Enabling Non-invasive Tracking of Vascular Endothelial Cells Derived from Induced Pluripotent Stem Cells Using Nuclear Imaging

The absence of clinically applicable imaging techniques for continuous monitoring of transplanted cells poses a significant obstacle to the clinical translation of stem cell-based therapies for vascular regeneration. This study aims to optimize a clinically applicable, non-invasive imaging technique to longitudinally monitor vascular endothelial cells (ECs) for vascular regeneration in peripheral artery disease (PAD).

Human induced pluripotent stem cells (HiPSCs) were employed to generate ECs (HiPSC-ECs). Lentiviral vectors encoding human sodium iodide symporter (hNIS) and enhanced green fluorescent protein (eGFP) genes were introduced to HiPSCs and HiPSC-ECs at varying multiplicities of infection (MOI). Through a combination of fluorescence microscopy and flow cytometry, an optimized transduction technique for introducing hNIS-eGFP into HiPSC-ECs was established. Subsequently, single-photon emission computed tomography (SPECT) was utilized for imaging of the transduced cells in vitro and in vivo after transplantation into the gastrocnemius muscle of nude mice.

Lentiviral transduction resulted in sustained co-expression of hNIS and eGFP in HiPSC-ECs when transduced post-endothelial differentiation. An optimal MOI of five yielded over 90% hNIS-eGFP expression efficiency without compromising cell viability. hNIS-eGFP⁺ HiPSC-ECs exhibited ^99mTc uptake and were detectable through SPECT in vitro. Additionally, intramuscular injection of hNIS-eGFP⁺ HiPSC-ECs with Matrigel^TM into the hindlimbs of nude mice enabled real-time SPECT/CT tracking, from which a reduction in signal exceeding 80% was observed within 7 days.

This study establishes an optimized cell modification and imaging protocol for tracking transplanted cells. Future efforts will focus on enhancing cell survival and integration via improved delivery systems, thereby advancing the potential of cell-based therapies for PAD.

In this study, we present an optimized approach for non-invasive tracking of transplanted vascular endothelial cells (HiPSC-ECs) using a combination of lentiviral transduction with hNIS and eGFP genes and single-photon emission computed tomography (SPECT) imaging. Our methodology allows real-time monitoring of HiPSC-ECs in vivo, paving the way for advancements in regenerative therapies for peripheral artery disease (PAD).