Halachic Challenges Emerging From Stem Cell Research

Jewish Political Studies Review 21:3-4 (Fall 2009)         

As a partner with God in the creation process,[1] human beings have developed innovative technologies to treat and cure disease, to enhance human living conditions, and to protect or improve the environment. In concert with the development of new technologies, the halachic (Jewish legal) process has elaborated specific mechanisms to incorporate and integrate these emerging technologies. As such, leading rabbinical authorities have evaluated and analyzed the halachic parameters surrounding the applications of innovative medical and biological technologies, such as blood transfusions, heart transplants, and assisted reproductive technologies. 

Recently, the biotechnological advances in the areas of stem cell research and reproductive medicine have presented new halachic challenges. This paper reviews and updates the underlying science of stem cell research, and highlights several new innovative breakthroughs emerging from stem cell research and reproductive medicine that in turn raise a variety of halachic issues to be evaluated by rabbinical authorities. In addition, the authors will suggest some concepts that may assist in the formulation of the crucial halachic parameters to govern these new scientific advancements.

Stem Cell Science

In order to better appreciate the role of stem cell research in reproductive medicine, there is a need to understand the critical biological principles of stem cell research and its potential applications to medicine. While there is a great deal published on the potential medical applications of stem cell research to treat or cure diseases such as diabetes, Alzheimer’s disease, Parkinson’s disease, cancer, and heart disease, much less has been published on the future impact of stem cell research in reproductive medicine.

Stem cell research is, in part, a quest to understand cellular differentiation, the process by which a human being develops from one fertilized cell into a multicellular organism composed of over 200 different cell types – for example muscle, nerve, blood cell, or kidney. Cellular differentiation begins with the fertilized egg which serves as the identifying characteristic of an embryonic stem cell. As the fertilized egg divides from one cell into two, physicians can separate these two cells and implant each one of them into a woman’s uterus to generate two genetically identical children. Similarly, when the fertilized egg divides from two cells into four cells, each of these four cells has the potential to individually form a human fetus. However, by the time the fertilized egg divides into 8 or 16 cells something changes and each respective cell, if separated, no longer has the potential to create a fetus.

Most researchers obtain embryonic stem cells from the inner mass of a blastocyst, an embryonic stage when a fertilized egg has divided into 128 cells. The stem cells derived from the inner mass of a blastocyst lack the ability to form a fetus when implanted into a woman, but are self-renewing and can be maintained for long periods of time in the laboratory as undifferentiated stem cells. In addition, specific proteins or biological substances can be added to these stem cell cultures to transform them in the laboratory into a large variety of specialized cell types, such as nerve, liver, muscle, bone, and blood cells.

The predominant bioethical concern arising from this technology is that the blastocyt-stage embryo must be destroyed in the process of isolating and separating the embryonic stem cells from the inner mass region of the pre-embryo. The destruction of the pre-embryo has been the critical issue in the U.S. behind imposing limits on federal government-sponsored research in embryonic stem cells. Many politicians, religious leaders, and bioethicists believe that any destruction of the pre-implanted embryo or fertilized egg is akin to murder. In 2009, in a major reversal of U.S. policy, President Obama signed an executive order pledging to “vigorously support” embryonic stem cell research. This policy is similar to that of other countries, including Israel, where scientists are funded by Government to study embryonic stem cells despite the aforementioned bioethical issue. Israeli policy is based on the belief that such a pre-embyro does not confer personhood and that many therapeutic applications can be derived from such research. 

Classical Applications of Stem Cell Technology to Medicine

Contrary to popular belief, stem cells are present in the human body throughout life and are found in many adult organs. They serve as a reservoir to replenish cells that are destroyed, damaged, or worn out within these organ systems. Therefore, a near term clinical application of stem cell research to medicine will be in the area of cell replacement therapy. Cell replacement therapy involves transplanting stem cells into damaged tissues or organs and stimulating these newly transplanted stem cells to grow and repair the diseased organ or tissue. A critical medical breakthrough in avoiding tissue rejection by the patient receiving this therapy will utilize stem cells obtained from the patient’s own body, such as the bone marrow, to biologically transform the cells in the laboratory before re-introducing them into the patient. In this manner, the patient’s body will not regard the reintroduced stem cells as foreign and thus will be accepted immunologically. The newly transplanted stem cells will either replace the damaged ones or will stimulate the release of various biological substances that will promote organ and tissue repair.

In contrast, conventional donor organ transplantation usually involves finding an organ donor who is as immuno-compatible as possible with the patient’s own tissue in order to reduce the chances of organ rejection. Since it is usually difficult to find appropriate immuno-compatible donors, recipients of organ transplants must often be placed on medications for at least a year to prevent their immune system from rejecting the transplanted organ. These medications have medical risks and are associated with many side effects, including infections and organ failure.[2]

Transplanting stem cells in patients with heart disease is one area of medicine in which cell replacement therapy may be tested in the near future because these stem cells can be derived from the patient’s own blood or bone marrow. This type of cell replacement therapy has the potential to relieve debilitating symptoms, such as severe angina pectoris (chest pain), by helping the body to create new blood vessels around the damaged area of the heart, improving blood flow as well as generating new tissue to replace damaged heart tissue.[3]

Another promising technology emerging from stem cell research is the development of drugs that can stimulate the body’s own natural stem cells to divide and repair damaged organs. For example, many anti-depressants work by stimulating the stem cells, normally idle in the brain, to divide and replenish damaged nerve cells in patients who suffer from chronic depression. Similarly, great progress is being made to identify new substances, natural and synthetic, that could stimulate the stem cells in other organs to proliferate and replenish the damaged cells.[4] Recent studies have shown that some populations of stem cells, when appropriately stimulated by drugs, have the capacity to promote endogenous nerve cell repair and might prove to be a useful therapy in patients with neurodegenerative diseases such as multiple sclerosis.[5]

Most recently, an exciting example of research emerging from stem cell studies relating to diabetes was published in the scientific magazine Nature.[6] In human diabetes a specific population of pancreatic cells called beta cells is destroyed, preventing the affected individual from producing the critical hormone, insulin. In this study, scientists injected a genetically engineered virus into a mouse-model of human diabetes to transform normal non-insulin producing pancreatic cells into insulin producing pancreatic beta cells. This genetically engineered virus is encoded for genes that can reprogram one type of pancreatic cell to become an insulin producing cell. Equally important, this study established an innovative technology for directing cell reprogramming from one cell type to another without necessitating reversion through a stem cell state.

Innovative Applications of Stem Cell Research

There are many aspects of stem cell science in the areas of reproductive medicine and organ transplantation that are less developed at this stage but nonetheless present some exciting future applications of stem cell research. The first focuses on the observation that every time a woman becomes pregnant with a child, stem cells from the child that the woman is carrying detach from the fetus and travel across the placenta into the woman’s body, implanting in a wide variety of organs of the pregnant mother, including the brain, muscle, and liver.

Thus, a woman who has had many children will have organs containing millions of cells derived from each of her children. Yet, it remains to be determined how these large numbers of “transplanted” fetal stem cells affect the various organs of the mother. Will the fetal stem cells that have implanted in the mother’s brain affect elements of her behavior or personality? In addition, recent evidence in mice reveals that maternal cells can transfer from the mother and implant in the fetus.[7] Interestingly, the presence and persistence of fetal cells in maternal tissue was first reported over 20 years ago in the mouse, although only recently has the occurrence and potential consequences of fetal to maternal cell trafficking in humans been investigated.[8]

The second area of research of embryonic stem cell science focuses on organ transplantation. Researchers can infuse human stem cells into the developing organs of animal fetuses to allow these fetuses to develop human organs. Esmail Zanjani, at the University of Nevada, is one of the pioneers developing new technology to transplant human stem cells into sheep fetuses. This will generate a new born sheep with a human liver genetically compatible with the stem cell donor. The human liver developed in the new-born sheep could then be transplanted into that stem cell donor with minimal danger of organ rejection and without the need to provide the lifelong anti-rejection drugs normally administered to most organ transplant patients.[9] Such technology would hopefully alleviate the backlog of organ donors since each patient could use their own stem cells to regenerate an organ in a sheep.

A third interesting futuristic application of stem cell research involves transplanting human stem cells into animal fetuses to generate mice that produce either human sperm or eggs.[10] No one has yet reported whether the human sperm from these mice can be used for in vitro fertilization of human eggs or whether mouse-derived human sperm and eggs can be fertilized in the laboratory and then implanted into a surrogate woman to produce a child. Astoundingly, yet scientifically feasible, is the potential for any individual to have their own stem cells transplanted into mice to generate a population of mice that carries their specific sperm or eggs. These animals could serve as a sperm or egg reservoir in case those individuals undergo medical treatments that may render them infertile. Even more futuristic, but scientifically possible, is the potential to create cows that produce a human uterus, sperm, or human eggs. These animals could, theoretically, be used as “artificial incubators” to carry a human fetus to term.

A final area of future stem cell research involves transplanting human nerve precursor stem cells into the brains of animal fetuses. In fact, scientists have already reported creating mice in which about 1% of their brains were reconstituted with human cells.[11] These scientists are interested in using this technology to develop animal models to study neurological diseases (such as Alzheimer’s or Parkinson’s disease) for which there are currently no good animal models. Historically, creating animal models for human disease has been highly successful in gaining a better understanding of the underlying pathology or to screen new drugs to treat or cure a variety of diseases.

In summary, stem cell research has captured the scientific imagination of both the scientific and lay community not only due to its potential applications for regenerating new organs or repairing injured organs, but also in the areas of reproductive medicine and organ transplantation.

Halachic Issues Emerging from Stem Cell Biotechnology

When Does a Fetus Attain Personhood?

There have been many excellent articles published on the halachic ramifications of basic stem cell research and its potential use in medicine.[12] In general, the halachic position on stem cell research differs from that of other major religions regarding the most contentious ethical questions – when does human life begin and when does a fetus attain personhood. In addition to discussing these issues, many of the halachic papers related to stem cell technology focus on the following questions:

1) When, if at all, is it permissible to destroy a human embryo to obtain stem cells for research purposes? and 2) Can stem cells be used for organ regeneration or cell replacement therapy to treat diseases even though this therapy is still in the research stage of development and has not been consistently demonstrated to save a person’s life or treat these diseases? In general, the use of embryonic stem cells obtained from pre-implanted embryos that have gestated less than forty days is permitted for basic scientific research by many halachicauthorities.[13] In addition, there is a general halachic consensus that stem cells may be used as a potential research therapy to treat or cure diabetes, Alzheimer’s disease, cancer, spinal cord injuries, or Parkinson’s disease provided there are valid medical justifications for these experimental procedures.

However, the halachic issues regarding when human life begins or when a fetus attains personhood, are quite complex. A review of a variety of sources from the Talmud, Midrash, andhalacha suggests that there appear to be halachic definitions of the various stages of an embryo which affect the issue of when human life begins. The Babylonian Talmud (BT), TractateSanhedrin 91a, for example, states that Antoninus asked Rebbi,

“When is the soul (neshama) placed in man? [Is it] as soon as it is pekidah [decreed – i.e., conception – Rashi claims it is the first drop when the angel decrees the fate of the child], or when [the embryo] is actually formed [when all the organs are in place, that occurs after about forty days of gestation]?” Rebbi replied, “From the moment the embryo is formed.” Antoninus objected: “Can a piece of meat remain unsalted for three days without becoming putrid? But it must be from the moment that [God] decrees [its destiny].”

In other words, Antoninus is asking Rebbi how can there be human embryological development in the absence of a human soul and Rebbi appears to agree with Antoninus that ensoulment occurs at conception. Rebbi even brings support for this view from a biblical verse: “Rebbi said: This thing Antoninus taught me, and scripture supports him, for it is written, And thy decree(uph’kudatcha) hath preserved my spirit [i.e., my soul] (Job 10:12).”[14]

However, other places in the BT, such as Yevamot 69a and Nidda 30b, view a fetus at less than forty days gestational development as “unformed,” implying that human life or personhood, and maybe even ensoulment, occurs after forty days of gestation, not at conception. Mishna, Nidda 30a, explains that a miscarriage prior to forty days gestation does not cause tumat leida (impurity due to contact with a corpse). BT Yevamot 69b quotes Rav Chisda who states that the daughter of a Cohen (priest) whose non-Cohen husband has died may continue eatingtrumah (tithes) as long as she has no children and is not pregnant from her deceased husband. Rav Chisda claims that if this woman is carrying a fetus that is less than forty days, the fetus is considered unformed matter and she is not halachically pregnant and may continue to eat trumah.

In an attempt to resolve the apparently contradictory statements in BT Sanhedrin, BT Yevamot, and Nidda concerning when human life begins, Rabbi Johanan in BT Menahot 99b may provide an innovative insight and approach. R. Johanan and R. Eleazar state that “The Torah was given in forty days and the soul (neshama) is formed in forty days.” Why did these sages compare the giving of the Torah to ensoulment? The answer may be that the transmission of Torah to Moshe did not occur in one instance or as a quantum event or prophecy, but required a forty day learning or incubation period. Similarly, the ensoulment of a human fetus is a process that begins at conception and requires forty days of development to complete its first stage. Forty days of embryological development thus represents the first stage of a spiritual milestone.[15]

Another halachic consideration regarding the forty day milestone of fetal development is whether Shabbat may be “violated” for the life of a fetus. While BT Arachin 7b affirms that one is permitted to engage in melachot (categories of work) on Shabbat in order to save a fetus, there is disagreement among the decision-makers of Jewish law as to whether or not this applies to a pre-forty day embryo. According to the Ramban’s[16] view of the Behag,[17] one can clearly engage in normally prohibited activities on Shabbat in order to save a fetus less than forty days old. In contrast, a responsum of R. Shmuel Wozner of B’nai Brak ruled that even according to the Behag one may not violate the work prohibitions of Shabbat on behalf of such a pre-embryo.[18]

There are other spiritual and halachic milestones in fetal development. BT Nidda 8b asks

at what stage is the embryo discernible? Symmachus citing R. Meir replied: Three months after conception. And though there is no actual proof for this statement there is an allusion to it, for it is said in Scripture, “And it came to pass about three months after….”[19]

In addition, Rabbi Shlomo Zalman Auerbach states that the three months milestone of fetal development affects the status of a fetus with respect to pidyon haben (redemption of the first born son). After three months of gestation, a fetus is considered formed and if it is spontaneously miscarried then any baby boy born after such a miscarriage should not be redeemed under the laws of pidyon haben.[20] Three months of gestation also represents a milestone as a halachic recognition of pregnancy. This is one reason why a woman cannot remarry for about ninety days after becoming widowed or divorced, in order to ensure that she is not pregnant and to avoid any doubt as to the genetic parentage of her newborn.[21]

Another halachic milestone in fetal development is birth. Mishna Ohalot 7:6, permits the termination of a fetus to save the life of the mother, even if the fetus is at full term and must be dismembered, because the mother’s life takes halachic precedence over that of the fetus.[22] But when the head emerges from the mother, the life of the child is then equal to that of the mother. Clearly with the emergence of the head, the child is no longer dependent on the mother’s respiration and has established independent human life. As seen from the above cases,halacha reevaluates the status of a human embryo at each developmental stage.

Use of Stem Cells to Engage in Genetic Screening of Early Embryos

Currently, scientists can perform genetic screening for diseases such, as Tay Sachs or Cystic Fibrosis, on a fetus or child using five or less fetal cells. In fact, in pre-implantation genetic diagnosis, only one fetal cell is required to screen an embryo and determine whether that potential child will carry any one of over 50 genetic diseases. Emerging technologies are being developed to screen fetal cells collected from the vaginal fluid of a woman who is in her first month of pregnancy. If the genetic status of a fetus can be established in the first weeks of pregnancy then halachic authorities may be more lenient in ruling that a fetus that has Tay Sachs or cystic fibrosis can be terminated within the forty day gestational period.

Use of Stem Cells in Reproductive Cloning

The medical risks in the classical cloning technology that were used to generate the sheep Dolly are still serious, but new emerging technology has ameliorated some of those risks. As scientists discover how stem cells transform into various kinds of organs they are also developing methods to transform stem cells into sperm and eggs. There are new methods, for example, that can transform a stem cell with its 46 chromosomes into a gamete-like cell that only has 23 chromosomes.[23] This gamete-like cell has the capacity to be used as a sperm-like cell to fuse with an egg and form a fetus for subsequent implantation into a woman. This type of technology has been used successfully to allow husbands who cannot produce sperm, due to a congenital problem or following cancer treatment with radiation and chemotherapy. to father children. In such cases, other cells, such as those obtained from the skin, can be used to generate these gamete-like cells for in vitro fertilization with eggs from the men’s wives to produce a child that is genetically related to both members of the couple. Like other reproductive technologies, this type of assisted reproductive technology may provide another halachically approved method for sterile couples to employ in order to have children and engage in the mitzva of priyah v’rivia (the commandment to procreate).  

However, this technology could also be used to clone a person. Theoretically, one could obtain stem cells from the bone marrow or skin of a woman and transform them into gamete-like cells with only 23 chromosomes. These gamete-like cells could then be fused with the woman’s own eggs to generate an almost perfect genetic clone of the woman. This cloning technology is thought to be safer for the child than classical cloning technology that uses somatic cell nuclear transfer. Animals that have been cloned using somatic cell nuclear transfer are often born with severe medical conditions. While most people would not want to use this technology to clone themselves, a single woman or a survivor of a war (like the holocaust) in which all members of the family were killed, may want to perpetuate the family lineage by using this technology to have genetically related children. This is another example in which halachic authorities would have to evaluate whether or not these women would be permitted to use such cloning technology to generate children and examine other halachic issues related to a child that has no biological father.

In deliberating the status of reproductive cloning, halachic authorities might consider BT Nidda 30 that states that there are three partners in the creation of a child – man, woman, and God. Man and woman are charged with donating the biological material while God infuses the spiritual elements. Does the Talmudic passage mean that three partners are required to generate a child or is this statement simply a recommendation or philosophical idea? Using assisted reproductive technologies to enable unmarried women to have children lacks halachic precedent. However, Rabbinical authorities, including Rabbi Shlomo Zalman Auerbach[24] and Rabbi Moshe Feinstein z”l,[25] looked askance at using classical assisted reproductive technologies to enable a single woman to produce a child. Nonetheless, the use of cloning technologies would avoid the need for the use of non-Jewish sperm for in vitro fertilization and may be more acceptable within Jewish law.

 Another halachic issue is whether reproductive technology is permitted to be used to clone talmidei hachamim (future experts in the knowledge of Jewish law)? Interestingly, BT Nedarim81a may relate to the issue of cloning a gadol hador (an international expert in Jewish law). The Talmud states that families of talmidei hachamim do not necessarily have children who are also talmidei hachamim because, according to Rav Joseph, the development of a talmid hacham is not determined “genetically” (literally yerusha). Nonetheless, genetic traits that determine intelligence and other behavioral traits are a necessary prelude to allow “nurture” to achieve intellectual superiority and leadership qualities required in a gadol hador

Reconstituting a Human Brain into Animals

Another halachic challenge that rabbinical authorities may have to face in the future is whether or not stem cells can be used to reconstitute a human brain in mice or monkeys. As mentioned above, one of the most amazing properties of stem cells is their ability to transform into any cell of the body. This property of stem cells provides a unique opportunity to examine and investigate areas of brain development that could never before be studied. In fact, several scientists are attempting to reconstitute areas of animal brains with human neurons, by transplanting human neural-like stem cells into the fetus of a mouse. The goal of these studies is not to develop animals that express human behavior or thought. Rather, scientists want to use this technology to gain a better understanding of human brain development in its earliest phases. This technology also affords the possibility of developing animal models to study human neurological diseases such as Alzheimer’s and Parkinson’s disease, and various forms of mental illness, which at present do not have good animal models. Finally, reconstituting areas of mouse brains with human cells provides the opportunity to examine, in an animal model, potential therapies to treat or cure various types of brain tumors.

While the motives for reconstituting areas of animal brains with human neurons are well intended and focus on learning basic principles of neuroscience or understanding neurodegenerative diseases, they do raise specific halachic concerns. One concern relates to the way halacha defines a species. Will the reconstitution of a mouse or monkey with a human brain transform the halachic classification of this animal into a human-like being?

In Jewish law, a species’ identity assumes tremendous significance in biblical and rabbinical laws such as the mitzvot (Jewish commandments) related to planting and harvesting crops.[26] In addition, Jewish law defines ritually pure and ritually impure – kosher and non-kosher – animals according to their physical characteristics and often utilizes the term “species” in these laws.[27] The Bible introduces essential physical characteristics of various mammals, birds, and fish.  BT Bechorot 5b introduces one non-physical characteristic in classifying a mammalian species: the identity of the species of an animal generally depends on its gestational mother rather than its own physiological makeup. For example, Jewish law prohibits the consumption of a mammal that lacks split hoofs.  If genetic mutations cause a calf to be born that expresses a clubbed foot and lacks a split hoof, that calf is still kosher because it was born from a kosher cow, even though it does not have the appropriate external physical characteristics of a kosher animal.

What halachic criteria would characterize an organism as homo sapiens? In halacha, the most important and absolute criterion in defining homo sapiens is being formed within, or born from, a human being.[28] Killing any organism born from another human, regardless of the offspring’s physical or mental characteristics, is considered murder. Three other characteristics that may serve as criteria for defining human beings include: a) the capacity to speak a complex language; b) the ability to differentiate between good and evil or the expression of free will; and c) the capacity to generate offspring with another human being.[29]

These halachic criteria in defining a human being may be important in reference to two areas. First, the New York Times reported on 14 July 2008 that the Spanish Parliament proposed to grant limited rights to chimpanzees, bonobos, gorillas, and orangutans. This law is based on the belief that specific characteristics such as experiencing fear and happiness, the ability to create tools, use languages, remember the past, and plan for the future are human-like properties. Since these non-human primates display human like characteristics they should be granted special human-like rights. Thus, the sacrifice of these animals in order to study diseases that affect humans would be prohibited. In halacha, there is a clear mandate that prohibits animal suffering, but permits the sacrifice of animals under controlled situations in which there is a clear medical benefit to develop new medical therapies.[30] In the final analysis, halachaviews non-human primates naturally found in the animal kingdom as animals and not as human beings.

A second area in which halachic authorities must establish clear criteria in defining human beings as a species relates to the above mentioned stem cell technology to reconstitute a human brain in an animal. The first question to be decided is whether the transplantation of human pre-neural stem cells into the fetus of an animal will actually induce human behavior, characteristics, or mental capacity. The answer to that scientific question is currently unknown. Transplanting even a few embryonic human precursor nerve stem cells into an animal’s brain may trigger the human cells to multiply and differentiate in sufficient numbers and fuse with the animal’s own brain substance in a manner that may impart human characteristics. If, in fact, human-like mental or behavioral characteristics appear in animals with reconstituted human brains, will halachic authorities classify this organism as human and obligate it to act as a human being and others to respect its human rights?  Halachic authorities may want to wait until such an organism is actually constructed to evaluate the mental capacity or “human” behavior characteristics that such an animal displays before identifying its status as animal or human.

Can Animals Serve as Incubators for Human Fetuses?

A final halachic challenge to be discussed is based on technology that enables human stem cells to be transformed in animals into reproductive cells. Scientists have already been able to transplant precursor testicular or ovarian human stem cells into the fetus of mice to create mice that produce either human sperm or eggs. It is theoretically possible that this technology can eventually be used to produce an animal with a human uterus. What would happen if a male sheep or cow that has the capacity to produce human sperm mates with another female sheep or cow that has the capacity to produce human eggs? Would fertilization be successful and lead to the creation of a human fetus that develops in that female animal?

Assuming that in fact that animal could serve as an incubator for a human fetus, how would Jewish law classify this offspring especially produced by a sexual mating of the two transgenic animals? Would halachic authorities classify the offspring as human, based on its human-like thought, speech, or intelligence, or would it still be considered an animal since it was born from a sheep or cow?

The Moral Principle of Respecting Human Dignity

While there are many specific halachic issues related to the above mentioned scenarios, it is important to stress the one overriding issue that might discourage the use of stem cell technology for reconstituting a human brain in an animal or to create an animal that can serve as an incubator for human fetal development:  respect of Human Dignity (kevod haberiyot). This concept is used to describe the dignity of creatures uniquely fashioned by the Almighty in BT Berachot 19b. The definition implies that human beings’ stature and worthiness emanate from being created by God. Humans deserve respect not only because of their characteristics and intelligence, but also as a result of being created in the “image of God.” These two features, being created by God and embodied in the “image of God” give rise to human beings’ uniqueness, significance, and responsibilities and elevate each individual spiritually in a responsible manner when they follow in God’s path of being just, merciful, and caring. In contrast, individuals are diminished and viewed as irresponsible when they exert their independence and autonomy by engaging in activities that are not within the guidelines set out by God.

 There are many examples in the Talmud and in Midrash that discourage the use of technologies that infringe on human dignity. BT Berachot 19b teaches that “Great is human sanctity, so much so that it overpowers a prohibition of the Bible.” In halacha, the sanctity of human beings affects the limits of human experimentation. Numerous Talmudic statements condemn specific human experimentations because they infringe on the sanctity of human dignity, for example BT Bechorot 45a. One could conclude from these examples that, in fact, human dignity may override the potential to save a human life – see BT Mo’ed Qattan 17b; Jerusalem Talmud Shabbat, 14. These are situations in which the Rabbis institute prohibitions to protect human dignity and sanctity even when it prevents healing a person.[31]

These examples also underscore the principle that scientists must evaluate and consider medical and social risks associated with any emerging technology. Application of new technology is not a simple matter and not all technology should be introduced to society. Technology that can lead to social upheaval and destruction should not be pursued, even though there may be medical benefits. All moral/halachic scientists must consider why they are doing specific experiments on animals or human beings and whether these experiments violate human dignity or whether they introduce technology that could pose serious risks or dangers to society.


Often, science fiction of yesteryear emerges as the clinical medicine of today. Here some of the exciting potential applications of stem cell research have been outlined, as well as severalhalachic challenges with which rabbinical authorities are currently dealing or will have to deal in the near future. The process of understanding new technological advancements is not simple, and often rabbinical authorities have to acquire a thorough understanding of the underlying science before determining the halachic ramifications. Rabbi Shlomo Zalman Auerbach used this approach in his analysis of halacha and technology,[32] when he wrote his classic work, Meorei Esh, published in 1935, on the issue of using electricity on Shabbat.

In addition, international conferences that bring together rabbis and scientists can help create an important platform for education and dialogue in exploring and examining the interface between emerging biotechnologies and Jewish law. It is hoped that this paper on stem cell technology and cloning will assist the rabbinical authorities in understanding the scientific principles that underscore these new technologies and facilitate the formulation of accurate and appropriate halachic responses.

Acknowledgements: This paper was written in commemoration of Chayah Pessa Loike-Schulman, Sassa Faga Stoltz, and Rebbetzin Shifra Tendler whose families suffered their losses. The authors would also like to thank all the grandchildren of Mrs. Loike and Mrs. Stoltz who reviewed this manuscript.


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[1]. See Ramban’s commentary on Genesis 1:26 and 1:28 and Sefer hahinnuchmitzva 2.

[2]. L.G. Griffith and G. Naughton, “Tissue Engineering – Current Challenges and Expanding Opportunities,”  Science 295/5557 (February 8, 2002): 1009-14.

[3]. C. Clavel and C.M. Verfaillie, “Bone-Marrow-Derived Cells and Heart Repair,” Current Opinion in Organ Transplantation 13/1 (February 2008): 36-43.

[4]. S.J. Chen, C.L. Kao, Y.L. Chang, C.J. Yen, J.W. Shui, C.S. Chien, I.L. Chen, T.H. Tsai, H.H. Ku and S.H. Chiou, “Antidepressant Administration Modulates Neural Stem Cell Survival and Serotoninergic Differentiation through bcl-2,” Current Neurovascular Research 4 (February 2007): 19-29.

[5]. R.H. Miller and L. Bai, “Cellular Approaches for Stimulating CNS Remyelination,” Regenerative Medicine 2/5 (September 2007): 817-29.

[6]. Q. Zhou, J. Brown, A. Kanarek, J. Rajagopal and D.A. Melton,  “In vivo Reprogramming of Adult Pancreatic Exocrine Cells to β-cells,” Nature 455 (2008): 627-632.

[7]. Science 322 (2008): 1450.

[8]. K.L. Johnson and D.W. Bianchi, “Fetal Cells in Maternal Tissue Following Pregnancy: What are the Consequences?” Human Reproduction Update 10/6 (November-December 2004): 497-502; D.W. Bianchi and N.M. Fisk, “Fetomaternal Cell Trafficking and the Stem Cell Debate: Gender Matters,” Journal of the American Medical Association 297 (2007): 1489-1491.

[9]. J. Chamberlain, T. Yamagami, E. Colletti, N.D. Theise, J. Desai, A. Frias, J. Pixley, E.D. Zanjani, C.D. Porada and G. Almeida-Porada, “Efficient Generation of Human Hepatocytes by the Intrahepatic Delivery of Clonal Human Mesenchymal Stem Cells in Fetal Sheep,” Hepatology 46/6 (December 2007): 1935-45.

[10]. www.timesonline.co.uk/tol/news/uk/science/article4276551.ece.

[11]. National Academy of Sciences, Guidelines for Human Embryonic Stem Cell Research, National Academy of Sciences (2005). 

[12]. D. Eisenberg, “Is the Destruction of Preexisting Pre-Embryos Permitted for Stem Cell Research?” www.aish.com/societyWork/sciencenature/Is_Stem_Cell_Research_Ethical$.asp; Y.A. Breitowitz, “Stem Cell Research,” http://mysite.verizon.net/jialpert/Judaism/JewMedEthics.htm.

[13]. www.rabbis.org/news/article.cfm?id=100553.

[14]. BT Sanhedrin 110b states an opinion that at conception a fetus can be worthy of receiving a portion in the “world to come” (see Rashi).

[15]. In fact, one could speculate that the statement in BT Menahot which compares the giving of the Torah to Moshe with early embryological development is even more profound. There is a fundamental difference in embryological development between the period of conception until forty days and the period of gestation post forty days. From conception until forty days of gestation there is a stepwise order where the embryonic cells and organs are sequentially developed. After forty days of gestation, most organs of the fetus have developed their elementary structures and the fetus is primarily programmed for overall organ growth and development in a process where all the organs are simultaneously growing and developing together. This is analogous to learning Torah. Teaching a child Torah requires an educational program in which is a set order and sequence to study the three basic elements of Torah. First, the child is taught chumash, then Mishna, and then gemara. This is analogous to the first forty day period of fetal development during which there is a programmed sequence to develop the three main components of the fetus: the ectoderm, endoderm, and mesoderm. The next phase of Torah learning occurs in adulthood and involves dividing one’s time equally between the three areas of Torah (tanachgemara, and halacha – see Rambam, Halachot limud hatorah, Chapter one). Similarly, after forty days of gestation, most of the rudimentary organs of a fetus develop simultaneously. One could therefore interpret the statement in BT Menahot to analogize and compare fetal development and Torah learning.

[16]. Y.A. Breitowitz, “The Preembryo in Halakha,” http://jlaw.com/Articles/preemb.html.

[17]. Ba’al Halachot Gedolot, ninth century Jewish author of the Halachat gedolot, a prominent work on Jewish law. The authorship of this work is a matter of debate. Some attribute it to Rav Yehudai the son of Shmuel Gaon, who headed the academy in Sura, Babylonia, and lived from approximately 820 through 905, while others claim that it was written by Rav Shimon of Kaira.

[18]. D. Eisenberg, “Stem Cell Research in Jewish Law,” http://jlaw.com/Articles/preemb.html; see also “Abortion: A Halakhic Perspective – Based on a Lecture by Harav Aharon Lichtenstein,” trans. Rav Nathaniel Helfgot, www.vbm-torah.org/halakha/abortion.htm; Tur, Orach Hayim, 517, BT Kettubot 39a; Rabbi Yehoshua Yeshaya Neuwirth, Shemirat Shabbat kehilchato, 36:2.

[19]. The translation is based on http://www.jcpa.org/program%20files/Local%20Settings/Temporary%20Internet%20Files/Content.IE5/Local%20Settings/Temporary%20Internet%20Files/Content.IE5/89V02J2F/www.come-and-hear.com/niddah/niddah_8.html

[20]. Rabbi Auerbach rules that a male child born after a miscarriage within forty days of conception should be redeemed as the firstborn (see also BT Berachot 47a). After three months of gestation, a fetus is considered formed and a baby boy born after such a miscarriage should not be redeemed. However, if the first fetus was found by ultrasound examination to be underdeveloped, the next newborn male should be redeemed as a firstborn. See A. Steinberg, “Medical-Halachic Decisions of Rabbi Shlomo Zalman Auerbach (1910-1995),” ASSIA – Jewish Medical Ethics III/1 (January 1997): 30-43, Nishmat Avraham, Yoreh de’ah, 305:4, and Otzar pidyon haben, chap. 1, note 19.

[21]. See Mishna Yevamot 4:10 and BT Yevamot 42a.

[22]. For a more detailed discussion on this issue see Avraham Steinberg and Fred Rosner, Encyclopedia of Jewish Medical Ethics. (Jerusalem-New York: Feldheim Publishers, 2003), 1-29; and “Abortion: A Halakhic Perspective-Based on a lecture by Harav Aharon Lichtenstein,” note 17 above.

[23]. U. Ullmann, C. Gilles, P. In’t Veld, H. Van de Velde, K. Sermon, M. DeRycke and I. Liebaers, “I. GSK-3 Specific Inhibitor Blocks the Epithelialmesenchymal Transition Process in hESCs Cultured in Feeder-Free Conditions,” Abstracts of the 23rd Annual Meeting of the ESHRE, Lyon, France, July 1-4, and Nature 452/913 (24 April 2008), doi:10.1038/452913a; published online 23 April 2008.

[24]. Nishmat Avraham, vol. 4, Even haezer 1:3.

[25]. R.V. Grazi and J.B. Wolowelsky, “Parenthood from the Grave,” The Jewish Spectator 65:4 (Spring 2001, Aviv 5761).

[26]. These commandments include bikkurim, orla, and kil’ayim. On the Jewish holiday of Shavuot Jews would bring the first fruits (bikkurim) to the Temple in Jerusalem. The bikkurimwere brought from the Seven Species for which the Land of Israel is praised: wheat, barley, grapes, figs, pomegranates, olives, and dates. At the Temple, each farmer would present hisbikkurim to a priest (kohen) in a ceremony that followed the text of Deuteronomy 26:1-10. According to the Jewish commandment of orla, it is not permissible to use the fruit growing on a newly planted fruit tree during the first three years of the tree’s life. Kil’ayim represents the multi-faceted prohibition of crossbreeding seeds, crossbreeding animals and mixing wool and linen within a garment.

[27]. BT Hullin 63a.

[28]. J.D. Loike and M.D. Tendler, “Revisiting the Definition of Homo Sapiens,” Kennedy Institute of Ethics Journal 4 (2002): 343-50; J.D. Loike, and M.D. Tendler, “Ma adam va-teda-ehu: Halakhic Criteria for Defining Human Beings,” Tradition 37/2 (Summer 2002): 1-19.

[29]. Ibid.

[30]. M. Isserles, Shulhan aruch (New York: Grossman, 1954), Section Even haezer 5:14 [Hebrew].

[31]. M. Soloveichik, Tradition 38/1 (2004):11-19.

[32]. Steinberg, “Medical-Halakhic Decisions of Rabbi Shlomo Zalman Auerbach (1910-1995),” see note 20 above.

Prof. Moshe D. Tendler

Prof. Rabbi Moshe D. Tendler is professor of biology and Rabbi Isaac and Bella Tendler Professor of Jewish Medical Ethics at Yeshiva University. Moshe David Tendler received his B.A. degree from New York University (NYU) in 1947, and a Master’s degree in 1950. He was ordained at RIETS in 1949, and earned a Ph.D. in biology from Columbia University in 1957. He is the rabbi of the Community Synagogue of Monsey, New York. He is a senior Rosh Yeshiva at Yeshiva University's RIETS and Professor of Biology at Yeshiva College. He has a Ph.D. in Microbiology and is noted as an expert on Jewish medical ethics and their relationship to Halakha.

Dr. John D. Loike

Dr. John D. Loike is the co-director of Graduate Studies Department of Physiology and Cellular Biophysics and director for Special Projects, Center for Biotethics at Columbia University College of Physicians and Surgeons.