Establishment of a stem cell administration imaging method in bleomycin-induced pulmonary fibrosis mouse models

Pulmonary fibrosis is a progressive disease caused by interstitial inflammation. Treatments are extremely scarce; therapeutic drugs and transplantation therapies are not widely available due to cost and a lack of donors, respectively. Recently, there has been a high interest in regenerative medicine and exponential advancements in stem cell-based therapies have occurred. However, a sensitive imaging technique for investigating the in vivo dynamics of transplanted stem cells has not yet been established and the mechanisms of stem cell-based therapy remain largely unexplored. In this study, we administered mouse adipose tissue-derived mesenchymal stem cells (mASCs) labeled with quantum dots (QDs; 8.0 nM) to a mouse model of bleomycin-induced pulmonary fibrosis in an effort to clarify the relationship between in vivo dynamics and therapeutic efficacy. These QD-labeled mASCs were injected into the trachea of C57BL/6 mice seven days after bleomycin administration to induce fibrosis in the lungs. The therapeutic effects and efficacy were evaluated via in vivo/ex vivo imaging, CT imaging, and H&E staining of lung sections. The QD-labeled mASCs remained in the lungs longer and suppressed fibrosis. The 3D imaging results showed that the transplanted cells accumulated in the peripheral and fibrotic regions of the lungs. These results indicate that mASCs may prevent fibrosis. Thus, QD labeling could be a suitable and sensitive imaging technique for evaluating in vivo kinetics in correlation with the efficacy of cell therapy.