GSK3b-inhibitor lithium chloride enhances activation of Wnt canonical signaling and osteoblast differentiation on hydrophilic titanium surfaces.

Promoting bone formation at the tissue interface is an important step to improve implant success. This study investigated whether stimulation of Wnt signaling by GSK3b inhibitor lithium chloride (LiCl) could affect the response of mesenchymal or osteoblastic cells growing on titanium surfaces with different topography and wettability, and improve their differentiation along the osteoblastic lineage. MATERIAL AND METHODS: Murine mesenchymal C2C12 cells were plated on Pickled, acid-etched/sand-blasted (SLA), and hydrophilic SLA titanium disks (modSLA) and stimulated with increasing doses of LiCl. Cell viability was measured using chemiluminescence-based ATP quantitation and activation of Wnt canonical signaling was measured using a Luciferase-based reporter assay. Gene expression was measured using real time PCR in C2C12 cells, murine osteoblastic MC3T3 cells or murine primary bone marrow cells. RESULTS: LiCl stimulated Wnt activation and expression of Wnt markers in C2C12 cells on modSLA. Addition of 1 mM LiCl increased levels for bone marker Osteocalcin in MC3T3 cells on modSLA surfaces. Similarly, LiCl potently enhanced Osteoprotegetrin levels in MC3T3 cells on modSLA. When primary bone marrow cells were stimulated with LiCl, the expression of Wnttarget genes and osteoblastic differentiation markers was increased on modSLA surfaces. CONCLUSIONS: Stimulation of the canonical Wnt pathway promoted osteoblast differentiation on hydrophilic modSLA surfaces. Taken together, these results demonstrate that Wnt activators such as LiCl should be further tested as a possible approach to improve implant osseointegration.