Adipose tissue was only recently considered as a potential source of mesenchymal stem cells (MSCs) for bone tissue engineering. To improve the osteogenicity of acellular bone allografts, adipose MSCs (AMSCs) and bone marrow MSCs (BM-MSCs) at nondifferentiated and osteogenic-differentiated stages were investigated in vitro and in vivo. In vitro experiments demonstrated a superiority of AMSCs for proliferation (6.1 2.3 days vs. 9.0 1.9 days between each passage for BM-MSCs, respectively, P< 0.001). A significantly higher T-cell depletion (revealed by mixed lymphocyte reaction, [MLR]) was found for AMSCs (vs. BM-MSCs) at both non- and differentiated stages. Although nondifferentiated AMSCs secreted a higher amount of vascular endothelial growth factor [VEGF] in vitro (between 24 and 72 h of incubation at 0.1e21% O2) than BM-MSCs (P< 0.001), the osteogenic differentiation induced a significantly higher VEGF release by BM-MSCs at each condition (P< 0.001). After implantation in the paraspinal muscles of nude rats, a significantly higher angiogenesis (histomorphometry for vessel development (P < 0.005) and VEGF expression (P < 0.001)) and osteogenesis (as revealed by osteocalcin expression (P< 0.001) and micro-CT imagery for newly formed bone tissue (P< 0.05)) were found for osteogenic-differentiated AMSCs in comparison to BM-MSCs after 30 days of implantation. Osteogenic-differentiated AMSCs are the best candidate to improve the angio-/osteogenicity of decellularized bone allografts.
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