In vitro assessment of cytotoxicity and labeling efficiency of 99mTc-HMPAO with stromal vascular fraction of adipose tissue

IntroductionNoninvasive radionuclide imaging of cells using technetium99m-hexamethylpropyleneamine oxime (99mTc-HMPAO) is a potential diagnostic tool for several applications. Herein we aimed to evaluate the labeling efficiency and cellular toxicity of 99mTc-HMPAO with Stromal Vascular Fraction (SVF) of adipose tissue to develop a process tool for theranostic purposes, in particular imaging cardiac stem cell therapy.MethodsTen million cells of SVF were labeled with 99mTc-HMPAO complex and excess radiolabel was cleared off through washing in PBS. The labeling efficiency of 99mTc-HMPAO was detected in labeled cells and their subsequent supernatant wash using isotope dose calibrator and gamma camera. The cytotoxicity was assessed for the comparative reactive oxygen species (ROS) by H2DCFDDA, apoptotic events by annexin-V and TUNEL assay and mitochondrial potential by JC-1.ResultsAn encouraging labeling efficiency of 33% was observed with 99mTc-HMPAO complex. The radionuclide labeling of SVF demonstrated significant safety profile as evaluated by apoptotic assays.Conclusion99mTc-HMPAO labeling efficiency of 33% of total SV fraction would produce sufficient radioactive signals that would enable for in vivo tracking of cells by SPECT-CT. The radionuclide did not demonstrate any significant impact on the structural or functional organization of the labeled cells. Our study indicates that SVF can be safely labeled with 99mTc-HMPAO without adverse cytotoxic events and for its potential role in imaging cardiac stem cell therapy.