New Novel Bone Fusion Using TAT-BMP Hydrogel in Rat Model
Authors: Jahng T. A. , Lee S. E. , Noh I. S. , Yook J. I. 
Published: June 2012

Introduction Despite bone fusion using BMP is promising, its clinical applications are limited due to high cost and unwanted ectopic bony fusion. Furthermore, its processing is complicated and low yield. Recently, new method of BMP producing has been developed using TAT protein domain, which can facilitate the passage of high molecular protein into the cell. Thus BMP precursor with TAT can pass the cell membrane and convert into BMP after chemical degradation. It can secret as BMP itself and activate intrinsic BMP production. Basic animal studies showed rapid diffusion of TAT-BMP in spite of carrier material. For stable release of TAT-BMP, Chitosan hydrogel was made with TAT-BMP and applied to rat model. Materials and Methods Under intraperitoneal anesthesia, the rat thoracolumbar spine was exposed as usual spinal procedure, 1–2 spinous processes were removed and TAT-BMP hydrogel (total 1 cc in volume) or Biopad (calcium bisphosphte) was implanted and operative wound was closed. Total 12 rats randomly assign for TAT-BMP hydrogel (8 rats) and Biopad (4 rats). Animals were survived for 2 months and sacrificed for radiologic and histological examination. Simple X-ray and micro-CT were taken, and histological examination (H & E staining) was done. Results On gross examination, all TAT-BMP hydrogel groups showed palpable mass, and it confirmed with histological finding. Unfortunately, mature bone formation was not even due to short survival period. There is insufficient release of hydrogel in some cases, but there were no ectopic bone formation. On micro-CT, bone trabeculation was visible, but not enough like mature bone. Conclusion Although it was preliminary results, bone fusion using TAT-BMP hydrogel was promising. Further studies using bigger animal and titration of hydrogel with longer survival period are mandatory for clinical implementation. 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