Abstract
BackgroundHuman muscle-derived stem cells (hMDSCs) have been shown to regenerate bone efficiently when they were transduced with Lenti-viral bone morphogenetic protein 2 (LBMP2). However, whether the age of hMDSCs and the animal host affect the bone regeneration capacity of hMDSCs and mechanism are unknown which prompted the current study.MethodsWe isolated three gender-matched young and old populations of skeletal muscle stem cells, and tested the influence of cells’ age on in vitro osteogenic differentiation using pellet culture before and after Lenti-BMP2/green fluorescent protein (GFP) transduction. We further investigated effects of the age of hMDSCs and animal host on hMDSC-mediated bone regeneration in a critical-size calvarial bone defect model in vivo. Micro-computer tomography (CT), histology, and immunohistochemistry were used to evaluate osteogenic differentiation and mineralization in vitro and bone regeneration in vivo. Western blot, quantitative polymerase chain reaction (PCR), and oxidative stress assay were performed to detect the effects of age of hMDSCs on cell survival and osteogenic-related genes. Serum insulin-like growth factor 1 (IGF1) and receptor activator of nuclear factor-kappa B ligand (RANKL) were measured with an enzyme-linked immunosorbent assay (ELISA).ResultsWe found LBMP2/GFP transduction significantly enhanced osteogenic differentiation of hMDSCs in vitro, regardless of donor age. We also found old were as efficient as young LBMP2/GFP-transduced hMDSCs for regenerating functional bone in young and old mice. These findings correlated with lower phosphorylated p38MAPK expression and similar expression levels of cell survival genes and osteogenic-related genes in old hMDSCs relative to young hMDSCs. Old cells exhibited equivalent resistance to oxidative stress. However, both young and old donor cells regenerated less bone in old than young hosts. Impaired bone regeneration in older hosts was associated with high bone remodeling due to higher serum levels of RANKL and lower level of IGF-1.ConclusionhMDSC-mediated bone regeneration was not impaired by donor age when hMDSCs were transduced with LBMP2/GFP, but the age of the host adversely affected hMDSC-mediated bone regeneration. Regardless of donor and host age, hMDSCs formed functional bone, suggesting a promising cell resource for bone regeneration.
Highlights
Human muscle-derived stem cells have been shown to regenerate bone efficiently when they were transduced with Lenti-viral bone morphogenetic protein 2 (LBMP2)
Bone morphogenetic protein 2 (BMP2) secretion levels and in vitro osteogenic differentiation In order to test whether the age of donor Human muscle-derived stem cells (hMDSCs) affects their osteogenic potential and bone regenerative capacity, we isolated three gender-matched pairs of young and old hMDSCs
We transduced each population of the three young and old hMDSC pairs with LBMP2/green fluorescent protein (LBMP2/GFP) under the same conditions using a multiplicity of infection (MOI) of 8
Summary
Human muscle-derived stem cells (hMDSCs) have been shown to regenerate bone efficiently when they were transduced with Lenti-viral bone morphogenetic protein 2 (LBMP2). The effects of age of stem cells on their self-renewal and differentiation capacities have been studied for both non-human animal and human cells; discrepancies exist between different studies. Both bone marrow mesenchymal stem cells (BMMSCs) and adipose-derived stem cells (ADSCs) isolated from aged rats have been shown to exhibit increased cell senescence and a trend of increasing p38 and p53 levels with age compared to neonatal and young rats [1]. Older BMMSCs exhibited impaired cell proliferation and multipotent differentiation, while muscle-derived stem cells (MDSCs) and ADSCs were not negatively affected by age [2]. Most of these studies have been conducted in vitro
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