Organ transplants are becoming increasingly common and the one year graft survival rates have risen sharply over the past 20 years due to aggressive immunosuppressive drug treatments. For example, renal transplants now have one year success rates of over 90% in most transplant centers. However, the long-term survival rate has not increased significantly over this same period. Subclinical inflammation (SCI) is a major contributor to transplant deterioration and to increase long-term success rates of organ transplants it is vital to have a measure of SCI in the transplant tissue. SCI is currently assesse by the invasive measure of a biopsy but could be more effectively evaluated by imaging of gene(s) that are activated during inflammation. We have developed a gene expression reporter system that can be used for imaging gene expression in deep tissue. The reporters are aptamers that are expressed from a chosen promoter and are visualized when they bind their target radioligand. The aptamers behave as intracellular receptors, binding their ligands tightly and thereby providing an image of the cells in which the promoter has been activated. The current veteran team, which includes expertise in cell and molecular biology, synthetic organic chemistry and radiochemistry, will develop an aptamer reporter system for imaging local inflammation of transplanted tissues by achieving the following specific aims: 1) Prepare mammalian cells that stably express neomycin aptamers as reporters of either a regulated (Lcn2) or constitutively expressed (actin) gene, 2) Develop the chemical procedures to synthesize and radiolabel aptamer ligands, and 3) Image actin and Lcn2 gene expression in vivo. The studies proposed here have broad implications for monitoring the health of tissue transplants to enable more informed decisions regarding medications. Such monitoring is anticipated to increase the survival of transplants that have been modified by the inclusion of the aptamer SCI reporter system prior to their transplantation. The same reporter platform may be applied to other imaging needs such as stem cell trafficking or their gene expression profile to monitor their differentiation stage.
Organ transplantation has become a highly successful means of extending a healthy life after organ failure. However, long-term transplant survival is diminished due to subclinical inflammation, which results in the deterioration and eventual functional failure of the transplanted organ. This proposal will develop a new approach to imaging subclinical inflammation in the transplanted organ to enable optimal management of its long-term survival.