Fetal Stem Cell Therapy Trial for Brittle Bone Disease

Dr. Cecilia Gӧtherström works as a medical researcher at the Karolinska Institutet in Stockholm, Sweden. Earlier this month, Dr Gӧtherström announced the commencement of the first clinical trial that utilizes fetal stem cell transplants to treat the brittle bone disease, Osteogenesis Imperfecta.

Osteogenesis imperfect (OI) was made famous by the Bruce Willis/Samuel Jackson movie “Unbreakable.” In this movie, Samuel Jackson played a wheel-chair bound savant whose bones were incredibly fragile, but acted as a mentor to Bruce Willis’ character who had a tendency to not become injured despite being in accidents and other traumatic events. Willis becomes a kind of local protector of the weak and innocent in his community under Jackson’s tutelage. I will not give away the surprising ending, but the fact that Jackson’s character had OI and his bones broke so easily put OI in the public’s consciousness.

OI is actually a group of genetic disorders that affects an estimated 6 to 7 per 100,000 people worldwide and prevents the bones from forming properly. This disease results from mutations in the COL1A1, COL1A2, CRTAP, and P3H1 genes. More than 90 percent of all cases of OI result from mutations in the COL1A1 and COL1A2 genes. The COL1A1 and COL1A2 genes encode the type I collagen proteins. Collagen is the most abundant protein in bone, skin, and other connective tissues. Patients with OI have fragile bones that break easily, sometimes with no apparent cause. OI can also cause loose joints, fatigue, early hearing loss, and respiratory problems. Multiple fractures are common, and in severe cases, can occur even before birth. Milder cases may involve only a few fractures over a person’s lifetime.

The publication SelectScience interviewed Dr. Gӧtherström who is the coordinator of this clinical trial that will use stem cell therapy to treat babies diagnosed with OI before they are ever born. Dr Gӧtherström told SelectScience that she and her colleagues selected OI as a disease to attack with stem cell treatment because “no good treatment exists.” Dr. Gӧtherström continued: “OI is a chronic disorder that affects the patient throughout their lifetime with reduced quality of life.” Also, because OI causes poor bone mineralization, fractures and malformation of the bones commences by the time the baby is born. Therefore, physicians can diagnose OI during pregnancy, and once it has been diagnosed, it is crucial to initiate treatment as soon as possible.

Dr. Gӧtherström and her colleagues will infuse stem cells into the fetal bodies of babies afflicted with OI by employing the same protocol that is generally used for blood transfusions during pregnancy. This is a very well-tested technique that carries a very little risk to the mother and her baby. According to Dr. Gӧtherström, there is a theoretical risk of the donor cells acquiring mutations that causing cancer in the mother, but this is very unlikely.

Fetal stem cell therapy has some benefits over other types of stem cell therapy. According to Dr. Gӧtherström, “Fetuses do not have a fully developed immune system, so the donor cells may have a better engraftment potential.” Also, fetal Mesenchymal Stem Cells (MSC) have a far better ability to form bone tissue than adult stem cells.

“If this proves to be safe and efficient, we will explore other disorders that can be treated prenatally, such as other skeletal dysplasias, or metabolic disorders,” Dr Gӧtherström explained. The success of this trial could open up new avenues for prenatal therapies to become more common. Dr. Gӧtherström believes that prenatal diagnosis of similar chronic disorders will shift, from delaying or slowing down the onset of a condition to actually treating it.

Regenerating Whole Teeth With A Tissue-Engineered Scaffold

As tissues go, teeth are relatively simple. They only consist of a few cell types, arranged in a rather straight-forward manner. Therefore, regenerating teeth, while more difficult than it seems, should represent a tractable problem for stem cell biologists and tissue engineers. While some progress has been made, tooth regeneration procedures will require more fine-tuning before they will be hailed as successful.

Tzong-Fu Kuo and others from the School of Veterinary Medicine, National Taiwan University, Taipei, Taiwan have examined the feasibility of whole-tooth regeneration in minipigs. Kuo and his group used a tissue-engineered tooth germ-like construct.

To construct their tooth germ constructs, Kuo and his colleagues extracted dental pulp from upper incisors, canines, premolars, and molars from mature miniature pigs. They grew the dental pulp tissue in culture in order to expand the faster-growing dental pulp stem cells (DPSCs) that can outgrowth everything else from the pulp in culture. They differentiated the DPSCs into odontoblasts, which make the dentine of the tooth, and osteoblasts, which make bone. Kuo’s team also acquired gingival epithelial cells from the gums of the minipigs.

Next the gum epithelial cells, odontoblasts, and osteoblasts were implanted onto the surface (upper, and lower layers, respectively), of a bioactive scaffold. This scaffold had the odontoblasts inside, the osteoblasts outside, and the gum epithelial cells outside the osteoblasts. Then Kuo and his coworkers transplanted these seeded bioactive scaffolds into the tooth sockets of the lower jaw of a minipig whose lower first and second molar tooth germs were removed.

13.5 months after the scaffolds were implanted, seven of eight pigs had formed two new teeth that had crowns, roots, and pulp. When the newly-formed teeth were extracted and sectioned, they had enamel-like tissues, dentin, cementum, odontoblasts, and periodontal tissues.

A fascinating finding in this study was that all the pigs, without exception, had regenerated molar teeth regardless of the original tooth from which the DPSCs were isolated. As an important control, minipigs that had their tooth germs removed or received empty scaffolds did not develop teeth.

This study from Kuo’s laboratory showed that implantation of a tooth germ-like structure can produce a complete tooth can do so successfully and efficiently. This study also established that the location of the implant seemed to deeply influence the morphology of the regenerated tooth.

Partial Repair of Full-Thickness Rotator Cuff Tears By Guided Application of Umbilical Cord Blood Mesenchymal Stem Cells

Baseball players, weight lifters, tennis players, basketball players, and other athletes have experienced the pain and frustration of a rotator cuff injury. The rotator cuff is the capsule that surrounds the shoulder joint, in combination with the fused tendons that support the arm at the shoulder joint. A tear in any of these tendons constitute a rotator cuff tear, and it is painful, and debilitating. Furthermore, rotator cuff tears are notoriously slow healing, if they heal at all.

The main option for a rotator cuff tear is microsurgical repair of the tendon. However, as Christopher Centeno at the Regenexx blog points out, sewing together atrophied tissue does not make a lot of sense, and consequently, rotator cuff repairs by means of microsurgery can have a high percentage of re-tearing. Is there a better way?

In the journal Stem Cells and Translational Medicine, Dong Rak Kwon and his two colleagues, Gi-Young Park and Sang Chui Lee, from the Catholic University of Daugu School of Medicine in Daegu, Korea have reported the results of treating whole-thickness rotator cuff tears in rabbits with human umbilical cord blood mesenchymal stem cells (UCB-MSCs). The results are quite interesting.

Kwon and his colleagues broke a colony of New Zealand White rabbits into three groups and surgically subjected all animals to full-thickness tears in the subscapularis tendon. Because rabbits are four-legged creatures, such tears severely compromise their ability to walk, and Kwon and his team measured the ability of these rabbits to walk and the speed at which they walked. All three groups of rabbits showed about the same ability to walk: they walked at about the same speed at for the same distance before giving up.

Human umbilical cord blood-derived mesenchymal stem cell (MSC) and ultrasound images. (A): Human umbilical cord blood-derived MSCs. (B): Injection was made in the left shoulder subscapularis (SCC) full-thickness tears under ultrasound guidance. (C): Longitudinal ultrasound image showed the needle (arrows) in the left shoulder SCC of the rabbit. Abbreviations: S, mesenchymal stem cell; T, tendon.

Human umbilical cord blood-derived mesenchymal stem cell (MSC) and ultrasound images. (A): Human umbilical cord blood-derived MSCs. (B): Injection was made in the left shoulder subscapularis (SCC) full-thickness tears under ultrasound guidance. (C): Longitudinal ultrasound image showed the needle (arrows) in the left shoulder SCC of the rabbit. Abbreviations: S, mesenchymal stem cell; T, tendon.

The first group of rabbits received injections of UCB-MSCs into their rotator cuffs. These injections were guided by ultrasound so that Kwon and his colleagues were able to place the stem cells directly on the damaged tendons. The second group of rabbits received injections of hyaluronic acid (HA), which is a component of connective tissue and the synovial fluid within bursal sacs that surround and lubricated some our joints. The third group received injections of sterile saline into their joints. The animals were then examined four weeks later.


The HA- and saline-injected animals showed few changes, but the UCB-MSC-injected animals were able to walk almost twice as far as the other rabbits and almost twice as fast. When the joint tissue of these animals was examined in detail, the HA and saline-injected animals still had full-thickness rotator cuff tears, although the HA-injected animals showed more healing that then the saline-injected rabbits. When the UCB-MSC-injected animals were examined, seven of the ten animals have rotator cuffs that had healed so that the tears could be classified as partial-thickness tears rather than full-thickness tears. Furthermore, a more detailed examination of these joint revealed that they showed regeneration of the tendon and the production of tough, high-quality collagen I.

Gross morphological (A–F) and histological (G–I) findings of the subscapularis tendons in groups 1, 2, and 3. The polygon in each of the first six images depicts the area of the full-thickness subscapularis tendon tear. (A–C): Pretreatment images. (D–F): Posttreatment images. (G): Parallel arrangement of hypercellular fibroblastic bundles (arrow) was noted in group 1. (H, I): Histological findings in groups 2 and 3 showed absence of fiber bundles. Group 1 received a 0.1-ml injection of MSCs; group 2, 0.1 ml of HA; group 3, 0.1 ml of saline. Hematoxylin-and-eosin stain, ×40. Abbreviations: MSC, human umbilical cord blood-derived mesenchymal stem cell; HA, hyaluronic acid; SSC, subscapularis muscle.

Gross morphological (A–F) and histological (G–I) findings of the subscapularis tendons in groups 1, 2, and 3. The polygon in each of the first six images depicts the area of the full-thickness subscapularis tendon tear. (A–C): Pretreatment images. (D–F): Posttreatment images. (G): Parallel arrangement of hypercellular fibroblastic bundles (arrow) was noted in group 1. (H, I): Histological findings in groups 2 and 3 showed absence of fiber bundles. Group 1 received a 0.1-ml injection of MSCs; group 2, 0.1 ml of HA; group 3, 0.1 ml of saline. Hematoxylin-and-eosin stain, ×40. Abbreviations: MSC, human umbilical cord blood-derived mesenchymal stem cell; HA, hyaluronic acid; SSC, subscapularis muscle.

Collagen I is the tough material that makes tendon. When rotator cuff surgeries fail, it can be for a variety of reasons, such as poor blood supply, intrinsic tendon degeneration, fatty infiltration, or muscle atrophy (see UG Longo, et al., British Medical Bulletin 2011, 98:31-59).

Histological micrographs of tissue from group 1 rabbits. (A): Newly regenerated tendons are shown in the blue-stained fibers (black arrow; Masson’s trichrome stain; magnification, ×12.5). (B): Regenerated tendon fibers (yellow arrowhead; Masson’s trichrome stain; magnification, ×250) are connected to adjacent M fibers. (C): The regenerated tendon fibers (black arrow) stained with anti-type 1 collagen antibody. The defect was reconstructed with human umbilical cord blood-derived mesenchymal stem cells (magnification, ×100). Abbreviation: M, muscle.

Histological micrographs of tissue from group 1 rabbits. (A): Newly regenerated tendons are shown in the blue-stained fibers (black arrow; Masson’s trichrome stain; magnification, ×12.5). (B): Regenerated tendon fibers (yellow arrowhead; Masson’s trichrome stain; magnification, ×250) are connected to adjacent M fibers. (C): The regenerated tendon fibers (black arrow) stained with anti-type 1 collagen antibody. The defect was reconstructed with human umbilical cord blood-derived mesenchymal stem cells (magnification, ×100). Abbreviation: M, muscle.

However, tendon failures after surgery usually result from the production of collagen III, which is mechanically weaker than collagen I, instead of collagen I (see MF Pittenger, et al., Science 1999, 284: 143-147; V Rocha, et al., New England Journal of Medicine 2000, 342: 1846-1854). None of the animals in the other groups showed any sign of collagen I production.

This experiment shows that full thickness tears in the subscapularis tendon of the rotator cuff of rabbits, which is functionally similar to the supraspinatus in humans (see figure below), can be partially healed by the ultrasound-guided infusion of UCB-MSCs.


If larger numbers of UCB-MSCs were implanted, it is possible that the tears would have been completely repaired. Also, it is possible that partial tears can be completely repaired by this procedure, but clearly more work is required.

Other questions also remain besides the optimal dose of the cells. What sized tears can be regenerated by this procedure? What immobilization procedures are appropriate after the stem cell injections and for how long? What are the most effective rehabilitation techniques after the surgery? These are all questions that are amenable to research so take heart athletes; a better cure is slowly, but surely on its way.

Combining Umbilical Cord Cells with Hyaluronic Acid Improves Heart Repair After a Heart Attack

Umbilical cord blood cells have an advantage over bone marrow or peripheral blood cells in that aging, systemic inflammation, and stress or damage caused by cell processing procedures can potentially compromise and diminish the regenerative capability of these cells. This problem is particularly acute in the case of treating patients who have recently suffered a heart attack, since transplanted cells experience a rather hostile environment that kills off most cells. Additionally, blood flow through the heart tends to wash out infused cells, which further decreases any regenerative activities the cells might have otherwise exerted.

With this in mind, Patrick Hsieh and his colleagues at the Academia Sinica, in Taipei, Taiwan tested if ability of human cord blood mononuclear cells (CB-MNCs) injected into the heart in combination with a hyaluronan (HA) hydrogel could extend the regenerative abilities of these cells in a pig model. HA is a common component of connective tissue, and, in general, it is very well tolerated by patients and implanted cells. Furthermore, it has the added bonus of shielding cells from a hostile environment and preventing them from being washed out of the heart.

Hsieh used a total of 34 minipigs and divided them into five different groups. One group was the sham operation group in which minipigs received surgical incisions but no heart attack was induced. The second group had heart attacks surgically induced and received infusions of normal saline solutions. The third group of minipigs also experienced heart attacks, and had HA injected into the heart walls. The fourth group also suffered heart attacks and received injections of human umbilical cord stem cells into their heart walls. The fifth group experienced heart attacks and received injections of both HA and human umbilical cord blood cells. The animals were kept and examined two months after surgery.

Two months after the surgery, the minipigs that received injections of human umbilical cord blood cells plus HA showed the highest left ventricle ejection fraction (51.32% ± 0.81%). This is significant when compared to 42.87% ± 0.97%, for the group that received injections of normal saline, 44.2% ± 0.63% for the group that received injections of HA alone, and 46.17% ± 0.39% for the group that received injections of umbilical cord blood cells only. Additionally, hearts from minipigs that received cord blood cells plus HA improved the systolic and diastolic function significantly better than the other experimental groups. Injections of either cord blood cells alone or in combination with HA significantly decreased the scar area and promoted the formation of new blood vessels in the infarcted region. In general, this study suggests that combined infusion of umbilical cord blood cells and HA improves the function of the heart after a heart attack and might prove to be a promising treatment option of heart attack patients.

This is a preclinical study, but it is a preclinical study in a larger animal model system. Umbilical cord blood cells have a demonstrated ability to induce healing in the heart after a heart attack. However, the combination of these cells with HA almost certainly significantly increases cell retention in the heart, thereby significantly improving cardiac performance, and preventing cardiac remodeling. Therefore, using healthy cells donated from another source to replace damaged or moribund cells may be a better option to treat a heart patient and repair their sick heart.

This work appeared in Stem Cells Trans Med November 2015, doi: 10.5966/sctm.2015-0092

Muscular Dystrophy is a Stem Cell-Based Disease

Michael Rudnicki, who has done pioneering work in muscle stem cell biology and muscle regeneration, and whose work has been featured several times on this blog, has struck again. Rudnicki, who serves as director of the Regenerative Medicine Program at The Ottawa Hospital and a professor at the University of Ottawa and holds the prestigious Canada Research Chair in Molecular Genetics, teamed up with workers from the Sprott Centre for Stem Cell Research and the Sinclair Centre for Regenerative Medicine to investigate the role of muscle-specific stem cells in patients who suffer from Duchenne muscular dystrophy. This new earth-shaking study, which was published in the journal Nature Medicine (November 16, 2015), has changed the way we think about muscular dystrophy and will almost certainly force people to rethink the treatments and cures for this dreadful disease.

According to this new study, Duchenne muscular dystrophy directly affects muscle stem cells, and is, largely a disease of muscle stem cells.

Rudicki said: “For nearly 20 years, we’ve thought that the muscle weakness observed in patients with Duchenne muscular dystrophy is primarily due to problems in their muscle fibers, but our research shows that it is also due to intrinsic defects in the function of their muscle stem cells. This completely changes our understanding of Duchenne muscular dystrophy and could eventually lead to far more effective treatments.”

Muscular dystrophy comes in several different forms, but the predominant sign of muscular dystrophy is progressive muscle weakness. Altogether, muscular dystrophy refers to a group of more than 30 genetic diseases, all of which cause progressive weakness and degeneration of skeletal muscles used during voluntary movement. Approximately half of all who suffer from muscular dystrophy have Duchenne muscular dystrophy (DMD). Because muscular dystrophy results from mutations in the dystrophin gene, which is on the X chromosome, the vast majority of muscular dystrophy patients are male. Girls can be carriers of muscular dystrophy and can be mildly affected.

Interestingly, somewhere around one-third of boys who suffer from DMD have no family history of the disease. Because the dystrophin gene is so large, spontaneous mutations in it are probably relatively common.

The signs and symptoms typically appear between the ages of 2 and 3, and may include frequent falls, difficulty getting up from a lying or sitting position, trouble running and jumping, a strange, shuffling way of walking or having a tendency to walk on their toes, calf muscles that are abnormally large, muscle pain and stiffness, and some learning disabilities.

Becker muscular dystrophy (BMD) has signs and symptoms that are largely similar to those of DMD, but BMD tends to be a milder form of the disease that progresses more slowly. Symptoms typically begin in the teens but, some patients may not experience symptoms until their mid-20s and some may not experience symptoms until later.

There are also several different types of muscular dystrophy-type diseases. Steinert’s disease or myotonic muscular dystrophy, which is characterized by an inability to relax muscles at after contractions, is the most common form of adult-onset muscular dystrophy. The first muscles to be affected are the muscles of the face and neck. Facioscapulohumeral muscular dystrophy affects the muscles of the face and shoulders, where symptoms first begin. When patients with facioscapulohumeral raise their arms, their shoulder blades noticeably protrude. This disease may first manifest itself in children, teenagers as late as age 40. This disease tends to affect one side more than the other.

Limb-girdle muscular dystrophy affects the muscles of the shoulders and hips. There are over 20 inherited forms of this disease, and because this condition is not due to mutations in dystrophin, but to mutations in genes that encode proteins that interact with dystrophin, the inheritance of limb-girdle muscular dystrophy is not sex-linked. Some forms of this disease are recessive and some are dominant. Patients with this type of muscular dystrophy usually trip more often because they have trouble raising the front part of their feet. Some autosomal recessive forms of the disorder are now known to be due to a deficits in proteins called sarcoglycans or dystroglycan.

Congenital muscular dystrophy is extremely varible and is probably a cluster of several different diseases caused by mutations in different genes. Some of types of congenital muscular dystrophy show sex-linked inheritance while others do not. Most cases of congenital muscular dystrophy result from the absence of a muscle protein called merosin, which is found in the connective tissue that surrounds muscle fibers. Other types of congenital muscular dystrophy have normal merosin and still others result from abnormal motor neuron migration. Clinically, this disease is also extremely variable and can manifest itself at birth or before age 2, progress slowly or rapidly, and cause mild disability or severe impairment.

Muscular dystrophy affects all ethnic groups and occurs globally. It affects around 1 in every 3,500 to 6,000 male births each year in the United States.  DMD affects approximately one in 3,600 boys.

Because DMD results from mutations in the dystrophin gene, the vast majority of muscular dystrophy research was based on a simple model in which the Dystrophin protein played a structural role in the structural integrity of muscle fibers. Abnormal versions of the Dystrophin protein caused the muscle fibers to become damaged and die as a result of contraction.  Dystrophin anchors the cytoskeleton of the muscle fibers, which are essential for muscle contraction, to the muscle cell membrane, and then to the extracellular matrix outside the cell that serves as a foundation upon which the muscle cells are built.


However in this current study, Rudnicki and his team discovered that muscle stem cells also express the dystrophin protein. This is a revelation because Dystrophin was thought to be protein that ONLY appeared in mature muscle. However, in this study, it became exceedingly clear that in the absence of Dystrophin, muscle stem cells generated ten-fold fewer muscle precursor cells, and, consequently, far fewer functional muscle fibers. Dystrophin is also a component of a signal transduction pathway that allows muscle stem cells to properly ascertain if they need to replace dead or dying muscle.  Muscle stem cells repair the muscle in response to injury or exercise by dividing to generate precursor cells that differentiate into muscle fibers.

“Muscle stem cells that lack dystrophin cannot tell which way is up and which way is down,” said Dr. Rudnicki. “This is crucial because muscle stem cells need to sense their environment to decide whether to produce more stem cells or to form new muscle fibres. Without this information, muscle stem cells cannot divide properly and cannot properly repair damaged muscle.”

Even though Rudnicki used mice as a model system in these experiments, the Dystrophin protein is highly conserved in most vertebrate animals. Therefore, it is highly likely that these results will also apply to human muscle stem cells.

Treatment for DMD patients is limited to steroids to decrease muscle inflammation and muscle cell death, and physical therapy to increase muscle use and prevent muscle atrophy. These approaches only delay the progression of the disease and alleviate symptoms. Gene therapy experiments and trials are in progress and even show some promise, but Rudnicki’s work tell us that gene therapy approaches must target muscle stem cells as well as muscle fibers if they are to work properly.

“We’re already looking at approaches to correct this problem in muscle stem cells,” said Dr. Rudnicki. “I’m not sure if we will ever cure Duchenne muscular dystrophy, but I’m very hopeful that someday in the future, we will have new therapies that correct the ability of muscle stem cells to repair the muscles of afflicted patients and turn this devastating, lethal disease into a chronic but manageable condition.”

This paper has received high praise from the likes of Ronald Worton, who was one of the co-discovers of the dystrophin gene with Louis Kunkel in 1987.  Worton later served as Vice-President of Research at The Ottawa Hospital from 1996 to 2007.

“When we discovered the gene for Duchenne muscular dystrophy, there was great hope that we would be able to develop a new treatment fairly quickly,” said Dr. Worton, who is now retired. “This has been much more difficult than we initially thought, but Dr. Rudnicki’s research is a major breakthrough that should renew hope for researchers, patients and families.”

Blocking Differentiation is Enough to Turn Mature Cells into Stem Cells

Hiroshi Kawamoto led a collaboration between the RIKEN Center for Integrative Medical Science and other institutions in Japan and Europe that examined the possibility that adult cells can be maintained in a stem cell-like state where they can proliferate without undergoing differentiation. They discovered that in immune cells, blocking the activity of one transcription factor can maintain the cells in a stem cell-like state where they continue to proliferate and still have the capacity to differentiate into different mature cell types.

Kawamoto and his team genetically engineered hematopoietic progenitor cells from mice to overexpress the Id3 protein. Id3, or inhibitor of DNA binding 3, is an inhibitory protein that forms nonfunctional complexes with other transcription factors. In particular, Id3 inhibits so-called “E-proteins,” (such as TCF3) which drive the progenitor cells to differentiate into immune cells.

Overexpression of Id3, in addition to soaking the cells in a cocktail of cytokines, cause the cells to continue to divide as stem cells. However, when the cytokines were withdrawn, the cells differentiated into various types of immune cells.

Next, Kawamoto and his collaborators infused these engineered hematopoietic progenitors into mice that had been depleted of white blood cells. They discovered that their Id3-overexpressing cells could expand and replenish the white blood cell population of these.

In a follow-up experiment, Kawamoto and his crew recapitulated this experiment using human umbilical cord blood hematopoietic progenitors. Just like their mouse counterparts, these umbilical cord cells could be maintained in culture, and then, upon change of culture conditions, could differentiate into blood cells.

Because these cells can be kept in an undifferentiated state and can extensively proliferate, this culture system provides a model for studying the genetic and epigenetic basis of stem cell self-renewal. And it might also allow scientists to inexpensively grow large quantities of immune cells for regenerative medicine or immune therapies.

This work was published in Stem Cell Reports, October 2015 DOI: 10.1016/j.stemcr.2015.09.012.

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.