Results of STAP Cell Paper Questioned


Reports of Stimulus-Triggered Acquisition of Pluripotency or STAP cells has rocked the stem cell world. If adult cells can be converted into pluripotent stem cells so easily, then perhaps personalized, custom stem cells for each patient are just around the corner.

However, the RIKEN institute, which was heavily involved in the research that brought STAP cells to the world has now opened an investigation into this research, since leading scientists have voiced discrepancies about some of the figures in the paper and others have failed to reproduce the results in the paper.

Last week, Friday (February 14, 2014, spokespersons for the RIKEN centre, which is in Kobe, Japan, announced that the institute is looking into alleged irregularities in the work of biologist Haruko Obokata, who works at the institution. Obokata was the lead author listed on two papers that were published in the international journal Nature. These papers (Obokata, H. et al. Nature 505, 641–647 (2014), and Obokata, H. et al. Nature 505, 676–680 (2014) described a rather simple protocol for deriving pluripotent stem cells from adult mouse cells by exposing them to acidic conditions, other types of stresses such as physical pressure on cell membranes. The cells, according to these two publications, had virtually all the characteristics of mouse embryonic stem cells, but had the added ability to form placental structures, which is an ability that embryonic stem cells do not have. The investigation initiated by the RIKEN centre comes at the behest of scientists who have noticed that some of the images used in these papers might have been duplicated from other papers. Also, several scientists have notes that they have been unable, to date, to replicate her results.

These concerns came to a head last week when the science blog PubPeer, and others, noted some problems in these two Nature papers and in an earlier paper from 2011. Obokata is also the first author of this 2011 paper (Obokata, H. et al. Tissue Eng. Part A 17, 607–15 (2011), and this paper contains a figure that seems to have been used for one of the figures in the 2014 paper. Also, there is another figure duplication.

Harvard Medical School anesthesiologist Charles Vacanti who was the corresponding author of one of the Nature papers has said that has learned last week about a data mix up in the paper and has contacted the journal to request a correction. “It certainly appears to have been an honest mistake [that] did not affect any of the data, the conclusions or any other component of the paper,” says Vacanti. Note that Vacanti is a co-author on both papers and a corresponding author on one of them.

In the other paper, Obokata serves as the corresponding author and this paper contains an image of two placentas that appear to be very similar. Teruhiko Wakayama works at Yamanashi University in Yamanashi prefecture, and he is a co-author on both of these papers. According to Wakayama, he sent more than a hundred images to Obokata and suggests that there was confusion over which to use. He says he is now looking into the problem.

Additionally, ten prominent stem-cell scientists have been unable to repeat Obokata’s results. One particular blog listed eight failures from scientists in the field. However, most of those attempts did not use the same types of cells that Obokata used.

Some scientists think that this could simply be a case of experienced scientists working with a system that they know very well and can manipulate easily, unlike outsiders to this same laboratory. For example, Qi Zhou, a cloning expert at the Institute of Zoology in Beijing, who says most of his mouse cells died after treatment with acid, says that “setting up the system is tricky; as an easy experiment in an experienced lab can be extremely difficult to others, I won’t comment on the authenticity of the work only based on the reproducibility of the technique in my lab,” says Zhou.

However, others are more deeply concerned. For example, Jacob Hanna, a stem-cell biologist at the Weizmann Institute of Science in Rehovot, Israel, however, says “we should all be cautious not to persecute novel findings” but that he is “extremely concerned and sceptical”. He plans to try for about two months before giving up.

It could be that the protocol is far more complicated that thought. For example, even Wakayama has been having trouble reproducing the results. To be sure, Wakayama and a student of his were able to replicate the experiment independently before publication, but only after being coached by Obokata. But since he moved to Yamanashi, he has had no luck. “It looks like an easy technique — just add acid — but it’s not that easy,” he says.

Wakayama says that his own success in replicating Obokata’s results has convinced him that her technique works. “I did it and found it myself,” he says. “I know the results are absolutely true.”

Clearly one way to clear this up is for the authors of this groundbreaking paper to publish a detailed protocol on how to make STAP cells. This should clear up any problems with the papers. Vacanti says he has had no problem repeating the experiment and says he will let Obokata supply the protocol “to avoid any potential for variation that could lead to confusion”.

The journal Nature has said that there are aware of the problems with the papers and looking into the matter.

For now, that’s where the issue sits. Frustrating I know, but until we know more we will have to just “wait and see.”

Both Copies of the Nanog Gene Are Expressed in Embryonic Stem Cells


Commonly held ideas are sometimes held because there is a great of evidence to substantiate them. However, other times, an idea is commonly held because simply because it has been repeated over and over and over even though the evidence for it is poor. Thus, when new evidence come to light showing the commonly held believe to be untrue, it becomes incumbent on us to readjust what we think.

When it comes to embryonic stem cells and the genes that keep them pluripotent, the transcription Nanog plays a very critical role in the self-renewal of embryonic stem cells and there is a great deal of evidence for this assertion. However, the expression of the gene that encodes Nanog was thought to follow the same mode of expression as some of the other pluripotency promoting genes. Namely, that only one of the copies of the Nanog gene were thought to be expressed in embryonic stem cells. This turns out to be probably false.

First a little background. In 2007, Ian Chambers and others published a paper in the journal Nature that examined the expression and function of Nanog in embryonic stem cells. Chambers and others found that Nanog expression levels in individual embryonic stem cells from a culture derived from a single cell varied wildly.  The figure from the Chambers et al paper is shown below.

Immunofluorescence of TNG cells for Oct4 and Nanog. Individual signals from 4,6-diamidino-2-phenylindole (DAPI), GFP, anti-Oct4 and anti-Nanog are shown on the left alongside a combined view of GFP with the stainings from anti-Oct4 and anti-Nanog.
Immunofluorescence of TNG cells for Oct4
and Nanog. Individual signals from 4,6-diamidino-2-phenylindole (DAPI),
GFP, anti-Oct4 and anti-Nanog are shown on the left alongside a combined
view of GFP with the stainings from anti-Oct4 and anti-Nanog.

The reason for this fluctuation in Nanog levels was uncertain, but Chambers and others showed that Nanog could be deleted from mouse embryonic stem cells without affecting their ability to contribute to various sundry embryonic tissues during mouse development, even though they do not make functional gametes (eggs and sperm).  In fact, mouse embryonic stem cells can self-renew under particular conditions without a functional copy of the Nanog gene even though they are prone to differentiation.  From this, Chambers and others concluded that Nanog stabilized rather than promoted pluripotency of embryonic stem cells by “resisting or reversing alternative gene expression states.”

Fast forward to 2012 and another Nature paper by Yusuke Miyanari and Maria-Elena Torres-Padilla from the IGBMC in Strasbourg, France, which showed that before mouse embryos implanted into the uterus, only one copy of the Nanog gene was expressed, but after implantation, both copies of the Nanog gene was expressed.  Miyanari and Torres-Padilla also made mouse embryonic stem cells that had copies of the Nanog gene labeled with different glowing proteins.  This ingenious experiment showed confirmed that Nanog levels were variable, but also showed that only one copy of the Nanog gene was expressed in growing embryonic stem cells in culture.

a, Schematic of the Nanog knock-in reporter NGR. A PEST motif in the carboxy terminus of the fluorescent proteins allows monitoring of dynamic Nanog expression. iHyg, internal ribosome entry site (IRES) hygromycin; iNeo, IRES neomycin; mChe, mCherry; NLS, nuclear localization signal; tGFP, TurboGFP. b, Representative image of NGR ES cells cultured with LIF or 2i/LIF. Scale bar, 10 µm. c, The incidence of allelic switching of Nanog expression in ES cells. Cells were classified into four groups: monoallelic (TurboGFP-positive, green), monoallelic (mCherry-positive, red), biallelic (TurboGFP- and mCherry-positive, yellow) and no expression (black). The proportion of cells undergoing a transition between these four groups during a single cell cycle is indicated. Overall, 47% of cells showed a colour change in this period. n, number of cells analysed. d, The asymmetric replication of Nanog in ES cells cultured with LIF changes to symmetric replication upon treatment with 2i. The cell nuclei were classified as single/double (SD), single/single (SS) and double/double (DD) according to DNA-FISH signals5. n, number of nuclei analysed. *, P < 4 × 10−7; **, P < 1.4 × 10−3 (Fisher’s exact test). e, Representative image of DNA-FISH for Nanog (arrowheads) and Oct4 in ES cells cultured with LIF or 2i/LIF. Scale bar, 2 µm. f, Nanog allelic expression is unaffected in the absence of DNA methyltransferase activity. Quantification of RNA-FISH for Nanog in wild-type (WT) ES cells and ES cells lacking all three DNA methyltransferases (TKO) cultured with LIF or 2i/LIF. g, ChIP for H3K4me3, MED12 or NIPBL along the Nanog locus (black line, top) in ES cells cultured with LIF or 2i/LIF. The position of the ChIP amplicons is depicted by the thick boxes below the line, the TSS by an arrow, the first exon by the black box on the line, and the distal enhancer by the blue box on the line. The Oct4 promoter region (Oct4 Pro) and distal enhancer (Oct4 DE) were positive controls (right)20. The mean ± s.d. of three independent biological replicates is shown.
a, Schematic of the Nanog knock-in reporter NGR. A PEST motif in the carboxy terminus of the fluorescent proteins allows monitoring of dynamic Nanog expression. iHyg, internal ribosome entry site (IRES) hygromycin; iNeo, IRES neomycin; mChe, mCherry; NLS, nuclear localization signal; tGFP, TurboGFP. b, Representative image of NGR ES cells cultured with LIF or 2i/LIF. Scale bar, 10 µm. c, The incidence of allelic switching of Nanog expression in ES cells. Cells were classified into four groups: monoallelic (TurboGFP-positive, green), monoallelic (mCherry-positive, red), biallelic (TurboGFP- and mCherry-positive, yellow) and no expression (black). The proportion of cells undergoing a transition between these four groups during a single cell cycle is indicated. Overall, 47% of cells showed a colour change in this period. n, number of cells analysed. d, The asymmetric replication of Nanog in ES cells cultured with LIF changes to symmetric replication upon treatment with 2i. The cell nuclei were classified as single/double (SD), single/single (SS) and double/double (DD) according to DNA-FISH signals5. n, number of nuclei analysed. *, P < 4 × 10−7; **, P < 1.4 × 10−3 (Fisher’s exact test). e, Representative image of DNA-FISH for Nanog (arrowheads) and Oct4 in ES cells cultured with LIF or 2i/LIF. Scale bar, 2 µm. f, Nanog allelic expression is unaffected in the absence of DNA methyltransferase activity. Quantification of RNA-FISH for Nanog in wild-type (WT) ES cells and ES cells lacking all three DNA methyltransferases (TKO) cultured with LIF or 2i/LIF. g, ChIP for H3K4me3, MED12 or NIPBL along the Nanog locus (black line, top) in ES cells cultured with LIF or 2i/LIF. The position of the ChIP amplicons is depicted by the thick boxes below the line, the TSS by an arrow, the first exon by the black box on the line, and the distal enhancer by the blue box on the line. The Oct4 promoter region (Oct4 Pro) and distal enhancer (Oct4 DE) were positive controls (right)20. The mean ± s.d. of three independent biological replicates is shown.

Now if we fast forward one more year and a paper from the journal Cell Stem Cell and a letter to the same edition of this journal, we have an article by Dina Faddah and others from the laboratory of Rudolf Jaenisch at the Whitehead Institute (MIT, Cambridge, MA), and a supporting letter from Adam Filipczyk and others from Germany and Switzerland.  In this article, the authors also double-labeled mouse embryonic stem cells and examined multiple cells and showed that BOTH copies of Nanog were expressed, and that the range of variability of Nanog expression was approximately the same as other pluripotency genes.

Filipczyk and others used a similar approach to examine the expression of Nanog in mouse embryonic stem cells and they came to the same conclusions as those of Faddah and others.

What is the reason for the differences in findings?  Faddah and others did an important experiment to answer this question.  Some of the cells that with labeled copies of the Nanog gene disrupted the production of a functional Nanog protein.  The constructs used in the papers by Faddah and others and by Filipczyk and others did not disrupt Nanog protein production.  When Faddah and others tested these other constructs that disrupted Nanog protein production to determine is the amount of glowing protein tracked with the amount of Nanog protein produced, it was clear that the amount of Nanog protein made by the cells did not reflect the amount of glowing protein produced.  According to Dina Faddah, “The way the reported was inserted into the DNA seems to disrupt the regulation of the alleles so that when the reported said Nanog isn’t being expressed, it actually is.”

Jaenisch sees this as an instructional tale for all stem cell scientists.  He noted: “Clearly, the conclusions for this particular gene need to be reconsidered.  And it raises the question for other genes.  For some genes, there might be similar issues.  For other genes, they might be more resistant to this type of disturbances caused by a reporter.”

Bottom line – read the materials and methods part of the paper carefully because the way these experiments are done can determine if the results are trustworthy.

SCIPIO Clinical Trial Shows Improved Heart Function


In an earlier post, I discussed the initial results of the SCIPIO clinical trial. This clinical trial extracts cardiac stem cells from the upper chambers of a heart attack patient’s heart. The cardiac stem cells are then cultured and reinjected back into the heart. The initial report was published in an internationally acclaimed medical journal called the Lancet.

The results were remarkable. After a heart attack, the heart usually deteriorates and undergoes remodeling. Remodeling consists of an enlargement of the heart, followed by congestive heart failure. However, those patients in the SCIPIO clinical trial who received transplants of their own cardiac stem cells (CSCs) showed significant improvements in heart function over those who received the placebo. Heart attack patients who had received CSC transplants showed shrinkage of their cardiac scars and greater ejection fractions.

Now a follow-up paper by the same research group has extended and confirmed these results.

In this paper, 33 patients were enrolled and of these patients, 20 were treated with their own CSCs and 13 served as controls. CSCs were isolated from each patient by means of a heart biopsy from the right atrial appendage during cardiac arterial bypass graft (CABG) surgery. These cells were harvested and processed during CABG surgery, but the harvesting of the CSCs did not increase the time required for CABG surgery.

CSC-treated patients showed a marked increase in the ejection fraction of the left ventricle. The ejection fraction is the percentage of blood pumped out of a filled ventricle by a heartbeat. After 4 months, the ejection fraction increased from 27.5±1.6% to 35.1±2.4% [P=0.004, n=8]. By 12 months after the procedure, the ejection fraction increased further to 41.2±4.5% [P=0.013, n=5]. This means that the efficiency with which blood is pumped by the heart increased after CSC infusions.

Secondly, the size of the infarct size was measured by a technique called “late gadolinium enhancement.” Gadolinium is a somewhat rare metallic element that us very useful because it is sensitive to electromagnetic resonance. Traces of it can be injected into the body to enhance the MRI pictures. Gadolinium also nicely outlines the noncontracting areas of the wall of the heart. MRIs after Gadolinium infusions revealed that the heart scars in those patients that had received CSC infusions had shrunk by -6.9±1.5 g [-22.7%] at 4 months [P=0.002, n=9] and -9.8±3.5 g [-30.2%] at 12 months [P=0.039, n=6]. The regions of the left ventricle (the main pumping chamber of the heart) that were dead also shrunk in CSC-treated patients. The dead regions shrunk -11.9±2.5 g [-49.7%] at 4 months [P=0.001] and -14.7±3.9 g [-58.6%] at 12 months [P=0.013]. Likewise, the total living mass of the left ventricle increased in CSC-treated patients: +11.6±5.1 g at 4 months after CSC infusion [P=0.055] and +31.5±11.0 g at 12 months [P=0.035].

This study confirms and extends the results of the initial report of SCIPIO. The isolation of CSCs during heart surgery is feasible and does not adversely affect CABG surgery. Also cardiac MRIs also reveal that CSC infusion produces a striking improvement in both global and regional function of the left ventricle. The CSCs also cause a reduction in infarct size, and an increase in viable tissue. These benefits persist for at least 1 year and are completely consistent with cardiac regeneration as a result of CSC infusion.

This is great news for heart attack patients.

See: Chugh AR, Beache GM, Loughran JH, Mewton N, Elmore JB, Kajstura J, Pappas P, Tatooles A, Stoddard MF, Lima JA, Slaughter MS, Anversa P, Bolli R. Administration of Cardiac Stem Cells in Patients With Ischemic Cardiomyopathy: The SCIPIO Trial: Surgical Aspects and Interim Analysis of Myocardial Function and Viability by Magnetic Resonance. Circulation. 2012 Sep 11;126(11 Suppl 1):S54-64.

Losing Your Skin to Gain Your Life


Regenerative medicine can find tips in the oddest corners of biology, and today’s tip is no different. African spiny mice (Acomys) are very unusual critters among mammals. Apparently some people like to keep them as pets, but other types of mammals find the mice rather tasty. If a predator gets its teeth into the mouse, pieces of the spiny mouse’s hide rip off in the mouth of the attacker, and the rodent runs free to live another day. Disgusting? The mouse gets the best end of the deal because its skin grows back almost as good as new. This discovery provides a viable model for the study of regeneration in a mammal, and since humans are mammals, such studies can apply to human regeneration.

Some lizards, salamanders, sea cucumbers, crustaceans, and other types of arthropods (insects, crabs, lobsters, and so on) have the ability to lose a body part to avoid capture and then replace it. Unfortunately, until now, this ability was completely unknown in mammals.

Developmental biologist Ashley Seifert of the University of Florida in Gainesville and his colleagues had their interest piqued when they heard rumors about an African mouse that could grow back its skin. The African spiny mouse is a rodent with stiff hairs on its back that resemble the spines of a hedgehog. Since the animal is kept as a pet by some people, owners have noticed that the animal has a tendency to lose patches of skin when handled.

Seifert and his colleagues were able to find the spiny mouse in the wild in parts of Kenya. When they took the animals into the laboratory, they discovered that spiny mice have skin that is 20 times weaker than the skin of standard laboratory mice. The weakness of the spiny mouse’s skin might result from the very large hair follicles. Further work with the spiny mouse showed that the animal’s wounds heal faster than those of standard laboratory mice. In addition to increase speed of healing, the skin heals without forming scar tissue, and even replaces the hair follicles after an injury.

The photograph comes from Ashley W. Seifert, Stephen G. Kiama, Megan G. Seifert, Jacob R. Goheen, Todd M. Palmer & Malcolm Maden, (2012) Skin shedding and tissue regeneration in African spiny mice (Acomys) Nature 489: 561–565.

How much skin can this animal replace at a time? Seifert’s team showed that African spiny mice can survive the loss of 60% of the skin off their backs and still regenerate it and bounce back. Elly Tanaka, who works as a developmental biologist at the Technical University of Dresden in Germany, but was not involved with the work, said: “It seems remarkable that an animal can lose so much skin and heal the skin so well that it looks normal,” Tanaka has a point. There are a few species of lizard that can shed their skin in a hurry as an escape response. For example, Anguis fragilis, a legless lizard can shed patches of its skin to escape a predator. In this case, however, only the top layer of skin falls off and the lower layers of skin regrow the upper layers. In the case of the African spiny mouse, however, the animals lose their entire skin with all its layers. Nothing remains but bare muscles, which makes the replacement of the skin a much more daunting process. “It’s a nice example that shows the maximum capacity of what the mammalian skin can do in terms of healing,” Tanaka says.

Seifert and his team investigated the mechanism of regeneration in spiny mice by punching holes in their ears. They discovered that regeneration in the ears mimicked limb regeneration in newts. Upon injury, the mouse’s body generates a population of embryonic-like cells that aggregate underneath the layer of cells that first cover the wound. These embryonic-like cells divide and differentiate into the different cell types that will re-form the ear tissue.

“It is truly exciting to discover that these mammals are capable of losing and regrowing complex tissue in such an efficient manner,” says Tara Maginnis, an evolutionary biologist at the University of Portland in Oregon who was not involved with the work. “It’s another ‘gripping’ example of how organisms can evolve alternative, adaptive traits not by inventing new structures or pathways but by modifying existing structures” such as the skin, she says.

Regeneration is not unheard of mammals, since rabbits also have the ability to replace bit of their ears is they go missing, and deer can regrow their antlers. However the ability to regrow large swaths of e lost skin is unique among mammals. In the words of University of Utah molecular biologist Shannon Odelberg, this constitutes a “surprising example of mammalian regeneration.” Odelberg continued: “This discovery puts scientists one step closer to being able to unravel the molecular bases of regeneration in vertebrates and possibly translating these discoveries into therapies.”

Let’s think about this for a while. These mice almost certainly have a genome that is not all that different from that of other mice. The differences are due to the way those genes are regulated. If we could truly understand how these mice get their cells to revert to an embryonic-like state and spread out to heal wounds, we could offer therapies to burn patients that could repair over 60% of their skin. Think of it. This would be nothing short of biblical.

This nicely illustrated why basic scientific research is so important, and why is must continue to occur. Model systems matter.

Hillsdale College Alum Calvin Freiburger Body-Slams RH Reality Check’s Eleanor Bader


Hillsdale College is an excellent, four-year institution of higher education just down the street from me in Michigan. The pro-choice website RH Reality Check ran a news piece on “fundamentalist colleges” on their website that was unflattering to Hillsdale to say the least.

A graduate of Hillsdale College named Calvin Freiburger has written a response to the RH Reality Check piece on the Live Action blog.  According to Freiburger, the RH Reality Check writer, Eleanor Bader, did not do a terribly good job fact-checking her piece when it came to Hillsdale, which is ironic given that Rh Reality Check advertises itself as “a resource for evidence-based information, provocative commentary, and interactive dialogue.”  Bader’s piece also dripped with a good deal of sarcasm and Freiburger took her to the woodshed more than once.  Read about here.

Cardiophere-Derived Cells Embedded in Platelet Gel Increases Heart Function and Improves Heart Structure After a Heart Attack


Biomaterials are organic compounds that can be molded into the shape of a particular organ or tissue, and can be seeded with cells that will form the shape of the organ or tissue and degrade the it, while using the biomaterial as a scaffold for their growth and development.

One organ where biomaterials can make a great difference is the heart, since implanted cells tend to either die to move away from the heart. By implanting cells into the heart that are embedded in biomaterials, the implanted cells stay put, are protected from cell death induced by the inhospitable environment of the heart after a heart attack, and tend to differentiate into heart-specific cells at the site at which they were implanted.

Injectable biomaterials are preferable for the heart, since non-injectable biomaterials require that the surgeon crack the chest and implant the biomaterial, which is a much more invasive procedure. One of the most appealing injectable biomaterials is platelet gel (also known as platelet fibrin scaffold).

The body naturally generates platelet gel after injury, however, it can be engineered as a tissue substitute to speed healing. The scaffold for platelet gel consists of naturally occurring biomaterials composed of a cross-linked fibrin network.

Platelet gel polymerization requires the enzyme thrombin and its substrate fibrinogen. Thrombin degrades fibrinogen to fibrin, which self-assembles to form the fibrin meshwork that composes the ground substance for platelet gel.  This reaction is affected primarily by the concentration of thrombin and temperature. Platelet gels are composed of fibers whose thicknesses vary according to the reaction conditions, and can be enriched by addition of other molecules (fibronectin, vitronectin, laminin, and collagen). Linking these molecules to the fibrin scaffold greatly affects the properties of the platelet gel, and the gel can also serve as a reservoir for growth factors and other molecules that speed healing.

Injection of platelet gel into a heart that has just experienced a heart attack prevents remodeling. Can stem cells that have a documented ability to heal damaged hearts have their healing capacities increased by implanting them in platelet gel?

A paper published workers in Eduardo Marban’s lab at Cedars-Sinai Medical Center in Los Angeles in the journal Biomaterials asks this very question, using rats as a model. In this article, Marban’s group used cardiosphere-derived cells (CDCs), which were successfully used in the CADUCEUS clinical trial to heal the hearts of human patients who have suffered a heart attack. The strategy used in these experiments was relatively simple (in principle): Induce heart attacks in the rats, treat once group with platelet gel alone, and the other group with CDCs embedded in platelet gel. Then compare the structural and functional integrity of the hearts in each group.

The results of these experiments come in several categories. First of all, the CDCs grown in platelet gel showed increased viability (reduced death) in comparison to CDCs grown on standard tissue culture plates. Furthermore, platelet gel-grown CDCs also differentiated into three-dimensional structures such as blood vessels. The CDCs also degraded the platelet gel and by two weeks of culture, two-thirds of the platelet gel was degraded. Furthermore, CDCs in platelet gel spread out and began to beat. Far more CDCs spread out and beat when grown in platelet gel than those grown in tissue culture plates. The contraction of the CDC-formed heart muscle cells was also much more robust in platelet gel than in tissue culture plates. Overall, the CDCs did much better in platelet gel than in standard tissue culture plates. They grew better, survived better, formed more heart-specific structures, and differentiated in more mature heart cell types when grown in platelet gel.

Another bonus to the platelet gel consists in its ability to trap growth factors. The CDCs in the platelet gel secrete a wide variety of growth factors, and these growth factors bind to the platelet gel and are concentrated by it. This recruits other cells to the platelet gel. That increases the ability of the platelet gel to facilitate stem cell-mediated healing.

Implanting platelet gel alone and platelet gel seeded with CDCs into damaged hearts caused increased heart wall thickness, decreased infarct size, and improved cardiac function. However in all cases, the CDC-seeded platelet gel causes even greater improvements than platelet gel alone.

These experiments show that stem cell-mediated healing is improved by the use of biomaterials. Furthermore, platelet gel is a very easily manufactured biomaterial that improves the growth and heart-specific differentiation of CDCs. Give the demonstrated healing capacities of CDCs, augmenting those capabilities with biomaterials such as platelet gel should be a priority for future clinical trials.

Regenerated Hair from Adult Stem Cells


Japanese researchers led by Takashi Tsuji from the Research Institute for Science and Technology at Tokyo University of Science have made bioengineered hair follicle germ cells from adult epithelial stem cells and dermal papillae cells. These hair follicle germ cells form functional hair follicles and grow hair. This is a proof-of-concept experiment for bioengineered organ replacement that may then proceed to human clinical trials.

These bioengineered follicle germs were made with epithelial and mesenchymal stem cells from skin found on the backs of mouse embryos (stage E18 for those who are interested). Once these cells were dissociated, they were combined with stem cells from adult hair follicles (the bulge region).

In a previous paper, Tsuji’s lab showed that a bioengineered hair follicle germ that was reconstituted from embryonic follicle germ-derived epithelial and mesenchymal cells could generate a bioengineered hair follicle and shaft if they used their new technique (Nakao, K. et al. The development of a bioengineered organ germ method. Nat. Methods 4, 227–230 (2007)). However, the Nature Methods paper did not transplant these bioengineered hair follicles into the skin of laboratory mice to determine if they could produce fully functional hair regeneration that includes hair shaft elongation, hair cycles, connections with surrounding tissues, and the regeneration of stem cells and their niches.

In this recent publication, Tsuji’s co-workers in his lab rigorously established that these bioengineered hair follicles could do everything a naturally produced hair follicle could do. In order to direct the growth of the hair toward the surface of the skin, Tsuji and others used a tiny plastic container with a fine nylon thread in the middle to direct the growth of the hair shaft. Previous experience had shown that implanting the bioengineered hair follicles into the skin caused them to form “epithelial cysts,” or fluid-filled vesicles that did not form hairs. The reason for this abnormal behavior is that the implanted follicles are connected with the surface of the skin, and therefore, lack polarity. The small, plastic containers provides a surface upon which the cells can grow toward the skin surface, and the nylon thread directs the extension of the hair shaft toward the skin surface.

These hair follicles expressed all the right genes and also cycled the way normal hair follicles cycle (growth of the hair, cessation of growth, dumping the hair shaft, and then regrowth of the hair shaft). This study definitely demonstrates the ability of adult tissue-derived follicular stem cells to serve as bioengineered organ replacements therapies.