Light-Controlled BMSC Sheet–Implant Complexes with Improved Osteogenesis via an LRP5/β-Catenin/Runx2 Regulatory Loop

The combination of bone marrow mesenchymal stem cell (BMSC) sheets and titanium implants (BMSC sheet–implant complexes) can accelerate osseointegration. However, methods of fabricating BMSC sheet–implant complexes are quite limited, and the survival of BMSC sheet–implant complexes is one of the key barriers. Here, we show that a light-controlled fabricating system can generate less injured BMSC sheet–implant complexes with improved viability and osteogenesis and that noninvasive monitoring of the viability of BMSC sheet–implant complexes using a lentiviral delivery system is feasible. Enhanced green fluorescent protein- and luciferase-expressing BMSC sheets were used to track the viability of BMSC sheet–implant complexes in vivo. The experiments of micro-computed tomography analysis and hard tissue slices were performed to evaluate the osteogenic ability of BMSC sheet–implant complexes in vivo. The results showed that BMSC sheet–implant complexes survived for almost 1 month after implantation. Notably, BMSC sheet–implant complexes fabricated by the light-controlled fabricating system had upregulating expression levels of low-density lipoprotein-receptor-related protein 5 (LRP5), β-catenin, and runt-related transcription factor 2 (Runx2) compared to the complexes fabricated by mechanical scraping. Furthermore, we found that Runx2 directly bound to the rat LRP5 promoter and the LRP5/β-catenin/Runx2 regulatory loop contributed to the enhancement of the osseointegrating potentials. In this study, we successfully fabricated BMSC sheet–implant complexes with improved viability and osteogenesis and established a feasible, noninvasive, and continuous method for tracking BMSC sheet–implant complexes in vivo. Our findings lay the foundation for the application of BMSC sheet–implant complexes in vivo and open new avenues for engineered BMSC sheet–implant complexes.