Adipose-derived stem cells and BMP2: Part 1. BMP2-treated adipose-derived stem cells do not improve repair of segmental femoral defects

Recombinant human bone morphogenetic protein-2 (rhBMP2) has been shown to induce both in vitro osteogenic differentiation and in vivo bone formation, with the capacity of rhBMP2 to elicit the repair of numerous bony defects (calvaria, spinal fusion, femora, and so on) well documented. In addition, rhBMP2 has been approved by the Food and Drug Administration (FDA) for selected human indications. Despite the fact that healing is often achieved, the challenge still remains to optimize the therapeutic use of rhBMP2. One avenue may be through the combination of rhBMP2 with stem cells capable of osteogenic differentiation. This study investigates the ability of rhBMP2 at various doses in combination with human adipose-derived stem cells (ASCs) to heal critical-sized rat segmental femoral defects. For this, different doses of rhBMP2 were incorporated with apatite-coated porous poly(L-lactide-co-DL-lactide) (70 : 30) (PLDLA) scaffolds, seeded with ASCs, and implanted into athymic rats. After 8 weeks, all implants were harvested and processed for bone formation using micro computed tomography (microCT) analysis and histology. Despite the findings that indicate no adverse effect of the apatite surface on ASC osteogenesis, no significant difference in bone formation could be qualitatively or quantitatively determined upon the implantation of ASC-seeded scaffolds absorbed to increasing doses of rhBMP2. Such results would suggest that the presence of ASCs within rhBMP2-absorbed scaffolds does not improve the bone-forming ability of the construct and that the formation of bone may be driven by the rhBMP2 alone. Based on these results, the addition of ASCs to rhBMP2-treated scaffolds may provide no significant advantage in terms of the ability to heal bone.