ABSTRAK
Application of Stem Cell Therapy
in Parkinson Disease
Ismail Setyopranoto
Stroke Unit, Department of Neurology, Faculty of Medicine, Gadjah Mada University/
Dr Sardjito General Hospital, Yogyakarta, Indonesia
Embryonic stem (ES) cells have been suggested as candidate therapeutic tools for
cell replacement therapy in neurodegenerative disorders. However, limitations for the
use of these cells lie in our restricted knowledge on the molecular mechanisms
involved in their specialized differentiation and in the risk of tumor formation.
Although most cells of the body, such as muscle cells, are committed to fulfilling
a particular function, a stem cell is uncommitted until it receives a signal to develop
into a specialised cell. Stem cells can be obtained from embryonic, foetal and adult
tissues. Based on their differentiation potential, stem cells can be:
(i) Pluripotent, meaning that they can individually give rise to all types of cells that
develop from the germ layers (endoderm, mesoderm and ectoderm) and germ
cells,
(ii) Totipotent, cells that have the capability of pluripotent cells plus the ability to
give rise to placental tissue,
(iii) Unipotent, can give rise to only one type of differentiated cell, and
(iv) Multipotent, a state between unipotent and pluripotent.
Parkinson's Disease exemplifies a type of disorder that could prove miraculously
tractable to stem cell therapies. Even early studies that injected crude human fetal
tissue extracts (presumably containing stem cells) appear to have had some long-term
benefits, although those results are continually re-evaluated. Unfortunately, this
approach has daunting drawbacks, including how much tissue is needed for each
treatment and a lack of uniformity in tissue extracts used for each individual
treatment.
There are parallels between Parkinson's and diabetes, that appears to respond to
stem cell therapies in a mouse model. Although molecular mechanisms are not
completely understood, in the initial progression of diabetes only islet cells die, and
therefore only one kind of cell needs regeneration. In research in mice, scientists took
cells from the pancreas and grew them in culture. Unable to characterize stem cells
visually, they simply took all the cultured cells and transplanted them. The mice
seemed to grow normal islet cells and their diabetic condition seemed to reverse
(long-term results are pending). An islet cell transplant protocol is being developed
for diabetes, but--as in Parkinson's--this approach is limited by the availability and
consistency of the cells.
Cermin Dunia Kedokteran No. 153, 2006
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