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Indiana University Researchers Extract Viable DNA from Decades-Old Preserved Tissue

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The work, published in the April 2012 issue of the American Journal of Translational Research, was conducted using post-mortem tissues preserved over the past century, including tissue from the National Disease Research Interchange at the National Institutes of Health and the Indiana Medical History Museum in Indianapolis. The post-mortem samples included kidney, liver, heart, lung, spleen and brain tissues.

“We were surprised that we could get such viable DNA from the oldest samples,” said George Sandusky, DVM, Ph.D., senior research professor of pathology and laboratory medicine at the IU School of Medicine. “The genes were well-preserved despite the age of the tissue. This research will allow us to acquire information hidden for many years. The next step will be to try and tie them to genetic markers for mental illness.”

The search for genetic markers for mental illness will come next summer when Dr. Sandusky compares the DNA results from the museum samples to genetic information collected from patients with mental conditions such as post-traumatic stress disorder. The samples from the museum — a former state mental hospital — come from early 20th-century mental patients. The genetic material to which it will be compared comes from DNA samples provided by recent war veterans to Alexander Niculescu, M.D., Ph.D., associate professor of psychiatry and medical neuroscience at the IU School of Medicine, whose research has identified several potential biomarkers for mental illness.

“We will be comparing the DNA from the museum tissues to the DNA from veterans in search of similar genetic risk factors for mental illness in both populations,” Dr. Sandusky said. “This will help physicians give more accurate, molecular diagnosis based on genetic analysis rather than a visual or cognitive diagnosis based on traditional psychiatric observation.”

The discovery of high-quality DNA, including in tissues more than 70 years old, will help Dr. Sandusky and other investigators advance the search for biomarkers to improve diagnosis and treatment for psychological illnesses by opening up new sources of genetic data. A biomarker is a specific region on a gene that suggests susceptibility to a certain illness. Biomarkers are an increasingly common focus in the fight against cancer and other diseases, but no reliable biomarker test currently exists for psychiatric disorders.

The search for identifiable biomarkers could help improve care for the mentally ill by reducing the role of trial and error in identifying mental illnesses and prescribing the most effective drug dosages, he said. Illnesses under investigation include bipolar disorder, schizophrenia and PTSD.

Different preservation techniques were used over the course of the 20th century. The IU scientists compared the genomic quality DNA of formalin-fixed paraffin-embedded tissues, formalin-fixed celloidin-embedded tissues, tissues fixed in an ethanol mixture and tissues fixed in unbuffered formalin.

They found that celloidin-embedded and paraffin-embedded tissues, commonly used in the early 1900s and again in recent years, yielded the highest DNA concentration and greatest DNA quality.

The other fixation techniques, including formalin in various concentrations, long-term formalin or ethanol-stored tissue, yielded the lowest DNA concentration and lowest quality of gene usability.

Many of the preservation techniques from the early 1900s were actually better at preserving DNA than techniques from the 1990s, Dr. Sandusky found.

The use of the collection of usable, historic DNA data from the museum and National Disease Research Interchange began in summer 2011. After evaluating more than 180 samples, the IU researchers concluded that factors influencing the ability to obtain high-quality DNA included the chemical composition and age of the fixative, the impact of oxygen deprivation and self-digestion on the tissue, the size of the tissue specimen and the length of storage time.

In addition, the scientists found that organs from the thoracic cavity (the heart and lungs) yielded higher quality RNA and DNA in comparison to abdominal organs (liver and spleen). These organs were rapidly overgrown with post-mortem enzymes and parasites, deteriorating their quality.

In addition to Dr. Sandusky, authors on the study are Mary H. Cox, operations manager for the Indiana Clinical and Translational Sciences Institute Specimen Storage Facility and Clinical and Translational Support Laboratory; and undergraduate researchers Audrey McGuire of the University of Wisconsin and Erin E. Niland of Indiana University. In February, McGuire and Niland presented the study findings at the Fifth Annual Biospecimen Research Network Symposium at the National Institutes of Health. The work was supported by the Department of Pathology and Laboratory Medicine at the IU School of Medicine and the Indiana CTSI.