Figure 7.

^99mTc-Pertechnetate Uptake Reflects In Vitro Cellular Energetics

(A) Schematic illustrating link between ^99mTc-pertechnetate uptake and cellular ATP levels. Cells transduced with NIS (using lentivirus) take up ^99mTc-pertechnetate, which permits cell tracking by single-photon emission computed tomography (SPECT). ^99mTc-pertechnetate transport by NIS is dependent on the transmembrane Na⁺ gradient, which is maintained by Na⁺-K⁺-ATPase. Because Na⁺-K⁺-ATPase activity is dependent on cellular ATP levels, cellular energetic state modulates ^99mTc-pertechnetate uptake. (B) Oligo treatment led to a 15% reduction of ^99mTc-pertechnetate uptake by NIS⁺ cells. ^99mTc-pertechnetate uptake by NIS⁺ cells was abolished by oligo treatment when NIS⁺ cells were cultured in pyruvate medium (OxPhos condition); oligo did not affect ^99mTc-pertechnetate uptake when cells were cultured with DMOG (anaerobic glycolysis condition). Statistical comparison was performed between cells cultured in medium containing pyruvate or DMOG with cells cultured in glucose medium, using the Student t test. (C) Oligo treatment led to a 15% reduction in total cellular ATP (Figure 5C2) and ^99mTc-pertechnetate uptake (B), suggesting that ^99mTc-pertechnetate uptake by NIS⁺ cells reflects cellular ATP levels. (D) In vitro ^99mTc-pertechnetate uptake was markedly reduced by suspension and restored by replating as monolayers or encapsulation in hydrogels. Statistical comparison of each condition was performed with 1-h suspension condition using the Student t test. Data is presented as mean ± SD; n = 6. **p < 0.01; ***p < 0.001. Abbreviations as in Figure 1.