Decreased osteogenesis in mesenchymal stem cells derived from the aged mouse is associated with enhanced NF‐κB activity

Abstract

Aging is associated with significant bone loss and delayed fracture healing. NF-κB activation is highly correlated with inflammatory-associated bone diseases including infection, wear particle exposure, and chronic inflammation during natural aging processes. The critical roles of NF-κB in both the pro-inflammatory response and osteoclast-mediated bone resorption have been well defined. However, the biological effects of NF-κB activation in mesenchymal stem cell (MSC)-mediated bone formation remain largely unknown. In the current study, bone marrow-MSCs were isolated from young (8 weeks old) and aged (72 weeks old) mice. NF-κB activity in MSCs at basal levels and under different biological conditions were determined by our recently established lentiviral vector-based luciferase reporter assay. We found that NF-κB activity was increased in aged MSCs at basal levels or when exposed to low dose (10 or 100 ng/ml) lipopolysaccharide (LPS); this effect was not seen when the cells were exposed to higher dose (1 μg/ml) LPS. During osteogenesis, NF-κB activity was increased in aged MSCs at weeks 1 and 2, but showed no significant difference at week 3. Both Smurf2 and TAZ, the NF-κB target genes that regulate osteogenic differentiation, were increased in aged MSCs. In addition, the expression of RANKL was dramatically increased, and OPG was decreased in aged MSCs. Our findings suggest that targeting NF-κB activity in MSCs has the potential to modulate aging-associated bone loss, or enhance bone-healing in aged patients. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:281-288, 2017.

Establishment of NF-κB sensing and interleukin-4 secreting mesenchymal stromal cells as an “on-demand” drug delivery system to modulate inflammation

“…2b). To clarify whether IL-4 can affect the secretion profiles in MSC NF-κBRE IL4 exposed to LPS in an autocrine manner, MSCs were infected with NF-κB luciferase reporter lentivirus as previously described [18]. The results showed that the NF-κB activation patterns induced by intermittent (Fig.…”

“…The lentiviral NF-κB luciferase reporter vector (pCDH-NF-κB-luc2p-copEGFP) was generated previously[18]. Murine MSCs were infected by the reporter viral vectors as described in the “preparation and infection of lentiviral vector” section.…”

NF-κB as a Therapeutic Target in Inflammatory-Associated Bone Diseases

“…In one study using a murine model, NF-κB activation (increased phosphorylation of RelA) has been reported in the trabecular bone in natural aging mice (Yu et al, 2014). Furthermore, increased NF-κB activity was found in the MSCs isolated from aged mice (15 months) compared with younger mice (Lin, Gibon, et al, 2016). Inhibition of the NF-κB pathway partially rescued the reduction of osteogenesis in aged MSCs.…”

“…Recognition of wear particles or DAMPs adhering to the particles via TLR2 and TLR4 induces the secretion of proinflammatory cytokines in the NF-κB-dependent pathway (Pearl et al, 2011). The proinflammatory cytokines including TNF-α and IL-1β further activate NF-κB in macrophages as a positive regulatory loop during the chronic inflammation, leading to OC activation, and osteolytic processes (Lin, Pajarinen, et al, 2016; Lin, Tamaki, et al, 2014). Inhibition of NF-κB activity suppresses PMMA and UHMWPE wear particle induced OC activation in vitro and in vivo, suggesting the therapeutic potential of targeting NF-κB pathway in the particle disease (Clohisy, Hirayama, Frazier, Han, & Abu-Amer, 2004; Lin, Pajarinen, et al, 2016).…”

Mesenchymal stem cells in the aseptic loosening of total joint replacements

“…RANKL and its receptor RANK expressed on osteoclast precursors is essential for osteoclast differentiation and activation . RANKL is expressed in differentiated osteoblast‐lineage cells and has also been reported to be expressed in MSCs isolated from aged mice . MSCs regulate osteoclast formation also by secreting osteoprotegerin (OPG), the RANKL decoy receptor.…”