Antimicrobial Peptide Combined with BMP2-Modified Mesenchymal Stem Cells Promotes Calvarial Repair in an Osteolytic Model.

Repair and regeneration of inflammation-induced bone loss remains a clinical challenge. LL37, an antimicrobial peptide, plays critical roles in cell migration, cytokine production, apoptosis, and angiogenesis. Migration of stem cells to the affected site and promotion of vascularization are essential for tissue engineering therapy, including bone regeneration. However, it is largely unknown whether LL37 affects mesenchymal stem cell (MSC) behavior and bone morphogenetic protein 2 (BMP2)-mediated bone repair during the bone pathologic remodeling process. By performing in vitro and in vivo studies with MSCs and a lipopolysaccharide (LPS)-induced mouse calvarial osteolytic bone defect model, we found that LL37 significantly promotes cell differentiation, migration, and proliferation in both unmodified MSCs and BMP2 gene-modified MSCs. Additionally, LL37 inhibited LPS-induced osteoclast formation and bacterial activity in vitro. Furthermore, the combination of LL37 and BMP2 markedly promoted MSC-mediated angiogenesis and bone repair and regeneration in LPS-induced osteolytic defects in mouse calvaria. These findings demonstrate for the first time that LL37 can be a potential candidate drug for promoting osteogenesis and for inhibiting bacterial growth and osteoclastogenesis, and that the combination of BMP2 and LL37 is ideal for MSC-mediated bone regeneration, especially for inflammation-induced bone loss.