mTOR inhibition induces endothelial progenitor cell death
S G Miriuka1, V Rao, M Peterson
1Department of Medicine, Toronto General Hospital, Faculty of Medicine, University of Toronto, Ontario, Canada.
Summary
Rapamycin causes rapid death in endothelial progenitor cells, crucial for blood vessel repair. This immunosuppressant may hinder graft survival by targeting these vital cells, unlike cyclosporine A or tacrolimus.
Area of Science:
- Immunology
- Vascular Biology
- Pharmacology
Background:
- Immunosuppressants are vital post-transplant but cause endothelial toxicity.
- Endothelial progenitor cells (EPCs) possess reparative properties and originate from bone marrow.
Purpose of the Study:
- To investigate the impact of common immunosuppressants (cyclosporine A, tacrolimus, rapamycin) on EPCs.
- To determine the specificity and mechanism of rapamycin's effect on EPCs.
Main Methods:
- Culturing peripheral blood mononuclear cells (PBMCs) to promote EPC outgrowth.
- Exposing EPCs and other cell types to varying concentrations of immunosuppressants.
- Analyzing cell viability and death pathways.
Main Results:
- Rapamycin induced rapid EPC death at sub-clinical concentrations.
- Cyclosporine A and tacrolimus showed no significant toxicity at clinical concentrations.
- Rapamycin's toxicity was specific to early-stage EPCs, with less effect on mature endothelial cells or macrophages.
Conclusions:
- Rapamycin significantly reduces EPC viability, potentially impairing vascular repair.
- The mechanism involves apoptosis, independent of caspase/cathepsin activation.
- Rapamycin may block essential survival signals for EPCs, highlighting a critical side effect.
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