Repairing critical-sized rat calvarial defects with progenitor cell-seeded acellular periosteum: a novel biomimetic scaffold.

Background: Many types of scaffolds have been used in bone tissue engineering, with none emerging as favorites. We propose the use of acellular periosteum as a biologic scaffold to allow for progenitor cell adherence, migration, and proliferation in vitro and to test the construct in vivo in a rat calvarial defect model.

Methods: Bovine periosteum was processed to remove all antigenic material (RTI Biologics), and its cambial layer was then seeded with adipose-derived stromal cells (ASCs) or periosteal-derived stromal cells (PSCs) and incubated for 14 days. Adherence required a fibronectin coat and was verified for both cell types via scanning electron microscopy and histology. Two 5-mm diameter calvarial defects were created in each of 19 rats. These were filled with xenograft bone chips and covered with acellular periosteum in combination with cells (ASC or PSC), growth factors (vascular endothelial growth factor, bone morphogenetic protein-2, or both), or alone (controls). Rats were killed 56 days postoperatively. Bone deposition was quantified by microcomputed tomography, and viability was determined histologically. Significance was determined through analysis of variance.

Results: Acellular allo-periosteum with a fibronectin coat permitted ASC and PSC adherence, migration, and proliferation in vitro. In the rat calvarial defects, the addition of stem cells (P < .001) and growth factors (P < .001) to the acellular periosteum increased de novo bone growth relative to controls. Although the stem cell source did not influence revitalization (P = .242), the combination of growth factors was more effective (P > .001) than either growth factor alone. The interaction indicated that the 2 cell types did not respond equally to growth factors (P = .039).

Conclusion: Acellular allo-periosteum is a biomimetic scaffold that permits pleuripotent cell adherence, migration, and proliferation in vitro. The combination of acellular periosteum, xenograft bone, stem cells, and growth factors may prove a viable combination for cranial bone tissue engineering.