Transmigration of NGF secreting cells

Cholinergic neurons of the basal forebrain degenerate in Alzheimers disease. The growth factor "nerve growth factor, NGF" exhibits the most potent neuroprotective activity on cholinergic neurons so far. Thus it is of interest to apply NGF clinically. Two clinical studies have been performed: NGF was infused directly into the brain of an Alzheimer patient (Sweden, 1992) and NGF secreting skin cells were transplanted into the human brain (USA, 2001). However, it is expected that the number of Alzheimer patients will increase dramatically within the next 50 years (approx. 230.000 patients in Austria). Surgical stereotaxic delivery methods will not be useful, thus alternative delivery methods need to be developed for the future, if NGF should be used as a neuroprotective molecule. The aim of this project is to use genetically modified blood-derived cells (monocytes and monocyte-derived cells), which secrete NGF, and to test the transmigration through the blood brain barrier. This project should be performed in 2 phases. In the first phase we want to use organotypic brain slices connected to a synthetic blood brain barrier and test and enhance transmigration of these cells. Application of genetically modified cells secreting NGF should be used to protect cholinergic neurons of the basal nucleus of Meynert against cell death in this model. In a second phase we want to show that these cells can transmigrate in vivo in the rat and optimize this migration. Using an in vivo lesion model, the fimbria-fornix lesion model, we want to demonstrate that application of genetically modified NGF secreting cells is useful to protect septal cholinergic neurons against fimbria-fornix induced cell death. This project should develop alternatives to introduce growth factors to the brain. Due to the progressive degeneration in Alzheimers disease it will be necessary to apply NGF as early as possible and continously, and such an application of transmigrating genetically modified cells may contribute to improve the delivery of NGF into the brain.

Alzheimers disease is a severe chronic disorder of the brain with massive dysfunction of cognition. In Alzheimers disease neurons degenerate, which synthesize and release a neurotransmitter, called acetylcholine. The cell death of these neurons can be counteracted by a protein, termed nerve growth factor (NGF). Thus, it is an aim in research to find strategies to introduce this protein into the brain, such as e.g. using transplantation of cells, which produce and secrete NGF (M. Tuszynski, USA) or to directly inject the protein into the brain (L. Olson, Sweden). However, such invasive treatments are very difficult and strategies to introduce NGF into the brain without a surgical treatment need to be developed. Such treatments need to find ways to get entry via a compact barrier between blood and brain (the blood-brain barrier, BBB). Since NGF is a very large protein, it cannot enter this barrier. Thus research tries to develop "NGF-drugs" or tries to couple NGF to BBB permeating molecules or to open the BBB for very short times. The aim of our FWF project P16130-B08 was to use blood cells as a vehicle to transport NGF into the brain. Previous experiments have shown that blood cells can enter the brain during a normal immune patrol. In this project we isolated blood cells (monocytes) of the rat and manipulated these cells to secrete NGF. We have tested the adhesion of monocytes to the BBB and the subsequent migration into the brain. Different attracting substances were tested to enhance this transmigration. In addition, we explored the effects of experimentally-induced inflammation on the transmigration. Last not least the neuroprotective effect of NGF on cholinergic neurons was tested in a simple in vitro organotypic rat brain slice model. The advantage of such a method should be to isolate blood cells from Alzheimer patients and to manipulate these cells to secrete NGF and to inject these cells into the same patient. These NGF cells should migrate to degenerating neurons and protect the cholinergic neurons in the brain. However, until this approach may enter clinical practice at least some decades may be gone.