Biodistribution and persistence of human umbilical cord-derived mesenchymal stem cells in NCG mice: a comparative study.

Introduction: This study aims to investigate the biodistribution and persistence of human umbilical cord-derived mesenchymal stem cells (hUC-MSCs) in NCG mice post-intravenous injection, utilizing ⁸⁹Zr-PET/CT, bioluminescence imaging, multiplex immunohistochemistry (mIHC), and quantitative polymerase chain reaction (qPCR).

Methods: hUC-MSCs were labeled with ⁸⁹Zr-oxine (⁸⁹Zr-MSCs) or transduced with luciferase gene (Luc-MSCs). Real-time tracking of ⁸⁹Zr-MSCs lasted for 14-days followed by mIHC staining of hCD73. Real-time tracking of Luc-MSCs lasted for 7-days, followed by mIHC staining of hCD73 and human Alu-based qPCR. All methods adhered to ICH and other regulatory guidelines for development of cell-based drugs.

Results: A biodistribution and persistence pattern was observed in the order of lung > liver > kidney > >spleen, although discrepancies were noted for the liver and kidney.

Conclusion: Each method exhibited strengths and weaknesses: ⁸⁹Zr-PET/CT enabled long-term tracking but encountered issues with ⁸⁹Zr shedding and dead cells; bioluminescence provided specific detection but was hampered by a rapid decline in signal; mIHC identified cells but relied on antigen abundance; qPCR detected minimal cell quantities but was unable to differentiate between live and dead cells. These limitations may obscure the true fate of cells in vivo, highlighting the need for more accurate and reliable assessment techniques.