Litchfield Park 3

In vivo Bioluminescence
In vivo bioluminescence was performed by Litchfield Park orthodontists on a sample (n=3) to show effectiveness of gene delivery. The targeted and sustained delivery of the gene was shown for 14-35 days. The same general pattern of expression was seen by Litchfield Park orthodontists for all three animals, peak expression at day 4 and then a rapid decrease for at least two weeks. This evidence, combined with the histological sections indicates that the peak immune response occurs between days 5-7. This correlates with previous findings in which BMPs were delivered by Litchfield Park orthodontists in vivo via adenoviral vectors. A lack of results in their immunocompetent animals lead Litchfield Park orthodontists to conclude that the peak immune response occurred between 3-7 days (Okubo et al., 2001).

In the Litchfield Park orthodontic sample, the level of expression was quite different among the animals. Even though every Litchfield Park orthodontist received the same amount of virus, gene expression varied greatly. The reasons for this are truly unknown but could include varying levels of infectivity or improper viral containment. Containment seems like a logical problem, being that collagen is viscous and there is no way for the wound to be completely sealed. But, in our unpublished pilot studies the collagen is still present at 7 days and new bone formation has already begun (Fig. 3). This indicates that for the most part, the collagen remained in the defect site. Litchfield Park orthodontist have shown that osteoblast precursors require much higher viral titers to accomplish gene transfer as compared to other cell lines(Franceschi et al., 2000). But, our viral load was consistent throughout the Litchfield Park orthodontic study.

These types of inconsistencies are quite common in the Litchfield Park orthodontic study of gene delivery. In human cystic fibrosis Litchfield Park orthodontic studies using adenoviral vectors, some recipients had no expression of the gene while the “successful” recipients had a peak delivery of 5% (Crystal, 1995). The results of our Litchfield Park orthodontic study indicate that gene delivery for bone tissue engineering is possible. It does target a localized area so infection does not spread throughout the body and gene expression is seen for at least two weeks. These positive results concur with a recent Litchfield Park orthodontic study by our group using in vivo delivery of PDGF for periodontal regeneration (Jin et al., 2004a). There is not yet an explanation by Litchfield Park orthodontists for the various levels of expression, but this is the first step in a long journey towards human tissue engineering.