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Scientists Take Step Toward Personalized Cell Therapy for Parkinsonís

Researchers funded by the Parkinson’s Disease Foundation (PDF) have made an important advance toward cell therapy for Parkinson’s disease (PD)—the idea of transplanting healthy cells into the brain to replace dopamine neurons lost to PD. They report, in a study published in the March 28 issue of Cell Reports, that they have created neuron-like cells from the skin cells of monkeys. These cells developed into normal neurons and other cell types after transplantation to the monkeys’ brains.

Many scientists have investigated the use of stem cells — immature cells that have the potential to become any of the body’s cell types — as a basis for cell replacement therapies. Recently, researchers have discovered how to transform mature skin cells from humans and animals into stem cells (induced pluripotent stem cells, or iPSCs). They have then been able to coax the stem cells to develop into different cell types, including dopamine neurons (the cells lost in PD).

These therapies have often been problematic because of immune rejection of transplanted cells, similar to rejection of an organ transplant from an unmatched donor. The new research, out of the University of Wisconsin, Madison, got around this roadblock by using an animal’s own cells as the basis for transplantation (the same concept has been used in other transplantation areas). 

Researchers started with skin tissue taken from three rhesus monkeys that had Parkinsonian symptoms as a result of a chemical exposure. In the laboratory, Su-Chun Zhang, M.D., Ph.D., and coworkers turned the monkeys' skin cells into iPSCs, then started them part way down the path of developing into dopamine neurons. They also engineered the cells to make a protein that glows under fluorescent light, in order to identify them later. Marina Emborg, M.D., Ph.D., then led a team using MRI-guided techniques to transplant the iPSCs into the monkey’s brains, with each animal receiving cells derived from its own skin.

Results

  • The cell transplants, which already had some characteristics of brain cells, developed further into three, more specialized, brain cell types: neurons, astrocytes, and myelinating oligodendrocytes.
  • The scientists found no signs of immune rejection in the monkeys’ brains.
  • Under the microscope, the brain tissue looked normal; the researchers could only identify transplanted cells by making them glow in fluorescent light.
  • The cell transplants did not grow into tumors, a setback seen in previous stem cell transplants studies.
  • The cell transplants survived up to six months, much longer than human embryonic stem cells (three months) in previous studies.
  • No improvement in the monkeys’ Parkinsonian symptoms was observed. This was likely due to the small size of the cell transplant. Symptom relief was not a goal of this initial study.

What Does It Mean?

Induced pluripotent stem cells (iPSCs), including those taken from adult cells, hold great promise for treating the motor symptoms of PD and other diseases. PDF has consistently supported innovation in this arena.

The new study is the first to transplant these types of cells back into the same animal (a non-human primate) from which they were taken. It demonstrates the potential of the technique, in turn advancing research toward the goal of personalized medicine. Other researchers supported by PDF were the first to transform iPSCs into dopamine neurons and transplant them into rodents.

Many questions remain to be answered in animal studies before potential stem cell therapies can be tested in people. For example, scientists need to know first whether the transplants are safe over long periods of time, and whether there are undesirable side effects. In one example, scientists will have to find a way to avoid “transmission” of PD to the transplanted iPSCs, which has occurred in other types of transplants.

Then the technique needs to be proven to improve symptoms in animals and people. For instance, researchers are not sure if these results would be similar in humans — the monkeys in this study showed dopamine deficiency similar to PD, but their symptoms do not imitate the progressive nature of PD. In addition, one challenge highlighted by this study will be producing greater numbers of dopamine neurons from the iPSCs.

Reference: Marina E. Emborg, Yan Liu, Jiajie Xi, Xiaoqing Zhang, Yingnan Yin, Jianfeng Lu, Valerie Joers, Christine Swanson, James E. Holden, Su-Chun Zhang. Induced Pluripotent Stem Cell-Derived Neural Cells Survive and Mature in the Nonhuman Primate Brain. Cell Reports (2013), 14 March 2013. http://dx.doi.org/10.1016/j.celrep.2013.02.016

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Source Date: Apr 10 2013