Mechanism of bone induction by KUSA/A1 cells using atelocollagen honeycomb scaffold

In order to induce new bone formation, mesenchymal stem cells were seeded onto atelocollagen honeycomb scaffold. We evaluated the mechanism of bone induction by KUSA/A1 cells combined with honeycomb atelocollagen scaffold. Scaffold alone, KUSA/A1 cells alone and with scaffold were implanted in the subcutaneous pockets of 4-week-old male SCID mice. The transplants were subjected to radiographical, histological and immunohistochemical examinations after 2 and 4 weeks of implantation. Radiographically, both KUSA/A1 cells alone and KUSA/A1-Scaffold showed some radiopaque areas formation but the latter disclosed a larger amount. Scaffold alone did not show any radiopacity. Histologically, Scaffold alone demonstrated only fibrous connective tissues in the periphery of the scaffold. KUSA/A1 cells alone showed few small islands of new bone formation surrounded by a thin layer of cellular proliferation. On the other hand, KUSA/A1-Scaffold revealed abundant new bone formation as well as cellular proliferation. We also determined the immunolocalization of type I collagen, CD34, Osteocalcin and PCNA in this newly formed bone. Our results indicated that less amount of stem cells are capable to induce the more amount of new bone in tissue engineering. This study support that atelocollagen honeycomb scaffold plays an important role in cellular anchorage and in vessel invasion, giving the precise shape and size for the new bone formation.