CD271 antibody-functionalized microspheres capable of selective recruitment of reparative endogenous stem cells for in situ bone regeneration

In the strategy of in situ bone regeneration, it used to be difficult to specifically recruit bone marrow mesenchymal stem cells (BM-MSCs) by a single marker. Recently, CD271 has been considered to be one of the most specific markers to isolate BM-MSCs; however, the effectiveness of CD271 antibodies in recruiting BM-MSCs has not been explored yet. In this study, we developed novel CD271 antibody-functionalized chitosan (CS) microspheres with the aid of polydopamine (PDA) coating to recruit endogenous BM-MSCs for in situ bone regeneration. The CS microspheres were sequentially modified with PDA and CD271 antibody through dopamine self-polymerization and bioconjugation, respectively. In vitro studies showed that the CD271 antibody-functionalized microspheres selectively captured significantly more BM-MSCs from a fluorescently labeled heterotypic cell population than non-functionalized controls. In addition, the PDA coating was critical for supporting stable adhesion and proliferation of the captured BM-MSCs. Effective early recruitment of CD271+ stem cells by the functionalized microspheres at bone defect site of SD rat was observed by the CD271/DAPI immunofluorescence staining, which led to significantly enhanced new bone formation in rat femoral condyle defect over long term. Together, findings from this study have demonstrated, for the first time, that the CD271 antibody-functionalized CS microspheres are promising for in situ bone regeneration.