Revitalization of cortical bone allograft by application of vascularized scaffolds seeded with osteogenic induced adipose tissue derived stem cells in a rabbit model.

Background: Adipogenous tissue derived stem cells (ASC) are available in abundance in the human body and can differentiate in the presence of lineage-specific induction factors, for example, in myogenic, adipogenic, chondrogenic and osteogenic cells. The aim of this study was to evaluate the impact of osteogenic induced ASC's (O-ASC) on revascularization and cellular repopulation of avital cortical bone employing a vascularized bovine scaffold.

Methods: An inguinal arterio-venous bundle was dissected in the groin of female white New Zealand rabbits (n = 6) and placed centrally inside an O-ASC seeded scaffold via a central drill hole. In the same surgical session this construct was placed into a segment of avital cortical bone allograft from a donor rabbit. Unseeded scaffolds that were implanted and treated in the same fashion served as controls (n = 6). In order to prevent external revascularization, all constructs were wrapped in silicon foil and finally implanted in the rabbits' groin. Three months later, the constructs were explanted and investigated for vascularization of (a) the scaffold (b) the surrounding bone allograft. Histological stainings to determine cell growth, cellular repopulation of the scaffold and the cortical bone matrix, as well as inflammatory parameters were carried out.

Results: O-ASC seeded scaffolds showed a significant increase in new vessel formation in the scaffold as well as in the bone allograft compared to unseeded scaffolds. Furthermore, new vital osteocytes as a sign of cellular repopulation inside the bone allograft were found only in the treatment group. Vital chondrocytes were only found in the O-ASC seeded scaffolds as well.

Conclusion: The presence of O-ASC significantly induce neo-vascularization and osteocytic repopulation of previously avital bone allograft as opposed to unseeded scaffolds in a rabbit model. Hence, this model might be of relevant value for future bone tissue engineering research and for re-vitalizing marginally nourished bone such as in avascular bone necrosis.