- •Sirt1 overexpression in MSCs promotes osteoblastic bone formation.
- •Sirt1 overexpression in MSCs reduces the acetylation level of FOXO3a.
- •Sirt1 overexpression in MSCs prevents bone loss in Bmi-1 deficient mice.
- •Sirt1 overexpression in MSCs restores the redox balance in Bmi-1 deficient mice.
- •NAM blocks the effect of overexpression of Sirt1 on osteogenesis and cell senescence.
B cell-specific Moloney murine leukemia virus integration site 1 (Bmi-1) deficiency (Bmi-1−/−) leads to an osteoporotic phenotype with a significant downregulation of Sirt1 protein expression. Sirtuin 1 (Sirt1) haploinsufficiency results in a bone loss by decreased bone formation; however, it is unclear whether Sirt1 overexpression in mesenchymal stem cells (MSCs) plays an anti-osteoporotic role. The aim of the study is to identify whether the overexpression of Sirt1 in MSCs could restore skeletal growth retardation and osteoporosis in Bmi-1 deficient mice.
We used our new generated transgenic mouse model that overexpresses Sirt1 in its MSCs (Sirt1TG) to cross with Bmi-1−/− mice to generate Bmi-1−/− mice with Sirt1 overexpression in MSCs, and compared their skeletal metabolism with those of their Bmi-1−/− and wild-type (WT) littermates (6 mice for each genotype) at 4 weeks of age using imaging, histopathological, immunohistochemical, histomorphometric, cellular, and molecular methods.
The levels of expression for Sirt1 were noticeably higher in the skeletal tissue of Sirt1TG mice than in those of WT mice. In Comparison to WT mice, the body weight and size, skeletal size, bone volume, osteoblast number, alkaline phosphatase and type I collagen positive areas, osteogenic related gene expression levels were all significantly increased in the Sirt1TG mice. Overexpression of Sirt1 in Bmi-1−/− mouse MSCs resulted in a longer lifespan, improved skeletal growth and significantly increased bone mass by stimulating osteoblastic bone formation and inhibiting osteoclastic bone resorption in the Bmi-1−/− mice, although the defects were not completely restored. Furthermore, Sirt1 overexpression in MSCs reduced the acetylation level of FOXO3a (Forkhead box O3a), increasing levels of expression for FOXO3a and SOD2 (Superoxide dismutase 2) in bony tissue, enhanced osteogenesis and reduced osteogenic cell senescence. We also demonstrated that nicotinamide, a Sirt1 inhibitor, blocks the effect of overexpression of Sirt1 in MSCs on osteogenesis and osteogenic cell senescence.
Taken together, these results demonstrate that Sirt1 overexpression in MSCs increased the osteoblastic bone formation and partially restores the defects in skeletal growth and osteogenesis in Bmi-1−/− mice by FOXO3a deacetylation and oxidative stress inhibition. Our data support the proposal that Sirt1 is a target for promoting bone formation as an anabolic approach for the treatment of osteoporosis.
Abbreviations:ALP (alkaline phosphatase), Bmi-1 (B cell-specific Moloney murine leukemia virus integration site 1), Bmi-1−/− (Bmi1 deficiency), Bmi-1+/− (Bmi-1 heterozygous), Col-I (type I collagen), Col-II (type II collagen), FOXO (Forkhead box O), GPX1 (Glutathione peroxidase 1), GSR (Glutathione reductase), H&E (hematoxylin and eosin), IP (immunoprecipitation), LPR (Low-density lipoprotein receptor-related protein), Micro-CT (micro-computed tomography), MSC (mesenchymal stem cell), NAM (nicotinamide), OCN (Osteocalcin), OPG (Osteoprotegerin), Prx1 (Paired Related Homeobox 1), RANKL (Receptor Activator for Nuclear Factor-κ B Ligand), ROS (Reactive Oxygen Species), Runx2 (Runt-related transcription factor 2), SA-β-Gal (Senescence associated β-Galactosidase), Sirt1 (Sirtuin 1), Sirt1TG (a transgenic mouse model overexpressing Sirt1 in MSCs driven by the Prx1 promoter), SOD1 (Superoxide dismutase 1), SOD2 (Superoxide dismutase 2), TRAP (tartrate-resistant acid phosphatase), TXN (Thioredoxin), WT (wild-type)
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- Sirtuins: Sir2-related NAD-dependent protein deacetylases.Genome Biol. 2004; 5: 224
- Sirtuin activators mimic caloric restriction and delay ageing in metazoans.Nature. 2004; 430: 686-689
- Caloric restriction and resveratrol promote longevity through the Sirtuin-1-dependent induction of autophagy.Cell Death Dis. 2010; 1: e10
- Sirtuins as mediator of the anti-ageing effects of calorie restriction in skeletal and cardiac muscle.Int J Mol Sci. 2018; 19
- Evolutionarily conserved and nonconserved cellular localizations and functions of human SIRT proteins.Mol Biol Cell. 2005; 16: 4623-4635
- The role of sirtuins in aging and age-related diseases.Adv Med Sci. 2016; 61: 52-62
- Beraprost sodium, a prostacyclin analogue, reduces fructose-induced hepatocellular steatosis in mice and in vitro via the microRNA-200a and SIRT1 signaling pathway.Metabolism. 2017; 73: 9-21
- Activation of the AMPK/Sirt1 pathway by a leucine-metformin combination increases insulin sensitivity in skeletal muscle, and stimulates glucose and lipid metabolism and increases life span in Caenorhabditis elegans.Metabolism. 2016; 65: 1679-1691
- Sirt1 improves healthy ageing and protects from metabolic syndrome-associated cancer.Nat Commun. 2010; 1: 3
- Silent information regulator (Sir)T1 inhibits NF-kappaB signaling to maintain normal skeletal remodeling.J Bone Miner Res. 2013; 28: 960-969
- Overexpression of Sirt1 in mesenchymal stem cells stimulates skeletal growth and osteoblastic bone formation.J Bone Miner Res. 2015; 30 ([Available at https://www.asbmr.org/education/AbstractDetail?aid=8bc8203e-339f-4e3c-8185-ee05958f1d21, Accessed October 10])
- Des-acyl ghrelin protects microvascular endothelial cells from oxidative stress-induced apoptosis through sirtuin 1 signaling pathway.Metabolism. 2014; 63: 469-474
- SIRT1 redistribution on chromatin promotes genomic stability but alters gene expression during aging.Cell. 2008; 135: 907-918
- Protein deacetylation by SIRT1: an emerging key post-translational modification in metabolic regulation.Pharmacol Res. 2010; 62: 35-41
- Sirt1 regulates aging and resistance to oxidative stress in the heart.Circ Res. 2007; 100: 1512-1521
- FOXO3a regulates reactive oxygen metabolism by inhibiting mitochondrial gene expression.Cell Death Differ. 2012; 19: 968-979
- Stress-dependent regulation of FOXO transcription factors by the SIRT1 deacetylase.Science. 2004; 303: 2011-2015
- Regulation of FOXOs and p53 by SIRT1 modulators under oxidative stress.PLoS One. 2013; 8e73875
- Defects in mesenchymal stem cell self-renewal and cell fate determination lead to an osteopenic phenotype in Bmi-1 null mice.J Bone Miner Res. 2010; 25: 640-652
- Bmi1 plays an important role in dentin and mandible homeostasis by maintaining redox balance.Am J Transl Res. 2016; 8: 4716-4725
- Posterior transformation, neurological abnormalities, and severe hematopoietic defects in mice with a targeted deletion of the bmi-1 proto-oncogene.Genes Dev. 1994; 8: 757-769
- PTHrP nuclear localization and carboxyl terminus sequences modulate dental and mandibular development in part via the action of p27.Endocrinology. 2016; 157: 1372-1384
- Targeting notch-activated M1 macrophages attenuates joint tissue damage in a mouse model of inflammatory arthritis.J Bone Miner Res. 2017; 32: 1469-1480
- Use of Hes1-GFP reporter mice to assess activity of the Hes1 promoter in bone cells under chronic inflammation.Bone. 2016; 90: 80-89
- Bmi-1 plays a critical role in protection from renal tubulointerstitial injury by maintaining redox balance.Aging Cell. 2014; 13: 797-809
- Type 5 adenylyl cyclase increases oxidative stress by transcriptional regulation of manganese superoxide dismutase via the SIRT1/FoxO3a pathway.Circulation. 2013; 127: 1692-1701
- SIRT2 deacetylates FOXO3a in response to oxidative stress and caloric restriction.Aging Cell. 2007; 6: 505-514
- Sirtuin-1 (SIRT1) is required for promoting chondrogenic differentiation of mesenchymal stem cells.J Biol Chem. 2014; 289: 22048-22062
- Sirt1 is a regulator of bone mass and a repressor of Sost encoding for sclerostin, a bone formation inhibitor.Endocrinology. 2011; 152: 4514-4524
- The importance of NAMPT/NAD/SIRT1 in the systemic regulation of metabolism and ageing.Diabetes Obes Metab. 2013; 15: 26-33
- The role of mammalian sirtuins in the regulation of metabolism, aging, and longevity.Handb Exp Pharmacol. 2011; 206: 125-162
- Sirt1 extends life span and delays aging in mice through the regulation of Nk2 homeobox 1 in the DMH and LH.Cell Metab. 2013; 18: 416-430
- SIRT1 regulates differentiation of mesenchymal stem cells by deacetylating beta-catenin.EMBO Mol Med. 2013; 5: 430-440
- Inhibition of SIRT1 catalytic activity increases p53 acetylation but does not alter cell survival following DNA damage.Mol Cell Biol. 2006; 26: 28-38
- SIRT1 longevity factor suppresses NF-kappaB-driven immune responses: regulation of aging via NF-kappaB acetylation?.Bioessays. 2008; 30: 939-942
- Bmi-1 is required for maintenance of adult self-renewing haematopoietic stem cells.Nature. 2003; 423: 302-305
- Enhanced self-renewal of hematopoietic stem cells mediated by the polycomb gene product Bmi-1.Immunity. 2004; 21: 843-851
- Bmi-1 promotes neural stem cell self-renewal and neural development but not mouse growth and survival by repressing the p16Ink4a and p19Arf senescence pathways.Genes Dev. 2005; 19: 1432-1437
- Lung stem cell self-renewal relies on BMI1-dependent control of expression at imprinted loci.Cell Stem Cell. 2011; 9: 272-281
- Bmi1 regulates murine intestinal stem cell proliferation and self-renewal downstream of Notch.Development. 2015; 142: 41-50
- Bmi1 regulates auditory hair cell survival by maintaining redox balance.Cell Death Dis. 2015; 6e1605
- SirT1 regulation of antioxidant genes is dependent on the formation of a FoxO3a/PGC-1alpha complex.Antioxid Redox Signal. 2013; 19: 1507-1521
- Acetylation-dependent nuclear arrangement and recruitment of BMI1 protein to UV-damaged chromatin.J Cell Physiol. 2012; 227: 1838-1850
- Bmi-1: at the crossroads of physiological and pathological biology.Genes Dis. 2015; 2: 225-239
Published online: July 03, 2018
Accepted: June 17, 2018
Received: February 9, 2018
☆Disclosure: The authors have declared that no conflict of interest exists.
© 2018 Published by Elsevier Inc.