Humanity of the Embryo, Part 2

Mr Frank’s objections against valuing the embryo as a human person included an historical analysis that, according to him, makes the 1869 proclamation of Pope Puis IX a complete novelty.  We saw in our last post that the intellectual history of Christian thinking on the unborn will not support this objection.  However, Frank’s objections also extend to Scripture, and modern developmental biology.

“There are no Scriptures on the matter,” writes Frank.  Scripture does not mention blastocyst-stage embryos.  The people who wrote down the words of Scripture did not have the means to observe such a small organism, and therefore, it is anachronistic to expect them to mention it.  having said that, Scripture is not unconcerned about the unborn.  Psalm 139:13 states:  “You have knit me together in my mother’s womb.”  This verse does not mention when the entity within the womb becomes a human person (James C. Peterson, “Is the Human Embryo a Human Being?” in God and the Embryo (Washington DC, Georgetown University Press, 2003).  However, it does say that God is intimately involved with the formation of the Psalmist’s body while he is in the womb.  One of the stages of that knitting is the blastocyst stage embryo.  If God is knitting your body together, stage by stage, bit by bit, then how legitimate is it to intervene and stop than process?  If the answer to this question is that it is not legitimate, then did not your humanity begin when the process of knitting together began?

Another Scripture is Jeremiah 1:5:  “Before you were in the womb I knew you, before you were born I set you apart.”  Once again, James Peterson points out that this verse does not mention when the prophet became a human person.  According to Peterson, this verse only states that God foreknew the prophet Jeremiah before he was in the womb of his mother.  To read more into it would suggest that the verse teaches preexistence, which is absurd.  Peterson has a point, but there is another point that modern embryology might make.  Human development begins in the oviduct and only moves into the womb after fertilization, conception, the first several cleavages, cavitation, and only then does the embryo enter the womb and implant into the endometrial layer of the uterus (about five days after fertilization).  Therefore, Jeremiah could be referring to that period of development before the embryo moves into the uterus.  If this is the case, then Jeremiah 1:5 certainly teaches that the embryo is foreknown by God and set aside by Him for a sacred purpose.  If this is too much of a stretch, then the verse definitely says that the developing unborn are particularly designated and set aside by God for specific purposes.  If this is the case, then aren’t the earlier stages as valuable as the later stages?

Other verses, suggest the value of he unborn.  For example in the Gospel of Luke, the in utero John the Baptist moves in response to the proximity of Mary the mother of Jesus, who is pregnant with the Savior

When Elizabeth heard Mary’s greeting, the baby leaped in her womb, and Elizabeth was filled with the Holy Spirit. In a loud voice she exclaimed: “Blessed are you among women, and blessed is the child you will bear! But why am I so favored, that the mother of my Lord should come to me? As soon as the sound of your greeting reached my ears, the baby in my womb leaped for joy.

Again, we do not know the developmental stage of Jesus in this verse, therefore, it is impossible to ascertain the exact moment that a developing human being becomes a human person.  Nevertheless, the proleptic movement of the fetal John the Baptist, shows that the unborn are regarded with worth for not only what they will be but for what they presently are.  Thus while Scripture is not definitive in this discussion its message is highly suggestive, and to dismiss it completely is illegitimate.

Finally, Mr Frank states that “Modern genetics and biochemistry raise doubt about called a zygote or blastocyst a human being.”  Why?  According to John Frank because it has no brain – “If left to develop it will become human life.”

This view is similar to that of Michael Gazzaniga, a member of the President’s Council on Bioethics (Robert George and Christopher Tollefson, Embryo, New York:  Doubleday, 2008).  Gazzaniga uses the criterion of brain death to argue that the embryo is not a human person since it does not have a brain.  Brain death is the time at which an individual can be used as an organ donor.  Therefore, since this criterion is used for adults and children, it should be equally applied to the embryo.

This suffers from several problems.  First of all irreversible brain death destroys the capacity of an organism to operate as a self-integrated entity.  A brain-dead person is a corpse and is not a unitary organism at all.  The embryo, however, is an integrated organism that will form a brain at some later time.  While a corpse is dead, the embryo is very much alive.  It has the full potential to make a brain (Embryo, pp. 133-134).  This also leads to another question:  Is there anything that can grow a human brain that is not human?

This argument also makes another crucial mistake.  It assumes that there is a symmetry between a brain-dead corpse and an early human embryo.  The brain-dead corpse had a life and it is over.  However the early embryo’s life is in the present and it also fully ahead of it.  Human beings in whatever developmental state they might be are part of an enduring being that begins its journey as a single-celled zygote.  They are not potential persons, but persons with potential.  Therefore, the fact that the early embryo does not have a brain is no reason to snuff its life out, since that is exactly what we expect at these early stages.

If Mr. Frank means that higher cortical functions are what constitutes a person, then he has thrown in his lot with David Boonin whose book A Defense of Abortion (New York:  Cambridge University Press, 2002) uses organized cortical brain activity as the criterion for a right to life.  Francis Beckwith’s Defending Life (New York:  Cambridge University Press, 2007) ably critiques Boonin’s criteria.  Beckwith uses two examples, the problem of the indoctrinated slave and problem of creating brainless human beings, to illustrate the problem with Boonin’s criterion.

The indoctrinated slave problem uses an example of a slave who has been indoctrinated to believe that she has no innate desires or interests.  Since Boonin uses the desires and interests as the yardstick for higher cortical function, this example works quite well.  According to Boonin, this person should lack a right to life.  Nevertheless, we would think that if this slave is killed, an injustice was done because this person’s interests and desires never came to fruition.  Boonin might respond that this indoctrinated slave has a right to life because she had an ideal desire to live.  However, this means that the slave is “a certain sort that ought to desire a right to life even when he does not actually desire a right to life” (Defending Life, p. 148).  This means that Boonin’s desire argument is flawed.

Secondly, Beckwith uses an example of “Uncle Jed” who has experienced a severe accident that has altered his memories such that he no longer remembers who he is, what his history was, where he came from, or what his interests and desires are or might have been.  Is it right to kill Uncle Jed?  According to Boonin, the answer should be yes.  However, if this is wrong, then “what precisely is doing the moral work in this judgment?” (Defending Life, p. 137).  His past?  But that will never come back.  Therefore, Boonin’s view does not work either, and Frank cannot depend on it.

Finally, Frank asserted that modern genetics and biochemistry argue against the personhood of the embryo.  But this is demonstrably false. Genetics shows that when the embryo comes into existence and the egg ceases to exist in the moment the egg and sperm nuclei fuse (syngamy). This process ends the event known as conception and the process of making a neonate has begun. The organism is a genetically new creature that beings the embryonic part of its life, transitioning to the fetal stage, to the neonate stage and so on. Development is continuous and seamless and defies providing a point where we can say that the embryo becomes a human person. Thus the life of the human person begins at the completion of conception.These are the conclusions of biochemistry and genetics. Thus embryos are human persons at their earliest stages of life.

The Humanity of the Early Embryo, part 1

John L. Frank writes in a Wall Street Journal Letter to the Editor that the “early-term abortion is not genocide.”  To read the entire letter, go here:  Mr Frank’s letter is about the University of Notre Dame’s invitation to President Barak Obama to deliver the commencement speech at this years graduation.  In particular, Mr. Frank is responding to William McGurn’s op ed article on the matter (see  His reasons for not regarding the early human embryo as a human person represent some of the contemporary thinking on this issue.  I would like to demonstrate why I think his reasons fail and the early human embryo should be treated as a full member of the human species with the right to not be harmed.

Mr. Frank begins by asserting that the Catholic Church did not regard the embryo as a human person for most of its recorded history.  Instead, according to Mr. Frank, early church leaders like Augustine, Aquinas, Pope Gregory XIV endorsed Aristotle’s concept that a new person does not exist until the first noticeable movements in the womb, which is popularly known as “quickening.”

Problems begin right away.  Frank depends upon the historical analysis of an Anglican scholar named G. R. Dunstan who claimed that absolute protection for the embryo in Christian thinking is a creation of the nineteenth century. This conclusion is completely without merit.  Dunstan’s conclusions are called into question by the work of David Albert Jones, whose book The Soul of the Embryo (London, UK:  Continuum, 2004), shows that the protection of the embryo at all stages is actually the original understanding of the Christian Church.

The earliest witnesses to the Christian ethical tradition regarding the unborn come from a variety of works. The earliest work is the Didache, otherwise known as the Teaching of the Twelve Apostles. This work dates to the first century AD, and states:“You shall not kill a child by abortion nor kill it after it is born (Didache 2:2). The second century Letter of Barnabus, makes the same statement (19.5).Both documents forbid abortion at any stage of development.

In AD 177, the Christian leader Athenagoras wrote in a letter to the Roman Emperor Marcus Aurelius that “those women who use drugs to bring about an abortion commit murder.”Athenagoras also stated that those who obtain an abortion would “have to give an account to God” for what they have done (A Plea for Christians 35.6).  This letter rebuts a rather malicious claim against Christians; namely that Christians practiced child sacrifice. Athenagoras invalidates this urban legend when he states that Christians view both abortion and infanticide as wrong. Twenty years later, the Christian apologist, Tertullian, would make a similar argument:“for us murder is once for all forbidden; so it is not lawful for us to destroy even the child in the womb” (Apology 9:8).

In the early third century, Minucius Felix pointed out that it was pagans and not Christians who treated the unborn with indifference.

It is among you that I see newly-begotten sons at times exposed to wild beasts and birds, or dispatched by the violent death of strangulation; and there are women who by the use of medicinal potions, destroy the unborn life in their wombs, and murder the child before they bring it forth (Octavius 30:2).

During the second or third century, several works pointed out the threat of divine judgment for procuring an abortion.  For example, the Apocalypse of Peter and Apocalypse of Paul both portrayed men and women having to face the children they had aborted. The threat of judgment displayed abortion both as a crime against the child and God. It must be emphasized that abortion was never viewed as an unforgivable sin, since Jesus Christ brought reconciliation for sinners.Judgment awaited those who did not accept the forgiveness available in Jesus Christ.

At the turn of the fourth century, Lactantius wrote that Christians not only were forbidden to kill in ways that were illegal and socially unacceptable, but also in ways that were tolerated and esteemed in the pagan world. This was the case with the strangulation of infants and the killing of unborn children who had yet seen the light of day (Divine Institutes 6:20).

There is also evidence from sermons and letters from the Early Church that particular Christians failed to live up to their high moral principles and participated in abortions.Such instances were met with condemnation.A few examples will suffice. Cyprian of Carthage accused the schismatic priest Novatus of inducing a miscarriage by kicking his wife with his heel (Letter 52 to Cornelius). Similarly, Hippolytus accused Callistus (then bishop of Rome) of recognizing mismatched marriages between high-born women and men of low social status that resulted in abortions:

Women who were reputed to be believers began to take drugs to render themselves sterile, and to bind themselves tightly so as to expel what was being conceived, since they would not, on account of relatives and excess wealth, want to have a child by a salve or by any insignificant person (Refutation of all Heresies 9.7).

In the fourth century, the practice of abortion became endemic among Christians.Instead of condoning it or using an argument that distinguished between killing formed and unformed fetuses, Christian leaders condemned it. For example, Jerome wrote

I cannot bring myself to speak of the many virgins who daily fall and are lost to the bosom of the church, … You may see many women widows before wedded, who try to conceal their miserable fall by a lying garb. Unless they are betrayed by swelling wombs or by the crying of their infants, they walk abroad with tripping feet and heads in the air. Some go so far as to take potions, that they may ensure barrenness, and thus murder human beings almost before their conception. Some, when they find themselves with child through their sin, use drugs to procure abortion, and when (as often happens) they die with their offspring, they enter the lower world laden with the guilt not only of adultery against Christ but also of suicide and child murder (Letter 22:13).

Notice that Jerome condemned the practice regardless of the age of the unborn.  Similarly Ambrose of Milan lamented that “even the wealthy, in order that their inheritance may not be divided among several, deny in the very womb their own progeny” (Hexameron 5.18.58).  John Chrysostom confronted men in his own congregation (married and single) for going to prostitutes.Such men were guilty of not only adultery, but if she became pregnant and procured an abortion, they were now doubly guilty of murder as well. Chrysostom stated that “even if she does the deed, you are the cause of it” (Homily 24 on Romans).

Other Christian teachers and bishops emphasized the harmful character of abortion. Clement of Alexandria drew out the dehumanizing effects of abortion.  According to Clement, those who obtained an abortion destroyed not only a child, also “destroy all humanity” (The Teacher 2:10).  Augustine of Hippo regarded abortion not only as an attack on human life but also as an attack on marriage.If a married couple agreed to abort their child, they were not spouses at all (On Marriage and Concupiscence 1.17).  John Chrysostom called abortion “something worse than murder” (Homily 24 on Romans).  His reason for this was that it turned the blessed act of childbearing into an occasion for killing and turned the womb, a chamber of new life, into a “chamber for murder” (ibid.).

Several Christian teachers referred to abortion at “parricide.”  Since parricide typically refers to the killing of a parent, this usage is rather strange since abortion is the killing by a parent.  However, parricide dredged up a particular horror in the Roman mindset, since it represented an attack upon authority.  Minucius Felix, Cyprian, Lactantius and Ambrose inverted this sense and associated the horrors of parricide with an attack upon the weak and powerless.  This reflects the Christian mindset with respect to abortion.

Since abortion was considered a heinous crime, and since Jesus’ death on the cross provided the means of forgiveness for those who had procured an abortion, what did the Church recommend for some who had had an abortion?  The fourth century is the first evidence of a codified attempt to restore those who had had an abortion.  In AD 305, the Council of Elvira in Spain, 81 canons were issued that dealt with issues like celibacy for the clergy and the administration of the sacraments.  Two of these canons dealt with abortion.

Canon 63:If a woman becomes pregnant by committing adultery while her husband is absent, and after the act she destroys the child, it is proper to keep her from communion until death, because she has doubled her crime.

Canon 68:If a catechumen becomes pregnant by committing adultery and after the act she destroys the child, she can be baptized only at the end of her life.

The canons on abortion were quite severe, but were no more severe than canons on other subjects accepted at the synod.

After AD 313, Emperor Constantine declared a policy of religious toleration. Two years later, a council of bishops met at the council of Ancyra in the Roman province of Galatia. One canon mentioned abortion.

Canon 21:  Concerning women who commit fornication, and destroy that which they have conceived, or who are employed in making drugs for abortion, a former decree excluded them until the hour of death, and to this some have assented.Nevertheless, being desirous to use somewhat greater leniency, we have ordained that they fulfill ten years of penance.

Similar attitudes were provided for other crimes as well. This was upheld by the first great ecumenical council at Nicaea in AD 325, “in the case of anyone whatsoever who is dying and seeks to share in the Eucharist, the bishop upon examining the matter shall give him a share in the offering” (Nicaea, canon 13).  Ancyra also included the man responsible for the events that led to the abortion.

In AD 375, Basil the Great wrote a series of letters that significantly influenced church legislation. Of these canons of Basil the Great, two are concerned with abortion.

Canon 2: The woman who purposely destroys her unborn child is guilty of murder.With us there is no nice enquiry as to its being formed or unformed …The punishment, however, of these women should not be for life, but for the term of ten years.

Canon 8: Women also who administer drugs to cause abortion, as well as those who take poisons to destroy unborn children, are murderesses.

Basil asserted that those who had an abortion or administered the drugs to induce the abortion were guilty of murder.  While there was disagreement as to the duration of the penance for such an act, there was no question as to the criminality of the act.  According to Basil, abortion is murder and it should be treated as such.  For the purpose of penance, Basil rejected the distinction between the unborn being “formed” or “unformed.”  This distinction was not discussed at the Councils of Elvira and Ancyra, but Basil seems to have heard of it.

This distinction between the formed unborn and the unformed unborn was already present in the Greek translation of the Hebrew Old Testament, which was known as the Septuagint and the first-century Jewish philosopher Philo of Alexandra.However, this strand of thinking regarding the unborn did not enter Christian thinking until the fourth and fifth centuries.

The late fourth century work the Apostolic Constitutions, drew on earlier material, and the seventh book closely followed the Didache. However, the Apostolic Constitutions added this gloss: “You shall not kill a child by abortion nor kill it after it is born.For everything that is shaped and has received a soul from God, if killed, shall be avenged, as having been unjustly destroyed” (Apostolic Constitution 7.3). Despite its name, this work was not apostolic and was rejected as a work of authentic apostolic authority by the Council of Trullo in AD 692.Other patristic sources that mentioned the distinction between killing a formed and unformed fetus were Jerome (Letter 121.4), Augustine’s commentary on Exodus (Questions on Exodus 80), and the Pseudo-Augustinian work Questions on the Old and New Testaments (23).

The Council of Trullo was influenced by the canons of Basil and added, in Canon 91: “Those who give drugs procuring an abortion and those who receive poisons to kill the fetus are subjected to the penalty of murder.” This canon was incorporated into the great canon legal collection of Photius the nomocanon in AD 883. The canons of Elvira, Ancyra and Trullo continue to inform canon law in the Orthodox Church to the present day. According to David Jones, at no point in its ethical or legal history has the Eastern Orthodox Church embraced an ethical or legal distinction between early and late abortion.

Two other councils produced results that influenced the debate over the unborn.First, the Council of Ledira in Spain in AD 524 distinguished between those who sinned by adultery, even if that sin led to an abortion and those who gave the poisons (venefici) to produce and abortion. The penance for the first offense was seven years, but for the last it lasted a lifetime.This reflects influences from Roman criminal law. The second was the Second Council of Braga, which met in Portugal in 572.At this council Martin of Braga used canons from the previous Eastern councils, but he altered the canon on abortion in his translation to include those who sought contraception with those who desired infanticide and abortion (Braga, canon 78). There had been some mention of this in previous works.Jerome (Letter 22:13), Caesarius of Arles (Sermon 1:12) and the Jewish Talmud regarded chemical sterilization with tremendous disdain; since it prevented the lives of those who might have been born (the Talmud condemns the spilling or wasting of the male seed, but allows women to take sterilizing drugs). Thus the Second Council of Braga followed Jerome, Caesarius, and Martin in regarding taking drugs that induce abortion or sterility as part of the same crime, since in many cases the same drugs were used to achieve either end.

Developments in church discipline also reflected varying perspectives on the embryo.One of the earliest Irish penitentials dates from the early sixth century and is known as the Finnian. This penitential treats abortion as type of poisoning (maleficium, a category taken from Roman law). The Finnian imposes a penance of six months bread and water plus two years abstinence from meat and alcohol for the person who caused the abortion. There was no variation according to the age of the embryo.However, in a later tradition from the late seventh century Irish canons, the Bigotian Penitential, and the Old Irish Penitential of the early ninth century distinguished penances for abortion according to the age of the embryo or fetus. The Old Irish Penitential gave three and a half years penance for abortion after the pregnancy had become established, but seven years if the flesh had formed and fourteen years if the soul had entered the unborn child. This three-stage process of development regarded he embryo as unformed “like water” in the first stage, with flesh but without a soul in the second stage, and ensouled and formed in the third stage. This three-fold pattern is not found in the Septuagint or Aristotle, but in Hippocrates, and is paralleled in the Talmud and Koran (which was influenced by Talmudic traditions). Thus for these writers, abortion was not true homicide if committed before the signs of movement or “quickening,” but was still regarded as a serious sin.

The first Anglo-Saxon penitentials were written in the seventh century (Theodore, Archbishop of Canterbury had much to do with their production). These made a distinction in penance if the embryo was older or younger than forty days old. The penance was more severe if the embryo was killed after 40 days of life (three years, the same as a homicide), and less severe if the embryo was less than forty days old when destroyed (only one year of penance).

These Celtic and Anglo-Saxon penitentials came into conflict with the older models of penance used in Spain. In AD 589, the Council of Toledo condemned the new penitentials as too lenient.Nevertheless, the Anglo-Saxon and Celtic models gained ascendancy in the centuries to come, and by the time of the eleventh century, there were three models for treating abortion:  1)  Abortion was homicide regardless of the stage of the pregnancy; 2) Abortion was homicide only after ensoulment; 3) Both contraception and abortion were homicide regardless of the stage of the pregnancy.

The first option represents the dominant tradition from the Didache to the Council of Trullo, which was reaffirmed in the West in AD 848 at the Council of Worms (canon 35).  The second and third options became increasingly influential from the late fourth century on.  The trouble was that the same authors could be used to support multiple options.  For example, Jerome could be used to support either option one, two or three, depending if you were reading Letter 22 or 121.

As an example of the confusion that reigned, Ivo of Chartes cited Jerome’s Letter 121.4, Augustine’s Questions on the Heptateuch 2.80, and Pseudo-Augutine’s Questions on the Old and New Testaments 23 in his Decretum to support the notion that abortion before ensoulment of the unborn was not homicide.  These same texts were used by Gratian (Concordance of Discordant Canons) and Peter Lombard (Sentences) in the twelfth century.  These two works constituted the foundation of church law and theology for the whole Middle Ages.  In the thirteenth century, the Dominican Raymond of Pennafort wrote a new canon law for Gregory IX, called the Decretals.  He used Ivo and Gratian and followed the Decretum of Burchard of Worms with regards to contraception and abortion (Decretals V, tit. 12, can. 5).  However, Raymond also included a decision by Pope Innocent III with regards to a monk who had caused a pregnant woman to miscarry while “acting with levity” (Decretals V, tit. 12, can. 20).  The pope decreed that the monk should be suspended only if the child was living (vivificatus).  This produced a contradictory situation in which the canons said one thing but a ruling from the same collection of canon law said a completely different thing.

This confusion continued.  Magister Rufinus, who died in AD 1190, claimed that killing an embryo before ensoulment carried the guilt of homicide but not the act of homicide.  Conversely, Roland Bandinelli, who died in 1181, asserted that abortion was homicide regardless of the age of the pregnancy because the intent was the same on both cases, a position that was adopted by the Franciscan theologian Bonaventure (d. 1274).  Thomas Aquinas held that contraception and early abortion were second only to homicide.  Aquinas wrote in Summa Contra Gentiles:  “after the sin of murder, this sort of sin seems to hold the second place, whereby the generation of human nature is precluded” (SCG III, Q.122).  Aquinas taught similar things in his Commentary on the Sentences IV, D. 31 & Q.4.

Abortion at any stage was condemned and the imposition of excommunication for abortion was upheld by local synods in Riez in 1234, Lille in 1288, Avignon in 1326, and Lavaur in 1368, but the proscribed penances continued to reflect the two-tiered system.

In 1588, in a decree called Effraennatum, Pope Sixtus V called upon the power of excommunication in an attempt to restrain the growing practice of abortion during the Renaissance.  He included contraception under this ban, since he used the Decretals, V.12.5 as his model.  Three years later, Pope Gregory lifted the scope of this excommunication in his Sedes Apostolicae.  He declared that only abortion of a formed fetus merited excommunication.

Thus the canonical change issued by Pope Puis IX in 1869 that protected the embryo from the moment of its creation until its natural death was not a novel decree, but the restoration of an ancient understanding with regards to abortion and the nature of the unborn.  The Christian church was unique in its defense of the unborn through the time of its development and Pope Pius IX merely returned to the original intent and understanding that the early Church possessed.

Thus Mr. Frank’s historical analysis is quite incorrect.  What about his other points?  The next post will examine his other points.

Induced Pluripotent Stem Cells

Embryonic stem cells might provide the means to heal a variety of physical ailments. However the problem with embryonic stem cells is not necessarily in their use, but in their derivation. In order to make embryonic stem cell lines, human embryos are destroyed.

The following video shows Alice Chen from Doug Melton’s laboratory at Harvard University destroying embryos to make embryonic stem cells:

Now that federal funding is available to not only work with existing embryonic stem cell lines but to MAKE new lines, there is nothing to stop researchers from thawing and (I’m sorry to be so blunt) killing human embryos. Can we have our “cake and eat it too?” Can we have the benefits of embryonic stem cells and not destroy embryos? Perhaps we can.

In 2001, Masako Tada reported the fusion of embryonic stem cells with a connective tissue cell called a fibroblast. This fusion reprograms the fibroblasts so that they behave like embryonic stem cells (Current Biology 11, no. 9 (2001): 1553–8). This suggests that something within embryonic stem cells can redirect the machinery of somatic cells to become more like that of embryonic stem cells. In 2006 Kazutoshi Takahashi and Shinya Yamanaka were able to generate embryonic stem cell lines by introducing four specific genes into mouse skin fibroblasts. These “induced pluripotent stem cells” (iPSCs) shared many of the properties of embryonic stem cells derived from embryos, but when transplanted into mouse embryos, they were not able to participate in the formation of an adult mouse (Cell 126, no. 4 (2006): 663–76). This experiment showed that it is possible to convert adult cells into something that resembles an embryonic stem cell. Could we push adult cells further? In 2007, three different research groups used retroviruses to transfer four different genes (Oct3/4, Sox2, c-Myc and Klf4) into mouse skin fibroblasts and completely transformed them into cells that had all the features and behaviors of embryonic stem cells (Cell Stem Cell 1, no. 1 (2007): 55–70; Nature 448 (2007): 313–7; Nature 448 (2007): 318–24.).

These experiments drew a great deal of excitement, but there were several safety concerns that had to be addressed before iPSCs could be used in human clinical trials.  Scientists used engineered retroviruses to introduce genes into adult cells in order to reprogram them into iPSCs (Current Topics in Microbiology and Immunology 261 (2002): 31-52).  Retroviruses insert a DNA copy of their genome into the chromosomes of the host cell they have infected.  If that viral DNA inserts into a gene, it can disrupt it and cause a mutation.  This can have dire consequences (see Folia Biologia 46 (2000): 226-32; Science 302 (2003): 415-9).  Fortunately this is not an intractable problem.  The conversion of adult cells into iPSCs only requires the transient expression of the inserted genes.  Secondly, scientists have created retroviruses that self-inactivate after their initial insertion (Journal of Virology 72 (1998): 8150-7; Virology 261, (1999).  One laboratory has also discovered a way to make iPSCs with a virus that does not insert into host cell chromosomes (Science 322 (2008): 945-9).  Other researchers have designed ingenious ways to move the necessary genes into adult cells without using viruses (Science 322 (2008): 949-53).  Both procedures avoid the dangers associated with the use of retroviruses.

A second concern involves the genes used to convert re-program adult cells into iPSCs.  One of these genes, c-Myc, is found in multiple copies in human and animal tumors.  Thus increasing the number of copies of the c-Myc gene might predispose such cells to form tumors (Recent Patents on Anticancer Drug Discovery 1 (2006): 305-26; Seminars in Cancer Biology 16 (2006): 318-30). Indeed, the increased ability of iPSCs made by Yamanaka to cause tumors in laboratory animals underscore this concern (Hepatology 46, no 3 (2009): 1049-9).  Several groups, however, have succeeded in making iPSCs from adult cells without the use of the c-Myc gene (Science 321 (2008): 699­-702; Nature Biotechnology 26 (2008): 101-6; Science 318 (2007): 1917–20), although the conversion is much less efficient.  Additionally, several groups have established that particular chemicals, in combination with the addition of a subset of the four genes originally used, can effectively transform particular cells into iPSCs (Cell Stem Cell 2 (2008): 525-8).   Thus the larger safety concerns facing iPSCs have been largely solved.

Finally, patient-specific iPSCs have been made in several labs, even though they have not been used in clinical trials to date.  Here is a short list of some of the diseases for which patient-specific iPSCs have been made:

Amylotrophic Lateral SclerosisScience 321 (2008): 1218­21.

Spinal Muscular AtrophyNature 457 (2009): 277­81.

Parkinson’ DiseaseCell 136, no. 5 (2009): 964­77.

Adenosine deaminase deficiency-related severe combined immunodeficiency – Cell 134, no. 5 (2008): 877­86.

Shwachman-Bodian-Diamond syndrome – Cell 134, no. 5 (2008): 877­86.

Gaucher disease – Cell 134, no. 5 (2008): 877­86.

Duchenne and Becker muscular dystrophy – Cell 134, no. 5 (2008): 877­86.

Huntington disease – Cell 134, no. 5 (2008): 877­86.

Juvenile-onset type 1 diabetes mellitus – Cell 134, no. 5 (2008): 877­86.

Down syndrome – Cell 134, no. 5 (2008): 877­86.

Lesch-Nyhan syndromeCell 134, no. 5 (2008): 877­86.

Thus iPSCs represent an exciting, embryo-free alternative to embryonic stem cells that provide essentially all of the opportunities for regenerative medicine without destroying embryos.