Human adipose-derived side population stem cells cultured on demineralized bone matrix for bone tissue engineering.

Background: Tissue engineering of new bone relies on the combination and application of osteoconductive, osteoinductive, and osteogenic elements. Natural scaffolds, such as demineralized bone matrix (DBM), contain collagenous networks with growth factors such as bone morphogenetic protein-2. Stem cells from readily available sources, including discarded adipose tissue, have the propensity to differentiate into bone. The present study examines a multi-component technique consisting of a novel side population of adipose stem cells cultured on DBM for tissue engineering applications. Methods: Adipose-derived side population stem cells were cultured on DBM for up to 14 days. Cell proliferation, alkaline phosphatase activity, extracellular matrix protein production, and calcium-containing mineral deposit formation were assayed. Ectopic bone formation in a rat model was also evaluated. Results: Side population stem cells attached to and proliferated on DBM while generating markers of new bone formation. When these cell/substrate composites were implanted into an ectopic model, newly formed bone was 30% greater than that of DBM alone. Conclusions: Novel populations of adipose-derived stem cells cultured on DBM compose a system that develops new bone matrix in vitro and in vivo. This strategy provides a novel approach using naturally occurring materials for bone repair in tissue engineering applications.