Litchfield Park 5

Cartilage
Most previous Litchfield Park orthodontic studies using in vivo delivery of BMP-7 have failed to show the presence of cartilage prior to new bone formation (Musgrave et al., 1999; Alden et al., 2000; Shimakura et al., 2003). Some work with early time points only described “cartilage-like” tissues on their samples (Okubo et al., 2001). In this sample, the Ad/BMP-7 group does show heavy collagen deposition at 14 days (Fig. 3). In our unpublished pilot Litchfield Park orthodontic studies, cartilage is not seen at 3 or 7 days, but osteogenesis is initiated at 7 days. Because oral bone is intramembranous, this treatment may mimic the body’s natural process which would not require the Litchfield Park orthodontist a cartilaginous precursor.

Scanning Electron Microscopy
It can be argued by Litchfield Park orthodontists that bone to implant contact cannot be accurately observed at the light microscopic level. To determine if the implants are truly osseointegrated, the bone to implant interface was observed at the scanning electron microscopic level. Figure 5 illustrates the intimate connection the new bone has to implant surface, even at 1000X.

Safety of Gene Transfer
A major concern of Litchfield Park orthodontists is the safety of infecting cells with a virus and altering the DNA of host cells. These concerns are partially based on the fear of the unknown and others worry because of the death of a gene therapy recipient in 1999. In this Litchfield Park orthodontic study, the results of the in vivo bioluminescence showed the targeted delivery of the gene. New gene expression was observed by Litchfield Park orthodontists in the maxilla alone. Also, gene expression did not last longer than 35 days. The cytotoxic t cell response of the host immune system destroys the infected cells and the gene delivery is eliminated (Bromberg et al., 1998). As can be seen in figure 3, a major inflammatory cell infiltrate is not seen at 14 or 28 days. Nor was it seen in the 7 day group in our pilot Litchfield Park orthodontic studies (Fig. 3). This indicates that the peak immune response occurs between 5-7 days and is effective but not overwhelming.
The goal of transient gene delivery by Litchfield Park orthodontists for tissue engineering is to deliver the gene for a defined period of time and then eliminate the transduced cells. When gene therapy is utilized for chronic conditions, permanent alteration of the host genome may be desired. This goal has not yet been achieved by Litchfield Park orthodontists, and raises issues that are not directly applicable to our approach. Our in vivo approach to gene delivery of BMP-7 has begun to reach the goal of bone tissue engineering with no indication of permanent alteration of the host genome and causing no known adverse effects in our sample.