The Regenexx blog has a very interesting article on knee plica surgeries. Knee plicas refer to collisions between the knee cap (patella) and the nearby synovial membrane, which surrounds the joint. The pinching of the synovial membrane irritates it and generates swelling and pain. The common surgical procedure to treat knee plica is to extirpate the irritated synovial membrane. Centeno points out that this portion of the synovial membrane houses a robust stem cell population that helps heal knee problems. Therefore, this procedure might not be the best choice for knee plica. Centeno suggests that the knee is not aligned properly and that realignment of the knee cap could solve the problem without surgery. Read his blog post here and see what you think.
The inimitable Wesley Smith has blogged about a remarkable child who was born without several portions of his brain. This little boy, Chase Britton, was born prematurely. He had a MRI scan at the age of one, and this scan showed that Chase was completely missing his cerebellum, and his pons. The cerebellum is a small lobe at the back of the brain that underlies the occipital and temporal lobes of the cerebral cortex. The cerebellum accounts for approximately 10% of the brain’s volume, but it contains over 50% of the total number of neurons in the brain. The cerebellum has several functions: 1) Maintenance of balance and posture; 2) Coordination of voluntary movements; 3) Motor learning; and 4) Cognitive functions.
Those small postural adjustments that help us maintain balance are all mediated by the cerebellum. It does this by means of input from receptors in the inner ear (vestibular receptors) and in the joints that tell your brain about the orientation of your body. Consequently, patients with damage to the cerebellum suffer from balance problems. Most movements result from different muscle groups acting together in a temporally coordinated fashion, and the cerebellum coordinates the timing and force of these different muscle groups to produce fluid limb or body movements. The cerebellum also plays a major role in adapting and fine-tuning motor movements in order to make accurate movements through a trial-and-error process. For example learning to hit a baseball, shooting a basketball, slapping a hockey puck or other types of fine motor processes. Finally, the cerebellum is involved in certain cognitive functions, especially those that require motor skills, for example, language acquisition.
The pons is a portion of the brain that lies just in front of the cerebellum. The pons contains many “vital centers.” Vital centers are clusters of neurons that control vital bodily functions such as breathing, heart beat, and other such functions.
Chase has forced neurologists to rethink how the brain works or how the brain rewires itself in response to damage or developmental abnormalities. From the story:
But instead of being unable to carry out tasks like sitting up or crawling, Chase has forced experts to rethink how the brain functions. His mother Heather Britton told AOL News: ‘We call him the Little Gremlin. He loves to play tricks on people. His goal in life is to make people smile. ‘No one had ever seen it before. And then we’d go to the neurologists and they’d say, “that’s impossible, he has the MRI of a vegetable”.’ Dr Adre du Plessis, chief of Foetal and Transitional Medicine at the Children’s National Medical Center in Washington D.C., told WGRZ: ‘There are some very bright, specialised people across the country and in Europe that have put their minds to this dilemma and are continuing to do so, and we haven’t come up with an answer.
This boy is disabled, but he is not a vegetable. If you do not believe me, see this video of him learning to walk here. However, in places like Holland, Chase would have been exterminated under the Groningen Protocol. According to the Groningen Protocol, Dutch doctors can euthanize infants with terminal and seriously disabling conditions. In Belgium too, disabled babies are murdered, and in most countries, Chase would have been done in. Even though his is not, Chase would have been classified as an “anencephalic” baby. Anencephalic babies are born without the tops of their heads and are missing their cerebral cortex. They have a brain stem and their hearts are still beating but there is no indication that they can feel pain, beyond simple reflexes. The majority of anencephalic babies are born dead (stillborn), and about one third of them live a few hours to a few days. In very rare cases, they will live a few weeks up to a few months. Anencephalic babies are also born blind, deaf, unconscious, and unable to feel pain. They still react with spinal or brainstem reactions to stimuli. They are typically given comfort care until death so that a peaceful environment for the parents, with support from chaplains, counselors, and hospital staff.
Anencephalic babies are considered a good source of organs for neonatal transplantation. The current Uniform Declaration of Death Act (UDDA) requires brain death and irreversible cessation of heart/lung function prior to organ donation. This prevents organ donation from living donors who might have some reversibility in their brain function. Unfortunately, many organs from anencephalic babies may not be usable as a result of damage from a lack of oxygen. With the shortage of fetal or neonatal organs for transplant, some have argued that anencephaly should be the exception to the UDDA requirements. However, the general consensus is that it is unethical to harvest organs from an anencephalic babies until they are “dead.”
Now, according to Smith, programs to procure organs from anencephalic babies often receive organs from babies that are not anencephalic, but from children who are disabled. Listen to these words from Smith’s excellent book, The Culture of Death: The Assault on Medical Ethics in America:
In 1988, Loma Linda University in California created an organ procurement protocol to use anencephalic babies as organ donors in which physicians from around the country were asked to transfer, with parental permission, qualified infants to the Loma Linda University Medical Center where the procurement would take place. The program only lasted eight months before it had to be suspended, in part because of the inability of Loma Linda doctors to procure usable organs in thirteen attempts. However, the primary reason for shutting down the initiative was that physicians referred non-anencephalic, disabled babies to Loma Linda for organ procurement.
Dr. Shewmon, USC bioethicist and law professor Alexander M. Capron and others, writing in the Journal of the American Medical Association described what happened:
[T]he experience at transplantation referral centers indicates that enthusiasm for using anencephalics does indeed quickly extend to other categories of dying infants. As a result of the national interest in Loma Linda’s protocol, for example, that institution received from ‘good’ physicians several referrals of infants with less severe anomalies for organ donation, such as ‘babies born with an abnormal amount of fluid around the brain or those born without kidneys but with a normal brain.’ Moreover, the referring physicians ‘couldn’t understand the difference’ between such newborns and anencephalics.” Joyce Peabody, MD, chief of neonatology there and primary drafter of the protocol, deserves much credit for her courageously candid statement: ‘I have become educated by the experience. … The slippery slope is real’ (D. Alan Shewmon, et al, “The Use of Anencephalic Infants as Organ Sources: A Critique,” Journal of the American Medical Association, Vol. 261, p. 1775).
Calling Chase Britton a vegetable is the height of absurdity and cruelty. He is a human being; a disabled one, but a human person. Thank God that his parents did not condemn him to death because of his disability. His perseverance is a testimony to his human spirit.
Brian Derby from the University of Manchester is using inkjet technology to distribute cells onto scaffolds that are shaped as a particular organ. Inkjet and laserjet technologies can build three-dimensional scaffolds that are coated with cells that will grow into the scaffold, assume its shape and degrade the scaffold, leaving only the tissue in its place.
This type of technology, which involves the simultaneous placement of biodegradable scaffold and cells in a three-dimensional structure that resembles that of an organ is called additive manufacture and it might very well be the future of replacement organ production. Additive manufacture recreates the biological structure in a three-dimensional, digital image, from which two-dimensional, digital slices are taken and fashioned one layer at a time. The summation of all the digital slices eventually produces a three-dimensional structure.
Inkjet technology dispenses the material that makes the scaffold in very small droplets that quickly solidify. The materials is loaded into an actual inkjet printer cartridge that is sprayed onto the surface. More droplets are placed on top of previous droplets in a very specific pattern and this repetitive distribution of droplets develop into a pattern that is very complex and forms a scaffold that nicely mimics the conditions inside the body. The scaffold also provides a surface the for cells to adhere, grow and thrive. The scaffold and its internal structure control the behavior and maintain the health of the cells embedded in the scaffold. This method of distributing cells onto a surface through a printer is called “bioprinting.”
In his article, published in the journal Science, Derby examines experiments in which porous structures are made by means of bioprinting. Bioprinting uses inkjet and laserjet technologies to distribute cells or molecules onto a surface in a desired pattern. In the case of porous structures, cells interweave throughout the scaffold and such cell-encrusted scaffolds can be placed in the body to encourage cell growth. Depending on the composition of the scaffold and the cells embedded in it, the scaffold can become a part of the body or the cells will dissolve it. Such a treatment can help heal patients with particular injuries such as cavity wounds.
Bioprinted cells can also be deposited onto scaffolds with various other chemicals, such as hormones, growth factors, or small molecules that influence the behavior of the cells. The inclusion of such molecules with the scaffold can coax cells to differentiate into distinct cell types, such as, for example, bone- or cartilage-producing cells.
Cells do suffer some damage during bioprinting, and the rule of thumb is the more energy is used to deposit the cells onto the scaffold, the lower the viability of the cells after bioprinting. To deposit and pattern cells in a scaffold there are three techniques that are used: inkjet printing, microextrusion, which is also known as filament plotting, and laser forward transfer. Bioprinting has probably the highest viability rates, and that has come after the techniques have been precisely worked out to ensure a minimum of damage. Microextrusion shows extremely variable rates of cell survival after the cells are deposited. Laser forward transfer suffers from the need for higher energy lasers to more precisely and efficiently deposit the cells, but this same higher energy kills off the cells.
Even though this technology has come a long way, it has a way to go before it is ready for the clinic. Scaffolds are being used in clinical trials, but scaffold synthesis suffers from inconsistency, and until a consistent high-quality is delivered, scaffold production will not be ready for commercial production.
Despite these caveats, there have been some successes. For example, D’Lima and others used an solution of chemicals in water (poly(ethylene glycol) dimethacrylate to be exact) that also contained cartilage-making cells (chondrocytes). They printed this suspension a bone defect in a cultured bone and then used a chemical not unlike what dentists use to harden tooth plastic called a photoinitiator. Such chemicals crosslink and bond together in response to particular wavelengths of light, and D’Lima used light to crosslink the chemicals to make a wet gel that contained the cells. After several days, this printed structure appeared to have integrated into the surrounding tissue. This experiment demonstrates that this technology is at least feasible. The hanging issue is the toxicity of the photoinitiator chemicals to cells (X. Cui, et al Tissue Eng. A 18, 1304 (2012). However, this has been studied, and it turns out the susceptibility to these chemicals is very cell type-specific. Thus, picking the right photoinitiator could potentially make this technique rather safe (see C. G. Williams, et al Biomaterials 26,1211 2005).
Scaffolds, however, can also be used to make external tissues, for example, skin patches. Derby is working with ear, nose, and throat surgeons at the Manchester Royal Infirmary. His goal is to use bioprinting to make patches that can be implanted into the inside of the nose or throat.
Derby explains: “It is very difficult to transplant even a small patch of tissue to repair the inside of the nose or mouth. Current practice, to transplant the patient’s skin to these areas, is regarded as unsatisfactory because they transplants do not possess mucous generating cells or salivary glands. We are working on techniques to print sheets of cells that are suitable for implantation in the mouth and nose.”
Derby hopes that someday bioprinting can be used to grow tumors in realistic cultures that will make superior models for drug testing and drug development.
Pluripotent stem cells have the ability to differentiate into a whole host of adult cell types. Unfortunately this ability to differentiate into any adult cell type also comes with it the tendency to form tumors. Controlling stem cell differentiation requires that you give a little “push” in the right direction. What is the nature of that push? It varies from stem cell to stem cell and it also depends on what type of cell you want you stem cells to make. Therefore, pluripotent stem cell differentiation is sometimes a matter of art as much as a matter of science.
A research group at Stanford University School of Medicine have designed an experimental protocol that uses the signals in the body to direct the differentiation of stem cells to a desired end.
Stanford University professor Michael Longaker, who is also the director of the Institute for Stem Cell Biology and Regenerative Medicine at Stanford University, explained it this way: “Before we can use these cells, we have to differentiate or ‘coach,’ them down a specific developmental pathway.” Longaker continued: “But there’s always a question as to exactly how to do that, and how many developmental doors we have to close before we can use the cells. In this study, we found that, with appropriate environmental cues, we could let the body do the work.”
Allowing the patient’s body to direct differentiation of pluripotent stem cells could potentially speed approval of stem cell-based treatments by the US Food and Drug Administration (FDA). If Longeker’s protocol pans out, it could eliminate long period of extended laboratory manipulation in order to force stem cells to differentiate into the desired cell type.
“Once we identify the key proteins and signals coaching the tissue within the body, we can try to mimic then when we use the stem cells,” said Longaker. “Just as the shape of water is determined by its container, cells respond to external cues. For example, in the future, if you want to replace a failing liver, you could put cells in a scaffold or microenvironment that strongly promotes liver cell differentiation and place the cell-seeded scaffold into the liver to let them differentiate in the optimal macroenvironment.”
Longaker does not work on liver, but bone. As a pedatric plastic and reconstructive surgeon who specializes in craniofacial malformations, finding ways to coax pluripotent stem cells to make bone is his research Holy Grail. “Imagin being able to treat children and adults who require craniofacial skeletal reconstruction, not with surgery, but with stem cells,” opined Longaker.
In this experiment, Longaker and his colleagues removed a four-millimeter circle of bone taken from the skulls of anesthetized mice and implanted a tiny, artificial scaffold coated with a bone-promoting protein called BMP-2 (bone morphogen protein-2) that was seeded with one million human pluripotent stem cells.
According to Longaker, these implants formed bone and repaired the defect in the skulls of the mice even the original stem cells were not differentiated when added to the wound. These human stem cells made human bone that was then replaced by mouse bone as time progressed. This shows that the repair was physiologically normal.
This bone growth was stimulated by the presence of BMP-2 and the microenvironment that induced the stem cells to differentiate into bone-making cells that made normal bone.
In this experiment, Longaker and his group used human embryonic stem cells and induced pluripotent stem cells and both stem types seemed to work equally well at repairing the skull defect.
Teratomas (tumors made by pluripotent stem cells) were observed but only rarely (two of the 42 animals that received the stem cell implants developed tumors). Interestingly, the few teratomas that formed developed in two laboratory animals that received embryonic stem cell implants and not induced pluripotent stem cell implants. This is surprising, since most stem cells researchers consider induced pluripotent stem cells to be more tumorigenic than embryonic stem cells. Standard tests of these stem cells (implantation under the kidneys of immunodeficient mice) showed that they did produce teratomas under these conditions.
Longaker commented: “We still have work to do to completely eliminate teratoma formation, but we are highly encouraged.” Longaker also thinks that by combining this technique with other strategies, he and his group might be able to completely prevent teratoma formation. For example, including other cell types that can act as shepherds for the stem cells as they differentiate into the desired cell type can also increase differentiation into a desired cell type.
Longaker said, “I want to see how broadly applicable this technique may be.” He was referring to tissues that do not heal well. For example, cartilage heals very poorly if at all. Longaker wonders if you could “add some cells that can form replacement tissue in this macroenvironment while you’re already looking at the joint.”
A study from the laboratory of Armand Keating at the University of Toronto and Princess Margaret Hospital has compared the ability of umbilical cord stem cells and bone marrow stem cells to repair the hearts of laboratory animals after a heart attack. The umbilical cord stem cells showed a clear superiority to bone marrow stem cells when it came to repairing heart muscle.
Keating used human umbilical cord perivascular cells (HUCPVCs) for his experiment, and these cells are widely regarded as a form of umbilical cord mesenchymal stem cell that surround the umbilical cord blood vessels.
Transplantation of cells from either bone marrow or umbilical cord into the heart soon after a heart attack improved the function and structure of the heart. However, functional measurements showed that the HUCPVCs were twice as effective as bone marrow stem cells at repairing the heart muscle.
Keating added: “We are hoping that this translates into fewer people developing complications of heart failure because their muscle function after a heart attack is better.”
In addition to further pre-clinical tests, Keating and his research team hope to initiate clinical trials with human patients within 12-18 months. Keating is also interested in testing the ability of umbilical cord stem cells to heal the hearts of those cancer patients who have experienced heart damage as a result of chemotherapy. In such patients, chemotherapy rids their bodies of cancer, but the cure is worse than the cancer, since the drugs also leave the patients with a severely damaged heart. Such stem cell transplantations could potentially strengthen the hearts of these patients, and give them a new lease on life. My own mother died from congestive heart failure as a result of an experimental arsenic treatment that killed her heart muscle. My mother suffered from chronic myelogenous disease and the arsenic was meant to kill off all the rogue cells in her bone marrow, but instead it killed her heart. If such a stem treatment were available then, my mother might still be with me.
There are over 250 clinical trials with mesenchymal stem cells to date to treat conditions ranging from Crohn’s disease to neurological conditions. Also, a recent meta-analysis has established the safety of mesenchymal stem cell treatments for several different conditions (see Lalu MM, McIntyre L, Pugliese C, Fergusson D, Winston BW, et al. (2012) Safety of Cell Therapy with Mesenchymal Stromal Cells (SafeCell): A Systematic Review and Meta-Analysis of Clinical Trials. PLoS ONE 7(10): e47559. doi:10.1371/journal.pone.0047559).
Mesenchymal stem cells (MSCs) have the ability to home to growing tumors, and for this reason, many researchers have examined the possibility of using MSCs to treat various types of cancers. However, there is a genuine safety concern with using MSCs in cancer patients, because in laboratory animals, MSCs can form blood vessels that help tumors grow and spread. Consider the following publications:
1. Klopp AH, Gupta A, Spaeth E, Andreeff M, Marini F 3rd (2011) Concise review: Dissecting a discrepancy in the literature: do mesenchymal stem cells support or suppress tumor growth? Stem Cells 29: 11–19.
2. Kidd S, Spaeth E, Klopp A, Andreeff M, Hall B, et al. (2008) The (in) auspicious role of mesenchymal stromal cells in cancer: be it friend or foe. Cytotherapy 10: 657–667.
3. Coffelt SB, Marini FC, Watson K, Zwezdaryk KJ, Dembinski JL, et al. (2009) The pro-inflammatory peptide LL-37 promotes ovarian tumor progression through recruitment of multipotent mesenchymal stromal cells. Proc Natl Acad Sci U S A 106: 3806–3811.
4. Karnoub AE, Dash AB, Vo AP, Sullivan A, Brooks MW, et al. (2007) Mesenchymal stem cells within tumour stroma promote breast cancer metastasis. Nature 449: 557–563.
Because MSCs are multipotental (that is they differentiate into several different adult tissues), they can serve the tumor as a source of blood vessels that augment tumor metastasis and growth. However, several pre-clinical studies with genetically engineered MSCs that deliver chemotherapuetic agents to tumors have proven quite successful (see Waterman RS, Betancourt AM (2012) The role of mesenchymal stem cells in the tumor microenvironment: InTech). So what are we to believe? After MSCs good or bad as tumor treatments?
In 2010, Aline M. Betancourt and colleagues at Tulane University, New Orleans, Louisiana defined two distinct MSC subypes in a MSC population. They referred to these subtypes as MSC1 and MSC2. When challenged with molecules normally found in invading microorganisms, MSC1 populations tend to promote the immune response, where as MSC2 populations tend to suppress the immune response. This simple priming experiment provided a way to distinguish between the two MSC subtypes, but it also gave stem cell scientists a reason why experiments with MSCs tend to give conflicting results in different laboratories – because the two labs were probably working with populations that consisted of different MSC subtypes. See Waterman RS, Tomchuck SL, Henkle SL, Betancourt AM (2010) A New Mesenchymal Stem Cell (MSC) Paradigm: Polarization into a Pro-Inflammatory MSC1 or an Immunosuppressive MSC2 Phenotype. PLoS ONE 5(4): e10088. doi:10.1371/journal.pone.0010088.
With this in mind, Betancourt and co-workers examined the ability of the distinct MSC subtypes to interact with cancers. When grown in culture with several different types of tumor-causing cell lines, they discovered that MSC1 do not support tumor growth but MSC2 robustly support tumors growth. MSC2 also increased the ability of the tumors to invade other tissues and migrate in culture whereas MSC1 supported neither tumor invasion nor tumor migration.
Other features were different as well. For example, MSC1 recruited a completely different cadre of white blood cells to the tumor when compared to MSC2. Also, the molecules deposited in the vicinity of the tumor by MSC1 and MSC2 differed greatly. By providing a bed of molecules upon which tumors cell like to move and grow, MSC2s promoted tumor cell activity, but the materials laid down by MSC1 were not nearly as attractive to the tumor cells.
These show why MSCs can promote the growth of particular tumors in some experiments but not others. Furthermore, it shows that there is a relatively simple test to separate these two MSC subtypes. All further pre-clinical experiments with MSCs, should account for these distinct MSC subtypes and determine if one MSC subtype is a better candidate for an anticancer treatment regime than the other.
See Waterman RS, Henkle SL, Betancourt AM (2012) Mesenchymal Stem Cell 1 (MSC1)-Based Therapy Attenuates Tumor Growth Whereas MSC2-Treatment Promotes Tumor Growth and Metastasis. PLoS ONE 7(9): e45590. doi:10.1371/journal.pone.0045590.
A very nice entry from the Stem Cell Blog. Danish stem cell scientists have had unparalleled success generating insulin-producing cells from stem cells if they grow them in a three-dimensional culture. Check it out. You will be glad you did.
Scientists have reported improved results for creating insulin-producing cells within a 3 dimensional environment, as opposed to the standard 2 dimension within a Petri dish. By creating an environment that mimics the inside of an embryo, scientists are able to use this new knowledge to improve diabetes treatment and stem cell treatments for chronic diseases of internal organs.
Scientists from The Danish Stem Cell Center (DanStem) at the University of Copenhagen are contributing important knowledge about how stem cells develop best into insulin-producing cells. In the long-term this new knowledge can improve diabetes treatment with cell therapy. The results have just been published in the scientific journal Cell Reports.
Stem cells are responsible for tissue growth and tissue repair after injury. Therefore, the discovery that these vital cells grow better in a three-dimensional environment is important for the future treatment of disease with stem cell therapy. “We can see that…
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