Alzheimer's, which is a neurodegenerative disease, is most often diagnosed in people over 65 years of age and accounts for approximately 60 % of cases of dementia. An increased worsening of cognitive abilities is characteristic for this disease, which leads to restrictions and behavioral changes in everyday life. Currently, there are no available treatments that cure Alzheimer's.

The so called "senile plaques" play a major role in
the development of Alzheimer's. They develop for an unknown amount of time before becoming fully apparent. This is the same process which is colloquially called "calcifi cation". In microbiological terms, abnormally folded amyloid beta peptides (Aß) are the main component of plaques. Aß is formed after cleavage of the precursor protein APP (Amyolic Precursor Protein) by the enzyme BACE1 (Beta-Site Amyloid Precursor Proteincleaving Enzyme 1). Consequently, the enzyme BACE1 plays a major role in the development of senile plaques.

In 2008 scientist Wang-Xia Wang and her research team found out that there is a significantly increased level of BACE1 in the brains of Alzheimer's patients while the level of the microRNA-107 is extremely low. (see Lit. 1) MicroRNAs (miRNA) are short, noncoding RNAs, which play a major role in gene regulation. They regulate highly specifically, for instance by degrading the target messengerRNA (mRNA) and influencing the development of the related protein.

 

Based on Wang's study we developed the hypothesis to control the BACE1-level, and consequently the development of the dangerous senile plaques, via an artificial increase and decrease of the miRNA- 107-level. We saw in it an opportunity to make a small but important contribution to the understanding of Alzheimer's.

Based on our hypothesis we designed our laboratory work: we wanted to artificially increase the miRNA- 107-level in "Alzheimer's cells" to check whether the BACE1-mRNA-level would be reduced. Our literature research showed that such an experiment has not been performed yet.

As cell culture model we chose the cell line SH-SY5Y which is common in medical research. They are special human brain cells with Alzheimer's characteristics. Therefore, safety level 1 was required in the lab, which could be ensured without any problems in our school lab. We reproduced the cell line in sufficient amounts and isolated their RNA. This RNA was transcribed to cDNA and with the help of a quantitative Realtime-PCR the mRNA-levels of BACE1 and miRNA-107 were measured.

Afterwards the miRNA-107-level was increased via transfection in parts of our cell culture. Therefore, a synthetically produced precursor-miRNA-107 was introduced into the cells which could mature in the cell and, if necessary, can interfere in the BACE1- level. We used 24 h and 72 h transfection times. The treated cells were finally compared with untreated control cells. We expected a high BACE1 level in the control cells and a comparably lower level in the transfected ones.

 

The result: in the 24 h transfection the BACE1-level dropped to 55.2 % and to 36.4 % in a second trial. In the 72 h transfection a reduction to 15.7 % could be achieved.

Our study shows that the transfection with miRNA- 107 affects the mRNA-level of BACE1 and suggests that this miRNA plays a major role in the regulation of this enzyme which is important for Alzheimer's. If we had the time and money to repeat our experiments often enough to achieve statistical significance, we would probably get a result suitable for scientific publication and, of course, a perfect addition to Wang's paper. Consequently, our study is a contribution to a better understanding of the molecular basis of Alzheimer's and a small contribution to find strategies for the treatment of the disease.

Apart from the molecular basis of Alzheimer's we were also interested in the clinical, psychological and social aspects of the disease. The work in the laboratory was very important for us but we also wanted to make our occupation more comprehensive. Therefore, we invited physicians to give lectures and we organized a workshop with a health psychologist. Finally, we visited with experts the old people's home in Kuchl and the geriatrics of the Christian-Doppler Clinic, where we had the possibility to talk to the persons concerned and their nurses. Thus we could learn a lot about the right and respectful way to deal with people who suffer from dementia.