We sought to compare the efficacy of fetal bone grafts engineered from amniotic mesenchymal stem cells (aMSCs) against acellular constructs in an autologous model of sternal repair.

Leporine aMSCs were isolated, identified, transfected with green fluorescent protein (GFP), expanded, and seeded onto biodegradable nanofibrous scaffolds (n=5) that were maintained for 23-41 weeks. Grafts were used to repair full thickness sternal defects in autologous rabbits (n=5), whereas control rabbits (n=5) received size-adjusted acellular nanofibrous scaffolds. Animals were killed at comparable time points (18-20 weeks) and grafts submitted to multiple analyses.

Non-union was present only in acellular implants (3/5, 60%) at necropsy, confirmed by micro-CT. Histologically, engineered grafts displayed GPF-positivity and had a seemingly more robust presence of bone. Mineral density was significantly higher in engineered grafts than in acellular scaffolds post-implantation, as assessed by extracellular calcium and micro-CT, with the latter having significantly greater variability in the acellular group. There was no difference in alkaline phosphatase activity between groups. 

Chest wall repair with autologous, osseous grafts, engineered from amniotic mesenchymal stem cells leads to improved, more consistent outcomes in the mid-term compared with acellular prosthetic repair. Amniotic fluid-derived engineered bone may be a practical alternative for perinatal chest wall reconstruction.