Acute transient inflammation is crucial for initiation of bone healing, osseointegration of implants, osteogenic
differentiation of MSCs, and immunomodulation. However, harmful chronic inflammation and bone loss
(osteolysis) are induced by adverse stimuli including wear byproducts from joint replacements (JR). Nuclear
Factor kappa B (NF-¿B) is a critical transcription factor in both macrophages (m¿) and MSCs that regulates
inflammation, bone formation/remodeling, and aging. We showed that preconditioning MSCs with lipopoly-
saccharide (LPS) and tumor necrosis factor-a (TNF-a) to induce acute transient activation of NF-¿B
synergistically enhances osteogenesis, and modulates m¿ polarization from a pro-inflammatory (M1) to an
anti-inflammatory pro-regenerative (M2) phenotype. Furthermore, inhibition of persistent NF-¿B signaling using
an NF-¿B decoy OligoDeoxyNucleotide (ODN) was shown to mitigate inflammatory bone loss. We have
genetically modified MSCs to sense NF-¿B activation and then increase production of the anti-inflammatory
pro-regenerative cytokine IL-4. The purpose of this grant is to accelerate net bone formation and mitigate
chronic inflammation and osteolysis via NF-kB driven immunomodulation using preconditioned or genetically
modified MSCs transplanted to the local environment.
Specific Aim #1a -To define the critical immunomodulatory interactions of preconditioned vs. NF-¿B sensing
and IL-4 secreting MSCs on m¿ exposed to wear byproducts from orthopaedic implants.
Specific Aim #1b - To enhance osteogenesis by using preconditioned vs. NF-¿B sensing and IL-4 secreting
MSCs in an MSC/m¿ co-culture model exposed to wear byproducts from orthopaedic implants.
Specific Aim #2a - To demonstrate the therapeutic effects of transplanted preconditioned MSCs on bone
during the acute inflammatory stage (simulating the stage of initial implantation of a prosthesis and
osseointegration) using the murine continuous femoral particle infusion model.
Specific Aim #2b - To demonstrate the therapeutic effects of preconditioned vs. NF-¿B sensing and IL-4
secreting MSCs on net bone formation during the chronic inflammatory stage (simulating established wear
particle disease) using the murine continuous femoral particle infusion model.
Specific Aim #3 - To demonstrate that the above principles of modulating acute and chronic inflammation are
valid irrespective of animal sex (male vs. female mice) or age (young vs. elderly mice) in vivo. We hypothesize
that NF-¿B preconditioning or NF-¿B sensing and IL-4 secreting MSCs will enhance the osteogenic and
immunomodulatory signaling of MSCs, enhancing bone formation via crosstalk by m¿ and MSCs. NF-kB driven
immunomodulation of MSCs should mitigate particle-induced inflammation, osteoclast activation, and enhance
bone formation in young and aged, male and female mice. NF-kB driven immune modulation of MSCs is novel,
mechanistic, and directly translational to inflammatory disorders in other organ systems.