New molecular imaging techniques may lead to advances in disease treatment

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A new technique may enable more accurate non-invasive PET imaging of new cells injected into the body, according to research presented at the 2008 Society of Nuclear Medicine (SNM) meeting, held June 14-18 in New Orleans.

The new technique, which involves engineering antibody fragments to act as reporter genes—or markers that signal cells of interest for PET imaging purposes—could advance the study of genetically engineered cells to treat diseases, according to researchers.

“Genetic cell engineering is the focus of intense research in almost all areas of medicine and shows great promise for treatment of common illnesses such as heart disease, diabetes, and Parkinson's disease and other neurodegenerative disorders," said the study’s lead author Wolfgang Weber, MD.

The department of molecular and medical pharmacology at University of California Los Angeles (UCLA), in collaboration with the department of chemistry at UC Davis, performed the study.

However, despite intense efforts, researchers said they have few solid, noninvasive methods for accurately tracking the location, function and viability of small numbers of transplanted cells.

“Our research shows that using antibodies as reporter genes in PET imaging provides these capabilities and could contribute to improved treatment of a number of potentially devastating diseases,” said Weber, professor of nuclear medicine at the University of Freiburg in Germany.

To improve PET imaging, the researchers have been studying the use of reporter gene–probe combinations. With the technique, cells are created to synthesize a protein that binds to or metabolizes radioactive reporter probes that are injected into the body and detected with PET imaging technology.

However, most available reporter gene combinations are not aptly sensitive or specific and have significant limitations in terms of tracking the cells of interest, according to the researchers.

In the new research, Weber and his colleagues explored using cell surface–bound antibody fragments as reporter genes. The engineered antibody fragments, developed by the group of Claude Meares at UC Davis, bind irreversibly to low-molecular-weight antigens, which act as reporter probes.

Cell culture and animal studies demonstrated intense and highly specific uptake of the probes in cells expressing the antibody fragment on the cell surface. The data indicate that antibody-based reporter genes represent a promising new platform for the development of new reporter gene and probe combinations, the researchers said.