Generate an Endogenous Reporter Transgenic Mouse to Track Cell Fates and Transplant Survival

A transgenic mouse that ubiquitously expresses a highly specific and endogenous reporter gene can serve as a valuable donor of immune cells, stem cells or cell/tissue transplants, as investigators can simply monitor the location and the expression of the reporter to gain insights of cell fates or transplant survival in nontransgenic recipient mice. We have successfully developed a universal noninvasive imaging system based on expressing mouse anti-polyethylene glycol antibodies (anti-PEG reporter) on cell surface to selectively trap PEG-labeled imaging probes (PEG-NIR797, PEG- 124I, PEG-SPIO) to assess the delivery of cells in vivo by different imaging systems (Optical, micro-PET, MRI). The anti-PEG reporter displayed an imaging specificity comparable to the conventional HSV-tk reporter (herpes simplex type 1 virus thymidine kinase) by micro-PET. Importantly, the endogenous anti-PEG reporter does not induce humoral or cellular immune responses, in contrast to the exogenous HSV-TK reporter which induces immune responses in Balb/c mice. Based on these results, the specific and nonimmunogenic anti-PEG reporter is a good candidate for constructing reporter-transgenic mice. In this project, we propose to generate a transgenic mouse that expresses the anti-PEG reporter ubiquitously to serve as a donor for stem cells or tissue/cell transplants. The stem cell fates or the transplant survival in non-transgenic recipients will be monitored by using PEGylated imaging probes. The anti-PEG transgenic mice has been constructed by the National Laboratory Animal Center (NLAC) using human ubiqitin (hUBC) promoter, and the founder lines (F1) which stably express anti-PEG reporter genes are continuously breeding. The hUBC-HSV-tk transgenic mouse (as control) is generating. We propose four main aims of investigation as following: (1) Characterize the expression patterns of the anti-PEG (or HSV-tk) transgenic mice. (2) Real-time image the tumor targeting and antitumor effect of tumor specific anti-PEG (or HSV-tk) T cells in vivo. (3) Noninvasively track the distribution, survival and arthritics tissue repairing of anti-PEG (or HSV-tk) mesenchymal stem cells in vivo. (4) Transplant anti-PEG (or HSV-tk) pancreatic islets to STZ-induced diabetic recipient mice, and then noninvasively monitor the survival of transplanted islets to correlate diabetes progression in the recipient mice. Successful development of the highly specific and nonimmunogenic anti-PEG reporter-transgenic mouse will provide a syngenic cell/tissue/organ donor for long-term studies of transplant survival, distribution and therapeutic efficacy in recipient (nontransgenic) mice by noninvasive imaging.