Sternal repair with bone grafts engineered from amniotic mesenchymal stem cells

Purpose: We aimed at determining whether osseous grafts engineered from amniotic mesenchymal stem cells (aMSCs) Could be used in postnatal sternal repair. Methods: Leporine aMSCs were isolated, identified, transfected with green fluorescent protein (GFP), expanded, and seeded onto biodegradable electrospun nanofibrous scaffolds (n = 6). Constructs were dynamically maintained in an osteogenic medium and equally divided into 2 groups with respect to time in vitro as follows: 14.6 or 33.9 weeks. They were then used to repair full-thickness sternal defects spanning 2 to 3 intercostal spaces in allogeneic kits (n = 6). Grafts were Submitted to multiple analyses 2 months thereafter. Results: Chest roentgenograms showed defect closure in all animals, confirmed at necropsy. Graft density as assessed by microcomputed tomographic scans increased significantly in vivo, yet there were no differences in mineralization by extracellular calcium measurements preimplantation and postimplantation. There was a borderline increase in alkaline phosphatase activity in vivo, suggesting ongoing graft remodeling. Histologically, implants contained GFP-positive cells and few mononuclear infiltrates. There were no differences between the 2 construct groups in any comparison. Conclusions: Engineered osseous grafts derived from amniotic mesenchymal stem cells may become a viable alternative for sternal repair. The amniotic fluid can be a practical cell source for engineered chest wall reconstruction. (C) 2009 Elsevier Inc. All rights reserved.