One of the major practical successes of stem cell therapy has been treatment of race horses and companion animals who have suffered joint injuries using stem cells from the fat. The company Vet-Stem has developed a procedure in which a small amount of fat is extracted from the injured animal, the fat is shipped to a processing plant where a stem cell-enrichment process occurs, and then the animal’s own cells are shipped back to the veterinarian who implants them into the injured tissue. This procedure, which can be seen on this representative video http://www.youtube.com/watch?v=hEkSJo3CmPc .

While the process of injecting stem cells into joints has demonstrated beneficial effects, one of the main goals of current regenerative research is to be able to develop brand new joint tissue (cartilage) in the laboratory in mass quantities that can subsequently be implanted surgically. This process has traditionally been difficult because the cartilage cells grow under highly specific conditions. A paper (Markway et al. Cell Transplant. Enhanced Chondrogenic Differentiation of Human Bone Marrow-Derived Mesenchymal Stem Cells in Low Oxygen Environment Micropellet Cultures. 2009 Oct 29) that appeared today in the journal Cell Transplantation addresses this issue.

The investigators used mesenchymal stem cells from the bone marrow together with micropellets, which are small biodegradable beads that the stem cells attach in order to mimic what occurs in the body when new cartilage is made. Two sizes of micropellets where compared, as well, different concentrations of oxygen were compared.
In order to detect which approach made cartilage that resembled the cartilage found in the body, the scientists assessed levels of proteins called sulfated glycosaminoglycans, proteoglycans and collagen II. These are proteins that allow cartilage to perform its normal function in the body, such as maintaining a smooth surface, and having ability to carrier water.

It was found that the micropellets that were larger in size could produce cartilage that resembled the natural form, and additionally, production was enhanced under conditions of lower oxygen.

These finds are important because they demonstrate that stem cells are guided not only by growth factors but also that they can detect other stem cells around them. Additionally, several other studies have demonstrated that oxygen levels contribute to the activity of stem cells. In general stem cells seem to prefer conditions of low oxygen. This may be because high oxygen content is associated with mutations and mutations in stem cells could have disastrous consequences in the body.

Acute lung injury is a major cause of death that can be caused by several conditions. Viral infections such as SARS, blunt for tissue trauma, and bacteria sepsis have all been associated with lung injury. It is believed that approximately 75,000 deaths per year in the United States alone occur because of this. Deaths are occur primarily in the intensive care units, and to date, there has been no treatment developed that works.

Scientists at the University of Illinois reported today in the international medical journal Stem Cells that adult stem cells isolated from the bone marrow of mice can protect against acute lung injury. The scientists reasoned that since in acute lung injury most of the damage occurs to the cells lining the blood vessels, addition of cells that can protect, or even regenerate these cells may be therapeutically useful.

It has been known for some time that the bone marrow contains stem cells that on the one hand can make new blood cells, these are called hematopoietic stem cells, but on the other hand, cells that can create new cells that make up the lining of the blood vessels, these are called endothelial progenitor cells.

The lead author of the study, Dr. Kishore Wary, stated "In ALI, the layer of cells that forms the lining of the blood vessels surrounding the lung’s air sacs is damaged, allowing fluid to leak in and fill the sacs. Repair of these breaks in the endothelium, or lining, is complicated by the fact that endothelial cells are long-lived."

In addition to demonstrating therapeutic effects of bone marrow stem cells, the authors identified a cell population that was responsible for the effects. Using a technique that detects cells based on unique marker proteins called flow cytometry, the investigators found that the bone cell cells containing the proteins FLK-1 and CD34 were causing the beneficial effects. Furthermore, the scientists found that by growing the cells outside of the body under special conditions, the numbers of cells could be increase, as well as their ability to attach to various organs.

The research group who performed this study was funded by grants from the National Institutes of Health. Stephen M. Vogel, Sean Garrean, Yidan D. Zhao and Asrar B. Malik, all of the department of pharmacology in the UIC College of Medicine, also were coauthors on the publication.

Embryonic stem cells have attracted tremendous attention based on their ability to become any of the 220 types of cell in the human body. Ethical issues, as well as the problem of cancer formation, have impeded their practical utilization. Recently scientists have been creating embryonic-like stem cells by inserting specific genes into skin cells so as to "reverse their age" and create cells that in many ways resemble embryonic stem cells. These cells are called inducible pluripotent stem cells, or iPS cells.

This approach is highly interesting to many researchers because: 1) It allows creation of stem cells that are of the same tissue type as the patient that may in the future receive them; 2) Their generation can be performed under defined conditions. This is in contrast to many of the existing embryonic stem cell lines which have been created years ago and contain animal products or mutations; and 3) They can be made from tissues containing rare genes, so as to be able to examine the effect(s) of the gene in every cell of the body. There are still limiting factors to the use of iPS: like embryonic stem cells, they cause cancer, and they are difficult to produce.

An advancement has been made in the issue of their production. Professor Sheng Ding from the Scripps Research Institute, also one of the founders of the company Fate Therapeutics, has recently published in the journal Nature Methods that administration of three chemicals to cells undergoing the iPS process makes their generation 200 times more efficient and in double the speed. Using the previous technique only 1 in 10,000 cells would become iPS and it would take a month.

Dr. Ding stated: "Both in terms of speed and efficiency, we achieved major improvements over conventional conditions, this is the first example in human cells of how reprogramming speed can be accelerated." He continued "I believe that the field will quickly adopt this method, accelerating research significantly."

The bone marrow contains several stem cell populations that are capable of healing numerous tissues after injury. One interesting question has been whether different types of "semi-artificial" organs can be generated by combining bioengineering with stem cells.
In a recent publication in the Proceedings of the National Academy of Sciences, researchers from Columbia University described the creation of a jaw bone (temporomandibular joint) made in the laboratory.

According to the researchers, this is the first time a complex, anatomically-sized bone has been accurately created in this way. The process involved creation of a "scaffold" that was based on a computer-generated image of the patient, and subsequently stem cells were added to the scaffold to allow them to generate tissue. This process was performed under conditions that replicate the inside of the body, using a device called a bioreactor.

Dr Gordana Vunjak-Novakovic, lead researcher of the study stated: "The availability of personalised bone grafts engineered from the patient’s own stem cells would revolutionise the way we currently treat these defects." She continued "We thought the jawbone would be the most rigorous test of our technique; if you can make this, you can make any shape."

Unfortunately, the laboratory creation only was made of bone and did not contain other body parts such as cartilage, which would have been needed to implant this into a patient. However this does not seem to be very far away.

Last year a beating heart was created using a similar approach in which a scaffold was made with heart tissue that was treated to remove cellular component, and subsequently seeded with stem cells. A video of this heart can be seen at http://www.stemcell.umn.edu/stemcell/faculty/Taylor_D/home.html

In a study that appeared today in the Journal Cell Stem Cell, Dr Kevin Eggan’s group from Harvard reported a novel way of generating stem cells from adult cells. The procedure of generating stem cells from skin cells and other adult cells was originally reported by a Japanese group that demonstrated introduction of 4 genes into adult tissue resulted in cells that resembled embryonic stem cells. We made a video describing this procedure http://www.youtube.com/watch?v=_RLlUdJLy74 . Essentially, the genes act on the DNA to “reprogram” it, causing the adult cells to be capable of becoming different tissues in a similar manner in which an embryonic stem cell can become different tissues. This was a great breakthrough for two reasons: Firstly it opens the door to performing stem cell therapy using the patient’s own cells; and secondly, the very fact that an adult cell can be made back into a younger cell demonstrates that it is possible, at least at a cellular level, to reverse aging.

Unfortunately the genes used to “retrodifferentiate” adult cells and make these stem cells, which are called “inducible pluripotent stem cells” (iPS), are also involved in formation of cancer. So besides the fact that iPS cells themselves cause cancers because they are similar to embryonic stem cells, the very methodology used for creating iPS cells involves introduction of cancer causing genes into the cells. This of course would make it very difficult to perform clinical trials because of the risk for cancer. The other main problem with this iPS approach is that in order to get the genes into the adult cells, the genes had to be transported by viruses. Giving genes by viruses into cells has several potential problems, including the possibility of contaminating the patient.

Several research groups have tried to circumvent the problems with the current technology. For example, one approach was to use the antiepileptic medication valproic acid in combination with only 2 of the genes. In a publication last year (Huangfu et al. Induction of pluripotent stem cells from primary human fibroblasts with only Oct4 and Sox2. Nat Biotechnol. 2008 Nov;26(11):1269-75) skin cells were made into iPS by administration of valproic acid with the genes Sox-2 and Oct-4. These two genes do not cause cancer. The reason why this strategy seemed to work was because valproic acid, in addition to having neurological effects, seems to modify the DNA of adult cells. DNA in adult cells is usually very compact. In the embryonic stem cell the DNA is more spreadout, and also is like a blank slate. As embryonic stem cells develop into liver cells, for example, certain parts of the DNA become “silenced” either because they are modified by chemicals that adult cells make, or because the DNA is more compacted in certain areas. Valproic acid has the ability to “loosen up” the DNA in adult cells and thereby allow them to act more like embryonic stem cells.

The use of chemicals like valproic acid for modifying stem cells is a very exciting area with practical consequences. For example, after a heart attack there are stem cells that reside in the cardiac muscle that try to heal the injured tissue. Valproic acid, by its ability to reprogram stem cells, albeit at a low level, actually seems to increase the ability of the heart to heal itself after injury, at least in animal models (Lee et al. Inhibition of Histone Deacetylase on Ventricular Remodeling in Infarcted Rats. Am J Physiol Heart Circ Physiol. 2007 Mar 30).

Another practical application of valproic acid’s ability to modulate stem cells is its potential use in the area of bone marrow transplantation. In patients with leukemias one of the commonly used procedures is autologous transplantation. This means taking out the patient’s bone marrow stem cells, the cells that make blood, giving the patient a very high dose of chemotherapy and radiation to kill the leukemic cells, and then giving back the patient’s own stem cells after they have been “cleaned up” so that they don’t have any more contaminating cells. One of the issues with this procedure is that sometimes there is not enough bone marrow stem cells to keep giving them back if the patient needs more. So for example, after the stem cells are administered, if the blood counts are too low, it would be ideal to have the patient’s own stem cells stored so that more can be given. Unfortunately it has been very difficult to expand stem cells outside of the body. In a recent publication, (Seet et al Valproic acid enhances the engraftability of human umbilical cord blood hematopoietic stem cells expanded under serum-free conditions. Eur J Haematol. 2009 Feb;82(2):124-32.) it was demonstrated that treatment of umbilical cord blood stem cells with valproic acid outside of the body led to increased expansion and ability to make the different types of blood cells needed after chemotherapy/radiation therapy. We actually made a video about an older paper in which valproic acid was used to expand bone marrow derived stem cells http://www.youtube.com/watch?v=3Hc4LCUOSiA

So based on the above two examples of chemical agents that modify “stemness” of cells, it is obvious that if newer methods were developed to make old cells young using chemical compounds instead of genes administered by viruses, these methods would have many potential applications and benefits. In the paper by Eggan, a new compound called RepSox was demonstrated to have ability of to take away the need for two of the genes when making iPS cells. With RepSox the investigators only needed to administer the genes Oct-4 and KLF, thus taking away the need for the cancer causing gene c-myc, and Sox-2.

It will be interesting to see if this new compound RepSox has similar activity to valproic acid, or to other compounds that have been demonstrated to activate patient’s own stem cells such as lithium, G-CSF, or the food supplement StemKine.

Scientists at the University of Wisconsin-Madison announced today that they have succeeded in generating retinal cells from stem cells. The retina is the light-sensitive portion of the eye that is responsible for seeing. Many types of blindness are caused by the cells in the retina not functioning properly. For example, in the disease wet macular degeneration, blood vessels start growing over the retina and induce death of the neurons that transmit light. Another conditions causing retinal damage include diabetic retinopathy and long term glaucoma. While treatmetns exist that slow down progression of conditions that cause retinal damage, to date, no treatments exist that reverse damage once it has occurred.

Dr. David Gamm was the head of the research group that successfully created retinal cells outside of the body, is a member of the Ophthalmology and Visual Sciences Department, and of the UW Eye Research Institute. He used a new type of stem cell called inducible pluripotent stem cells (iPS) as the starting material for the experiments. These iPS cells are stem cells created from the skin. By introducing certain pieces of DNA into skin cells, the cells literally “become younger” and take the characteristics of stem cells. These “artificial” stem cells have been previously used for generating a variety of tissues in the test tube and even in some animal experiments. For example, iPS cells have been previously made into pancreatic islets that produce insulin (Zhang et al. Highly efficient differentiation of human ES cells and iPS cells into mature pancreatic insulin-producing cells. Cell Res. 2009 Apr;19(4):429-38) and could one day be used in the treatment of diabetes. The advantage of iPS cells is that they can be made from the same individual for which they will be used. In other words people are able to use their own cells as stem cells.
Unfortunately, the disadvantage of iPS cells is that they are very similar to embryonic stem cells. While obviously they do not have the ethical concerns associated with embryonic stem cells, since they come from the skin, iPS cells cause cancer. There is a specific type of cancer, called a teratoma, that forms when embryonic stem cells or iPS cells are injected into animals. One of the reasons for this type of cancer is because the cells are very primitive and do not know how to interact with the body around them. To date there as been one approval by the FDA for an embryonic stem cell based clinical trial by the Menlo Park company Geron Inc, but that approval was withdrawn due to concerns about some of the animal safety data without any patients being treated.

For generating treatments based on either iPS or embryonic stem cells, it will be essential to make sure that the cells are made to mature in the test tube before implantation into humans. To date, this has been one of the major stumbling blocks.

The discovery of making retina from iPS cells is, however, a major finding. One reason is that by being able to make retina cells in large quantities, the possibility of using these cells to screen for drugs that may protect them from damage or death emerges.

Retinal-like cells have been previously made from other stem cells, including from bone marrow (Wang et al. Transplantation of quantum dot-labelled bone marrow-derived stem cells into the vitreous of mice with laser-induced retinal injury: Survival, integration and differentiation. Vision Res. 2009 Sep 25) and cord blood (Koike-Kiriyama et al. Human cord blood cells can differentiate into retinal nerve cells. Acta Neurobiol Exp (Wars). 2007;67(4):359-65) stem cells, which do not have the problems of cancer formation associated with embryonic or iPS cells.