Regenerative medicine: Opening the door to innovations

As a leading research center, Mayo Clinic has embraced regenerative medicine and its potential to find innovative solutions for devastating neurodegenerative diseases. Research and clinical trials at all Mayo Clinic campuses are generating tools for the study of, and potential stem cell-based therapies for, diseases such as amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD) that currently lack treatments.

"Stem cells provide incredibly powerful ways to study disease, and the potential for trying therapy in patients is opening quickly," says Anthony J. Windebank, M.D., a consultant in Neurology at Mayo Clinic in Rochester, Minnesota. "We've determined that we can put a person's own cells into places where they don't normally reside. The cells survive and don't cause bad side effects."

Among Mayo Clinic's efforts in neuroregenerative medicine, recent developments include the discovery of a biomarker for the most common genetic risk factor for ALS and FTD, and clinical trials of stem cell therapy for ALS.

Biomarker for ALS and FTD

An innovative technique for generating induced pluripotent stem cells (IPSCs) from fibroblasts, developed at Mayo Clinic in Jacksonville, Florida, led to the discovery there of a biomarker — abnormal proteins resulting from a repeat expansion in a portion of the C9orf72 gene. The repeat expansion, which is the most common known genetic cause of ALS and FTD, causes RNA strands to misfold and form clumps, and produces an abnormal protein, called c9RAN proteins.

"The abnormal proteins only exist in patients carrying a C9orf72 repeat expansion, and they now represent the hallmark pathology of disorders collectively referred to as c9FTD/ALS," says Leonard Petrucelli, Ph.D., chair of Neuroscience at Mayo Clinic's campus in Florida.

Using IPSCs generated from people with the mutation, Mayo Clinic researchers developed in vitro models of C9orf72 pathology. In collaboration with The Scripps Research Institute in Jupiter, Florida, the researchers then designed bioactive molecules to target and bind to the aberrant RNA.

In a study published in the Sept. 3, 2014, issue of Neuron, the researchers showed that the molecules significantly inhibited abnormal RNA translation and protein formation and that abnormal c9RAN proteins can be detected in the cerebrospinal fluid (CSF) of c9ALS patients.

"We've developed antibodies and assays that can detect the amount of this abnormal protein not only in the brain but also in CSF," Dr. Petrucelli says. "In the future, a spinal tap could be used to measure protein levels in order to assess disease progression and to determine the efficacy of therapies designed to reverse pathological features associated with the mutation."

Reprogramming the immune system

Stem cell transplants can induce sustained remission in patients with severe autoimmune diseases, such as systemic lupus erythematosus, that are refractory to standard therapies. Evidence suggests an autoimmune mechanism might be present in ALS. Researchers at Mayo Clinic in Phoenix/Scottsdale, Arizona, are developing a clinical trial using a similar strategy for ALS.

Although previous attempts to use stem cell transplantation for ALS failed to demonstrate improvement in motor function, "we believe the immune suppression in those early studies wasn't strong enough to inhibit all of the disease process," says Angel (A Arturo) A. Leis, M.D., a consultant in Neurology at Mayo Clinic's campus in Arizona. "But we now have the capability to produce very intense immunosuppression, which we hope will abolish the immune mechanisms that may contribute to ALS progression."

Immunoablation is achieved through high doses of chemotherapy. Stem cells are removed from the patient's bone marrow before chemotherapy starts and reinserted in the patient afterward. "The stem cells return to the bone marrow very rapidly and then start building up the patient's blood and immune system again," says Jose F. Leis, M.D., Ph.D., a consultant in Hematology/Oncology at Mayo Clinic's campus in Arizona.

The procedure requires about three and a half weeks of hospitalization, from harvest of stem cells to regrowth of the immune system. "You have essentially erased that patient's immune system, and then, with stem cells, developed a new immune system that is naive and self-tolerant," says Dr. Angel Leis. "We are looking forward to this being a future mechanism that can halt the progression of ALS."

Injecting stem cells into CSF

Through the Center for Regenerative Medicine at Mayo Clinic's campus in Minnesota, Dr. Windebank is directing several studies involving injection of ALS patient stem cells into CSF in an effort to promote nerve regeneration. The work is co-directed by Nathan P. Staff, M.D., Ph.D., a consultant in Neurology at Mayo Clinic's campus in Minnesota, and also involves Mayo Clinic's Human Cellular Therapy Laboratory, which is conducting more stem cell trials than any other facility in the United States.

One of the Mayo Clinic studies, done in conjunction with Massachusetts General Hospital and the University of Massachusetts, uses stem cells that are harvested from an ALS patient's bone marrow, treated in the laboratory for six weeks and then injected into the patient's CSF. "The laboratory treatment makes the cells more neurotrophic," Dr. Windebank says. Results from the phase IIA study are expected by the end of 2016.

Two other trials use adipose stem cells. The first — a dose-escalation safety trial — is nearly complete. "The safety profile is excellent," Dr. Windebank says. "We're up to the highest dose levels, and although we are noticing some side effects, they're relatively minor and self-limited." A phase IIA study involving all Mayo campuses is expected soon.

The second adipose trial is being developed in conjunction with the Karolinska Institutet in Stockholm; Paracelsus Medical University in Salzburg, Austria; Trinity College Dublin; and the National University of Ireland, Galway. "An international trial allows us to demonstrate that this kind of very novel cell therapy can be replicated in multiple centers," Dr. Windebank says.

Regenerative medicine is conducive to finding treatment for ALS because the disease progresses quickly and affects a specific population of nerve cells in the brain and spinal cord. "In regenerative medicine you're asking the body to heal itself," Dr. Windebank says. "Of course the nervous system doesn't regenerate quickly because it's so complicated. Focusing on specific diseases such as ALS, in which a specific type of nerve cell is dying, simplifies the target.

"The next phase of our research is going to be even more exciting," Dr. Windebank adds. "Our gene-editing technology — which allows us to genetically manipulate cells in very specific ways to make them do more of what we want them to do — is coming along very rapidly. In the future there might be a modification for ALS, for multiple system atrophy and maybe for Parkinson's disease."

For more information

Su Z, et al. Discovery of a biomarker and lead small molecules to target r(GGGGCC)-associated defects in c9FTD/ALS. Neuron. 2014;83:1043. (Erratum in Neuron. 2014;84:239.)

Mayo Clinic. A dose-escalation safety trial for intrathecal autologous mesenchymal stem cell therapy in amyotrophic lateral sclerosis. ClinicalTrials.gov.

Mayo Clinic. Phase 2, randomized, double blind, placebo controlled multicenter study of autologous MSC-NTF cells in patients with ALS (NurOwn). ClinicalTrials.gov.