Interleukin-17A Augments Mesenchymal Stem Cell Function


One of the biggest problems with organ transplantations is that the immune system can reject the transplanted tissue. Transplant rejection requires the patient to go through another traumatic surgery, and if another organ is not available, then they might very well die. Is there a way to reduce organ rejection?

Our bodies have on our cell surfaces a series of “bar codes” that are the result of “Major Histocompatibility Antigens” or MHC proteins. These proteins are encoded by genes that vary extensively. Therefore, each person has a distinct combination of cell surface proteins that decorate the outside of their cells. If your immune system finds cells that have a different set of MHCs that what you were born with, the immune system, which has been “taught” to accept your own proteins and reject different proteins, will attack and destroy the transplanted tissue. This is known as “Graft vs Host disease” or GvHD. To avoid GvHD, transplant physicians try to find organs that match your own tissue type as closely as possible. However, it is virtually impossible to find organs that perfectly match your own. Even if the patient is given anti-rejection drugs, sometimes the immune system begins to reject the transplanted organ. Is there a way around this?

Mesenchymal stem cells (MSCs) have the ability to suppress unwanted immune responses. If MSCs are pre-treated with cytokines, they can do this even better. Typically, MSCs are pre-treated with a molecule called interferon-γ. This molecule stimulates MSCs and causes then to suppress the immune response, but it also causes MSCs to express proteins that cause them to be rejected by the immune system. Thus interferon-γ seems to cause problems that prevent the MSCs from working properly.

In a really beautiful paper by Kisha Sivanathan in the Coates lab at the School of Medical Sciences, Adelaide, Australia and her colleagues, showed that pre-treating human MSCs with interleukin-17A did a better job at stimulating MSCs without sensitizing the cells to the immune system.

When Sivanathan and her co-workers treated human bone marrow-derived MSC with interleukin-17A, this molecule enhanced the ability of MSCs to suppress the immune response without making the MSCs subjects for rejection by the immune system.  These interleukin-17A-treate MSCs (MSC-17s) showed no induction or upregulation of molecules that the immune system reacts against (MHC class I, MHC class II, and T cell costimulatory molecule CD40), and the the interleukin-17A-treated MSCs maintained normal MSC morphology and made all the common MSC markers.

When MSC-17s were placed in culture with activated human T cells, the MSCs-17s potently suppressed T cell proliferation.  Additionally, MSC-17s prevented activated T-cells from making the whole cocktail of molecules they normally make once they are activated.

Not all T-cells are created equal. There is a group of T-cells called “regulator T-cells” or T-regs for short. T-regs tend to down regulate the immune response. It turns out that MSCs-17s turn on T-regs and stimulate them to potently suppress T-cell activation. They do this without inducing immunogenicity in the MSCs.

Thus, pre-treating MSCs with interleukin-17A represents a superior way for stimulate MSCs to suppress T cell activity in clinical situations.  Dr. Coates and his colleagues are hopeful that this protocol can be the subject of clinical trials in the near future.

Liver-Based Stem Cells Regenerate Animal Livers


Biologists from the MRC Center for Regenerative Medicine at the University of Edinburgh have managed to restore liver function in mice by using stem cell transplants to regenerate them. This is the first time such a procedure has succeeded in a living animal.

If liver stem cells from human livers behave the same way as did the mouse cells in this study, then this procedure could potentially be used in place of liver transplants in human patients. This work was published by Professor Stuart Forbes and his colleagues in the journal Nature Cell Biology.

According to Forbes: “Revealing the therapeutic potential of these liver stem cells brings us a step closer to developing stem cell based treatments for patients with liver disease. It will be some time before we can turn this into reality as we will first need to test our approach using human cells. This is much needed as liver disease is a very common cause of death and disability for patients in the UK and the rest of the world.”

Liver cells are also called “hepatocytes” and even though such cells are used for liver transplants, the technology does not yet exist to easily propagate human hepatocytes in the laboratory. In this study, Forbes and his group designed a protocol that could wipe out close to 98% of the cells in the liver of laboratory mice. They genetically engineered mice whose liver cells would delete the MDM2 gene. The MDM2 gene encodes a protein called “E3 ubiquitin ligase,” which is an enzyme that tags junk proteins so that they are properly degrades and recycled. Without a functional E3 ubiquitin ligase, the vast majority of the liver cells underwent programmed cell death. Under these conditions, a group of liver-specific stem cells called hepatic progenitor cells or HPCs were transplanted from healthy mice into the adult mice with severely damaged livers. The transplanted HPCs significantly restored the structure of the liver, regenerating hepatocytes and the cells of the “biliary epithelia,” which compose the ducts that move bile into the gall bladder. This highlights the potency of these transplanted HPCs as liver regenerators. Essentially, after several months, Forbes and his coworkers discovered that major areas of the liver had regrown and these new cells significantly improved the liver’s physiological performance.

Transplanted hepatic progenitor cells can self-renew (yellow, left image) and differentiate into hepatocytes (green) to repair the damaged liver. Image credit: Dr Wei-Yu Lu.
Transplanted hepatic progenitor cells can self-renew (yellow, left image) and differentiate into hepatocytes (green) to repair the damaged liver. Image credit: Dr Wei-Yu Lu.

This is the first time that biologists have succeeded in regenerating an organ in a living animal by using stem cells. Even human cells have significant differences from mouse cells, if these human cells can be manipulated so that they behave in a similar manner to these mouse stem cells, transplanting stem cells or, perhaps administering drugs that activate a patient’s own liver to produce stem cells and regenerate itself, could replace liver transplants.

In a press release, Dr. Rob Buckle, director of science programs for the U.K.’s Medical Research Council, said: “This research has the potential to revolutionize patient care by finding ways of co-opting the body’s own resources to repair or replace damaged or diseased tissue. Work like this, building upon a precise understanding of the underlying human biology and supported by the UK Regenerative Medicine Platform, will give doctors powerful new tools to treat a range of diseases that have no cure, like liver failure, blindness, Parkinson’s disease and arthritis.”

Supercharging Stem Cells for Organ Transplant Patients


A biomedical research team at the University of Adelaide has designed a novel protocol for culturing stem cells that drives the cells to grow faster and become therapeutically stronger. This research was recently published in the international journal, Stem Cells, and is expected to lead to new treatments for transplant patients.

Kisha Sivanathan , a PhD student at the University of Adelaide’s School of Medicine and the Renal Transplant Unit at the Royal Adelaide Hospital, spoke about this exciting breakthrough in stem cell research: “Adult mesenchymal stem cells, which can be obtained from many tissues in the body including bone marrow, are fascinating scientists around the world because of their therapeutic nature and ability to cultivate quickly. These stem cells have been used for the treatment of many inflammatory diseases but we are always looking for ways in which to increase stem cells’ potency,” said Ms. Sivanathan, who is the lead author on this study.

Ms. Sivanathan continued: “Our research group is the first in the world to look at the interaction between mesenchymal stem cells and IL-17, a powerful protein that naturally occurs in the body during times of severe inflammation (such as during transplant rejection). We discovered that when cultured mesenchymal stem cells are treated with IL-17 they grow twice as fast as the untreated stem cells and are more efficient at regulating the body’s immune response.”

Stem cell therapy continues to show very promising signs for transplant patients and according to Ms Sivanathan, the IL-17 treated stem cells could potentially be even more effective at preventing and treating inflammation in transplant recipients. The particular goal in this case is to treat patients who have received organ transplants; and even help control organ rejection in transplant patients.

“Current drugs (immunosuppressant drugs) used to help prevent a patient rejecting a transplant suppress the whole immune system and can cause severe side effects, like cancer. However, stem cell therapy (used in conjunction with immunosuppressant drugs) helps patients ‘accept’ transplants while repairing damaged tissue in the body, resulting in less side effects,” says Ms Sivanathan. “We are yet to undertake clinical trials on the IL-17 treated stem cells but we anticipate that because this treatment produces more potent stem cells, they will be more effective than the untreated stem cells,” she said.

New Tissue Engineering Technique Could Lead to Growing Larger Organs in the Laboratory


Tissue engineers from the Universities of Liverpool and Bristol have invented a novel tissue “scaffold” technology that might one day enable the growth large organs in the laboratory.

According to data generated by these experiments, it is possible to combine cells with a special scaffold to produce living tissues in the laboratory. Hopefully, such organs can then be implanted into patients who need to have a diseased body part replaced. To this point, growing large organs in the laboratory has been impossible because growing larger structures in the laboratory limits the delivery of oxygen supply to the cells in the center of the organ. Therefore, growing tissues in the laboratory has been restricted to small structures that are readily served by the diffusion of oxygen.

In the experiments conducted by the University of Liverpool and Bristol teams, cartilage tissue engineering was employed as a model system for testing strategies for overcoming the oxygen limitation problem.

They manufacture a new class of artificial membrane binding proteins that attached to stem cells. Then they attached to these cell surface proteins the oxygen-carrying protein, myoglobin, before they used the cells to engineer cartilage. Since myoglobin is an oxygen-storage molecule, it will bind oxygen and provide a reservoir of oxygen for cells that cells can access when the oxygen in the scaffold drops to dangerously low levels.

Professor Anthony Hollander, Head of the University of Liverpool’s Institute of Integrative Biology, said: “We have already shown that stem cells can help create parts of the body that can be successfully transplanted into patients, but we have now found a way of making their success even better. Growing large organs remains a huge challenge but with this technology we have overcome one of the major hurdles. Creating larger pieces of cartilage gives us a possible way of repairing some of the worst damage to human joint tissue, such as the debilitating changes seen in hip or knee osteoarthritis or the severe injuries caused by major trauma, for example in road traffic accidents or war injuries.”

These results could expand the possibilities in tissue engineering, not only in cartilage, but also for other tissues such as cardiac muscle or bone. This new methodology in which a normal protein is converted into a membrane binding protein to which helpful molecules can be attached, is likely to pave the way for the development of a wide range of new biotechnologies.

Dr Adam Perriman, from the University of Bristol, added: “From our preliminary experiments, we found that we could produce these artificial membrane binding proteins and paint the cells without affecting their biological function. However, we were surprised to discover that we could deliver the necessary quantity to the cells to supplement their oxygen requirements. It’s like supplying each cell with its own scuba tank, which it can use to breathe from when there is not enough oxygen in the local environment.”

Previous work by Hollander’s group includes the development of a method of creating cartilage cells from stem cells. This method helped make the first successful transplant of a tissue-engineered trachea, which utilized the patient’s own stem cells, possible.

This work appeared in the paper, “Artificial membrane-binding proteins stimulate oxygenation of stem cells during engineering of large cartilage tissue,” which was published in Nature Communications.

Multipotent Adult Progenitor Cells for Immunomodulation after Liver Transplantation


Mesenchymal stem cells and multipotent adult progenitor cells (MAPCs) have received a good deal of discussion by scientists as agent for solid organ transplant recipients. Why? Because these cells, with their ability to suppress unwanted immune responses might be able to reduce the need for drugs that suppress the immune system, which have extensive side effects.

The study under discussion today is the clinical course of the first patient of the phase I, dose-escalation safety and feasibility study, MiSOT-I (Mesenchymal Stem Cells in Solid Organ Transplantation Phase I).

The patient received a living-related liver graft, each patient was given one intraportal injection (injection into the portal vein) and one intravenous infusion of third-party MAPC in combination with a low-dose of an anti-tissue-rejection drug.

The results so far are still coming in, but it seems that the administration of the cells is easy and is technically feasible. How well did the patients tolerate them? Quite well it turns out. There was no evidence of acute toxicity associated with infusions of the MAPCs. Also, there was some indication that the patient’s white blood cells were less reactive to foreign substances. However, it is difficult to make definitive statements about the efficacy of this treatment at this time.

Recruitment and follow-up of participants in the MiSOT-I trial continue, and completion of the study is currently projected for autumn 2016.

Growing Human Esophagus Tissue from Human Cells


Tracy Grikscheit of the Saban Research Institute of Children’s Hospital Los Angeles and her colleagues have successfully grown a tissue engineered esophagus on a relatively simple biodegradable scaffold after seeding it with the appropriate stem and progenitor cells.

Progenitor cells have the ability to differentiate into specific cell types and can migrate to a particular target tissue. Their differentiation potential depends on the parent cell type from which they descended and their “niche” or local surroundings. The scaffold upon which these cells were seeded is composed of a simple polymer, but interestingly, several different combinations of cell types were able to generate a replacement organ that worked well when transplanted into laboratory mice.

“We found that multiple combinations of cell populations allowed subsequent formation of engineered tissue. Different progressive cells can find the right “partner” cell in order to grow into specific esophageal cell types; such as epithelium, muscle or nerve cells, and without the need for exogenous growth factors. This means that successful tissue engineering of the esophagus is simpler than we previously thought,” said Grikscheit.

Videos published the paper show a network of muscle cells properly wired with nerves that properly self-organizes whose muscles spontaneously contract.  Such structures are called an esophageal organoid unit (EOU) in culture. Spontaneous contraction is observed within these EOUs.

This study could be the impetus for clinical procedures that can treat children born with portions of their esophagus missing. Since the esophagus carries liquids and food to the stomach from the mouth, it is a vitally important part of the body.

This protocol, could also be applied to patients who have suffered from esophageal cancer and had to have their esophagus removed. Esophageal cancer is one of the fastest growing types of cancer in the United States to date. Alternatively, people who have accidentally swallowed caustic liquids may also benefit from this type of esophageal repair.

This simple scaffold made of a polyglycolic acid/poly-L-lactic acid and coated with the protein collagen is inexpensive and versatile and completely sufficient for the growth of tissue-engineered esophagi from human cells, according to this study. When established in culture, this system can also serve as a model system to study the cell dynamics and physiology of the esophagus.

A deeper understanding of how esophageal cells behave in response to injury and how various donor cells could potentially expand the pool of potential donor cells for engineered tissue.

Even though this technique has only been tested in animals to date, fine-tuning of this technique might very well ready it for clinical trials in the future.

Mesenchymal Stem Cells Assist Kidney Transplants in Cats


Dr. Chad Schmiedt, a veterinary surgeon from the University of Georgia (UGA) Veterinary Teaching Hospital, and his colleagues have used mesenchymal stem cells from the fat of cats to optimize the acceptance of a new kidney in cats.

The recipient of this kidney transplant was a four-year-old flame point Siamese male cat named Arthur. Arthur’s owners brought him from Virginia to the University of Georgia after he was diagnosed with chronic renal failure about a year ago. Two other veterinary hospitals declined to operate on Arthur, since they did not deem this cat an optimal candidate for a kidney transplant. As it turns out, Arthur has trouble absorbing cyclosporine, which is the anti-rejection drug used to prevent the recipient of the kidney transplant from rejecting it.

Arthur
Arthur

In his initial consultation with Arthur’s owners, Schmiedt had the idea of using adult feline stem cells as a part of Arthur’s immunosuppressive protocol. There was precedent for this, since a cat that was operated on at University of Georgia Veterinary Teaching Hospital in 2013 had received a kidney transplant with doses of its own mesenchymal stem cells to prevent rejection of the transplanted organ. This cat was doing well one year after surgery.

“To the best of my knowledge, UGA is the only veterinary facility in the world to use adult stem cells in feline kidney transplantation,” said Schmiedt, who actually heads UGA’s feline kidney transplant program.”

Schmiedt continued: “We used feline adult stem cells in one other transplant that we did last year. A study published in 2012 found that the use of MSCs during renal transplant surgery i humans lowered the risk of acute organ rejection, decreased the risk of infection, and the patients had better estimated renal function one year after surgery.”

Mesenchymal stem cells can be harvested fat, bone marrow, and umbilical cord or placenta. Before the transplant surgery, Schmiedt isolated mesenchymal stem cells (MSCs) from Arthur’s fat and the UGA Regenerative Medicine Service grew the stem cells from the fat sample for use in Arthur after his surgery.

Arthur has his kidney transplant on May 15, 2014. The first surgery harvests a kidney from the donor cat (named Joey) and the second surgery transplants the donated kidney into Arthur. The UGA transplant program for cats requires that the donor cat be adopted by the recipient family’s family, which means that Joey and Arthur will become lifelong playmates.

“Cat owners who seek kidney transplants for their sick cats have to be very dedicated,” said Schmiedt. “They will give their car medication twice a day for the rest of its life. They also must be willing to take their cats to the veterinarian for frequent check-ups… a significant amount of time and expense is involved in keeping the recipient and donor cats healthy. But cat lovers who will go to this extent are willing to extend this kind of care to all cats they own.”

Apparently, Joey will be joined by Arthur and five other felines as well.

Stem cells do not replace the need for antirejection medication, and since Arthur’s body poorly absorbs cyclosporine, he will need to take a second antirejection drug as well called mycophenolate. Schmiedt, however, and his colleague stem cell scientist Dr. John Peroni sees MSCs making an important contribution to transplant medicine: “MSCs in veterinary species have been primarily used to treat musculo-skeletal injury – problems with bones, tendons, and joints – and those are our most frequent uses here at the UGA College of Veterinary Medicine. But there is good evidence to support using stem cells to modulate the immune system and regulate inflammation. So, the transplant setting might be another optimal use for these types of stem cells.”

In order to access the efficacy of MSCs in a transplant setting, controlled studies must be done. It is clear that transplanted MSCs do not improve kidney function, but they do seem to slow down the progression of kidney disease. Schmiedt thinks that benefits to patients are possible: “The only down side is harvesting the cells seven to 10 days ahead of the surgery, which adds to the cost of transplant procedure.”

Adaptation of this procedure to animals could smooth the path to making this procedure readily available in humans as well.