Georgia Tech Scientists Reverse Aging in Adult Stem Cells

A research group from the Buck Institute for Research on Aging and the Georgia Institute of Technology has managed to reverse the aging process for human adult stem cells. Because stem cells are responsible for helping old or damaged tissues regenerate, these findings could lead to medical treatments that repair tissues when they deteriorate as a result of aging. This research was published in the September 1, 2011 edition of the journal Cell Cycle

Aging causes the regenerative power of tissues and organs to wane. The modern-day stem cell hypothesis of aging postulates that living organisms are as old as their tissue-specific (adult) stem cells. This implies that an understanding of the molecules and processes that enable human adult stem cells to initiate self-renewal and to divide, proliferate and subsequently differentiate in order to rejuvenate damaged tissues might be the key to regenerative medicine and an eventual cure for many age-related diseases.

Victoria Lunyak, associate professor at the Buck Institute for Research on Aging, who was involved with this study, said: “We demonstrated that we were able to reverse the process of aging for human adult stem cells by intervening with the activity of non-protein coding RNAs originated from genomic regions once dismissed as non-functional ‘genomic junk.”

Adult stem cells keep human tissues healthy by replacing cells that have gotten old or damaged. These same stem cells are “multipotent,” which means that they can grow and replace any number of body cells in the tissue or organ to which they belong. However, just as the cells in the liver, or any other organ, can suffer damaged over time, adult stem cells undergo age-related damage. When this occurs, the body can’t replace damaged tissue as well as it once could, which leads to a host of diseases and conditions. However, if physicians can use procedures and treatments that keep these adult stem cells young, they could possibly use these adult stem cells to repair damaged heart tissue after a heart attack; heal wounds; correct metabolic syndromes; produce insulin for patients with type 1 diabetes; cure arthritis and osteoporosis and regenerate bone.

This research team hypothesized that DNA damage in the genome of adult stem cells would look very different from age-related damage occurring in regular body cells. Bodily cells are known to experience a shortening of the caps found at the ends of chromosomes, known as telomeres. However, adult stem cells are known to maintain their telomeres, and much of the damage in aging is widely thought to be a result of telomere loss. Therefore, there must be different mechanisms in play that are essential to explaining how aging occurs in these adult stem cells, they thought.

Researchers used adult stem cells from humans and combined experimental techniques with computational approaches to study the changes in the genome associated with aging. They compared freshly isolated human adult stem cells from young individuals, which can self-renew, to cells from the same individuals that were subjected to prolonged passaging in culture. This accelerated model of adult stem cell aging exhausts the regenerative capacity of the adult stem cells. Researchers looked at the changes in genomic sites that accumulate DNA damage in both groups. King Jordan, associate professor in the School of Biology at Georgia Tech, said, “We found the majority of DNA damage and associated chromatin changes that occurred with adult stem cell aging were due to parts of the genome known as retrotransposons. Retroransposons were previously thought to be non-functional and were even labeled as ‘junk DNA’, but accumulating evidence indicates these elements play an important role in genome regulation.”

While the young adult stem cells were able to suppress transcriptional activity of these genomic elements and deal with the damage to the DNA. However, older adult stem cells were not able to scavenge this transcription. This new discovery suggests that this event is deleterious for the regenerative ability of stem cells and triggers a process known as cellular senescence. Victoria Lunyak described it this way: “By suppressing the accumulation of toxic transcripts from retrotransposons, we were able to reverse the process of human adult stem cell aging in culture. Furthermore, by rewinding the cellular clock in this way, we were not only able to rejuvenate ‘aged’ human stem cells, but to our surprise we were able to reset them to an earlier developmental stage, by up-regulating the “pluripotency factors” – the proteins that are critically involved in the self-renewal of undifferentiated embryonic stem cells.”

In the future, the team plans to use further analysis to validate the extent to which the rejuvenated stem cells may be suitable for clinical tissue regenerative applications.

Spinal Cord Stem Cell Transplant Performed

The Biotechnology company StemCells, Inc. announced that the first patient in the company’s Phase 1/2 clinical trial to treat chronic spinal cord injury was successfully transplanted with the company’s HuCNS-SC adult neural stem cells. These stem cells were administered at Balgrist University Hospital, University of Zurich and the transplant surgery was performed by a team of surgeons led by Raphael Guzman, MD, a visiting staff neurosurgeon also on faculty at department of neurosurgery, Stanford University, and K. Min, MD, an orthopedic surgeon at Balgrist University Hospital.

The first patient transplanted in the trial is a 23-year-old German man, who suffered a spinal cord injury in an automobile accident in April, 2011. This gentleman sustained a complete loss of sensation and mobility from the waist down. Stephen Huhn MD, FACS, FAAP, vice president and head of the CNS program at StemCells Inc said “With this first patient enrolled and dosed, we remain on track to meet our goal of treating the first cohort of patients by the end of this year. While the trial’s first cohort will consist of patients with the most severe, complete injury, the second and third cohorts will progress to patients with less severe, incomplete injury. This unique trial design will allow us to evaluate the potential of our HuCNS-SC cells as a treatment for a broad spectrum of spinal cord injury patients. Even a small improvement could have a marked impact on quality of life for the millions of people who suffer from this debilitating condition.”

StemCells Inc’s phase I/II clinical trial of their HuCNS-SC purified human adult neural stem cell line is designed to assess both safety and preliminary efficacy. Twelve patients with thoracic (chest-level) neurological injuries at the T2-T11 level are planned to be enrolled in this exciting trial. The first three patients will all have injuries classified as ASIA A, in which there is no apparent neurological function below the injury level, the most severe level identified by the American Spinal Injury Association (ASIA) Impairment Scale. The second and third cohorts will be patients classified as ASIA B and ASIA C, those with less severe injury, in which there is some preservation of sensory or motor function. In addition to assessing safety, the trial will assess preliminary efficacy based on defined clinical endpoints, such as changes in sensation, motor and bowel/bladder function.

All patients will receive HuCNS-SC cells through direct transplantation into the spinal cord and will be receive temporary suppression of the immune system to ensure that the transplanted cells are not rejected by the patient’s immune system.  Patients will be evaluated regularly in the post-transplant period in order to monitor and assess the safety of the HuCNS-SC cells, the surgery and the immunosuppression, as well as to measure any recovery of neurological function below the injury site.  The company intends to follow the effects of this therapy long-term, and a separate 4-year observational study will be initiated at the conclusion of this trial.

UBC-Vancouver Coastal Health Researcher Discovers New Type Of Spinal Cord Stem Cell

University of British Columbia and Vancouver researchers have discovered a new type of spinal cord stem cells that seems to possess the ability to regenerate components of the central nervous system in patients with spinal cord injuries and neurological diseases like Lou Gehring’s Disease. These newly characterized cells, called radial glial cells, have long projections that can find their way through brain tissue. They had never been observed in adult spinal cord, and these cells are instrumental in building the brain and spinal cord during embryonic development of the nervous system. Radial glial cells vastly outnumber other potential stem cells in the spinal cord and are much more accessible.

Stem cells can divide replacement cells and can also differentiate into more specialized types of cells. This differentiation can occur either during the growth of an organism or when there is a need to help replenish other cells. The search for spinal stem cells of the central nervous system has previously focused upon cells located deep within the spinal cord. Jane Roskams, professor in the UBC Dept. of Zoology, broadened the search by using genetic profiles of nervous system stem cells that were developed and made publicly accessible by the Allen Institute for Brain Science in Seattle. Roskams, in collaboration with researchers at the Allen Institute, McGill University and Yale University, found cells with similar genes – radial glial cells – along the outside edge of spinal cords of mice.

Roskams noted, “That is exactly where you would want these cells to be if you want to activate them with drugs while minimizing secondary damage.” Roskams’ team also found that radial glial cells in the spinal cord express a unique set of genes that are also expressed in particular types of neural stem cells. Mutations in several of these genes can lead to human diseases, including those that target the nervous system. This discovery opens new possibilities for potential gene therapy treatments that would replace mutated, dysfunctional spinal cord cells with healthier ones produced by the radial glial cells.

Roskams continued, “These long strands of radial glial cells amount to a potentially promising repair network that is perfectly situated to help people recover from spinal cord injuries or spinal disorders. For some reason, they aren’t re-activated very effectively in adulthood. The key is to find a way of stimulating them so they reprise their role of generating new neural cells when needed.”

The Successful Culturing of Blood-Making Stem Cells

The blood-making stem cell within the bone marrow (hematopoietic stem cell or HSC) is a marvelous thing. It grows throughout our lives and replenishes red and white blood cells, and also contributes to the production of new blood vessels. However, attempts to culture this cell in the laboratory have met with only limited success; until now. Researchers at the Stowers Institute for Medical Research investigated the molecular mechanisms that HSCs from mice and applied their insights to expand cultured HSCs one hundred fold.

Stowers investigator Linheng Li led the study and these findings have been published in the Sept. 15, 2011, edition of Genes & Development. This paper demonstrates that self-renewal requires three complementary events: proliferation and active suppression of differentiation and programmed cell death during proliferation. Li said: “The previous efforts so far to grow and expand scarce hematopoietic stem cells in culture for therapeutic applications have been met with limited success. Being able to tap into stem cell’s inherent potential for self-renewal could turn limited sources of hematopoietic stem cells such as umbilical cord blood into more widely available resources for hematopoietic stem cells.” Li added that their findings have yet to be replicated in human cells.

HSC transplantations have been used to treat conditions like anemia, immune deficiencies and other diseases, including cancer. However, bone marrow transplants require a suitable donor-recipient tissue match, and this limits the number of potential donors is limited. Hematopoietic stem cells isolated from umbilical cord blood could be a good alternative source, since they are readily available and not readily recognized by the immune system. Therefore, umbilical cord HSCs allow the donor-recipient match to be less than perfect without the risk of immune rejection of the transplant. Unfortunately, the therapeutic use of HSCs is limited since umbilical cord blood contains only a small number of stem cells.

John Perry, first author on this paper, noted, “The default state of stem cells is to differentiate into a specialized cell types. Differentiation must be blocked in order for stem cells to undergo self-renewal.” Although self-renewal is typically considered a single trait of stem cells, Li and his team wondered whether it could be pulled apart into three distinct requirements: proliferation, maintenance of the undifferentiated state, and the suppression of programmed cell death or apoptosis. Stem cell proliferation in an undifferentiated state activates genes called “tumor suppressor” genes into action. Tumor suppressor genes help prevent cancer by inducing a programmed death (also known as apoptosis). Consequently, self-renewal of adult stem cells must also include this third event and that even it suppression of apoptosis.

Perry and his colleagues isolated mouse HSCs from mouse bone marrow and analyzed two key genetic pathways—the Wnt/β-catenin and PI3K/Akt pathways. Wnt proteins are “self-renewal factors,” while PI3K/Akt activation has been shown to induce proliferation and promote survival by inhibiting apoptosis. Activation of the Wnt/β-catenin pathway alone blocked differentiation but eventually resulted in cell death. Activation of the PI3K/Akt pathway alone increased differentiation but facilitated cell survival. However, when both pathways were simultaneously activated, the pool of HSCs started expanding in culture. This demonstrates that both pathways must cooperate to promote self-renewal.

Although altering both pathways drives HSC self-renewal, it also permanently blocks the ability of these cells to mature into fully functional blood cells. To prevent the block to differentiation and generate normal, functioning HSCs usable for therapy, the Stowers scientists used small molecules to reversibly activate both the Wnt/β-catenin and PI3K/Akt pathways in culture. As Li put it, “We were able to expand the most primitive hematopoietic stem cells, which, when transplanted back into mice gave rise to all blood cell types throughout three, sequential transplantation experiments,” says Li. “If similar results can be achieved using human hematopoietic stem cells from sources such as umbilical cord blood, this work is expected to have substantial clinical impact.”

Induced Pluripotent Stem Cells are almost exactly like Embryonic Stem Cells when it comes to Protein production

Induced pluripotent stem cells (iPSCs) have many characteristics of embryonic stem cells (ESCs), but they also have some differences. Ever since iPSCs were discovered, there has been a great deal of interest in determining if these cells are similar enough to ESCs for their use in clinical settings.

The similarities are striking: (1) iPSCs and ESCs both cell types have the ability to differentiate into any cell in the body; (2) both can cause teratomas when transplanted into mice with nonfunctional immune systems; (3) both can be grown in culture for long periods of time. However, they have different origins; ESCs come from embryos and iPSCs come from adult tissue. Furthermore many of the genes they express are not completely the same.

A recent study by researchers at the University of Wisconsin at Madison has used assessments of the full range of proteins made by iPSCs and ESCs. Their conclusions are 99% of the proteins made by both types of stem cells (they examined four embryonic stem cell lines and four IPS cell lines) are 99% similar.

According to Joshua Coon, principal investigator of the study and associate professor of chemistry and biomolecular chemistry, “We looked at RNA, at proteins, and at structures on the proteins that help regulate their activity, and saw substantial similarity between the two stem-cell types.”

This study used mass spectroscopy to classify each protein made within the cells and this work, which was published in Nature Methods online. This is the first comprehensive comparison of proteins made in the two stem cell types. Cells make proteins for structural, metabolic, and informational purposes, and protein synthesis is often a direct read-out of gene expression, since many genes encode messenger RNAs that are translated into proteins. Doug Phanstiel at Stanford University, who was a contributor to this project , who is now at Stanford University, said, “From a biological standpoint, what is novel is that this is the first proteomic comparison of embryonic stem cells and IPS cells.”

This study also examined the examined all RNAs made by the cells, the proteins synthesized from them, and the concentrations of these molecules. Also because this study compared four lines of each type of stem cell, and the comparisons were run three times, the statistics in this study are exceedingly robust. According to Coon, embryonic stem cells and IPS cells are quite similar. The protein production of an embryonic stem cell was closer to that of an IPS cell than to a second embryonic stem cell.

This study is not the last word in determining the similarity of the two types of pluripotent stem cells. Clinical uses of either type of stem cells will require that they be transformed into more specialized cells, and researchers still need to know more about protein production after stem cells are differentiated into another cell type.

This technology, Coon says, “is now well-positioned to study how closely molecules contained in these promising cells change after they are differentiated into the cells that do the work in our bodies – a critical next step in regenerative medicine.”

Human colon stem cells have been identified and grown in a lab-plate for the first time

Human colon stem cells have been identified and grown in a lab-plate for the first time. This achievement, made by researchers of the Colorectal Cancer Lab at the Institute for Research in Biomedicine in Barcelona, which was published in Nature Medicine, is a crucial advance towards regenerative medicine.

Colonic stem cells regenerate the inner layer of the large intestine throughout out lives on a weekly basis. Evidence of the existence of these cells existed for decades, but culturing them was difficult. Now scientists as the ICREA, led by Professor Eduard Batlle discovered the precise localization of the stem cells in the human colon and designed a method to isolate and expand these stem cells in culture (propagating them in laboratory plates). Growing cells outside the body generally requires providing the cells with the right mix of nutrients, hormones, and growth factors, plus the right environment in a lab dish. Batlle and colleagues tried many concoctions, until they final hit upon the right one. They established the conditions to maintain living human colon stem cells (CoSCs) outside the human body and in culture: This is the first time that it has been possible to grow single CoSCs in lab-plates and to derive human intestinal stem cell lines in defined conditions in a laboratory setting.

After more than ten years of work, a close collaboration between Batlle’s team and the group led by Hans Clevers at the Hubretcht Institute and University Medical Center Utrecht in The Netherlands, and María A. Blasco at the Spanish National Cancer Research Centre in Madrid (Spain) made this momentous find possible. Scientists have been trying to grow intestinal tissue in the laboratory for many years. Because the vast majority of cells in this tissue are fully differentiated, they do not grow when placed in a culture dish. This study found a way to identify and select individual CoSCs and to grow them while maintaining their undifferentiated and proliferative state under laboratory conditions. Now researchers have a defined ‘recipe’ for isolating CoSCs and deriving stable CoSCs lines that have the ability to grow will in an undifferentiated state for months. Scientists were able to maintain CoSCs for up to 5 months, but they can also be differentiated as needed.

This could potentially produce a huge breakthrough in regenerative medicine. Now that the proper guidelines for growing and maintaining colon stem cells in the lab are known, there is an ideal platform that could help the scientific community determine the molecular bases of gastrointestinal cell proliferation and differentiation. Alterations in the properties of CoSCs are responsible for gastrointestinal diseases like colorectal cancer or Crohn’s disease (an autoimmune and inflammatory disorder of the GI tract). This discovery potentially opens new ways to start exploring this exciting field.