Pro-angiogenic and osteogenic effects of adipose tissue-derived pericytes synergistically enhanced by Nel-like protein-1

Abstract Background One of important objectives of regeneration of vascularized tissues is to develop agents for osteonecrosis. We aimed to determine pro-angiogenic and osteogenic efficacies of adipose tissue-derived (AD) pericytes combined with Nel-like protein-1 (NELL-1) to investigate their therapeutic effects for osteonecrosis. Methods The experimental groups were configured to evaluate additional effects of NELL-1 on pericytes (i.e., Control, the group treated with only NELL-1, the group treated with only pericytes, and the group treated with pericytes and NELL-1). Tube formation and cell migration were assessed to determine pro-angiogenic efficacy. In vivo vessel formation was evaluated using the chorioallantoic membrane assay. A mouse model with a 2.5-mm necrotic bone fragment at the femoral shaft was used as a substitute for osteonecrosis in humans. Bone formation was assessed radiographically (plain radiographs, three-dimensional images, and quantitative analyses). Histomorphometric analyses were also performed. To identify factors related to additional effects of NELL-1, microarray, qRT-PCR analysis, and western blot were performed. Results The results for pro-angiogenic efficacy indicated there were synergistic effects of pericytes and NELL-1 on tube formation, cell migration, and vessel formation. For the results for osteogenic efficacy, the mouse models of osteonecrosis treated with pericytes and NELL-1 revealed the greatest bone formation in radiographic images and quantitative analyses, compared with other settings. The corresponding models treated with pericytes and NELL-1 revealed robust bone and vessel formation in the histomorphometric analyses. Using additional arrays, we found an association of FGF2 between the effects of NELL-1. Conclusion Combinational therapy using AD pericytes and NELL-1 has potential as a novel treatment for osteonecrosis.