a single trunk, He made the one man Adam to be the origin of all mankind, both male and female, and made it impossible for men and women to be self-sufficient.” This suggests that independent procreation may be objectionable in the Orthodox Christian tradition.

Human Embryo Research and the Orthodox Tradition

Human embryos often are destroyed subsequent to IVF undertaken with reproductive intentions either because a couple does not want to have more children or because pre-implantation genetic diagnosis reveals an anomaly. Sometimes those embryos are discarded and sometimes they are donated for research, where they may be destroyed to obtain ESCs. There are other research endeavors beyond ESC research involving human embryos, both those created for reproductive purposes originally and embryos created for research purposes, that result in their destruction. These raise important questions for Orthodox Christians, some of which are the same as those associated with embryo destruction already noted.

There have been significant developments in human embryo research in recent years. After the first successful report of IVF in humans, a series of reports in the United States and UK recommended that research on human embryos be permitted up to fourteen days post fertilization or when the primitive streak emerges (U.S. Department of Health, Education and Welfare 1979; Warnock 1984). Different reasons were offered for this limit. For some, the possibility that this is the final point at which twinning is thought to be possible indicates that it marks individuation. For some, the primitive streak is significant because it is observable immediately before neural tube formation and indicates significant organization of the embryo (Matthews et al. 2021). Historically, scientists have been unable to keep embryos alive in vitro for anywhere close to the fourteen-day limit, so the limit was an in-principle limit but posed no barrier for research. Instead, scientists were limited by their own technical abilities. This changed in 2016 when two labs reported that they had successfully cultured human embryos in vitro up to fourteen days post fertilization (Deglincerti et al. 2016; Shahbazi et al. 2016). They destroyed the embryos to comply with the guidelines to which they were subject in the United States and the law that restricted the group working in the UK. Leading up to those announcements and subsequently, numerous scientists and scholars have called for the fourteen-day limit to be either extended, allowing embryo-destructive research to a later time, or lifted altogether. In jurisdictions where the law limits human embryo research to fourteen days post fertilization, this requires legal action. However, in jurisdictions such as the United States in which scientists have self-regulated and agreed to follow international guidelines on human embryo research but there is no law, no legal action is required. Thus, in 2021 when the International Society for Stem Cell Research (n.d.), which describes itself as “the preeminent global, cross-disciplinary, science-based organization dedicated to stem cell research and its translation into the clinic,” issued new guidelines that no longer restricted human embryo research to fourteen days post fertilization, the door was opened in the United States for research on embryos beyond fourteen days post fertilization (Lovell-Badge et al. 2021).

The fourteen-day mark is an irrelevant distinction for Orthodox Christians given that it is impermissible to destroy embryos at any stage, as noted. It is possible that destroying more developed embryos and fetuses dulls us even more to the sinfulness of destroying human life. It may further contribute to an attitude of disrespect or disregard for vulnerable others. In that sense, permitting embryo-destructive research beyond fourteen days could introduce additional concerns in the Orthodox tradition.

The possibility of growing embryos to later stages and gestating embryos in artificial wombs introduces another option for reproduction outside of marriage and even of reproduction without any identified parents since, in theory, children could be “farmed” in laboratories full of artificial wombs. For reasons already cited, this raises specific concerns for Orthodox Christians.

Embryoids and the Orthodox Tradition

At the intersection of SCBR and human embryo research we find an emerging area of research that involves the use of various types of stem cells to build models of early human development, sometimes called embryoids or synthetic embryos. Many different names have been used to refer to a wide variety of stem cell-based models of early human development (Matthews et al. 2021). Interest in embryoids stems largely from the possibility of using them to study embryo development, organogenesis, specific diseases, and teratogenicity of drugs, among other things. They raise a host of ethical, social, and policy considerations (Iltis et al. 2023). Some embryoids are created using ESCs such that involve embryo destruction, raising the same concerns noted. Others rely on iPSCs, which come from adult stem cells. Beyond concerns about embryo destruction, embryoids raise a number of metaphysical questions about what they are and whether they are human beings with or without a soul.

How closely must a model of early human development mimic an embryo to be treated as an embryo? Currently, there are significant differences among embryoids with respect to the sources of cells used to generate them and how closely they resemble human embryos. Although the science has not yet developed to the point that these models are sophisticated enough to closely model human embryos and are able to be gestated, many believe that it will (Denker 2021; Matthews and Moralí 2020). At what point, if any, ought we to treat these as embryos or do they become embryos? Some scholars speculate that embryoids could become sophisticated enough that it would be plausible to gestate them to the point of live birth. For Orthodox Christians, that possibility raises concerns comparable to some of the concerns raised regarding cloning, including asexual reproduction and reproduction outside the union of husband and wife.

As culture techniques improve, and scientists can grow embryos in culture for longer periods of time, it is likely that it will also be possible to develop embryoids for longer periods of time. This introduces the possibility of attempting to gestate embryoids and use them for reproductive purposes or as sources of organs and tissues. All of these raise serious concerns within the Orthodox tradition for reasons outlined related to the destruction of embryos and reproduction outside the union of husband and wife. Questions regarding the possibility of creating humans deprived of a soul raises concerns comparable to those associated with cloning.

Chimeras and the Orthodox Tradition

Animal–animal and human–animal chimeras have long been of interest in science as well as in art and literature. Recent science has involved developing various chimeras, including human–animal chimeras (Wu et al. 2017; Tan et al. 2021). Chimeras are entities created with a mixture of cells from different species, and in the case of animal–human chimeras, a mixture of animal and human cells. The National Institutes of Health in the United States prohibited use of its funds for animal–human chimera research until 2016 (Kaiser 2016). Reports of first human–monkey embryos indicate that some of the embryos lived twenty days in culture and had up to 7% human cells in one embryo (Tan et al. 2021). Chimeras are of interest to scientists because of the possibilities they offer for generating new knowledge about a wide variety of important biomedical questions about human development as well as human disease (Tarifa et al. 2020). There is also interest in using chimeras to generate organs that could be used for transplantation into humans (xenotransplantation).

Human–animal chimera research raises numerous questions (Kwisda et al. 2020). These include metaphysical questions such as whether they are human and, if not, what they are. For instance, is there a percentage cut-off? Does the type of tissue involved matter? Would we treat human–animal chimeras with human neural cells differently from a chimer with human kidney cells, for instance? This research is in early stages today, but future developments likely will lead to questions regarding reproduction and permissible uses of chimeras. Many of the concerns noted here are not unique to Orthodox Christians and have been raised in the broader literature (Kwisda et al. 2020).

Conclusion

In a paper on organ transplantation and Orthodox Christianity, Gayle Woloschak (2003, 703) framed consideration of bioethics issues this way:

[C]ommitting or accepting actions that denigrate humanity creates a rift between us and our intended role in the creation; one thing that sets humanity apart from the remainder of creation is responsibility. We humans are meant to take responsibility for ourselves, for each other, for our children, for the world in which we live, for the world that we refashion, for the cosmos around us, for our actions and inactions, for our good deeds and bad deeds. Taking responsibility is human, and to not take it is to be less than human. In the ongoing debate about cloning, about xenotransplantation, and about other related biomedical research, we must not lose sight of this responsibility to ourselves, to each other, and to our world.

As Orthodox Christians contemplate SCBIs and SCBR and various connected areas of research, the overall question is: How are we to understand and approach such matters as responsible Orthodox Christians? Another way of asking that is: What does it mean to think and act as a being created in the image and likeness of God in the face of this particular issue or question? This article is offered in the spirit of informing such an assessment of SCBIs and SCBR.