The image shows a tissue biopsy from the epithelium of the human duodenum, the main area of nutrient and drug uptake, shown here enlarged for illustration. This type of tissue is 1 to 2 millimetres in diameter and can be taken by a physician during a gastric examination. Doctors often use biopsies for assessment to make the correct diagnosis, while biopsies are also commonly used by researchers to answer scientific questions. Since the inner lining of the gastrointestinal tract can change in its permeability properties, e.g. in case of disease, a question we want to address is, whether or not the tissue function also changes in terms of permeability due to chronological aging or not. For this reason, we are collecting human tissues from the upper and lower intestine to investigate the expression of proteins that are important for tissue permeability. Biopsies need to be immersed in a preservative solution and stored at -80°C to maintain the sensitive RNA intact, that contains valuable information.

The image shows a human tissue biopsy from the epithelium of the human duodenum, the main area of nutrient and drug uptake, shown here enlarged for illustration. This biopsy was immersed and stored in a preservative solution that crystallized as soon as the biopsy was removed from the liquid, giving the impression that the biopsy was frozen. The biopsy embedded in the crystals of the preservative solution is here surrounded by real ice, as the preserved biopsies are normally stored at -80 degrees. This type of tissue biopsy is 1 to 2 millimetres in diameter and can be taken by a gastroenterologist during a gastroscopy using special forceps. Doctors use biopsies to further examine the epithelium, which can help them detect epithelial damage and make the correct diagnosis. In our research, biopsies are taken from the duodenum, ascending colon and descending colon and used as starting material for the extraction of RNA. The extracted RNA is used to synthesize DNA, which is used to compare the gene expression of tight junction proteins known to regulate paracellular permeability, in biopsies of young and older adults using real-time PCR. Since the RNA contained in biopsies is highly susceptible to degradation by the enzyme RNase, tissue biopsies must either be stabilized in a preservative solution that inactivates RNase or they are shock-frozen in liquid nitrogen.