Strontium-modified titanium substrate promotes osteogenic differentiation of MSCs and implant osseointegration via upregulating CDH2.

Abstract

Our previous studies showed that strontium (Sr)-modified sand-blasted, large grit, acid etched titanium surface (Sr-SLA) is beneficial for osseointegration; however, the supporting mechanisms have not been explored in detail. Whole-transcriptome RNA sequencing of peri-implant bone tissue was performed, and CDH2 was selected as a key mediator of Sr-SLA-mediated osseointegration. To test this hypothesis, a lentivirus-mediated vector targeting the silencing of the CDH2 gene was used in mesenchymal stem cells (MSCs) prior to seeding on Ti substrates. The effects of CDH2 interference on MSCs vitality, differentiation, and β-catenin signaling activity were evaluated. In vivo, a recombinant adeno-associated virus 9 vector carrying an artificial siRNA that target CDH2 (AAV9-CDH2i) was intravenously injected in mice, followed by tibial surgery with implant placement. Osseointegration were monitored using micro-CT analysis. CDH2 expression in MSCs on Sr-SLA was higher than the control group, which was in parallel with the enhanced cell migration, adhesion, and upregulation of early osteogenic markers. Knocking down CDH2 in MSCs resulted in decreased cell viability and osteogenic differentiation, and the elevated biocompatibility and osteoinductive effect of Sr-SLA were greatly diminished. Surprisingly, Sr-SLA-induced upregulation of CDH2 was not followed by restriction of β-catenin signaling because Sr-SLA also promoted the expression and nuclear translocation of β-catenin. Systemic administration of AAV9-CDH2i effectively knocked down CDH2 expression in bone marrow cells, and in turn, inhibited bone formation induced by Sr-SLA. The results indicated that CDH2 is required for Sr-SLA-mediated bone regeneration, which reveals a new mechanism to explain the osteoinductive effect of Sr-SLA. Thus, biomaterial modifications targeting CDH2 may help improve early osseointegration and bone healing.