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.