The REPAIR-AMI clinical trial was a double-blind placebo-controlled trial in which 204 recent heart attach patients received either an infusion of bone marrow stem cells or a placebo. The results of this clinical trial have been published in three different papers (Schächinger, et al., N Engl J Med 2006 355: 1210-1221; Schächinger, et al., Eur Heart Journal 2006 27: 2775-2783; Schächinger, et al., Nat Clin Pract Cardvasc Med 2006 3(Suppl 1): 523-528).
This clinical trial showed that the bone marrow-treated group showed significant functional improvements over the placebo group. However, a long-term follow-up of these patients was required to demonstrate that the benefits conferred by the stem cell treatments were long-lasting and not merely transient.
Upon 5-year examination, the stem cell-treated group showed lower rates of a second heart attack, hospitalization, strokes, cancer, surgical interventions to open blocked vessels and death. Thus, the stem cell-treated group fared better in almost all the major categories.
There was, however, an additional experiment that gave a truly remarkable result. After each patient had their bone marrow extracted, the stem cells were subjected to individual tests, one of which were mobility tests. When this research group examined the stem cell motility data and correlated it to the five-year follow-up, they discovered a very tight association between the motility of the bone marrow stem cells and the absence of cardiac events. More active bone marrow cells provided greater recovery and fewer post-procedural events.
These data show that the quality of the bone marrow is a significant factor in the success of the stem cell treatment.
This also brings up another question: Can be beef up the quality of the bone marrow some how? Culturing stem cells can expand them, but it can also significantly change them. Therefore, this remains a fertile field for research and development, and the bone marrow quality may also explain why bone marrow transplants into the heart work so well or some patients and not at all for others.
A new analysis of stem cell trials that targeted degenerative disc disease of the spine in animals has shown that these treatments are effective in halting or even reversing this disease. Such results should facilitate the implementation of human clinical trials.
Our spinal cords are encased in a protective body of bone known as the vertebral column. The vertebral column consists of a stack of vertebral bodies that are positioned with one vertebra one on top of the other. Between each pair of vertebral bodies is a cushion-like structure known as the intervertebral disc. The intervertebral disc absorbs the stress and shock placed on the vertebral column when someone walks, runs, moves, bends, or twists. The discs prevent the vertebral bodies from grinding against each other.
Structurally, the intervertebral discs are unique. They have no blood supply of their own, and are, as a matter of fact, the largest structures in the body without their own blood vessel system. Instead they absorb the nutrients they need from circulating blood by means of osmosis.
Each intervertebral disc is composed of two parts: an outer annulus fibrosus (fibrous ring) and the nucleus pulposus (pulpy interior). The annulus fibrosus is a ring-like structure that completely encases the nucleus pulposus. It is composed of water and strong elastic collagen fibers bound together by glue-like material called proteoglycan. The arrangement of these collagen fibers at varying angles relative to each other makes the annulus fibrosus a rather strong structure. The annulus fibrous stabilizes the intervertebral disc and helps the spine can rotate properly and resist compression or other stresses placed on the spine.
The center portion of the intervertebral disc that is protected by the annulus fibrosus is a gel-like elastic substance called nucleus pulposus. The nucleus pulposus transmits and transfers stress and weight placed on vertebrae during movement and activity. The nucleus pulposus is made of the same basic materials as the nucleus fibrosus: water, collagen, and proteoglycans. The main difference between the ring-like annulus fibrosus and the gel-like nucleus pulposus is the relative amounts of these substances. The nucleus pulposus contains more water than the annulus fibrosus.
Recent developments in stem cell research have made it possible to measure the effects of stem cells treatments on intervertebral disc height. Researchers at the Mayo Clinic in Rochester, Minnesota have pioneered such techniques.
In preclinical animal studies, stem cell treatments have been used to treat animals with degenerative disc disease. Because degenerative disc disease can great affect someone’s quality of life and productivity, such a treatment has been highly sought after.
Wenchun Qu, MD, PhD, of the Mayo Clinic in Rochester, Minn said that stem cell injections into degenerating intervertebral discs not only increased disc height, but also increased disc water content and improved the expressed of particular genes. “These exciting developments place us in a position to prepare for translation of stem cell therapy for degenerative disc disease into clinical trials,” said Qu.
Animals that had received stem cell injections into their intervertebral discs had a disc structure that was large restored. The nucleus pulposus showed an increased water content and improved abilities to transfer shear forces.
In their analysis, Qu and his colleagues examined six preclinical trials and only examined those studies that were randomized and properly controlled. Because of various methodological differences between these studies, Qu and his gang used a random-effects model to analyze the data. Random-effects models, put simply, put all the animals in a group of studies together and assumes that they can be placed in a hierarchy of those who are the sickest to those who are the least sick. By placing the individuals in a hierarchy like this they can be classified accordingly and the effects of their treatments assessed fairly.
When properly and rigorously analyzed, the intervertebral disc height increases were significant in all six studies. What they found was an over 23.6% increase in the disc height index in the transplant group compared with the placebo group (95% confidence interval [CI], 19.7-23.5; p < 0.001). None of the 6 studies showed a decrease of the disc height index in the transplant group. Increases in the disc height index were statistically significant in all individual studies.
On the strength of these preclinical studies, Qu and his colleagues think that it is time to determine the safety, feasibility, and efficacy of stem cell transplants for degenerative disc disease in human patients.
Because intervertebral discs show such poor regenerative capabilities, degenerative disc disease is an excellent candidate for stem cell treatments. Also, present treatments tend to be very invasive and often make the disc worse.
Adi Shruster and Daniel Offen from Tel Aviv University in Israel have shown in a rodent model of Alzheimer’s disease (AD) that stimulating brain cell regeneration can alleviate some of the symptoms of AD.
A particular mouse strain called 3xTgAD serves as a model system for the study of AD. These mice have several genetic modifications that cause the formation of senile plaques in the brain that also lead to behavioral abnormalities and cognitive decline. In short, the Presenilin gene, which plays a definitive role in the onset of AD, has a mutation engineered in it. This particular mutation (M146V) shows a very strong causative link to inherited forms of AD (MA Riudavets, et al., Brain Pathology 2013 23(5): 595–600).
Additionally, 3xTgAD mice have a synthetic gene inserted in them that overproduces two proteins that also contribute to the onset of AD: amyloid precursor protein (APP) and another protein called tau. The combination of these three genes causes the formation of amyloid plaques and neurofibrillary tangles that are so characteristic of AD, although these plaques are not exactly the same as those observed in human AD patients (see Matthew J. Winton, et al., Journal of Neuroscience 31(21):7691–7699).
Shruster and Offen used these 3XTgAD mice to determine if inducing new brain cells in the brain could improve their condition. Offen overexpressed a gene called Wnt3a in a part of the brain known to play a role in regulating behavior. Wnt3a is known to drive cell proliferation in this part of the brain. After driving Wnt3a expression in the brains of 3XTgAD mice, Offen subjected them to behavioral tests.
Normal mice tend to pause and assess their surroundings when they enter unfamiliar places. However, 3xTgAD mice tend to charge straight in when entering new surroundings. This lack of proper danger assessment in 3xTgAD mice disappeared when Wnt3a was expressed in their brains. Upon post-mortem examination, these mice showed the formation of new nerve cells in their brains. When new brain cell formation was abrogated with X-rays, the behavioral defect was maintained.
Offen commented: “Until 15 years ago, the common belief was that you were born with a finite number of neurons. You would lose them as you age or as a result of injury or disease.”
Human AD patients can lose their sense of space and reality and do very inappropriate things at particular times. Therefore, these mice do recapitulate particular features of the human disease.
Offen and his colleagues think that establishing the growth of new brain cells in human AD patients might alleviate some of the behavioral abnormalities. Furthermore, stem cell treatments might also have a positive role to play in the treatment of AD, although Offen will readily admit that more work must be done.
The absence of recruited neutrophils to the periodontal tissue in LAD patients leads to unrestrained local production of IL-23 and hence IL-17 and G-CSF. Increased IL-17 leads to inflammatory bone loss and dysbiosis, whereas increased G-CSF leads to excessive release of mature neutrophils from the bone marrow. In contrast, normal recruitment of neutrophils regulates the expression of the same cytokines maintaining homeostasis in terms of periodontal health and release of mature neutrophils from the bone marrow. Credit: Copyright Niki Moutsopoulos and George Hajishengallis
Patients with leukocyte adhesion deficiency, or LAD, suffer from frequent bacterial infections, including the severe gum disease known as periodontitis. These patients often lose their teeth early in life. New research by University of Pennsylvania School of Dental Medicine researchers, teaming with investigators from the National Institutes of Health, has demonstrated a method of reversing this bone loss and inflammation.
Nrf2 is a protein that regulates the response of cells to oxidative damage, This protein normally sits in the cytoplasm of cells where it is routinely degraded by other proteins. However, once cells are exposed to oxidative damage by ultraviolet light, reactive oxygen species, various chemicals, or other conditions that damage cellular structures, the degradation of Nrf2 slows way down and this protein moves into the nucleus where it binds DNA and stimulates the expression of a host of genes that encode proteins with anti-oxidant activity. Thus Nrf2 is one of the primary cellular defenses against the toxic effects of oxidative stress.
Raj Soorappan and his colleagues have discovered that the muscles of these Nrf2-deficient mice do not regenerate as they get older.
Soorappan explained: “Physical activity is the key to everything.” He continued: “After this study we believe that moderate exercise could be one of the key ways to induce stem cells to regenerate especially during aging.”
Sarcopenia or the age-related loss of muscle mass, begins in most people around the age of 30. To delay this inevitable slide, muscle=producing stem cells help regenerate muscle lost by means of aging and the production of antioxidant molecules help protect stem cells populations so that they can maintain muscle mass.
However, as we age, the production of reactive oxygen species (ROS) overwhelms our endogenous antioxidant systems, and our stem cell populations take a hit. This compromises our ability to regenerate muscle and other tissues as well.
As previously mentioned, Nrf2 regulates the production of these antioxidant molecules. Soorappan used mice that were 23 months old or older (these are rodent senior citizens to be sure). One group of old mice made normal levels of Nrf2, but the other group had no functional Nrf2 protein. Soorappan and his colleagues put these mice through endurance training to determine the effects of ROS on these animals. Interestingly, the Nrf2-deficient mice showed an inability to mobilize their muscle stem cells (satellite cells) to regenerate their muscles. The Nrf2-containing mice, however, were able to properly regenerate their muscles.
“We now know that the antioxidant protein Nrf2 guards the muscle regeneration process in elderly mice and loss of Nrf2, when combined with endurance exercise stress, can cause severe muscle stem cell impairment,” said Mudhusudhanan Narasimhan, the primary author of this research and a research associate with Soorappan.
Soorappan thinks that by understanding the precise role of Nrf2 in muscle regeneration, he an his co-workers will be able to design more informed therapies of muscle loss in aging animals and humans.
Next on Soorappan’s agenda is to examine the effects of exercise on Nrf2 and whether or not an active lifestyle affects the function of Nrf2 and the efficiency of the anti-oxidant pathway it mediates.
The take-home message for now seems to be: “If you don’t use your muscles, you will lose them. At the same time, overdoing endurance training may detract from muscle regeneration,” said Soorappan.
Researchers from Chicago, Illinois have shown that a fatty fold of tissue within the abdomen contains a rich source of stem cells that can help heal diseased kidneys.
Scientists from the laboratory of Ashok K. Singh at Hospital of Cook County used a rat model of chronic kidney disease to examined the efficacy of these cells.
In past experiments, transplanted stem cells have failed to live very long in the body of the recipient. To solve this problem, Singh and his co-workers connected the a fatty fold of tissue located close to the kidney called the “omentum” to the kidney. The omentum is a wonderfully rich source of stem cells and by connecting the kidney to the omentum, Singh and his colleagues subjected the diseased kidney to a constant supply of stem cells.
After 12 weeks of being connected to the kidney, the kidney showed significant signs of improvement.
The progression of chronic kidney disease was slowed due to this continuous migration of stem cells from the omentum to the diseased kidney. The influx of these stem cells seemed to direct healing of the kidney.
This experiment is significant in that it suggests that resident stem cells that facilitate healing of the kidney, but only when they are in contact with the tissue over a long period of time. Also, it implies that a supposedly useless organ that lies close to the kidney can be fused with the kidney to heal it with a patient’s own stem cells. This therapeutic strategy seems to be ideal for kidney patients.
Patients who suffer from malformation of the spinal cord or have suffered a severe spinal cord injury sometimes have bladder malfunction as well. Replacing a poorly functioning bladder is a goal of regenerative medicine, but it is not an easy goal. The bladder is lined with a special cell population called “urothelium.” Urothelium is found throughout the urinary tract and it is highly elastic. Persuading stem cells to form a proper urothelium has proved difficult.
Now scientists from the University of California, Davis (my alma mater), have succeeded in devising a protocol for differentiating human pluripotent stem cells into urothelium. The laboratory of Eric Kurzock, chief of the division of pediatric urologic surgery at UC Davis Children’s Hospital, published this work in the journal Stem Cells Translational Medicine. This work is quite exciting, since it provides a way to potentially replace bladder tissue for patients whose bladders are too small or do not function properly.
Kurzock explained: “Our goal is to use human stem cells to regenerate tissue in the lab that can be transplanted into patients to augment or replace their malfunctioning bladders,”
In order to make bladder cells in the laboratory, Kurzrock and his coworkers used two different types of human pluripotent stem cells. First, they used two types of induced pluripotent stem cells (iPS cells). The first came from laboratory cultures of human skin cells that were genetically engineered and cultured to form iPS cultures. The second iPS line was derived from umbilical cord blood cells that had been genetically reprogrammed into an embryonic stem cell-like state.
Even though further work is needed to establish that bladder tissues made from such stem cells are safe or effective for human patients, Kurzrock thinks that iPS cell–derived bladder grafts made from a from a patient’s own skin or umbilical cord blood cells represent the ideal tissue source for regenerative bladder treatments. This type of tissue would be optimal, he said, because it lowers the risk of immunological rejection that typifies most transplants.
One of the truly milestone developments in this research is the protocol Kurzrock and his colleagues developed to direct pluripotent stem cells to differentiate into bladder cells. This protocol was efficient and, most importantly, allowed the stem cells to proliferate in culture over a long period of time. This is crucial in order to have enough material for therapeutic purposes.
“What’s exciting about this discovery is that it also opens up an array of opportunities using pluripotent cells,” said Jan Nolta, professor and director of the UC Davis Stem Cell program and a co-author on the new study. “When we can reliably direct and differentiate pluripotent stem cells, we have more options to develop new and effective regenerative medicine therapies. The protocols we used to create bladder tissue also provide insight into other types of tissue regeneration.”
To hone their urothelium-differentiation protocol, Kurzrock and his colleagues used human embryonic stem cells obtained from the National Institutes of Health’s human stem cell repository. These cells were successfully differentiated into bladder cells. Afterwards, the Kurzrock group used the same protocol to coax iPS cells made from skin and umbilical cord blood into urothelium. Not only did these cells look like urothelium, but they also expressed the protein “uroplakin,” which is unique to the bladder and helps make it impermeable to toxins in urine.
In order to bring this protocol to the clinic, the cells must proliferate, differentiate and express bladder-specific proteins without depending on any animal or human products. They must do all these things independent of signals from other human cells, said Kurzrock. Therefore, for future research, Kurzrock and his colleagues plan to modify their laboratory cultures so that they will not require any animal and human products, which will allow use of the cells in patients.
Kurzrock’s primary goal as a physician is with children who suffer from spina bifida and other pediatric congenital disorders. Currently, when he surgically reconstructs a child’s defective bladder, he must use a segment of their own intestine. Because the function of intestine, which absorbs food, is almost the opposite of bladder, bladder reconstruction with intestinal tissue may lead to serious complications, including urinary stone formation, electrolyte abnormalities and cancer. According to Kurzrock, developing a stem cell alternative not only will be less invasive, but should prove to be more effective, too, he said.
Another patient group who might benefit from this research is bladder cancer patients. More than 70,000 Americans each year are diagnosed with bladder cancer, according to the National Cancer Institute. “Our study may provide important data for basic research in determining the deviations from normal biological processes that trigger malignancies in developing bladder cells,” said Nolta. More than 90 percent of patients who need replacement bladder tissue are adults with bladder cancer. Kurzrock said “cells from these patients’ bladders cannot be used to generate tissue grafts because the implanted tissue could carry a high risk of becoming cancerous. On the other hand, using bladder cells derived from patients’ skin may alleviate that risk. Our next experiments will seek to prove that these cells are safer.”