Evaluating Nonintegrating Lentiviruses as Safe Vectors for Noninvasive Reporter-Based Molecular Imaging of Multipotent Mesenchymal Stem Cells
Bibliographic record
Abstract
Reporter gene-based molecular imaging can provide invaluable information on the fate of cellular therapies postimplantation. Integrating lentiviral vectors (ILVs) are commonly used for stably engineering cells; however, their potential for insertional mutagenesis poses a significant safety concern and barrier to widespread clinical adoption. In cells that slowly divide or are postmitotic in vivo, such as mesenchymal stem cells (MSCs), nonintegrating lentiviral vectors (NILVs) may be a safer alternative option because NILVs remain episomal and can provide prolonged expression profiles. Here, NILVs coexpressing fluorescence and bioluminescence imaging (BLI) reporters were engineered and used to longitudinally image the viability of human MSCs in vitro and in vivo in mice. In vitro, ILV-transduced cancer cells and MSCs maintained steady reporter gene expression over time, whereas NILV-transduced cells progressively lost signal. NILV reporter loss was accelerated in highly proliferative cancer cells compared with less proliferative MSCs. In vivo, ILV- and NILV-transduced MSCs were each detectable with BLI postintramuscular implantation, with significantly higher ILV-based signal compared with NILV-based signal. BLI signal was observed to similarly diminish over time for both cell populations, which was attributed to cell death. Despite the reduced signal intensity with NILVs and the minimal number of cells injected (40,000), live NILV-transduced MSCs were reliably visualized for up to 2 weeks. Safety is a concern for future clinical reporter gene applications. We present NILVs as a safe means of imaging reporter gene expression for slowly dividing or nondividing cells and showed effective tracking of the viability of a small number of live transplanted MSCs over time with optical imaging. Future work will evaluate improvements to episomal NILV reporter expression, explore sensitive clinically relevant reporters, and apply this approach to clinically relevant MSC applications in preclinical models. NILVs may have broad clinical applications for expression of imaging reporters and other gene products in MSC-based therapies.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".