Investigation of the effect of nicotinamide riboside on primary human bone-marrow derived mesenchymal stromal cells in vitro

Abstract

INTRODUCTION: Mesenchymal stromal cells (MSC) have been identified as important cell-based therapy candidates for cartilage, bone and intervertebral disc diseases [1]. During prolonged in vitro expansion prior to administration, MSC become senescent which impairs their therapeutic potential [2]. Here, we aimed to investigate whether extracellular nicotinamide riboside (NR) is beneficial for MSC expansion with respect to delaying the senescence, improving cellular activity and growth kinetics. METHODS: MSC were isolated from human bone marrow aspirates by gradient centrifugation of the bone marrow and subsequent expansion in α-MEM + 10% fetal bovine serum + 2.5 ng/ml bFGF2. The cytotoxicity of NR was measured at day 4 for 29 concentrations in a range from 5 nM to 4 mM. The long-term effects of NR were tested at concentrations of 10, 100 and 1,000 μM by measuring the population doubling level (PDL), relative confluency (real-time live-cell imaging with IncuCyte S3 ® ), mitochondrial activity by resazurin reduction, senescence-associated β-galactosidase assay (SA-β-gal) and NAD/NADH ratio. RESULTS & DISCUSSION: MSC treated with 3 and 4 mM NR had a significantly higher mitochondrial activity at day 4 than the negative control (p=0.0027 and p<0.0001 respectively, N=3). However, in the weeks 3 to 8, cells treated with ≥100 μM NR died reaching a maximum PDL of 13.43 (N=4). In two donors, the experimental group with 10 μM NR reached a 2-fold higher PDL than the negative control. The relative confluency at passage (P) 2 after 6 days in culture was higher with 10 μM NR compared to the negative control (35.00 ± 9.29% and 26.19 ± 5.41% respectively, mean ± SD, N=2). The mitochondrial activity was significantly higher with 10 μM NR at P4, P8 and P10 (p<0.01, N=4). At all passages, the percentage of SA-β-gal positive cells was under 5%, except in the negative control medium at P11 (18.17% ± 18.18%, mean ± SD, N=1). All experimental groups treated with NR had a higher NAD/NADH ratio which exhibited a dose-dependent trend (N=1). CONCLUSIONS: Extracellular NR elevated the intracellular NAD/NADH ratio. NR is not cytotoxic within 4 days of culture at concentrations up to 4 mM. Long-term culture with 10 μM NR improved the growth kinetics markedly in two donors. ACKNOWLEDGEMENTS: Financial support was received by the Competence Center for Applied Biotechnology and Molecular Medicine (CABMM) start-up grant to BG. REFERENCES [1] Vedicherla S et al. J Orthop Res. 2017; 35(1):8-22 [2] Turinetto V et al. Int J Mol Sci. 2016;17(7):1164