The restorative neuroscience research lab at Inselspital, led by Prof. Dr. Hans Rudolf Widmer conducts internationally recognized research with a focus on cell therapy for neurodegenerative and neuropathological diseases.
Nerve cells under the microscope. This microscopic image shows cultured nerve cells with their neural processes extending from the cell body in all directions.
In the origin are the stem cells
The human brain is a highly complex organ not only because of the different types of nerve cells, but also because of the immense network of nerve connections. From so called Stem cells all cell types of the brain develop. The initially simple cells develop into increasingly complex cells as the brain develops. There is a necessary expression, or differentiation, of cells and groups of cells that perform specific tasks in the brain. From still immature and dividing stem and progenitor cells, the different cell types are finally formed. This specialization of certain cells that occurs within an individual’s development is known as the Cell differentiation.
Growth factors control wiring in the brain
An important means for the brain, the differentiation resp. the cell growth. The first test to be carried out is the coordinated expression of growth factors. Every minute, more than one hundred thousand neurons are formed in the brain of a newborn baby. This cell growth decreases continuously with increasing age. The brain now grows predominantly by forming new wiring and associated new glial cells. Interestingly, the connections between the individual nerve cells are modulable, i.e. the interconnections on the dendrites (nerve cells) are not fixed but are built up and broken down. In adults, new nerve cells are only produced in certain areas of the brain and in modest numbers. However, other brain areas are thought to be capable of generating new cells and taking over brain functions after brain injury or disease. Here, too, it is suspected that growth factors play a major role in this process.
Research is important for a better understanding of the brain
Knowledge in the field of developmental biology is a prerequisite for understanding the function of neurons in the neural network. If we know how growth factors work, we will gain information on how specific nerve cells develop, and we hope that this will open up new ways of treating neurodegenerative and neuropathological diseases.
Research projects
Background
Nerve Cell Transplantation. Dead cells (A) are replaced by healthy neurons (B) to repair brain functions.
The concept of neuronal cell transplantation as a new therapeutic long-term strategy in the treatment of patients with Parkinson’s disease is actually quite simple: The aim is a functional restoration of the diseased brain by replacing the dead cells with implanted healthy nerve cells. Why is this specifically interesting in Parkinson’s disease?? And why have transplantation studies been performed mainly in this disease so far?
The human brain has more than 100 billion nerve cells. The progressive death of a specific, small, dopamine-producing subpopulation of neurons in the substantia nigra is a characteristic feature of Parkinson’s disease. Due to the lack of dopamine, the transmission of excitation in the striatum is disturbed. As a consequence, the typical symptoms such as rigor, akinesia and resting tremor develop. As the disease progresses, patients become immobile and also severely disabled in social interaction due to impairment of the mimic muscles. When the disease is first noticed, it is already far advanced. More than 70% of dopamine-containing brain cells have been lost by then. It can therefore be postulated that this neurodegenerative disease – with a specific nigrostriatal dopamine deficiency – offers easier access for this therapy than comparatively more ‘complex’ diseases, such as Alzheimer’s disease. It is important to note here the particular importance of experimental animal models of Parkinson’s disease. Thus, extensive studies have shown that transplanted embryonic dopaminergic neurons successfully innervated the striatum, released dopamine in a physiological manner, and improved motor functions.
Parkinson’s disease is common. Approximately 1 % of all persons over 60 years of age are affected by it. Due to the population development with an ever increasing life expectancy, the disease will be encountered much more frequently in the developed industrialized countries in the future. Nevertheless, the triggering factors are still largely unclear today. In addition to age-related changes, a corresponding genetic predisposition as well as the influence of a wide variety of environmental factors or a combination of these are discussed. To date, the disease is incurable. For a long time, therefore, great efforts have been made to find new treatment options for Parkinson’s disease.
History
The possibility of clinical application of neural transplantation was first discussed in the late 1970s. This was done against the background of numerous encouraging results obtained with brain cell transplantation in the rat model of PD, showing that motor deficits, as well as sensorimotor integration, improved * * * .
Beginning in the early 1980s, the first large-scale transplantation studies with human tissue were carried out. In more than 400 cases worldwide, the patient’s own cells were transplanted from the adrenal medulla, with the idea of circumventing the immunological and ethical problems of cell transplants. The results of these studies were sobering, but at the same time they paved the way for further development of the brain cell transplantation method. Thus, continuing animal experimental studies showed that transplantation of embryonic ventral mesencephalic tissue resulted in improved behavior combined with significant cell survival and substantial innervation of the denervated striatum. In the late 1980s, the first clinical transplantations of fetal ventral mesencephalic tissue were performed, in some cases describing substantial clinical improvements and demonstrating the survival of the transplanted cells in the recipient brain * * * .
Thus, it could be postulated that the transplanted tissue is able to functionally take over the task of the destroyed cells in the substantia nigra. However, from the results of these studies, it could also be seen that although in individual patients the clinical benefit was significant (which was accompanied by a substantial reduction or even complete elimination of L-dopa administration), there was a high variability in the results. This is probably mainly due to the fact that the pathological process varies in individual patients and the survival of the transplanted neurons and the innervation of the recipient brain were different. The first double-blind placebo-controlled study with fetal cell transplants in advanced PD was published in 2001 . Results were variable across the patient group and rather modest compared to the high expectations. However, patients who responded well to L-dopa improved significantly in bradykinesia and rigidity. Rather unexpectedly, about 12% of patients developed more severe side effects such as dyskinesia. A second controlled study also raised the question of how to evaluate the earlier results * .
In the meanwhile well over 300 realized brain cell transplantations, predominantly cells were transplanted which were taken from aborted embryos. The problems associated with this are discussed in the following section.
What exactly is brain cell transplantation and what are the parameters involved??
Cell grafts are obtained from the fetal ventral mesencephalon (age approximately 5.5 to 9 weeks after conception), i.e., from the area in which the substantia nigra develops at a later time. The neurons are stereotactically implanted into the target area (usually the post-commissural putamen) in the brain of the PD patient using a special needle. There, the nerve cells will further differentiate, forming connections to their target cells in the striatum and releasing the missing neurotransmitter dopamine there. They act, in other words, like a "biological dopamine pump". For practical reasons (it has not yet been possible to overcome the distance from the substantia nigra to its target cells in the striatum), the implantation is not performed in the damaged substantia nigra itself, but directly into the patient’s striatum.
The limited availability of donor tissue, of which only a tiny amount is available in each abortion, is a major problem. It is calculated that approximately 100,000 to 150,000 surviving dopaminergic neurons are needed to achieve substantial clinical improvement in symptoms. This corresponds to the number of approximately 3-4 human embryos. A successful operation thus requires considerable amounts of donor tissue, which is difficult to obtain. The current method can therefore at best only be offered to a fraction of all suitable Parkinson’s patients and also requires extremely complex and cost-intensive logistics.
Thus, there are important ethical aspects to be considered in brain cell transplantation, due to the fact that the cell grafts are obtained from tissue material of abortions. To mention just a few points: The decision of an abortion must not be influenced in any way by a possible later use of the tissue for a transplantation. It is essential to ensure that the demand for donor tissue does not influence the performance of abortions and that no commercial interests are involved. Only after written consent of the woman terminating her pregnancy, donor tissue may be removed and further processed exclusively anonymously.
Researchers are currently making great efforts to avoid having to rely on the controversial embryonic human tissue in the future. First transplantations in patients have already been performed with fetal brain cells of pigs (the so-called xenotransplantation), which from today’s point of view must rather be regarded as an "intermediate step" due to the unresolved immunological questions. Genetically modified cell lines and stem cell technology are considered to have a better chance of success, although many questions remain unanswered, such as the precise control of cell development before and after transplantation. Advantages of this technology are the practically unlimited amount of tissue and the lack of risk of rejection or transmission of infectious diseases (as with implantation of foreign donor tissue).
Nerve cells are highly sensitive and extraordinarily complex structures and react extremely sensitively to external influences such as those that occur during transplantation. The slightest mechanical damage or change in environmental biochemical conditions is sufficient to provide a lethal stimulus to the brain cell. It is therefore not surprising that only about 5-10% of the transplanted cells survive the procedure.
Research has observed that cell death before and during transplantation is due in part to the initiation of programmed cell death, or apoptosis. In addition to metabolic disturbances, excitotoxicity (the death of a nerve cell due to prolonged stimulus overload) and oxidative stress are thought to play important roles in this process. It is hoped that the use of various neuroprotective substances will make an important contribution to improving cell survival and minimizing the amount of tissue required. In addition to pretreatment of the tissue to be transplanted, the appropriate drugs would probably also need to be administered during and after surgery to improve graft survival. Interestingly, in a recent study, pretreatment of donor tissue with a lipid peroxidase inhibitor (and subsequent administration to the patient) significantly reduced the number of embryos required for transplantation * . Of particular interest are growth factors such as glial cell line-derived neurotrophic factor (GDNF), which are secreted by neurons and supporting cells during normal embryonic brain development and play an important role in the control and coordination of neuronal growth. GDNF, for example, stimulates the morphological differentiation of dopamine-containing neurons * . Since growth factors can hardly pass the blood-brain barrier, attempts are being made to deliver the growth factor directly into the brain by implanting special capsules filled with genetically modified GDNF-producing cells. In fact, animal experiments showed that the graft grew in faster and better * .
Of great importance in brain cell transplantation is the selection of patients. criteria, which are considered necessary by most centers:
- No other severe disease is present.
- No dementia or psychosis is present.
- Patients tend to be young (between 40 and 65 years old).
- The patients show "on-off" fluctuations with good "on" periods.
- Patients suffer from severe hypokinesia and rigidity in ‘off’ phases, but do not show pronounced tremor.
- As an important parameter, according to the studies of Curt Freed * , the response of symptoms to L-dopa appears to be.
In summary, much research remains to be done before widespread clinical application of brain cell transplantation can be thought of. The undisputed great possibilities of this form of therapy should not be forgotten despite the currently rather critical voices. Although I am convinced that substantial progress can be expected in the coming years – especially in the field of stem cell research – brain cell transplantation should still be considered "experimental" at the present time and should be discussed cautiously with the patient.
Disturbed cellular energy metabolism plays an important role in many neurodegenerative diseases. In our studies, we investigate the potential of the phosphocreatine/creatin system to protect neurons from toxic influences.
Nerve growth factors play an eminent role in the development of the nervous system and are important team players for the survival of brain cells. We are investigating which factors play a role in Parkinson’s disease.
This research project is pursuing a novel approach to the future treatment of vascular diseases that can lead to heart attacks, for example: Not by transplanting stem cells, but by activating existing stem cells.
Background
Ischemia is a reduction in blood flow to a tissue. The affected tissue subsequently suffers from oxygen and nutrient deprivation and may die off. If the heart muscle is affected, this can lead to an infarction. If arms and legs are affected, this can lead to so-called arterial occlusive disease.
There are various approaches to treating these diseases, such as the idea of using stem cell transplants to grow new blood vessels. However, such transplantations are always associated with hurdles, such as possible rejection reactions. In addition, stem cells are difficult to find and are reluctant to divide in the laboratory.
Significance
If this project is successful, a clinical trial would be the next logical step. Hundreds of thousands of patients in Switzerland alone could benefit from a medical application – patients with a heart attack, with a stroke, with atherosclerosis.
This research project follows a novel approach: Damaged vessels are not to be treated by transplantation, but the researchers try to stimulate the stem cells already resident in the tissue to divide. Therefore, this therapy is also called "cell-free". The researchers focus on so-called EPC cells (EPC stands for Endothelial Progenitor Cells), because these cells play an important role in the formation of new blood vessels. Researchers will investigate which source is best suited to stimulate these EPC cells. The blood of healthy donors? Umbilical cord blood?
Collaborations
Cluster for Regenerative Neuroscience Bern
- Eye Clinic, Inselspital, Bern
PD Dr. V. Enzmann, research group leader
Prof. S. Wolf, clinical director - Institute for Infectious Diseases (IFIK), Inselspital, Bern
Prof. S. Leib, Research group leader - Department of Gynecology, Inselspital, Bern
Prof. D. Surbek; Co-Clinical Director and Head of Research - Neurology, Inselspital, Bern
Prof. S. Saxena, Head of Research
Department of Biomedicine
Institute of Neurobiology, Odense, Denmark
References
Kordower JH, Freeman TB, Snow BJ, Vingerhoets FJ, Mufson EJ, Sanberg PR, Hauser RA, Smith DA, Nauert GM, Perl DP, Olanow CW. Neuropathological evidence of graft survival and striatal reinnervation after the transplantation of fetal mesencephalic tissue in a patient with Parkinson’s disease. N Engl J Med.1995;332(17):1118-1124
Lindvall O, Brundin P, Widner H, Rehncrona S, Gustavii B, Frackowiak R, Leenders KL, Sawle G, Rothwell JC, Marsden CD, et. al. Grafts of fetal dopamine neurons survive and improve motor function in parkinson’s disease. Science. 1990;247(4942):574-577.
Freed CR, Greene PE, Breeze RE, Tsai WY, DuMouchel W, Kao R, Dillon S, Winfield H, Culver S, Trojanowski JQ, Eidelberg D, Fahn S. Transplantation of embryonic dopamine neurons for severe parkinson’s disease. N Engl J Med. 2001;344(10):710-9.
Olanow CW, Goetz CG, Kordower JH, Stoessl AJ, Sossi V, Brin MF, Shannon KM, Nauert GM, Perl DP, Godbold J, Freeman TB. A double-blind controlled trial of bilateral fetal nigral transplantation in Parkinson’s disease. Ann Neurol. 2003;54(3):403-14.
Brundin P, Pogarell O, Hagell P, Piccini P, Widner H, Schrag A, Kupsch A, Crabb L, Odin P, Gustavii B, Bjorklund A, Brooks DJ, Marsden CD, Oertel WH, Quinn NP, Rehncrona S, Lindvall O. Bilateral caudate and putamen grafts of embryonic mesencephalic tissue treated with lazaroids in Parkinson’s disease. Brain. 2000;123(Pt 7):1380-90.