Osteotropic properties of mesenchymal stromal cells generated in Masquelet's induced membrane technique.

Masquelet's induced membrane technique (MIMT) is widely applied two-step surgery of large bone defects. MIMT involves the fibrous encapsulation of a polymethyl methacrylate cement spacer inserted into the bone defect in the primary surgery. Although the biological characteristics of the fibrous membrane have been studied, the postoperative environment of the bone defect encapsulated with the induced membrane has not been investigated. In this study, critical-sized bone defects encapsulated with the induced membrane were filled with porous calcium-deficient bioresorbable hydroxyapatite granules in the secondary surgery. Single-step non-Masquelet conventional surgery (NMCS) was also performed, and the biological characteristics of the stromal tissues induced around the ceramic granules were compared between the two procedures. Compared with NMCS, the stromal tissue induced in MIMT expressed significantly higher levels of CXCL3, RANKL, BMP-2, and BMP-7. Coculture of the primary osteoblast-like cells with the stromal tissue derived from MIMT significantly stimulated the differentiation of primary osteoblast-like cells compared with that derived from NMCS. When hydroxyapatite granules mixed with bone isografts (50% v/v) were implanted, the amount of newly formed bone was significantly larger in MIMT than in NMCS. These results suggest that MIMT induces mesenchymal stromal cells that support bone metabolism and promote bone regeneration.