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Judaism and Stem Cell Research

by Yoel Jakobovits

With one spectacular development tumbling over the next in ever more rapid succession, our generation is witnessing the compression of history in the scientific and medical realm just as much as in the geopolitical realm. Indeed, it may well be that in the long term, the direction of humanity and its history ultimately will be affected more profoundly by these scientific and medical developments than even by the current unprecedented global political upheavals.

Medical ethics concentrates largely on the opposite ends of life. For example, the beginning of life questions relate principally to abortion, contraception and conception issues even before birth. At the other end of life, inquiries relate to the management of dying, the moment of death, autopsies and organ harvesting even before death...

This article outlines the essential medical facts pertaining to stem cell Research and therapy, and summarizes the principal approaches in Jewish law which have been proposed thus far. Clearly, given the novelty of these innovations, both the medical and scientific questions as well as Jewish legal answers are in flux, and must be tentative at this point in time.


Every discussion of medical ethics must be governed by the axiom: good ethics -- and good Jewish law -- require good facts.

All the various parts of a plant or tree -- the trunk, branches, leaves and fruits -- develop from the stem. Similarly, all the cells of a living organism develops from precursor cells, known as stem cells.

Mammalian development begins with the union of a male's sperm cell with a female's egg. The resultant cell has the inherent potential to develop into the entire gamut of cells forming the organism. This prime cell divides, within several hours of fertilization, into two identical duplicate cells, each of which retains this broad potential. After several more divisions, by about the fourth day, these cells began to specialize, forming a hollow sphere called a blastocyte, which is composed of an outer and inner layer of cells. Cells of the outer layer are destined to form the placenta and other supporting tissues of pregnancy. The inner layer cells go on to develop into all of the organs and tissues of the developing fetus.

These cells are now somewhat more limited in their potential -- they can give rise to many but not all the types of cells necessary for fetal development. As stem cells "mature" their potential to develop into any kind of human tissue decreases. Soon after, these stem cells undergo further specialization (called differentiation), becoming cells committed to developing into a given line of cells.

Ultimately stem cells develop into "master cells," designed to multiply into specific tissue types. For example, blood stem cells will develop into the various types of blood cells; skin stem cells into the various types of skin cells. Once they reach this level of specialization, they're committed to developing specific tissues.

The cells related to developing the blood are the best understood stem cells. They reside in the bone marrow of all children and adults, and are, in fact, usually present in very small numbers in the circulating blood stream as well. Because red and white cells in the peripheral blood have limited life spans, the stem cells are crucial to maintaining an adequate blood supply in the healthy person...


At present there several sources of stem cells:

- Early human embryos. In general these embryos are developed as a result of couples using in vitro fertilization to conceive a child. The union of sperm and eggs in a petri dish produces many embryos. Implementing them all into the mother's uterus would freeze and a grave danger to her because of the multiple fetuses she would have to carry. Therefore, only a few are implanted; the remaining are leftover or spare. These pre-implanted embryos are a widely used source of stem cells.

- Tissue obtained from aborted fetuses.

- Cells obtained from the umbilical cord.

- Using somatic cell nuclear transfer (SCNT), an adult cell's gene-containing nucleus can be combined with an egg from which the nucleus has been removed. Using special techniques, the resultant cell can be induced to divide and develop as an early stem cell to form a blastocyte from which very potent cells can be obtained. This is the basis of cloning.


Why isolate and develop pluripotent stem cells, that is, stem cells that have the ability to become any human tissue? At the most fundamental level, stem cell research will help enormously in understanding the complex events of early mammalian development. Secondly, such research could dramatically change the way in which drugs are developed and tested. Specific healthy and diseased cell lines could be exposed to specific drugs, largely obviating the need for much more dangerous and expensive human testing.

The most far-reaching applications would come in the area of cell therapies. Thousands of people are on waiting lists for organ transplants. Because the supply of donors is much smaller than the number of waiting patients, many patients will die of their illnesses before suitable donors can be found... Ultimately it is hoped that stem cells could be stimulated to develop into a source of replacement cells to create banks of transplantable human tissue. There is already reason to believe that this will be possible in replenishing the diseased or absent brain cells caused by Parkinson's or Alzheimer's diseases, strokes, spinal cord injuries, various heart diseases, diabetes, and arthritis.


We begin the outline of the Jewish legal approach to stem cell research by stressing some general overarching principles. In contrast with other religions, Judaism has no problem with "playing God," provided we do so according to His rules as expressed by authentic Jewish legal mandate. Far from being shunned, "playing God" in the Jewish tradition is, in fact, a religious imperative: the concept of emulating God is implicit in the mandate to heal and provide effective medical relief wherever possible. Of note, the only two "professions" ascribed to God Himself are those of teaching and healing. By teaching and/or healing, we fulfill the obligation to "play God." There's no reason that microscopic manipulation of a faulty genetic blueprint should be any different than surgical manipulation of a defective macroscope -- that is, visible to the unaided eye -- tissue or organ. Normative Jewish law sanctions -- nay, encourages -- medical intervention to correct both congenital and acquired defects, and makes no distinction between stem and somatic (body) cell tissues.

The crucial distinction here is between the permissible act of correcting a defect and the forbidden act of attempting to improve on God's creations (generally proscribed by the laws of cross-breeding). For example, it would be permitted, were it possible, to correct the genetic defect which leads to Down's syndrome, but manipulating genes to produce a "perfect-bodied" six-footer with blue eyes would be prohibited.

There would, therefore, be no Jewish legal problem with using stem cells derived from adult tissue. Similarly, it would appear that using cells from umbilical cord tissue would be permissible. A rather minor concern here might be the following: May one have umbilical tissue collected and frozen so that the cells will be available in case one requires stem cell therapy sometime in the future? Is this degree of effort, in trying to ensure one's health, appropriate or excessive?

While there are few Jewish legal objections to deriving the stem cells from adult or umbilical cord tissue, the problems arise, however, with deriving stem cells from the embryonic tissue.

Post-implantation embryonic tissue (that is an embryo already implanted into the uterine wall) is after all, an early fetus; clearly no sanction would be given to aborting a fetus in order to obtain stem cell tissue. Even were fetal tissue necessary to provide life-sustaining therapy for a patient, no sanction would be given to sacrifice an innocent fetus even in the interest of saving another life. The only exception to this rule is the obligation to forfeit the life of the "non-innocent" fetus when its continued existence constitutes a danger to its mother by virtue of the fetus's pursuer ("rodef") status.

Even fetal life before the 40th day of gestation -- which is considered "mere water" -- could not be aborted in order to obtain stem cell tissue. Prior to 40 days, a miscarried fetus does not trigger birth-related purity issues, and therefore is of lesser status than a more mature fetus. (There is a large body of rabbinical writings regarding the 40-day status of a fetus.)...


The prime source of embryonic stem cell tissue is embryos that have not been implanted into the uterine wall. As discussed above, they are usually the "by-products," spare embryos left aside during in vitro fertilization in order not to dangerously overload the mother's uterus. The Jewish legal status of these spare, non-implanted embryos is somewhat unclear. Some rabbinical opinions suggest that in addition to the 40-day milestone, an embryo doesn't reach fetal status until it is implanted into the uterus. Prior to that, while still in a petri dish, or other artificial medium, it cannot develop into a viable fetus. Therefore such early embryos have no real life potential at all and they're not considered alive. Consequently, there would be no Jewish legal opposition to disposing of them, researching on them, or deriving stem cell tissue from them.

The status of pre-implantation embryos has another potentially important Jewish legal consequence. Pre-implantation genetic diagnosis (PGD) offers a promising approach to prevent the birth of genetically defective children. By studying embryos before implantation into the uterus, it is possible to identify those defective genes. By selecting only genetically intact embryos for implantation, the development of genetically defective fetuses would be avoided. Assuming the pre-implanted embryo has not reached the level of a fetus, Jewish legal sanction may be possible.

The ethical issues raised by stem cell research and therapy are, of course, not only of interest to Jews. In an unprecedented national broadcast, President Bush defined some fairly restrictive regulations. Just recently the administration argued strongly in favor of banning all research into human cloning. Evidently the crossroads of medical science and the generation of life itself raises fears and genuine concern in the minds of many thinking people.

It appears that Jewish legal concerns may be more permissive than is generally understood. Clearly, it behooves us, as Jews, to avail ourselves of whatever Torah and scientific knowledge we can -- not only as we try to find the Jewish legal guidance for ourselves, but perhaps equally importantly -- as we strive to fulfill our national mandate to be a Light Unto the Nations -- to help shed light on these vexing issues for society at large.

The author is on the staff of Johns Hopkins University School of Medicine in Baltimore, MD.

Article reprinted with permission from Jewish Action magazine (Summer 2002), published by the Orthodox Union

Presented in cooperation with Heritage House, Jerusalem. Visit



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