New Method Developed to Expand Blood Stem Cells for Bone Marrow Transplant

 More than 50,000 stem cell transplants are performed each year worldwide. A research team led by Weill Cornell Medical College investigators may have solved a major issue of expanding adult hematopoietic stem cells (HSCs) outside the human body for clinical use in bone marrow transplantation — a critical step towards producing a large supply of blood stem cells needed to restore a healthy blood system.

In the journal Blood, Weill Cornell researchers and collaborators from Memorial-Sloan Kettering Cancer Center describe how they engineered a protein to amplify adult HSCs once they were extracted from the bone marrow of a donor. The engineered protein maintains the expanded HSCs in a stem-like state — meaning, they will not differentiate into specialized blood cell types before they are transplanted in the recipient’s bone marrow.

Finding a bone marrow donor match is challenging and the number of bone marrow cells from a single harvest procedure are often not sufficient for a transplant. Additional rounds of bone marrow harvest and clinical applications to mobilize blood stem cells are often required.

However, an expansion of healthy HSCs in the lab would mean that fewer stem cells need to be retrieved from donors. It also suggests that adult blood stem cells could be frozen and banked for future expansion and use — which is not currently possible.

“Our work demonstrates that we can overcome a major technical hurdle in the expansion of adult blood stem cells, making it possible, for the first time, to produce them on an industrial scale,” says the study’s senior investigator, Dr. Pengbo Zhou, professor of pathology and laboratory medicine at Weill Cornell.

If the technology by Weill Cornell passes future testing hurdles, Dr. Zhou believes bone marrow banks could take a place alongside blood banks.

“The immediate goal is for us to see if we can take fewer blood stem cells from a donor and expand them for transplant. That way more people may be more likely to donate,” Dr. Zhou says. “If many people donate, then we can type the cells before we freeze and bank them, so that we will know all the immune characteristics. The hope is that when a patient needs a bone marrow transplant to treat cancer or another disease, we can find the cells that match, expand them and use them.”

Eventually, individuals may choose to bank their own marrow for potential future use, Dr. Zhou says. “Not only are a person’s own blood stem cells the best therapy for many blood cancers, but they may also be useful for other purposes, such as to slow aging.”

A Scrambled Destruction Signal

Bone marrow is the home of HSCs that produce all blood cells, including all types of immune cells. One treatment for patients with blood cancers produced by abnormal blood cells is to remove the unhealthy marrow and transplant healthy blood stem cells from a donor. Patients with some cancers may also need a bone marrow transplant when anticancer treatments damage the blood. Bone marrow transplantation can also be used to treat other disorders, such as immune deficiency disorders.

The process of donating bone marrow, however, can be arduous and painful, requiring extraction of marrow with a needle from a large bone under general anesthesia. A donor may also need to undergo the procedure multiple times in order to provide enough stem cells for the recipient.

Because of these issues of extracting donor bone marrow, there have been a number of attempts to expand HSCs that have focused on the transcription factor HOXB4, which stimulates HSCs to make copies of themselves. “The more HOXB4 protein there is in stem cells, the more they will self-renew and expand their population,” Dr. Zhou says.

But all previous efforts are limited in their applicability. HSCs are notoriously refractory to gene transfer. Virus-based vehicles are thus far the most efficient means to deliver therapeutic genes into HSCs in the laboratory setting. In the past, scientists used a virus as a vehicle to deliver a therapeutic gene into patients with severe combined immunodeficiency disease (SCID) to correct their immune deficiency. However, four children receiving SCID gene therapy developed treatment-related leukemia due to the inability to control where the virus inserts itself in the genome, often on the so-called “hot spots” that activate oncogenes or inactivate tumor suppressor genes. Also, other investigators have shown that it is possible to directly insert HOXB4 protein into extracted bone marrow stem cells. “All you do is add a little tag to the protein, which acts like a vehicle, driving the proteins through the cell membrane, directly into the nucleus,” Dr. Zhou says. “But the half-life of the natural protein is very short — about one hour. So that means that in order to expand blood stem cells, these HOXB4 proteins have to be added all the time. Because the proteins are very costly, this process is both expensive and impractical.” 

Dr. Zhou and his team, in collaboration with Dr. Malcolm A. S. Moore’s group from Memorial Sloan-Kettering Cancer Center, took a different approach. They examined why HOXB4 protein doesn’t last long in HSCs, once these cells are removed from the protective stem cell niche that they nest quietly in. They found that HOXB4 is targeted for degradation so that stem cells can start differentiating — that is, turn into different kinds of adult blood cells. “HOXB4 prevents blood stem cells from differentiating, while, at the same time, allows them to renew themselves,” Dr. Zhou says.

The researchers found that a protein, CUL4, is tasked with recognizing HOXB4 and tagging it for destruction by the cell’s protein destruction apparatus. They discovered that CUL4 recognizes HOXB4 because it “sees” a set of four amino acids on the protein. “HOXB4 carries a destruction signal that CUL4 recognizes and acts on,” Dr. Zhou says.

The research team engineered a synthetic HOXB4 protein with a scrambled destruction signal. They produced large quantities of the protein in bacteria, and then delivered the protein into human blood stem cells in the laboratory. “When you mask the CUL4 degradation signal, HOXB4’s half-life expands for up to 10 hours,” Dr. Zhou says. “The engineered HOXB4 did its job to expand the stem cell, while keeping all its stem cell properties intact. As a result, cells receiving the engineered HOXB4 demonstrated superior expansion capacity than those given natural HOXB4 protein. Animal studies demonstrated that the transplanted engineered human stem cells can retain their stem cell-like qualities in mouse bone marrow.”

Dr. Zhou says the engineered protein HOXB4 can potentially be administered every 10 hours or so to make the quantity of blood stem cells necessary for patient transplant and for banking. “This is the ultimate goal for what we are trying to achieve,” he says. “There are likely many roadblocks ahead to reach our goals, but we appear to have found ways to deal with one major hurdle of adult hematopoietic stem cell expansion.”

Cornell Center for Technology Enterprise and Commercialization (CCTEC), on behalf of Cornell University, has filed a patent application that covers the work described here. Other co-authors include Dr. Jennifer Lee, Dr. Jianxuan Zhang, Dr. Liren Liu, Dr. Yue Zhang, and Dr. Jae Yong Eom from Weill Cornell Medical College; Dr. Giovanni Morrone from the University of Catanzaro “Magna Graecia,” Catanzaro, Italy; and Dr. Jae-Hung Shieh from the Cell Biology Program, Memorial Sloan-Kettering Cancer Center.

The study was supported by grants from the National Institutes of Health (CA118085, CA098210 and NIHA12008023), the Leukemia and Lymphoma Society Scholar Award and the Irma T. Hirschl Career Scientist Award.

 

Source: http://www.sciencedaily.com, Weill Cornell Medical College

The Value of Cord Blood Stem Cells in Healthcare and Research

Currently, cord blood is most commonly used in the treatment of childhood leukemia.  Cord blood offers advantages over treating the disease with bone marrow transplants. In an earlier blog titled “UC Davis Set to Launch California’s First Public Umbilical Cord Blood Bank,” we outlined some of the primary advantages of using cord blood over bone marrow including:

• Shorter time from donor match to transplantation – Frozen cord blood cells can be shipped immediately.  With bone marrow donation, the donor has to be contacted, permission has to be given, and testing and collection has to be conducted before cells are available for transplant.

• Cord blood is easy and painless to obtain – Bone marrow collection on the other hand can be painful for the donor and a potential donor has to be tested with their information on the registry to be selected as a match.  Unfortunately many people may be matches and don’t realize it.

• Cord blood is easier to match donor and patient due to reduced immunogenicity in cells coming from a newborn – HLA matching is the method used when determining a match for transplant.  The process, used with both bone marrow and cord blood matching, looks at 6 proteins in the blood.  Bone marrow requires 5 of 6 proteins to match to be a donor, but in cord blood only 4 of 6 proteins have to match. It is estimated that around 25% of people needing a bone marrow match will not find it and cord blood donations could help reduce this percentage significantly.

Potential New Therapies for Disease

Cord blood stem cells are also being studied as a way to treat many diseases including, Juvenile (Type 1) diabetes, pediatric stroke, traumatic brain injury, Cerebral Palsy, Autism and many others. A few of the trials are described in more detail below:

• A clinical study for traumatic brain injury (TBI) in pediatric patients. TBI is one of the leading causes of death in children and those that survive often have serious brain disabilities. A Phase I TBI study beginning at UT Health is using a patient’s own cord blood that was banked for them as newborns.  This study will enroll 10 children between the ages of 18 months and 17 years with moderate to severe TBI.  Treatment will be administered within 6-18 months of injury and will have safety as the primary endpoint.  Dr. Charles Cox, Director of the Pediatric Trauma Program at Children’s Memorial Hermann Hospital and principal investigator, is leading the study.

• A clinical study for Autism. The double blind, placebo controlled study, conducted by the Sutter Neuroscience Institute will enroll thirty children between the ages of 2-7 years old. Over thirteen months, the children will receive either two infusions of their own cord blood (banked at birth) or two infusions of placebo. There is evidence that some children with Autism suffer from a dysfunctional immune system and this study will examine whether the cord blood cells can help to repair the damaged immune system of these children.

• A clinical study for Cerebral Palsy. Georgia Health Sciences University is conducting a placebo controlled study on forty children between the ages of 1-12. There is research in animals indicating that an infusion of stem cells can induce healing in the brain. This study will look at whether cord blood cells can help to repair damage in the brain.

Cord Blood Stem Cells for Research

One group conducting extensive research using cord blood is The University of California, Davis Institute for Regenerative Cures. The philosophy behind the UC Davis Institute is to bring together physicians, research scientists, biomedical engineers and other experts to work in disease teams all with a focus on moving research into clinical trials.  There are 14 disease teams that address every major area of the human body and the Institute has planned or initiated clinical trials in retinal occlusion, heart attack, peripheral vascular disease, bone repair and Huntington’s disease.  The Institute is also home to one of the largest GMP (Good Manufacturing Practice) facilities for stem cells in the nation.  It has 7,000 square feet of space with a suite of six specially designed rooms created to safely process cellular and gene therapies for clinical trials.

A major research tool for the Institute is the use of neonatal stem cells in research applications.  The neonatal stem cells are collected from placental tissues and cord blood. Researchers at the Institute study neonatal cells in a number of ways.  One way researchers use these cells is to compare the neonatal cells of a newborn with any health problems they may have had at birth to see if there is a link on a cellular level.  They are also studying the environment of these cells in the placenta to find better ways to culture stem cells.  Perhaps the most revealing studies done on these cells are when researchers create “disease in a dish” scenarios.  One example conducted at the institute was on newborns at risk for Huntington’s disease. Researchers isolated hematopoietic stem cells from the cord blood of newborns at risk for Huntington’s disease.  The cells were cultured, induced into a pluripotent state and were differentiated into neurons.  By studying these neurons they could see if the neurons were developing normally and they could examine how the neurons responded to various drugs as a way to look for cures or to slow progression of the disease.  This “disease in a dish” model is applicable across a wide range of disease types and allows researchers to conduct extensive research about a disease without invasive patient procedures.

Potential Hurdles to Success

While there are many exciting opportunities available using cord blood there are also some challenges that need to be overcome. One of the primary challenges is that there the percentage of donors is very low. In the Fierce Biotech Research article, Dr. Mary Laughlin, a physician and expert in marrow and stem transplants at the University of Virginia School of Medicine, stated, “cord blood is only saved from about 4% out of all births. Those are very useful cells that are going in the trash.” One possible solution is a focus on educating parents on the value and importance of donating their child’s umbilical cord. Another important consideration is creating more public cord blood banks to collect, store, test, and register cells on donor registries.

Another possible challenge is the number of cells collected from each umbilical cord and the possibility that there may be an insufficient amount to provide the number of cells necessary for treatment. One possible solution would be to culture and expand the cells to increase the number of cells.  Another improvement could be the use of better, more consistent collection techniques and optimal culture to ensure the highest number of cells possible.

Source: bsargent, cellculturedish.com