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Maxillary sinus floor elevation using a tissue-engineered bone complex with beta-TCP and BMP-2 gene-modified bMSCs in rabbits.

OBJECTIVES
To study the effects of maxillary sinus floor elevation by a tissue-engineered bone complex with beta tricalcium phosphate (beta-TCP) and bone morphogenetic protein-2 (BMP-2) gene-modified bone marrow stromal cells (bMSCs) in rabbits.


MATERIAL AND METHODS
bMSCs derived from New Zealand rabbit bone marrow were cultured and transduced with the adenovirus with BMP-2 (AdBMP-2), adenovirus with enhanced green fluorescent protein gene (AdEGFP) in vitro. Gene transfer efficiency was detected by EGFP expression. These gene-modified autologous bMSCs were then combined with a beta-TCP granule scaffold at a concentration of 2 x 10(7) cells/ml and used to elevate the maxillary sinus floor in rabbits. Twenty rabbits were randomly allocated into groups and sacrificed at weeks 2 and 8. For each time point, 20 maxillary sinus floor elevation surgeries were made bilaterally in 10 rabbits for the following groups (n=5 per group): group A (beta-TCP alone), group B (untransduced bMSCs/beta-TCP), group C (AdEGFP-bMSCs/beta-TCP), and group D (AdBMP-2-bMSCs/beta-TCP). All samples were evaluated by histology and histomorphometric analysis. The fate of implanted bMSCs was traced initially by a confocol fluorescent microscope in the AdEGFP group.


RESULTS
Gene transfer efficiency reached up to 60-80% with 50 PFU/cell transduction as demonstrated by fluorescent microscopic analysis in the AdEGFP group. The augmented maxillary sinus height was maintained for the four groups till 8 weeks post-surgery, while new bone area increased over the time. At week 2, bone areas in groups B-D were significantly larger than those in group A, while at week 8, in group D, the BMP-2 gene-enhanced tissue-engineered bone had the largest bone area among the groups (P<0.05, ANOVA). In that group, a mature bone structure was detected in the center of the elevated space. Under a confocal microscope, green fluorescence in newly formed bone was observed for the EGFP group, which suggested that those implanted bMSCs might have contributed to the new bone formation.


CONCLUSION
bMSCs modified with the AdBMP-2 gene can promote new bone formation and maturation in the rabbit maxillary sinus. BMP-2 regional gene therapy and a tissue engineering technique could be effectively used in maxillary sinus elevation and bone regeneration.