by Cheryl Dawes
Revealing what happens in the brain cells that Alzheimer's disease (AD) damages is a crucial part of understanding the progression of this relentless disease and how to slow or stop it. Researchers nationwide are investigating the cellular processes that occur in AD in an effort uncover information that will lead to new strategies to combat the disease. Such research requires a reliable supply of suitable cells.
To meet this demand for cells, ADRC investigator Dr. Karen Swisshelm, associate professor of pathology, is beginning a new cell-culturing project. She and her colleagues are working to develop ways to grow large numbers of cells that have characteristics important in studying AD.
As project leader of the UW ADRC's Cell and Tissue Bank, Swisshelm oversees maintenance of a bank of over 1900 lymphocyte (blood) and skin fibroblast lines from blood specimens derived from AD patients, family members and from patients with other neuro-degenerative diseases. It was one of the first repositories of its kind and continues to be an important resource for AD researchers nationwide. The new project will expand and enhance the collection of biological materials available to researchers.
In the first aspect of the project, Swisshelm is collaborating with UW ADRC researcher Dr. David Cook to develop an ongoing source of cells derived from mouse models of AD. One model Cook works with has been genetically engineered to produce the human form of beta amyloid, the protein that builds up in the characteristic plaques in the brains of Alzheimer's patients. Another model has lost the ability to produce a key protein involved in beta amyloid processing in brain cells. These models provide different windows on cellular processes in AD.
"Our role is to produce cell lines from skin, lung or brain tissues of these animals," says Swisshelm. "We are developing means to allow these cells to be cultured in an unlimited fashion in dishes, so that Dr. Cook and his colleagues can study protein-processing events related to AD."
With proper conditions in a petri dish, most tissue-derived cells will grow and divide, producing additional cells for a limited number of generations. Such a lineage of cells is known as a cell strain. To be especially useful in research, many generations of a particular cell lineage are needed-a cell strain must be "immortalized" to become a cell line that researchers can use to replicate and verify study results.
In most cases, skin biopsy material from individual humans can be split and subcultured 20 to 60 times to obtain more cells from growing and dividing cultures, explains Swisshelm. As the cells age-go through senescence-they slow down and eventually cease to divide. In the case of mouse cultures, the cells may undergo a stage called "crisis" either early or mid-way through their growing and dividing. During this crisis stage, some of the cells may spontaneously escape cellular senescence and become immortal. However, the crisis stage is often accompanied by chromosomal changes in the cells that could confound research results. Therefore, the techniques Swisshelm is developing are aimed to obtain long-lived cultures before the crisis stage occurs.
"In order to test the possibility of immortalizing cells very early in the processing of splitting and subculturing, we will use the mouse form of a cellular enzyme that maintains the ends of chromosomes," explains Swisshelm. "The ends of chromosomes are thought to be involved in setting the molecular clock for cellular aging. By maintaining these ends that may normally erode, we hope to maintain cells from these animals indefinitely."
Swisshelm and her colleagues plan to apply the techniques developed in culturing mouse cells to studies with human cells. Together with UW ADRC researchers Drs. George Martin and Galynn Zitnick, Swisshelm is working to produce lines of human neuronal precursor cells. It is likely to take two years or more to overcome the challenges presented by the specialized growing conditions required for culturing neuronal precursor cells. Ultimately, though, this work should allow production of large quantities of cells, proteins, membranes and other reagents, which will provide an important resource for further AD research.