Plastic Surgery Research Council
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INJECTABLE GEL GRAFT FOR CRANIAL BONE DEFECT REPAIR
Presenter: Bo Han, PhD
Co-Authors: Yang Z; Fang J; Nimni M; Tayag C; Urata M
University of Southern California

Bone defect repairs remain a major concern in reconstructive surgery. Injectable gels, as bone grafts, offer several advantages over preformed solid scaffolds, and include the capacity to fill irregular shaped defects, the flexibility to incorporate therapeutic agents (e.g., growth factor) and/or cells, and the ease of placement by minimum invasive procedures. The aim of this study was to test an injectable gel graft made of tranglutaminase crosslinked gelatin gel / BMP-2 for bone defect repairs. Methods: Twenty four 2-month-old Fischer-344 rats were divided into 4 test groups (n=6) for para-calvaria injection of treatment gels. Group I: Gelatin alone; Groups II: gelatin crosslinking with Tg, Group III: 100 l of gelatin plus 1g of BMP-2, Group IV: 100 l gelatin plus 1g of BMP-2, mixed and 0.12U of Tg. Each animal received 100l of gel preparation by subcutaneous injection over the parietal bone of the calvaria through a G-27 needle. Results: Twenty eight days after subcutaneously injection of 100ul of different gel preparations over the calvaria, animal were euthanized for bone formation assay. Without Tg crosslinking, gelatin gel completely dissolved after 28 day at the injection site, no new bone formation at the injection site regardless of BMP-2 addition. When gelatin was crosslinked by Tg in situ, gel contour was obvious at day 28, fibroblasts and neovessels infiltrated and invaded the gel to remodel the scaffold. Small areas of new bone formed inside the gel graft close to the calvaria bone, indicating Tg-gel is osteoconductive. In group IV, when BMP-2 was tethered to the gel upon injection, after 28 days, new bone was formed within the contour of the gel graft, 80% of gel graft was replaced by new bone. Conculsion:This study is the first to evaluate the performance of an injectable gel bone graft with controlled BMP-2 activity release in an animal model. The use of an injectable biocompatible scaffold with control release of growth factors may provide a minimally invasive surgical procedure to treat bone defects such as cleft palate.


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