[Autoradiography reporter gene (Ad5-tk carrying HSV1-tk gene) expression imaging in rat myocardium].
OBJECTIVE
Radionuclide imaging of reporter gene expression holds promise for noninvasive monitoring of gene therapy. Herpes simplex virus 1-thymidine kinase (HSV1-tk) has been successfully applied to the tumor tissue.We explored the feasibility of the expression imaging of HSV1-tk reporter gene in rat myocardium by using SPECT reporter probe (131)I-2'-fluoro-2'-deoxy-1-beta-D-arabinofuranosyl-5-iodouracil ((131)I-FIAU) and autoradiography (ARG).


METHODS
The recombinant Ad5-tk carrying HSV1-tk gene and adenovirus (Ad5-null) as vector were constructed and intramyocardially injected into SD rats. Experiment was grouped for different aims as follows: (1) Influence of time on the imaging after transfection reporter gene: rats were injected with (131)I-FIAU at day 1, 2, 3, 5 and 7 after transfection of 1 x 10(8)pfu Ad5-tk; (2) Influence of various titers on the imaging: rats underwent intramyocardial injection with various titers of Ad5-tk (5 x 10(8), 1 x 10(8), 5 x 10(7), 1 x 10(7)pfu). After 2 days, rats were injected with (131)I-FIAU in tail vein. Equal volume Ad-nulls was intramyocardially injected to control rats. Rats were killed 24 h after injection of (131)I-FIAU and the hearts were rapidly dissected for gamma counts measurement. The total myocardial (131)I-FIAU accumulation was quantified in percent of injected dose per gram myocardium (%ID/g). The myocardial reporter gene expression was semi-quantitatively determined by ARG and RT-PCR.


RESULTS
ARG and RT-PCR showed that the local expression of reporter gene increased in proportion with increasing titer and decreased in proportion with time post injection. The semi-quantitative assay showed there were significant correlations among %ID/g, RT-PCR and ARG: r(2) = 0.963, P < 0.05 for RT-PCR and ARG; r(2) = 0.996, P < 0.01 for %ID/g and ARG in rats received various reporter gene titers at identical time point post injection; r(2) = 0.950, P < 0.05 for RT-PCR and ARG; r(2) = 0.980, P < 0.01 for %ID/g and ARG for rats received identical reporter gene titer on various time points post injection.


CONCLUSIONS
The present study showed that cardiac reporter gene imaging with HSV1-tk as reporter gene and (131)I-FIAU as reporter probe was feasible in rats. The optimal Ad5-tk titer is 1 x 10(8) pfu and the optimal imaging time is 24 h to 48 h post gene transfer. HSV1-tk/FIAU may be used for the noninvasive monitoring of cardiac gene therapy.
Department of Nuclear Medicine, Union Hospital, Huazhong University of Science and Technology, Hubei Key Laboratory of Molecular Imaging, Wuhan 430022, China.
Ying
Y
Liu
Xiao-li
XL
Lan
Tao
T
Wu
Xiao-hua
XH
Yin
Yong-xue
YX
Zhang
D000818:Animals; D001345:Autoradiography; D005260:Female; D015870:Gene Expression; D017930:Genes, Reporter; D018259:Herpesvirus 1, Human / Q000235:genetics; D032383:Myocytes, Cardiac / Q000166:cytology* / Q000000981:diagnostic imaging* / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D013937:Thymidine Kinase / Q000235:genetics; D015899:Tomography, Emission-Computed, Single-Photon; D014162:Transfection
D013937:Thymidine Kinase