Skin Cells Converted into Placenta-Generating Cells


Yosef Buganim and his colleagues from Hebrew University of Jerusalem have successfully reprogrammed skin fibroblasts in placenta-generating cells.

The placenta is a marvelously complex, but it is also a vital organ for the unborn baby. It supplies oxygen and nutrients to the growing baby and removes waste products from the baby’s blood. The placenta firmly attaches to the wall of the uterus and the umbilical cord arises from it.

The placenta forms from a population of cells in the blastocyst-stage embryo known as trophoblast cells. These flat, outer cells interact with the endometrial layer of the mother’s uterus to gradually form the placenta, which firmly anchors the embryo to the side of the uterus and produce a structure that serves as an embryonic kidney, endocrine gland, lung, gastrointestinal tract, immune system, and cardiovascular organ.

Trophoblast form after an embryonic event known as “compaction,” which occurs at about the 12-cell stage (around day 3). Compaction binds the cells of the embryo tightly together and distinguishes inner cells from outer cells. The outer cells will express the transcription factor Cdx2 and become trophoblast cells. The inner cells will express the transcription factor Oct4 (among others too), and will become the cells of the inner cell mass, which make the embryo proper.

Fetal growth restriction, which is also known as intrauterine growth restriction, refers to a condition in which a fetus is unable to achieve its genetically determined potential size. It occurs when gas exchange and nutrient delivery to the fetus are not sufficient to allow it to thrive in utero. Fetal growth restriction can lead to mild mental retardation or even fetal death. This disease also cause complications for the mother.

Modeling a disease like fetal growth restriction has proven to be very difficult largely because attempts to isolate and propagate trophoblast cells in culture have been unsuccessful. However, these new findings by Buganim and his colleagues may change that.

Buganim and his coworkers screened mouse embryos for genes that support the development of the placenta. They identified three genes – Gata3, Eomes, and Tfap2c – that, when transfected into skin fibroblasts, could drive the cells to differentiate into stable, fully-functional trophoblast cells. Buganim called these cells “induced trophoblast stem cells” or iTSCs.

In further tests, Hana Benchetrit in Buganim’s laboratory and her colleagues showed that these iTSCs could integrate into a developing placenta and contribute to it.

Buganim and his team are using the same technology to generate fully functional human placenta-generating cells.

If this project succeeds, it might give women who suffer from the curse of recurrent miscarriages or other placenta dysfunctions diseases the chance to have healthy babies. Also, since these iTSCs integrate into the placenta and not the embryo, they pose little risk to the developing baby.

This work was published in Cell Stem Cell 2015; DOI: 10.1016/j.stem.2015.08.006.

Skin Cells Converted into Placenta-Generating Cells


Researchers from the laboratory of Yosef (Yossi) Buganim at Hebrew University of Jerusalem have used genetic engineering techniques to directly reprogram mouse skin cells into stable, and fully functional placenta-generating cells called induced trophoblast stem cells (iTSCs).

The placenta forms a vital link between a mother and her baby. When the placenta does not work as well as it should, the baby will receive less oxygen and nutrients from the mother. Consequently, the baby might show signs of fetal stress (that is the baby’s heart does not work properly), not grow nearly as well, and have a more difficult time during labor. Such a condition is called “placental insufficiency” and it can cause recurrent miscarriages, low birth weight, and birth defects.

Placental dysfunction has also been linked to a condition called fetal growth restriction (AKA Intrauterine growth restriction). Intrauterine growth restriction or IUGR is a condition characterized by poor growth of a baby while in the mother’s womb during pregnancy.

How can scientists study the placenta? Virtually all attempts to grow placental cells in culture have been largely unsuccessful.

Buganim and his colleagues have solved this problem. A screen for genes that support the development of the placenta yielded three genes: GATA3, Eomes, and Tfap2c. Next the Buganim team took mouse skin fibroblasts and forced the expression of these three placenta-specific genes in them. This initiated a cascade of events in the cells that converted them into stable and fully functional placenta-generating cells.

These skin-derived TSCs behave and look like native TSCs and they also function and contribute to developing placenta. The Bugamin laboratory used mouse cells for these experiments, but they want to expand their experiments to include human cells to make human iTSCs.

The success of this study could potentially give women who suffer from recurrent miscarriage and placental dysfunction diseases the ability to have healthy babies. The embryo is not at risk from such cells, since iTSCs integrate into the placenta and not into the embryos itself.

See Cell Stem Cell. 2015 Sep 22. pii: S1934-5909(15)00361-6. doi: 10.1016/j.stem.2015.08.006.

Prenatal Stem Cell Treatment Improves Mobility in Lambs With Spina Bifida


UC Davis fetal surgeon Dr. Diana Farmer has been at the forefront of treating spina bifida in infants while they are still in their mother’s womb. Now, Dr. Farmer and her colleagues have used a large animal model system to study the use of stem cells to improve the clinical outcomes of children who undergo these types of in utero procedures.

Spina bifida is a congenital birth defect that results from abnormal development of the spinal cord. During development, the spinal cord, which beings as a tube (the neural tube), is open at both ends, and these ends eventually close. However, if the posterior opening to the neural tube does not close properly, then the developing spinal cord will have severe structural defects. These structural defects adversely affect the nerves that issue from the spinal cord and spinal bifida can cause lifelong cognitive, urological, musculoskeletal and motor disabilities.

Dr. Farmer’s chief collaborator was another UC Davis science named Aijun Wang, who serves as the co-director of the UC Davis Surgical Bioengineering Laboratory.

“Prenatal surgery revolutionized spina bifida treatment by improving brain development, but it didn’t benefit motor function as much as we hoped,” said Farmer, who serves as chair of the UC Davis Department of Surgery and is the senior author of this study, which was published online in the journal Stem Cells Translational Medicine.

“We now think that when it’s augmented with stem cells, fetal surgery could actually be a cure,” said Wang.

Years ago, Farmer and her colleagues showed in an extensive clinical trial called the Management of Myelomeningocele Study (MOMS) that babies who were diagnosed with spina bifida and were eligible for in utero surgery had better outcomes that babies who underwent surgery after they were born. Babies with spina bifida who were operated on in utero had a better chance of walking, and not needing a shunt to deal with the pressure problems in the brain that some children with spina bifida experience (see N. Scott Adzick, et al., New England Journal of Medicine 2011;364(11):993-1004). Even with this study, the majority of the babies who were treated with in utero surgery were still unable to walk. To improve a baby’s chances of walking, Farmer and her collaborators turned to stem cell treatments.

Farmer and Wang combined fetal surgery with a the transplantation of stem cells from human placentas to improve neurological capabilities of babies born with spina bifida. In children, spina bifida can range from barely noticeable to rather severe. Myelomeningocele is the most common and, unfortunately, the most disabling form of spina bifida. In babies with myelomeningocele, the spinal emerges through the back and usually pulls brain tissue into the spinal column, which causes cerebrospinal fluid to fill the interior of the brain. Therefore, such patients require permanent shunts in their brains in order to drain the extra cerebrospinal fluid.

Myelomeningocele
Myelomeningocele

In this study, lambs with myelomeningocele were operated on in utero in order to return exposed spinal cord tissue into the vertebral column. Then human placenta-derived mesenchymal stromal cells (PMSCs), which have demonstrated neuroprotective qualities (see Yun HM, et al., Cell Death Dis. 2013;4:e958), were embedded in hydrogel and applied to the site of the lesion. A scaffold was placed on top to hold the hydrogel in place, and the surgical opening was closed.

Six of the animals that received the stem cell treatment were able to walk without noticeable disability within a few hours following birth. However, the six control animals that received only the hydrogel and scaffold were unable to stand.

“We have taken a very important step in expanding what MOMS started,” said Wang. “Next we need to confirm the safety of the approach and determine optimal dosing.”

Farmer and Wang will continue their efforts with funding from the California Institute for Regenerative Medicine. With additional evaluation and FDA approval, the new therapy could be tested in human clinical trials.

“Fetal surgery provided hope that most children with spina bifida would be able to live without shunts,” Farmer said. “Now, we need to complete that process and find out if they can also live without wheelchairs.”

Human Placenta-Derived Multipotent Cells Modulate Cardiac Injury in Large and Small Animal Models


Placental-derived multipotent cells or PDMCs have been isolated from human term placental tissues. PDMCs have the ability to differentiate into neurons, bone, fat, and liver. Can cells like these help heal a damaged heart?

Men-Luh Yen and his colleagues from the National Taiwan University Hospital, Taipei, Taiwan, have recently published a large study of PDMCs that have examined the characteristics of these cells in culture and in small and large animals.

In culture, when PDMCs are grown with mouse heart muscle cells for eight days that differentiate into cells that look a lot like heart muscle cells.  These cells express the heart-specific gene alpha-sarcomeric actinin.  This is not evidence that PDMCs can differentiate into heart muscle cells, but it is evidence that they differentiate into heart muscle-like cells.  It is possible that these cells might be able to completely differentiate into heart muscle cells with the right signals.

When the culture medium from PDMCs are used to grow human umbilical vein endothelial cells, the human umbilical vein endothelial cells formed blood vessel-like tubes.  This indicates that PDMCs secrete a host of growth factors that induce the formation of blood vessels.  When Yen and his group examined the genes expressed by cultured PDMCs, they discovered that they expressed several growth factors known to induce blood vessel formation, such as hepatocyte growth factor (HGF), interleukin-8 (IL-8), and growth-regulated oncogene (GRO).  When these growth factors were given to cultured umbilical vein endothelial cells, they formed blood vessel-like tubes.  Thus HGF, GRO and IL-6 promote the formation of blood vessels.

When PDMCs were used to treat the heart of mice that had suffered a heart attack.  This part of the paper is less satisfying because many of their mice died as a result of this procedure (5 or 18).  However, the PDMS-treated mice did show a steady improvement in their ejection fractions (percentage of blood volume ejected from the heart) compared to mice that were only injected with culture medium.  These PDMC-injected mice also had extensive capillary beds in their heart tissue, suggesting that the increased heart function was due to the induction of new blood vessels.  In all honesty, this section of the paper should have had better controls and more animals should have been tested.  A sham group should have been included with an untreated group as well.

To extend their experiments in living animals, Yen’s group used a similar experimental strategy in Lanyu minipigs.  Here again, a lack of proper controls and large numbers of dead animals (5 of 17) diminish the clarity of the data.  The PDMC-treated minipigs showed a significant increase in ejection fraction (53.8 plus or minus 4.4 percent in the PDMC-treated minipigs vs. 39.2 plus or minus 2.3 percent in the culture medium-treated minipigs).  Also the blood vessel density in the hearts of the PDMC-treated pigs was over three times that of the other group.  Cell death studies showed that the hearts of the PDMC-treated minipigs that half that of the non-stem cell-treated minipigs.  This shows that PDMCs secrete molecules that promote cell survival.

Finally, Yen and others present what they think is evidence that the injected PDMCs in the hearts of the minipigs differentiated into heart muscle cells.  First of all, implanted PDMCs were observed eight weeks after they were injected.  There is little reason to suppose that these cells would have survived if they were not tightly associated with resident heart cells.  Secondly, these PDMCs expressed two heart-specific genes:  cardiac troponin T (cTNT), which is important for heart muscle contraction, and connexin 43, which is integral for forming gap junctions between heart muscle cells.  Gap junctions allow heart muscle cells to stay electrically connected with one another and allow them to contract as a single unit and these cells were expressing connexin 43 and were apparently integrated into the heart muscle.

I must say that I do not find this convincing, since the fusion of heart muscle cells and injected stem cells can account for such data.  Before I would believe that PDMCs can transdifferentiate into heart muscle cells, I would need to see compelling evidence that the connexin 43, cTNT, and human HLA-expressing cells also do not express minipig-specific genes.  Secondly, I would need to see PDMCs express the genes for the calcium-handling system that is unique to heart muscle cells.  The lack of express of these proteins is the single best reason to doubt that mesenchymal stem cells can transdifferentiate into heart muscle cells.  There is evidence that mesenchymal stem cells that stimulate endogenous heart stem cells to make new heart muscle, but little good evidence that mesenchymal stem cells can form mature, functional heart muscle cells.

All in all, the Yen paper shows some interesting data, even if some of it is not top quality.  Clear PDMCs are interesting cells that have a potential future in regenerative medicine.

Cells from placentas safe for patients with multiple sclerosis


A new Phase I clinical trial has demonstrated that Multiple Sclerosis (MS) patients were able to safely tolerate treatment with cells cultured from human placental tissue.  The results of this study were recently published in the journal Multiple Sclerosis and Related Disorders.  This pioneering study was conducted by researchers at Mount Sinai, Celgene Cellular Therapeutics, which is a subsidiary of Celgene Corporation, and collaborators at several other institutions, including the Swedish Neuroscience Institute in Seattle, WA, MultiCare Health System-Neuroscience Center of Washington, London Health Sciences Centre at University Hospital in London, the Clinical Neuroscience Research Unit at the University of Minnesota, the University of Colorado Denver, The Ottawa Hospital Multiple Sclerosis Clinic, and the MS Comprehensive Care Center at SUNY.

Even though this clinical trial was designed solely to determine the safety of this treatment, the data collected from the participating patients suggested that a preparation of cultured cells called PDA-001 may repair damaged nerve tissues in patients with MS.  PDA-001 cells resemble “mesenchymal,” stromal stem cells, which are found in many tissues of the body.  However, in this study, the cells were grown in cell culture systems, which means that one donor was able to supply enough cells for several patients.

“This is the first time placenta-derived cells have been tested as a possible therapy for multiple sclerosis,” said Fred Lublin, MD, Director of the Corinne Goldsmith Dickinson Center for Multiple Sclerosis, Professor of Neurology at Icahn School of Medicine at Mount Sinai and the lead investigator of the study. “The next step will be to study larger numbers of MS patients to assess efficacy of the cells, but we could be looking at a new frontier in treatment for the disease.”

MS is a chronic autoimmune disease.  The body’s immune system attacks the insulating myelin sheath that surrounds and protectively coats the nerve fibers in the central nervous system.  The myelin sheath greatly improves the speed at which nerve impulses pass through these nerves and without the myelin sheath, nerve impulse conduction becomes sluggish, and the nerves also eventually die off.  Long-term, MS causes extensive nerve malfunction and can lead to paralysis and blindness.  MS usually begins as an episodic condition called “relapsing-remitting MS” or RRMS.  Patients will have occasional outbreaks of nerve malfunction, pain, or numbness.  However, many MS patients will see their condition evolves into a chronic condition with worsening disability called “secondary progressive MS” or SPMS.

This Phase I trial examined 16 MS patients, 10 of whom had  RRMS and six of whom were diagnosed with SPMS and were between the ages of 18 and 65.  Six patients were given a high dose of the placental-based cell line PDA-001, and another six were given a lower dose.  The remaining four patients were given placebos.  Dr. Lubin noted that alteration of the immune system by any means can cause MS to worsen in some patients.  Therefore, all participating subjects were given monthly brain scans over a six-month period to ensure they did not acquire any new or enlarging brain lesions, which are indicative of worsening MS activity.  However, none of the subjects in this study showed any paradoxical worsening on MRI and after one year.  The majority had stable or improved levels of disability.

“We’re hoping to learn more about how placental stromal cells contribute to myelin repair,” said Dr. Lublin. “We suspect they either convert to a myelin making cell, or they enhance the environment of the area where the damage is to allow for natural repair. Our long-term goal is to develop strategies to facilitate repair of the damaged nervous system.”

Pluristem’s Phase I/II Muscle Injury Trial Shows that Placental Stem Cells Augment Muscle Healing After Surgery


Pluristem Therapeutics Inc. a leading developer of placenta-based cell therapies, has announced top-line results from its Phase I/II clinical trial that accesses the safety and efficacy of PLacental eXpanded (PLX-PAD) cells in the treatment of muscle injury. This clinical trial showed that PLX-PAD cells were safe and effective. These results provide evidence that PLX cells may be efficacious in the treatment of orthopedic injuries including muscles and tendons.

This Phase I/II trial was a randomized, placebo-controlled, double-blinded study conducted at the Orthopedic Clinic of the Charité University Medical School under the auspices of the Paul-Ehrlich-Institute (PEI), Germany’s health authority. The injured muscle studied was the gluteus medius muscle in the buttock. Hip-replacement patients undergo a surgical procedure that injuries the gluteus medius muscle healing of this muscle after hip replacement surgery is crucial for joint stability and function.

Gluteal Muscles

The 20 patients in the study were randomized into three treatment groups. Each patient received an injection in the gluteal muscle that had been traumatized during surgery. One group was treated with 150 million PLX-PAD cells per dose (n=7), the second was administered 300 million PLX-PAD cells per dose (n=6), and the third received placebo (n=7).

The primary safety endpoint was clearly met since no serious adverse events were reported at either dose level. The study showed that PLX-PAD cells were safe and well tolerated.

The primary efficacy endpoint of the study (how well the stem cells worked) was the change in maximal voluntary isometric contraction force of the gluteal muscle at six months after surgery. Efficacy was shown in both PLX-PAD-treated patient groups. The group that received a dose of 150 million cells showed a statistically significant 500% improvement over the placebo group in the change of the maximal contraction force of the gluteal muscle (p=0.0067). Patients who received the lower dose (300 million cells) showed a 300% improvement over the placebo (p=0.18).

An analysis of the overall structure of the gluteal muscle using magnetic resonance imaging (MRI) indicated an increase in muscle volume in those patients treated with PLX-PAD cells versus the placebo group. The patients who had received the 150 million cell dose displayed a statistically significant superiority over the placebo group. Patients treated at the 150 million cell dose showed an approximate 300% improvement over the placebo in the analysis of muscle volume (p=0.004). Patients treated at the 300 million cell dose showed an approximate 150% improvement over the placebo in the change of muscle volume (p=0.19).

The study’s Senior Scientist, Dr. Tobias Winkler of the Center for Musculoskeletal Surgery, Julius Wolff Institute Berlin, Charité – Universitaetsmedizin Berlin, Germany, commented, “I am very impressed with the magnitude of the efficacy results seen in this trial. PLX cells demonstrated safety and suggested that the increase in muscle volume could be a mechanism for the improvement of contraction force.”

Zami Aberman Chairman and CEO stated, “This was a very important study not only for Pluristem but for the cell therapy industry in general. The study confirms our pre-clinical findings that PLX-PAD cell therapy can be effective in treating muscle injury. Having a statistically significant result for our primary efficacy endpoint is very encouraging and consistent with our understanding of the mechanism of action associated with cell therapy. Based on these results, we intend to move forward with implementing our strategy towards using PLX cells in orthopedic indications and muscle trauma.”

Placenta-Based Stem Cells Increasing Healing of Damaged Tendons in Laboratory Animals


Pluristem Therapuetics, a regenerative therapy company based in Haifa, Israel, has used placenta-based stem cells to treat animal with tendon damage, and the results of this preclinical study were announced at a poster presentation at the American Academy of Orthopedic Surgeons’ (AAOS) annual meeting in New Orleans.

Dr. Scott Rodeo of New York’s Hospital for Special Surgery (HSS) is the principal investigator for this preclinical trial. His poster session showed placental-based stem cells that were grown in culture and applied to damaged tendons seemed to have an early beneficial effect on tendon healing. In this experiment, animal tendons were injured by treatments with the enzyme collagenase. This enzyme degrades tendon-specific molecules and generates tendon damage, which provides an excellent model for tendon damage in laboratory animals. These placenta-based cells are not rejected by the immune system and can also be efficiently expanded in culture. The potential for “off-the-shelf” use of these cells is attractive but additional preclinical studies are necessary to understand how these cells actually help heal damaged tendons and affect tendon repair.

“Although our findings should be considered preliminary, adherent stromal cells derived from human placenta appear promising as a readily available cell source to aid tendon healing and regeneration,” stated Dr. Rodeo.

“These detailed preclinical results, as well as the favorable top-line results we announced from our Phase I/II muscle injury study in January, both validate our strategy to pursue advanced clinical studies of our PLX cells for the sports and orthopedic market,” stated Pluristem CEO Zami Aberman.

Dr. Rodeo and his orthopedic research team at HSS studied the effects of PLX-PAD cells, which stands for PLacental eXpanded cells in a preclinical model of tendons around the knee that had sustained collagenase-induced injuries. Favorable results from the study were announced by Pluristem on August 14, 2013. Interestingly, Dr. Rodeo, the Principal Investigator for this study is Professor of Orthopedic Surgery at Weill Cornell Medical College; Co-Chief of the Sports Medicine and Shoulder Service at HSS; Associate Team Physician for the New York Giants Football Team; and Physician for the U.S.A. Olympic Swim Team.

Placental Stem Cell Provides Model System for Pregnancy Complications


Preeclampsia occurs during pregnancy, and is characterized by a gradual rise in blood pressure to dangerous levels. It usually presents after the 20th week of pregnancy, and can even persist after delivery.

How common is preeclampsia? In the United States, preeclampsia affects 5-8% of all births. Among the women of Canada, the United States, and Western Europe, the births affected by preeclampsia range from 2-5%. (5,6) In the developing world, the percentage of births affected by preeclampsia range from 4% of all deliveries to as high as 18% in parts of Africa. In Latin America, preeclampsia is the number one cause of maternal death.

Globally, ten million women develop preeclampsia each year, and 76,000 pregnant women die each year from preeclampsia and related disorders. The number of babies who die from these disorders is thought to be on the order of 500,000 per year.

In developing countries, a woman is seven times more likely to develop preeclampsia than a woman in a developed country, and between 10-25% of those cases will result in the death of the mother.

Now that I’ve hopefully convinced you that preeclampsia is a problem, how do we address it? Research in laboratory mice have told us a great deal about preeclampsia and other disorders that arise during pregnancy, but finding a sound model system that can be used to develop effective and safe treatments requires something closer to humans.

To that end, Hanna Mikkola and her research team and the University of California, Los Angeles Eli and Edythe Broad Center of Regenerative Medicine and Stem Cell Research (that’s a mouthful), have identified a type of progenitor cell that is key to the growth of a health placenta.

Work in laboratory mice has shown that preeclamsia often arises because of a malformed placenta. This poorly-formed placenta does not provide enough oxygen and nutrients for the growth needs of the baby at the fetal stages of development, and the mother’s body responds by increasing the mother’s blood pressure in order to increase blood flow through the placenta.

The work by Mikkola and her colleagues have provided physicians and developmental biologists with a new “tool box” for understanding the development of the placenta and the different cell types that compose it. Hopefully, various complications during pregnancy might be due to malfunctions of these particular cell types and the progenitor cells that produce them.

Mikkola and others started with laboratory mice, since it is possible to label single cells in mouse embryos and track exactly where those cells and their progeny go and what they do. The powerful genetic tools available in laboratory mice also allows scientists to identify the various biochemical signaling pathways that cells use to communicate with other cells during placental development. Also, if something goes wrong with particular cell signaling pathways, the mouse model allows scientists to precisely characterize the developmental consequences of much dysfunction.

Through their work in the mouse, Mikkola and her co-workers identified a placental progenitor cells called the Epcamhi labyrinth trophoblast progenitor or LaTP. The LaTP is like a multipotent adult of tissue-specific stem cell that can become many of the cells required to make the placenta.

Mikkola and her group also showed that the “c-Met” signaling pathway was required to sustain the growth of LaTPs during placental development and that this same signaling pathway was required to form a specific group of cells (syncytiotrophoblasts) that form the interface between the placenta and the mother’s endometrium. Elimination of c-Met signaling completely compromised the growth of the fetus and its development.

g abs7

This new cell type should provide a wealth of opportunities to examine complications during pregnancy like preeclampsia and others and design treatments that can save the lives of mothers and their babies.

Radio Interview About my New Book


I was interviewed by the campus radio station (89.3 The Message) about my recently published book, The Stem Cell Epistles,

Stem Cell Epistles

It has been archived here. Enjoy.

Developmental Regression: Making Placental Cells from Embryonic Stem Cells


A research group from Copenhagen, Denmark has discovered a way to make placental cells from embryonic stem cells. In order to do this, the embryonic stem cells must be developmentally regressed so that they can become wither placenta-making cells rather than inner cell mass cells.

This study is significant for two reasons. First of all, it was thought to be impossible to make placental cells from embryonic stem cells because embryonic stem cells (ESCs) are derived from the inner cell mass cells of 4-5-day old human blastocysts. These early embryos begin as single-celled embryos that divide to form 12-16-cell embryos that undergo compaction. At this time, the cells on the outside become trophoblast cells, which will form the trophectoderm and form the placenta and the cells on the inside will form the inner cell mass, which will form the embryo proper and a few extraembryonic structures. Since ESCs are derived from inner cell mass cells that have been isolated and successfully cultured, they have already committed to a cell fate that is not placental. Therefore, to differentiate ESCs into placental cells would require that ESCs developmentally regress, which is very difficult to do in culture.

Secondly, if this could be achieved, several placental abnormalities could be more easily investigated, For example, pre-eclampsia is a very serious prenatal condition that is potentially fatal to the mother, and is linked to abnormalities of the placenta. Studying a condition such as pre-eclampsia in a culture system would definitely be a boon to gynecological research.

Because human ESCs can express genes that are characteristic of trophoblast cells if they are treated with a growth factor called Bone Morphogen Protein 4 (BMP4), it seems possible to make placental cells from them (see Xu R.H., Chen X., Li D.S., Li R., Addicks G.C., Glennon C., Zwaka T.P., Thomson J.A. BMP4 initiates human embryonic stem cell differentiation to trophoblast. Nat. Biotechnol. 2002;20:1261–1264, and Xu RH. Methods Mol Med. 2006;121:189-202). However, a study by Andreia S. Bernardo and others from the laboratory of Roger Pedersen at the Cambridge Stem Cell Institute strongly suggested that BMP4 treatment, even in the absence of FGF signaling (another growth factor that has to be absent for BMP4 to induce trophoblast-like gene expression from ESCs) the particular genes induced by BMP4 are not exclusive to trophoblast cells and more closely resemble mesodermal gene profiles (see AS Bernardo, et al., Cell Stem Cell. 2011 Aug 5;9(2):144-55).

Into the fray of this debate comes a paper by stem cells scientists at the Danish Stem Cell Center at the University of Copenhagen that shows that it is possible to rewind the developmental state of ESCs.

In this paper, Josh Brickman and his team discovered that if they maintained mouse ESCs under specific conditions, they could cause the cells to regress into very early pre-blastocyst embryonic cells that can form trophoblast cells or ICM cells.

“It was a very exciting moment when we tested the theory, said Brinkman. “We found that not only can we make adult cells but also placenta, in fact we got precursors of placenta, yolk sac as well as embryo from just one cell.”

“This new discovery is crucial for the basic understanding of the nature of embryonic stem cells and could provide a way to model the development of the organism as a whole, rather than just the embryonic portion,” said Sophie Morgani, graduate student and first author of this paper. “In this way we may gain greater insight into conditions where extraembryonic development is impaired, as in the case of miscarriages.”

To de-differentiate the ESCs, Brinkman and his colleagues grew them in a solution called “2i.”  This 2i culture medium contained inhibitors of MEK and GSK3.  MEK is a protein kinase that is a central participant in the “MAP kinase signaling pathway, which is a signaling pathway that is central to cell growth and survival.  This particular signaling pathway is the target of the anthrax toxin, which illustrates its importance,  GSK3 stands for “glycogen synthase kinase 3,” which is a signaling protein in the Wnt pathway.

When the mouse ESCs were grown in 2i medium they expressed genes normally found only in pre-blastocyst embryos (Hex, for example).  Therefore, the 2i medium directs mouse ESCs to de-differentiate.  When ESCs grown in 2i were implanted into mouse embryos, they divided and differentiated into cells that were found in placental and embryonic fates.  This strongly argues that the ESCs grown in 2i became pre-blastocyst embryonic cells.  When the ESCs grown in 2i were also grown with LIF, which stands for “leukemia inhibitory factor” (LIF is a protein required for the maintenance of mouse ESCs in culture), the 2i cells were maintained in culture and grew while maintaining their pre-blastocyst status.  These cells differentiated into placental cells, embryonic or fetal cells.  Essentially, the 2i-cultured cells when from being pluripotent to being “totipotent,” or able to form ALL cell types in the embryo, fetus, or the adult.

ESC de-differentiation in totipotence

“In our study we have been able to see the full picture unifying LIF’s functions: what LIF really does, is to support the very early embryo state, where the cells can make both embryonic cells and placenta. This fits with LIFs’ role in supporting implantation,” said Brinkman.

This study definitively shows that ESCs are NOT embryos.  ESCs can regress in their development but embryos develop forward, becoming more committed as they develop and more restricted in the cell fates they can form.  This should effectively put the nail in the coffin of Lee Silver’s argument against Robert P. George that embryonic stem cells are embryos.  They are definitely and unequivocally, since embryos do NOT develop in reverse, but ESCs can and do.

Robert P. George argues that early human embryos, like the kind used to make ESCs are very young  members of the human race and deserve, at the minimum, the right not to be harmed.  Silver counters that George’s argument is inconsistent because George would not extend the same right to an ESC cell line, which is the same as an embryo.  His reasoning is that mouse ESCs can be transplanted into other mouse embryos that have four copies of each chromosome.  The messed up mouse embryo will make the placenta and the ESCs will make the inner cell mass and the mouse will develop and even come to term.  This is called tetraploid rescue, and Silver thinks that this procedure is a minor manipulation, but that it shows that ESCs are functionally the same as embryos.

I find Silver’s argument wanting on just about all fronts.  This is not a minor manipulation.  The tetraploid embryo is bound for certain death, but the implanted ESCs use the developmental context of the tetraploid embryo to find their place in it and make the inner cell mass.  The ESCs do not do it all on their own, but instead work with the tetraploid embryo in a complex developmental give-and-take to make an embryo with the placenta from one animal and the embryo proper from another.

Thus Silver’s first argument does not demonstrate what he says it does.  All it demonstrates is that ESCs can contribute to an embryo, which is something we already knew and expected.  This new data completes blows Silver’s assertion out of the water, since ESCs can take developmental steps backward and embryos by their very nature and programming, do not.  Thus these two entities are distinct entities and are not identical.  The early embryo is a very young human person, full stop.  We should stop dismembering them in laboratories just to stem our scientific curiosity.

Stem Cells from Human Placenta Repair Damaged Lungs


The placenta does more than provide yet unborn babies with oxygen from the mother’s blood supply; they are also a rich source of stem cells. Vladamir Serikov from the Children’s Hospital Oakland Research Institute in Oakland, California first isolated and characterized “chorionic mesenchymal stem cells” from human placenta in 2009 (see Exp Biol Med 2009 234:813-23), and since that time, his work has been conformed by several other research labs (Cell Stem Cell 2009 5:385-95 & Dev Biol 2009 327:24-33). Now Serikov and his research team have used his hCMSCs to repair damaged lungs in laboratory animals.

In this present publication, the Serikov team grew placenta-derived hCMSCs in culture and discovered that these grew like gangbusters. After 100 doublings, the cells showed no signs of giving up and their chromosomes show no signs of shortening, which is a symptom of aging when cells are grown in culture. Stem cells, have the ability to properly maintain the ends of their chromosomes and not show these signs of aging. Serikov’s hCMSCs have this definitive stem cell ability.

Next, the Oakland-based team tried to get these hCMSCs to differentiate into various cell types using published protocols. The hCMScs formed fat cells, bone cells, blood vessel-like cells, and liver cells in culture. When treated with a molecule called nerve growth factor, hCMSCs even sprouted nerve cell-like extensions and expressed genes common found in neurons (the cells that make a propagate nerve impulses).

To determine if these cells had the capacity to heal damaged tissue, Serikov and co-workers treated human lungs that were donated by a deceased individual but were denied for transplantation with a bacterial toxin that tends to really screw up the lungs. One lobe of the lung was treated with toxin only but the other side was treated with the toxin and five million hCMSCs. The side that received only the toxin showed damage to the lining of the lungs that was reflected in poor gas exchange and high fluid uptake by the lung tissue, but the side that received the hCMSCs was able to properly pump out the liquid and maintain the structure of the lung. When this same assay was applied to cultured lung tissue from humans, it was clear that the hCMSCs helped repair the columns of lung cells through the modicum of growth factors that they secrete. Certainly, hCMSCs have the capacity to heal the lungs after they are ravaged by a deadly bacterial toxin.

Two other experiments underscored the therapeutic capacity of these cells. When hCMSCs were infused into mice after the animals have been hit with high doses of radiation, they took up residence in multiple tissues, including the intestine, lungs, brain, and liver. Therefore, hCMSCs can not help heal tissues by means of what they secrete (so-called paracrine mechanisms), but by incorporating into tissues and becoming an integral part of it. Finally, when hCMSCs were implanted into mice and examined one year later, none of the mice showed any signs of tumors. There were also no signs of pain, heart problems, distress, fever, or weight loss. Therefore, these cells seem to be well tolerated, and do not have a high capacity for tumor formation.

These preclinical studies should give way to studies in larger animals, and if those are successful, hopefully, the first human clinical trials with these amazing stem cells that come from an abundant source, the human afterbirth.

See Igor Nazarov et al., “Multipotential Stromal Stem Cells from Human Placenta Demonstrate High Therapeutic Potential,” Stem Cells Translational Medicine 2012 1:359-72.