Mevalonate Depletion Impairs Survival of Primary Human Mesenchymal Stem Cells through Down Regulation of NF-κB

Abstract

Background: Circulating progenitor cells of bone marrow origin have been implicated to neointima formation and constructive remodeling in vascular injury and transplant cardiac allograft vasculopathy (CAV). Hydroxymethylglutaryl-Coenzyme A (HMG-CoA) reductase inhibitors (“statins”) have been shown to slow the progression of CAV and improve patient survival, which was presumed to be as a result of altered lipid metabolism. Statins also exhibit other positive pleiotropic properties such as modulation of inflammatory response via a mechanism independent of cholesterol reduction. We examined the effect of HMG-CoA reductase inhibition with three statins (atorvastatin, simvastatin and pravastatin) on the viability of primary human bone marrow derived mesenchymal stem cells (MSC) in culture. Methods: The protocol received IRB approval. MSC were isolated from bone marrow collected from the sternum of patients undergoing open heart surgery and were cultured in standard conditions. Cells were treated with atorvastatin, simvastatin or pravastatin 0.1, 1.0 or 10 μM ± mevalonate for 48 or 96 hours. Optical MTT assay was performed to assess cell viability. Viability was also assessed based on physical and biochemical properties of the cell using live-dead assay. NF-κB p65 expression was assessed by western blot. Rescue of NF- κB pathway function was achieved through overexpression of Ikk-β with an adenoviral vector. Results: Treatment of MSC with 0.1, 1 or 10 μM atorvastatin or simvastatin resulted in progressively reduced cell viability up to 50% in a time and dose dependent manner which was associated with a corresponding progressive decline in NF-κB p65 expression. Viability could be rescued by coincubation with mevalonate or pretreatment with Ikk-β adenoviral vector. Treatment with pravastatin did not show any effect on cell viability or NF-κB p65 expression. Conclusions: Mevalonate depletion through HMG-CoA reductase inhibition impairs the viability of primary human MSC in culture through NF-κB p65 depletion. This additional pleiotropic effect of statins may provide an insight into the benefits of this therapy independent of its effect on lipid metabolism. The lack of effect on MSC viability by pravastatin could be due to the hydrophilic nature of the molecule.