Ectopic and in situ bone formation of adipose tissue‐derived stromal cells in biphasic calcium phosphate nanocomposite

Abstract Adipose‐derived stromal cells (ASCs) have the potential to differentiate into a variety of cell lineages both in vitro and in vivo. A novel biodegradable biphasic calcium phosphate nanocomposite (NanoBCP) comprising β‐tricalcium phosphate matrix and hydroxyl apatite nanofibers is favorable for bone tissue engineering. In this study, ASCs were harvested from Sprague‐Dawley (SD) rats and induced to osteogenesis before seeded into porous NanoBCP scaffold. To determine ectopic in vivo osteogenic differentiation, these constructs were implanted in nude mice subcutaneously. Meanwhile, the ability of engineered constructs to stimulate in situ bone repair was assessed in rat critical‐size cranial defects. The defects were filled with NanoBCP containing osteogenic ASCs in experimental group; with cell‐free NanoBCP in negative controls; and with nothing in blank controls. The retrieved specimens were analyzed with morphological, histological, and molecular methods. Histological analysis of the retrieved specimens from nude mice in experimental group showed obvious ectopic bone formation. There were positive expression of osteopontin (OPN) and osteocalcin (OCN) at RNA and protein level. As for the cranial defects, there was complete repair in experimental group, but only partial repair in negative controls. The radiographs, H&E staining, and Masson's trichrome method showed better bone regeneration at experimental sites. Combining osteogenic ASCs with NanoBCP can lead to formation of ectopic new bone. Furthermore, the approach can also stimulate bone regeneration and repair for the large size bone defects. © 2007 Wiley Periodicals, Inc. J Biomed Mater Res, 2007