JOURNAL OF TISSUE ENGINEERING AND REGENERATIVE MEDICINE RESEARCH ARTICLE J Tissue Eng Regen Med 2007; 1: 450–456. Published online in Wiley InterScience (www.interscience.wiley.com) DOI: 10.1002/term.58 Dehydrothermal treatment of collagen influences on bone regeneration by octacalcium phosphate (OCP) collagen composites Shinji Kamakura 1 *, Kazuo Sasaki 2 , Yoshitomo Honda 3 , Takahisa Anada 3 , Keiko Matsui 4 , Seishi Echigo 4 and Osamu Suzuki 3 1 Division of Clinical Cell Therapy, Department of Translational Research, Center for Translational and Advanced Animal Research (CTAAR), Tohoku University School of Medicine, 2-1 Seiryo-Machi, Aoba-Ku, Sendai 980-8574, Japan 2 Nippon Meat Packers Inc., 3-3 Midorigahara, Tsukuba, Ibaraki 300-2646, Japan 3 Division of Craniofacial Function Engineering, Tohoku University Graduate School of Dentistry, 4-1 Seiryo-Machi, Aoba-Ku, Sendai 980-8575, Japan 4 Division of Oral Surgery, Tohoku University Graduate School of Dentistry, 4-1 Seiryo-Machi, Aoba-Ku, Sendai 980-8575, Japan Abstract We have engineered a scaffold constructed of synthetic octacalcium phosphate (OCP) and collagen composites (OCP – collagen) and report that OCP – collagen significantly enhanced bone regeneration more than the implantation of OCP. We hypothesized that the dehydrothermal treatment (DHT) during the fabrication of OCP–collagen might influence bone regeneration by OCP–collagen. To examine this hypothesis, bone regeneration by the implantation of OCP–collagen with DHT [OCP/Col(+)] was compared with that by OCP–collagen without DHT [OCP/Col(−)]. It was confirmed that both OCP/Col(+) and OCP/Col(−) contained the characteristics of OCP structure in X-ray diffraction. Before implantation, calcium deposition derived from OCP was observed within the collagen of both OCP/Col(+) and OCP/Col(−) by undecalcified histological sections. OCP/Col(+) or OCP/Col(−) was implanted into the critical-sized defects in rat crania. Radiographic and histological examination was performed and the percentage of newly formed bone (n-Bone%) in the defect was determined by a histomorphometrical analysis. N-Bone% treated with OCP/Col(+) was significantly higher than that with OCP/Col(−) at 4 and 12 weeks after implantation, because fast degradation of the implanted collagen of OCP/Col(−) elicited disappearance of the scaffold for bone regeneration. The stiffness of the calcified collagen in OCP–collagen would be more important than the existence of calcified collagen to enhance the bone regeneration by OCP–collagen composites. The present study suggests that the dehydrothermal treatment would influence effective bone regeneration by OCP–collagen. Copyright  2008 John Wiley & Sons, Ltd. Received 29 June 2007; Revised 8 November 2007; Accepted 15 November 2007 Keywords bone regeneration; octacalcium phosphate; calcium phosphate; collagen; dehydrothermal treatment; rat; bone defect 1. Introduction It is accepted that the main components of bone regeneration are stem or precursor cells, cytokines and *Correspondence to: Shinji Kamakura, Division of Clinical Cell Therapy, Department of Translational Research, Center for Translational and Advanced Animal Research (CTAAR), Tohoku University School of Medicine 2-1 Seiryo-Machi, Aoba- Ku, Sendai 980-8574, Japan. E-mail: kamakura@mail.tains.tohoku.ac.jp appropriate biological scaffolds (Rose et al., 2002). As a scaffold for bone regeneration, we have paid attention to octacalcium phosphate [Ca 8 H 2 (PO 4 ) 6 5H 2 O; OCP], which is a precursor of biological apatite in bone and teeth (Brown et al., 1962, 1987; Crane et al., 2006). Synthetic OCP has been investigated as a bone substitute material in various forms, such as a coating on metallic implants (Barrere et al., 2001, 2003; Bigi et al., 2005; Dekker et al., 2005). OCP is an intermediate transitory phase and converts to the apatitic phase if implanted (Suzuki et al., 1991). Recently it was reported that OCP facilitates Copyright  2008 John Wiley & Sons, Ltd.