JOURNAL OF TISSUE ENGINEERING AND REGENERATIVE MEDICINE RESEARCH ARTICLE J Tissue Eng Regen Med 2011; 5: 32–40. Published online 5 July 2010 in Wiley Online Library (wileyonlinelibrary.com) DOI: 10.1002/term.285 Prevention of osteonecrosis by intravenous administration of human peripheral blood-derived CD34-positive cells in a rat osteonecrosis model Hiroshi Terayama 1 , Masakazu Ishikawa 1 *, Yuji Yasunaga 2 , Takuma Yamasaki 1 , Takanari Hamaki 1 , Takayuki Asahara 3 and Mitsuo Ochi 1 1 Department of Orthopaedic Surgery, Graduate School of Biomedical Sciences, Hiroshima University, Japan 2 Department of Artificial Joints and Biomaterials, Graduate School of Biomedical Sciences, Hiroshima University, Japan 3 Department of Regenerative Medicine Science, Tokai University School of Medicine, Japan Abstract Aseptic idiopathic osteonecrosis of the femoral head is a painful disorder of the hip that can lead to collapse of the femoral head and the need for total hip replacement following joint destruction. Treatment of this disease still remains a clinical challenge. Adult human circulating CD34 + cells have been demonstrated to contribute to vasculogenesis and osteogenesis in immunodeficient rat non- union models in vivo. We hypothesized and proved that the transplantation of CD34 + cells could have a role for improvement of osteonecrosis by promoting vasculogenesis and osteogenesis. Vascular deprivation-induced femoral head necrosis was developed in immunodeficient rats and we then administered human G-CSF mobilized CD34 + cells intravenously. At 4 weeks after administration, the structure of the femoral head and neck were evaluated histologically and morphometrically with haematoxylin and eosin (H&E) staining and micro-CT imaging. Microangiography was carried out for macroscopic evaluation of neovascularization, and the contribution of human cells to vasculogenesis and osteogenesis was evaluated by immunofluorescent staining with human-specific antibodies. Our treatment resulted in an obvious improvement of osteonecrosis after CD34 + cell administration and demonstrated the differentiation potential of CD34 + cells into endothelial cells and osteoblasts. In conclusion, this new therapeutic approach using circulating cell fraction could be a promising cell-based therapy for early-stage osteonecrosis of the hip. Copyright  2010 John Wiley & Sons, Ltd. Received 11 February 2009; Accepted 25 February 2010 Keywords osteonecrosis; CD34-positive cells; cell therapy; vasculogenesis; osteogenesis 1. Introduction An impeded blood flow through the femoral head is incriminated in the aetiopathogenesis of osteonecrosis of the femoral head. This painful disorder of the hip is a debilitating disease that ultimately leads to destruction of the hip joint, requiring total hip replacement. Treatment of osteonecrosis of the femoral head still presents a clinical challenge and various efforts have been made in an *Correspondence to: Masakazu Ishikawa, Department of Orthopaedic Surgery, Graduate School of Biomedical Sciences, Hiroshima University, Kasumi 1-2-3, Minami-ku, 734-8551 Hiroshima, Japan. E-mail: goemon1217@hotmail.co.jp attempt to enhance the healing of osseous defects in the femoral head before collapse occurs. Examples of non- invasive treatment modalities include pharmacological measures (Mont et al., 1998), electrical stimulation (Trancik et al., 1990), shock wave therapy (Lugwig et al., 2001), electromagnetic field therapy (Massari et al., 2006) and cell-based therapy (Kawate et al., 2006; Noth et al., 2007). Recent clinical trials have demonstrated that transplantation of bone-marrow mononuclear cells, as a source of mesenchymal stem/progenitor cells, could be a promising new approach for osteonecrosis of the hip as a cell-based strategy (Gangji et al., 2004, 2005; Gangji and Hauzeur, 2005; Hernigou and Beaujean, 2002; Yamasaki et al., 2008, 2009). Copyright  2010 John Wiley & Sons, Ltd.