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Embryonic stem cells, which frequently (and controversially) make the news, are derived from a developing fetus.
Research into embryonic stem cells resulted in the identification of certain genes that were expressed in, and required by, stem cells. By far the best way of avoiding rejection, however, is to transplant the recipient’s own tissue. We have long had the capacity to grow cells in vitro (which literally means “within a glass”). In the case of transplantation, the stem cells can be derived from the patient who will receive the cultured tissue, thus removing the chance of complications arising due to donor incompatibility.
However, I searched and searched and there is no Nature paper, which honestly baffled me too…. No publication or clinical trial from her procedure either and as you point out- she’s been doing it for years + some potentially unethical tests on victims of terrorist attacks). Would this work on a aged skin, skin damaged other than fire, frostbite, gangrene, cancer, etc? Originally, monogenic inherited diseases (those caused by inherited single gene defects), such as cystic fibrosis, were considered primary targets for gene therapy.
While the positive therapeutic outcome was celebrated as a breakthrough for gene therapy, a serious drawback subsequently became evident. A small number of more recent gene therapy clinical trials, however, are concerned with monogenic disorders. Gene therapy relies on similar principles as traditional pharmacologic therapy; specifically, regional specificity for the targeted tissue, specificity of the introduced gene function in relation to disease, and stability and controllability of expression of the introduced gene.
Gene therapy can be performed either by direct transfer of genes into the patient or by using living cells as vehicles to transport the genes of interest. A major disadvantage, however, is the additional biological complexity brought into systems by living cells.
After in vitro manipulation, these cells may be retransplanted into patients by injection into the bloodstream, where they travel automatically to the place in the bone marrow in which they are functionally active. The traditional method to introduce a therapeutic gene into hematopoietic stem cells from bone marrow or peripheral blood involves the use of a vector derived from a certain class of virus, called a retrovirus. The major drawback of these methods is that the therapeutic gene frequently integrates more or less randomly into the chromosomes of the target cell. Another major limitation of using adult stem cells is that it is relatively difficult to maintain the stem cell state during ex vivo manipulations. Embryonic stem cells are capable of unlimited self-renewal while maintaining the potential to differentiate into derivatives of all three germ layers. Murine (mouse) embryonic stem cells were isolated over 20 years ago,12,13 and paved the way for the isolation of nonhuman primate, and finally human embryonic stem cells.14 Much of the anticipated potential surrounding human embryonic stem cells is an extrapolation from pioneering experiments in the mouse system. Following derivation, human embryonic stem cells are easily accessible for controlled and specific genetic manipulation. First, human embryonic stem cells could be genetically manipulated to introduce the therapeutic gene. An important parameter that must be carefully monitored is the random integration into the host genome, since this process can induce mutations that lead to malignant transformation or serious gene dysfunction. Homologous recombination is a very rare event in cells, and thus a powerful selection strategy is necessary to identify the cells in which it occurs. Gene targeting by homologous recombination has recently been applied to human embryonic stem cells.22 This is important for studying gene functions in vitro for lineage selection and marking. Despite promising scientific results with genetically modified stem cells, some major problems remain to be overcome.
The addition of human embryonic stem cells to the experimental gene therapy arsenal offers great promise in overcoming many of the existing problems of cellular based gene therapy that have been encountered in clinic trials (see Figure 4.3). Proponents of using embryonic stem cells say the field could transform medicine, providing treatments for brain diseases like Parkinson’s, juvenile diabetes or severe injuries. Advanced Cell Technology’s cells come from a single cell taken from an embryo in a process the company says could in theory leave the embryo whole with the potential to be implanted and grow into a living baby.
We welcome comments that advance the story through relevant opinion, anecdotes, links and data. At its core, this treatment relies on the unique properties of stem cells, so that’s where I’ll begin. They are unique amongst all other cells of the body in two ways; their capacity for self-renewal, and their ability to give rise to many different cell types. They are the ultimate in stem cell-iness because they have the potential to direct the development of an entire organism. While adult stem cells are not as versatile as embryonic stem cells, they do have the potential to direct the development of certain cell lineages. In 1959 the French surgeon Georges Mathe treated six nuclear power plant workers who had been so severely irradiated that their hematopoietic stem cell populations had been destroyed.
This rejection occurs because of subtle cellular differences between each and every one of us.
In certain procedures, such as small areas of skin grafting, such auto-grafting is a viable option. Bacterial cells grow happily in test tubes when provided with simple nutrients and an incubator, as do yeast cells.
As you saw in the video, skin grafts have been performed in this way for quite some time, but with variable success. The researchers in the your post now use stem cells, which makes it look even more incredible in my opinion. Hopefully from that some concrete data can be collected as to the precise efficacy of the cell spray system, as well as a peer-reviewed article on the subject. I think stem cell therapy like this has potential for aiding wound healing, ie where large amounts of skin have had to be removed.
Its emergence is a direct consequence of the revolution heralded by the introduction of recombinant DNA methodology in the 1970s.
For instance, in pioneering studies on the correction of adenosine deaminase deficiency, a lymphocyte-associated severe combined immunodeficiency (SCID), was attempted.1 Although no modulation of immune function was observed, data from this study, together with other early clinical trials, demonstrated the potential feasibility of gene transfer approaches as effective therapeutic strategies. Out of the approximately 1000 recorded clinical trials (January 2005), fewer than 10% target these diseases (see Figure 4.1). To integrate all these aspects into a successful therapy is an exceedingly complex process that requires expertise from many disciplines, including molecular and cell biology, genetics and virology, in addition to bioprocess manufacturing capability and clinical laboratory infrastructure. In this scenario, genes are delivered directly into a patient's tissues or bloodstream by packaging into liposomes (spherical vessels composed of the molecules that form the membranes of cells) or other biological microparticles. In many cases, direct gene transfer does not allow very sophisticated control over the therapeutic gene. This procedure is relatively complex in comparison to direct gene transfer, and can be divided into three major steps. Isolation of a specific cell type requires not only extensive knowledge of biological markers, but also insight into the requirements for that cell type to stay alive in vitro and continue to divide.
The role of adult stem cells is to sustain an established repertoire of mature cell types in essentially steady-state numbers over the lifetime of the organism. One type of retroviral vector was initially employed to show proof-of-principle that a foreign gene (in that instance the gene was not therapeutic, but was used as a molecular tag to genetically mark the cells) introduced into bone marrow cells may be stably maintained for several months.9 However, these particular retroviral vectors were only capable of transferring the therapeutic gene into actively dividing cells.
In principle, this is dangerous, because the gene therapy vector can potentially modify the activity of neighboring genes (positively or negatively) in close proximity to the insertion site or even inactivate host genes by integrating into them. Even after months and years of growth in the laboratory, they retain the ability to form any cell type in the body. Experiments performed with human embryonic stem cells in the last couple of years indicate that these cells have the potential to make an important impact on medical science, at least in certain fields.


When this facility is combined with their rapid growth, remarkable stability, and ability to mature in vitro into multiple cell types of the body, human embryonic stem cells are attractive potential tools for gene therapy. This gene may either be active or awaiting later activation, once the modified embryonic stem cell has differentiated into the desired cell type.
The levels of immune system reconstitution observed in the mice were quite modest (<1% of normal), while the methodology employed to achieve hematopoietic engraftment is not clinically feasible.
Since these cells can be differentiated in vitro into many cell types, including presumably tissue-specific stem cells, they may provide a constant in vitro source of cellular material. However, several copies of the therapeutic gene may also be integrated into the genome, helping to bypass positional effects and gene silencing. Specific proteins stabilizing these episomal DNA molecules have been identified as well as viruses (adenovirus) that persist stably for some time in an episomal condition. Recombinant DNA is altered in vitro, and the therapeutic gene is introduced into a copy of the genomic DNA that is targeted during this process. Usually, the introduced construct has an additional gene coding for antibiotic resistance (referred to as a selectable marker), allowing cells that have incorporated the recombinant DNA to be positively selected in culture. For therapeutic applications in transplantation medicine, the controlled modification of specific genes should be useful for purifying specific embryonic stem cell-derived, differentiated cell types from a mixed population, altering the antigenicity of embryonic stem cell derivatives, and adding defined markers that allow the identification of transplanted cells. The more specific and extensive the genetic modification, the longer the stem cells have to remain in vitro. Transgenic genes, as well as vectors introducing these genes (such as those derived from viruses), potentially trigger immune system responses. Further research is essential to determine the full potential of both adult and embryonic stem cells in this exciting new field. Molecular analysis of T lymphocyte-directed gene therapy for adenosine deaminase deficiency: long-term expression in vivo of genes introduced with a retroviral vector.
A serious adverse event after successful gene therapy for X-linked severe combined immunodeficiency. Correction of ADA-SCID by stem cell gene therapy combined with nonmyeloablative conditioning. Non-hematopoietic bone marrow stem cells: molecular control of expansion and differentiation.
Gene marking to determine whether autologous marrow infusion restores long-term haemopoiesis in cancer patients.
Isolation of a pluripotent cell line from early mouse embryos cultured in medium conditioned by teratocarcinoma stem cells.
Correction of a genetic defect by nuclear transplantation and combined cell and gene therapy. Lack of expression from a retroviral vector after transduction of murine hematopoietic stem cells is associated with methylation in vivo.
High-level sustained transgene expression in human embryonic stem cells using lentiviral vectors. Functional gene screening in embryonic stem cells implicates Wnt antagonism in neural differentiation.
HoxB4 confers definitive lymphoid-myeloid engraftment potential on embryonic stem cell and yolk sac hematopoietic progenitors.
Food and Drug Administration has approved the second human trial of human embryonic stem cells — this one testing cells in people with a progressive form of blindness, the company said on Monday. Last month Geron Corp (GERN.O) enrolled the first patient in its study using the cells in people whose spinal cords have been crushed. Researchers have discovered how to make embryonic-like cells from ordinary cells, called induced pluripotent stem cells. If this company succeeds in restoring sight to people who are going blind, what will those who oppose this research on moral grounds say?
If you see a comment that you believe is irrelevant or inappropriate, you can flag it to our editors by using the report abuse links. I have to admit I double-checked the date when my friend forwarded me the National Geographic link, but April first it was not. For example hematopoietic stem cells, which reside in your bone marrow, can divide asymmetrically into all the different cells of your blood.
Since then much work has gone into understanding the potential of these induced stem cells.
Our immune system recognizes these differences as foreign, much as it would any other pathogenic invader, and mounts a formidable defense.
Mammalian cells are a little more difficult to deal with, but again we have been culturing them in the lab for over a hundred years. Not only do the cells have to grow and divide, they have to interact with one another and take on specialized roles within the tissue. Skin stem cells that had been destroyed in the burn are replaced, and then the tissue is allowed to heal. Perhaps the spray gun as a means of stem cell delivery is unique to skin regeneration, but there are a couple of features that should be transferable to other transplants, particularly the ability to enrich a patients own stem cells and re-apply them to damaged tissue. Gene therapy is still highly experimental, but has the potential to become an important treatment regimen. The majority of current clinical trials (66% of all trials) focus on polygenic diseases, particularly cancer.
Alternately, the genes are packaged into genetically-engineered viruses, such as retroviruses or adenoviruses.
This is because the transferred gene either randomly integrates into the patient's chromosomes or persists unintegrated for a relatively short period of time in the targeted tissue. In the first step, cells from the patient or other sources are isolated and propagated in the laboratory. Unfortunately, specific biological markers are not known for many cell types, and the majority of normal human cells cannot be maintained for long periods of time in vitro without acquiring deleterious mutations.
Although adult tissues with a high turnover rate, such as blood, skin, and intestinal epithelium, are maintained by tissue-specific stem cells, the stem cells themselves rarely divide.
These properties reflect their origin from cells of the early embryo at a stage during which the cellular machinery is geared toward the rapid expansion and diversification of cell types. In particular, this impact includes: a) differentiation of human embryonic stem cells into various cell types, such as neurons, cardiac, vascular, hematopoietic, pancreatic, hepatic, and placental cells, b) the derivation of new cell lines under alternative conditions, c) and the establishment of protocols that allow the genetic modification of these cells. Two possible scenarios whereby human embryonic stem cells may benefit the gene therapy field are discussed below. Recently published reports establish the feasibility of such an approach.15 Skin cells from an immunodeficient mouse were used to generate cellular therapy that partially restored immune function in the mouse. This methodology involved using a more severely immunodeficient mouse as a recipient (which also had the murine equivalent of the human X-linked SCID mutation) and genetically engineering the hematopoietic engrafting cells with a potential oncogene prior to transplantation.
Positional effects are caused by certain areas within the genome and directly influence the activity of the introduced gene. Next, recombinant DNA is introduced by transfection into the cell, where it recombines with the homologous part of the cell genome. However, antibiotic resistance only reveals that the cells have taken up recombinant DNA and incorporated it somewhere in the genome. Additionally, since the therapeutic gene can now be introduced into defined regions of the human genome, better controlled expression of the therapeutic gene should be possible. Although human embryonic stem cells in the culture dish remain remarkably stable, the cells may accumulate genetic and epigenetic changes that might harm the patient (epigenetic changes regulate gene activity without altering the genetic blueprint of the cell). If stem cells are not autologous, they eventually cause immuno-rejection of the transplanted cell type. Researchers at the University of Pittsburg’s McGowan Institute for Regenerative Medicine have made the skin cell spray gun a very real, very effective treatment for burn victims.


And naturally this pluripotency (from the Latin pluri meaning many, and potency or potential) seemed like a fantastic quality for biologist to understand. However due to genetic manipulation and lack of correct genomic imprinting (small chemical modifications in our DNA that are laid down in the egg), induced pluripotent stem cells have the unfortunate ability to become cancerous.
With the development of tissue typing procedures and administration of immunosuppressive drugs, transplant rejection has significantly decreased.
All they require is a container to grow in that protects them from infection, liquid media containing essential amino acids and other nutrients, and a warm humid chamber in which to grow. Normally in our bodies external forces and small molecules send signals between cells that direct this process. As in the case of tissue culture in a lab, these cells require a sterile and nutrient rich environment to thrive. This will likely be advanced from burgeoning knowledge on where adult stem cells reside in our body, in so-called stem cell niches.
However, despite publishing countless papers about his findings, he was dismissed as a fraud by the medical establishment. In my opinion the only way a consensus can be reached is through a thorough, scientific and transparent trial.
You’d have to remove the whole leathery mess and start again…a new era of cosmetic surgery? In principle, it allows the transfer of genetic information into patient tissues and organs.
Because of biosafety concerns, the viruses are typically altered so that they are not toxic or infectious (that is, they are replication incompetent). Additionally, the targeted organ or tissue is not always easily accessible for direct application of the therapeutic gene. Second, the therapeutic gene is introduced into these cells, applying methods similar to those used in direct gene transfer. However, in certain situations, such as during tissue repair after injury or following transplantation, stem cell divisions may become more frequent.
Vectors derived from other types of retroviruses (lentiviruses) and adenoviruses have the potential to overcome this limitation, since they also target non-dividing cells. In these experiments, embryonic stem cells were generated from an immunodeficient mouse by nuclear transfer technology. Usually, small molecules, such as liposomes, as well as other cationic-lipid based particles are employed to facilitate the entry of DNA encoding the gene of interest into the cells.
Gene silencing refers to the phenomenon whereby over time, most artificially introduced active genes are turned off by the host cell, a mechanism that is not currently well understood.
This in turn results in the replacement of normal genomic DNA with recombinant DNA containing genetic modifications. To select for cells in which homologous recombination has occurred, the end of the recombination construct often includes the thymidine kinase gene from the herpes simplex virus. Indeed, sporadic chromosomal abnormalities in human embryonic stem cell culture have been reported, and these may occur more frequently when the cells are passaged as bulk populations. Opponents of embryonic stem cell research say research can focus on this field, but most experts in the field agree all approaches must be pursued. Not only were there fundamental developmental principles to be learned, the medical applications were endless. As detailed in a recent paper in Cell however, while these cells are not yet ready for the clinic, this should not prevent them from being used in a laboratory setting. Culturing a tissue in vitro requires a significant understanding of how the tissue forms, and an ability to isolate the stem cells from which the tissue is derived. After the initial spraying, the wound is covered with a dressing that contains a synthetic circulatory system that brings nutrients to the infant skin and removes any toxins and waste products. But Alan Spievack was transfixed, asking Badylak afterwards why his methods were not being used to save human lives.
But should the therapy prove itself in that setting, I think it is a fantastic advancement in the therapeutic use of adult stem cells. These basic tools of gene therapists have been extensively optimized over the past 10 years. The prototypic example of adult stem cells, the hematopoietic stem cell, has already been demonstrated to be of utility in gene therapy.4,5 Although they are relatively rare in the human body, these cells can be readily isolated from bone marrow or after mobilization into peripheral blood. The nucleus of an egg cell was replaced with that from a skin cell of an adult mouse with the genetic immunodeficiency. Additionally, some viruses (particularly retroviruses) only infect dividing cells effectively, whereas others (lentiviruses) do not require actively dividing cells.
In these cases, integration of several copies may help to achieve stable gene expression, since a subset of the introduced genes may integrate into favorable sites. Cells that randomly incorporate recombinant DNA usually retain the entire DNA construct, including the herpes virus thymidine kinase gene. This observation reinforces the necessity to optimize culture conditions further, to explore new human embryonic stem cell lines, and to monitor the existing cell lines.23,24 Additionally undifferentiated embryonic stem cells have the potential to form a type of cancer called a teratocarcinoma. However, glaring ethical issues arose regarding the taking of a life to save a life (that I won’t get into here) that have resulted in the stringent regulation of embryonic stem cell research. Furthermore, the procedure allows the addition of new functions to cells, such as the production of immune system mediator proteins that help to combat cancer and other diseases.
Specific surface markers allow the identification and enrichment of hematopoietic stem cells from a mixed population of bone marrow or peripheral blood cells. All of these techniques have been applied to various stem cells, including human embryonic stem cells. In most cases, the genetic information carried by the viral vector is stably integrated into the host cell genome (the total complement of chromosomes in the cell).
In cells that display homologous recombination between the recombinant construct and cellular DNA, an exchange of homologous DNA sequences is involved, and the non-homologous thymidine kinase gene at the end of the construct is eliminated.
Safety precautions are therefore necessary, and currently, protocols are being developed to allow the complete depletion of any remaining undifferentiated embryonic stem cells.25 This may be achieved by rigorous purification of embryonic stem cell derivatives or introducing suicide genes that can be externally controlled.
Or will we be able to harvest healthy stem cells from a niche before a disease such as leukemia becomes debilitating? The recent development of the stem cell gun has basically increased the efficiency of the system, reduced damage caused to the stem cells during spraying, and made the technique more user friendly in a hospital setting. In the laboratory dish (in vitro), cells can be manipulated much more precisely than in the body (in vivo). However, the destiny of the introduced DNA is relatively poorly controlled using these procedures.
Cells expressing the thymidine kinase gene are killed by the antiviral drug ganciclovir in a process known as negative selection. Some of the cell types that continue to divide under laboratory conditions may be expanded significantly before reintroduction into the patient. In most cells, the DNA disappears after days or weeks, and in rare cases, integrates randomly into host chromosomal DNA. Therefore, those cells undergoing homologous recombination are unique in that they are resistant to both the antibiotic and ganciclovir, allowing effective selection with these drugs (see Figure 4.2). Moreover, some cell types are able to localize to particular regions of the human body, such as hematopoietic (blood-forming) stem cells, which return to the bone marrow. In principle, this approach may be employed for treating human patients with immunodeficiency or other diseases that may be corrected by cell transplantation.



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