Monthly Archives: March 2012

Cheek Progenitor Cells Found to Be Vastly More Potent at Immunosupression Than Bone Marrow MSCs

A recently described progenitor cell (PC) type found in the mucosal layer of the cheek may have wide-ranging potential as a cell therapy for immune-related disorders, including the prevention of graft-versus-host reactions in organ transplant patients, scientists claim. The cells, known as oral mucosal lamina propria progenitor cells (OMLP-PCs) are a clonally derived PC population of neural crest origin, which can differentiate into both mesenchymal and neuronal cell types. 

A team at Cardiff University’s Cardiff Institute of Tissue Engineering and Repair in the U.K. first described the cell type in 2010. Now, working with colleagues at Huddinge University Hospital in Sweden, they describe in vitro studies demonstrating that OMLP-PCs are far more potent than bone marrow-derived mesenchymal stem cells (BBMSCs) at inhibiting unwanted immune reactions, and require only very low doses.

Moreover, the team points out, a major advantage of OMLP-PCs over cells such as MSCs is that the cheek-derived cells can be clonally expanded, with each clone originating from a single cell. This allows production of homogeneous cell populations that are well-characterized and generate predictable and reproducible results. The Cardiff Institute’s Phil Stephens, M.D., and colleagues describe their findings in Stem Cells and Development in a paper titled “Oral Mucosal Progenitor Cells Are Potently Immunosuppressive in a Dose-Independent Manner.”

The well-characterized immunosuppressive and immunoprivileged features of BBMSCs are being in clinical trials as allogeneic cell therapy for immune-related disorders, including acute and chronic graft-versus-host disease, and in hematopoietic stem cell (HSC) transplantation. One drawback of BBMSCs, however, is that harvesting the cells requires invasive procedures. The number of BMMSCs also decreases with age, the investigators point out.

Previous work by the Cardiff team has demonstrated that OMLP-PCs have a similar cell surface marker expression profile to BMMSCs, in that they are CD90+ , CD105+ , CD166+ , CD44+ , CD34-,  and CD45-. Separate analyses have confirmed the cells are also CD29+ and CD73+. To evaluate whether OMLP-PCs may represent a more easily accessible source of immunosuppressive cells for potential therapeutic applications, the team carried out a series of in vitro studies using OMLP-PCs isolated from buccal mucosa biopsies taken from patients undergoing routine dental procedures. OMLP-PCs were isolated from the biopsies, separated by differential adhesion to fibronectin, and clonally expanded.

Analysis of cell surface and specific intracellular expression of key markers of alloantigen presentation were measured by flow cytometry and, for HLA class II molecules, Western blotting. The OMLP-PCs were found to constitutively express HLA class I on their surface, which was upregulated slightly on exposure to IFN-γ. In contrast, there was no constitutive cell surface or intracellular expression of HLA class II. Intracellular expression of HLA class II was, however, visualized by Western blotting in response to IFN-γ exposure, and led to cell surface expression of HLA class II, but only after seven days. “These results demonstrate significant differences to those previously reported for BMMSCs that constitutively express intracellular HLA class II,” the team notes.

Flow cytometry analyses confirmed that OMLP-PCs did not express FasL (CD178) or the costimulatory molecule CD40 and its ligand CD154, CD80, or CD86, either in the absence or presence of IFN-γ for seven days.

To determine whether OMLP-PCs could suppress the proliferation of PBLs, the researchers applied one-way mixed lymphocyte culture (MLC) assays, and stimulated the cells with the T cell mitogen PHA.  The tests were carried out separately on OMLP-PCs that had been prestimulated using IFN-γ (to trigger cell surface HLA class II expression), and those that hadn’t been subjected to IFN-γ.

The results from both MLC and mitogen assays demonstrated that the OMLP-PCs could completely inhibit PBL proliferation, “demonstrating the ability of OMLP-PCs to respond to both allogeneic and mitogenic stimuli,” the researchers write. Moreover, induction of HLA class II expression on the cell surface following prestimulation with IFN-γ had no effect on this inhibitory capacity, indicating that that OMLP-PC immunosuppression occurs via a HLA class II–independent mechanism. These results contrast with those obtained using BMMSCs, where pre-exposure to IFN-γ increases the inhibition of PBL proliferation.

Interestingly, there was no difference in the levels of PBL inhibition when one-way MLC assays were set up with OMLP-PCs either in direct contact with the PBLs or separated by a membrane. This further suggested that OMLP-PCs can completely suppress the proliferation of PBLs through the release of soluble factors, again in a dose- and HLA class II-independent manner. Analyses demonstrated that OMLP-PC inhibition of PBL proliferation wasn’t linked with the induction of cell death, but instead appeared to protect PBLs from apoptosis. In other words, the immunosuppressive effects are apparently due to true inhibition, rather than simply due to the induction of apoptosis.

“This is the first time that a PC population has been demonstrated to immunosuppress to this extent and in such a dose-independent manner,” the authors state. “These findings have implications in the clinical application of stem cell populations for both allogeneic tissue engineering applications as well as in the treatment of immune-related disorders such as GVHD where BMMSCs are currently the preferred cell source…These cells offer direct advantages over currently utilized BMMSCs in that not only would fewer cells be required to induce immunosuppression (hence a significant impact on scale-up and cost for development as a therapeutic) but cells can be reliably isolated from an easily accessible biopsy site with no/minimal scarring for the donor.”

Source: Genetic Engineering & Biotechology News

Advertisements

Stem cell research allows for mismatched kidney transplants

 Donating a kidney may save a person’s life – but only if the conditions are precise.

Kidney donors must be related and immunologically matched to their donors – and even then, the recipient must take a lifetime of anti-rejection medications, which don’t guarantee the organ won’t be rejected.

But a new clinical trial from Northwestern Memorial Hospital in Chicago, IL has shown how stem cells can be used to “trick” a recipient’s immune system into believing the new organ has been part of that person’s body all along.

The breakthrough has the potential to eliminate both the risks associated with kidney transplantation and the need for anti-rejection medications within one year after surgery.

“It’s the holy grail of transplantation,” said lead author Dr. Joseph Leventhal, transplant surgeon at Northwestern Memorial Hospital and associate professor of surgery and director of kidney and pancreas transplantation at Northwestern University Feinberg School of Medicine in Chicago, IL.  “This notion of being able to achieve tolerance through donor derived cells has been around for more than 50 years, but it’s translation to the clinic has been quite elusive.  This article details the first successful attempt of this in mismatched and unrelated kidney recipients.”

The research was published Wednesday in the journal Science Translational Medicine, and it is the first study of its kind in which the donor and recipient were not related and did not have to be immunologically matched.  Only 25 percent of siblings are immunologically identical, severely limiting the possibility of being a kidney donor.

The procedure worked by extracting a little bit more from the kidney donor than just their kidney.  They also donated part of their immune system.  About one month before surgery, bone marrow stem cells were collected from the donor and then enriched with “facilitating cells” – becoming stem cells that will ultimately fool the donor’s immune system allowing the transplant to succeed.

One day after the kidney transplant occurs, the facilitating cell-enriched stem cells are also transplanted in the recipient, which then prompts the formation of stem cells in the bone marrow.  This then causes specialized immune cells – similar to the donor’s immune cells – to develop, creating a dual bone marrow system environment, so both the donor’s immune system and the recipient’s immune system function inside the person’s body.

Leventhal said that the ultimate goal is for the recipient to initially take anti-rejection medications but then slowly wean off of them within a year.  According to Leventhal, the drugs come with their own share of negative side effects.

“The foundation of clinical transplantation revolves around the use of medicines and suppressive drugs to control the immune system,” Leventhal said.  “These drugs have been very successful in reducing the rates of loss of organs due to acute rejection – where side effects include increase risk of infection and cancer, and metabolic side effects, such as the increase risk of hypertension and bone disease.  But the drugs themselves are potentially harmful to the organs we transplant.  Despite our ability to reduce rates of acute rejection, most individuals go on to lose organs because of chronic (long-term) rejection.”

One of the eight patients involved in the clinical trial, 47-year-old Lindsay Porter of Chicago, IL, currently lives free of anti-rejection medication, sometimes forgetting she even had the kidney transplant in the first place.

“I hear about the challenges recipients have to face with their medications and it is significant,” Porter said.  “It’s almost surreal when I think about it because I feel so healthy and normal.”

To qualify for this experiment, donors and recipients have to be blood-type compatible, and the recipient must not have antibodies in the blood that would reject the new kidney.  Leventhal, along with co-author Dr. Suzanne Ildstad, director of the Institute of Cellular Therapeutics at the University of Louisville, hope to expand this research into a larger clinical trial and eventually make this procedure the standard of care used in kidney transplant recipients.

“This is a transformative clinical trial,” Leventhal said.  “It will likely change the direction of how we approach immune tolerance in transplantation over next five to 10 years.  This has been a long standing goal in the field.  The fact that we’ve been able to show that tolerance is achievable and we can reproduce these findings in more than one patient, it opens the door to broader application for this approach.”

“It’s fair to say this could be a game changer,” Leventhal added.
Source: Loren Grush, FoxNews.com


Human Stem Cells Improve Vision In Rats With “Glaucoma-Like” Nerve Cell Damage

Scientists funded by the Medical Research Council have successfully used adult human retinal stem cells to repair nerve cells damaged in glaucoma, partially restoring vision in rats. 

If the success can be replicated in humans it may eventually lead to new treatments for glaucoma, the leading cause of irreversible blindness in the world, and other degenerative eye conditions by slowing sight deterioration, or reversing it altogether. The research is published in the journal Stem Cells Translational Medicine.

Glaucoma occurs when a build up of pressure in the eye leads to the death of retinal ganglion cells (RGCs), which form the nerve fibres of the optic nerve and that transmit visual information from the eye to the brain. The condition can be treated in the early stages, but if diagnosis is late or treatment doesn’t work, damage to the eye cannot be reversed.

The researchers looked at whether injecting a type of adult human stem cell, known as the Müller glia stem cell, could stimulate repair of damaged RGCs in an animal model. Müller glia are found in the retina of humans and other vertebrates and are multipotent, meaning they can grow into any of the different nerve cells found in the retina.

The researchers used chemicals to induce Müller glia to grow into precursors of RGCs, before transplanting them onto the retinas of rats which had damage to their own RGCs.

After four weeks, the injected cells appeared to have formed new connections (synapses) with existing nerve cells and the rats had significantly improved retinal function when their vision was tested under very low light conditions. The scientists hope that, with further work, they will be able to develop new treatments to improve or restore vision in patients with untreatable glaucoma.

Dr Astrid Limb, who led the study at the UCL Institute of Ophthalmology, UCL, said:

“Although this research is still a long way from the clinic, it is a significant step towards our ultimate goal of finding a cure for glaucoma and other related conditions. We are optimistic that after further work on animal models to perfect our transplantation technique we will be in a good position to start early-stage clinical trials on humans in around three to five years.

The human eye is actually very efficient. We can still have fairly good vision with very few functioning retinal nerve cells, which is why many glaucoma patients don’t show symptoms until it is too late to treat the underlying cause of their vision loss. If we can restore even a small number of RGCs through cell therapy, and achieve functioning vision, we could potentially delay or even reverse blindness caused by glaucoma.”

Professor Peng T Khaw, director of the NIHR Biomedical Research Centre at Moorfields and the Institute of Ophthalmology and a co-author of the paper, said:

“These results are very exciting. We see patients with glaucoma whose lives would be transformed with an improvement of only a small percentage of nerve cell function. The results of these experiments suggest that this may be possible in the future using cells we all have in our own eyes to achieve this. Translational research like this gives hope to the many millions of people who have lost vision due to glaucoma.”

Dr Rob Buckle, head of regenerative medicine at the MRC, said:

Regenerative medicine is a key priority for the MRC and it’s wonderful to see another example of how our significant investment in stem cell research in recent years is beginning to deliver results. Repair of the eye is an area that is now at the forefront of this field, and this study highlights a new route for delivering the promise of regenerative medicine to treat disabling conditions such as glaucoma.”

Source: National Glaucoma Research adapation of Stem Cells Translatable Medicine