Biomedical subjects
Nicola Petrie
Publications and source records attributed to Nicola Petrie.
Gene therapy in soft tissue reconstruction.
Gene therapy is defined as the introduction of a therapeutic gene into a cell, whose expression can lead to a cure of a disease or offer a transient advantage for tissue growth and regeneration. The delivery of genes can be undertaken for a number of purposes, usually it is attempted to enhance or add a function to a cell or a tissue or to delete or reduce another function. In this brief overview we describe various vehicles and techniques that have been developed to deliver therapeutic genes into cells, such as viral vectors and physical/chemical gene delivery methods including naked DNA and particle-mediated gene transfer, the microseeding technique and the application of lipids. Furthermore we review the potential utility of gene therapy from the perspective of a reconstructive surgeon. Several tissues will be discussed, particularly muscle, tendon, nerve, bone, skin and wounds.
In vivo gene delivery of Ad-VEGF121 to full-thickness wounds in aged pigs results in high levels of VEGF expression but not in accelerated healing.
We have previously reported that endogenous vascular endothelial growth factor (VEGF) concentration in older pig wounds peaked later and at one-fourth the level of young pigs. These data suggested that VEGF might play a major role in the healing of full-thickness wounds in the aged pig. By in vivo gene transfer using the microseeding technique, we treated full-thickness wounds with different doses of VEGF-expressing adenoviral vector (Ad-VEGF) varying from 1 x 10(7) to 2.7 x 10(11) particles per wound (ppw). We found that the VEGF expression in wound fluid followed a dose-response pattern. However, when wounds were microseeded with the highest concentration of Ad-VEGF (2.7 x 10(11) ppw), diminished healing rates were found. We then determined the minimal functional concentrations of Ad-VEGF. We used five aged Yucatan minipigs, all retired breeders, to analyze the role of over-expression of 1 x 10(8) and 1 x 10(9) ppw of Ad-VEGF (n= 78) in terms of healing of full-thickness wounds, all 2.5 x 2.5 x 1 cm in size (n= 158). The Ad-VEGF solutions were delivered to the wound floor and borders by in vivo microseeding. Control wounds (n= 80) were microseeded with Ad-Lac-Z (n= 25), treated with saline (n= 49) or treated dry (n= 6). All wounds except for the dry-treated ones were covered with a wound chamber and a wet environment was created by injecting 2.5 ml saline into the chamber. Peak VEGF expression (2300-4000 pg/ml) was detected on days 2 or 3 post gene delivery. This level of VEGF expression was not seen in the saline (n= 49) or Ad-null (n= 25) control groups. The VEGF expression in wounds treated with 1 x 10(8) and 3 x 10(8) ppw (n= 39) exhibited a slower onset with a peak concentration of 400-920 pg/ml on days 5-7. Although high levels of VEGF expression were achieved in the local wound environment, we could not show a significant increase in neovascularization as compared to saline-treated wounds. No significant differences were observed in the rate of reepithelialization and wound contraction among groups of full-thickness wounds treated with Ad-VEGF, Ad-null mutant, or saline in the aged "wet wound healing" pig model. These results indicate that increased levels of VEGF in wounds produced by in vivo gene transfer have little effect on the healing of full-thickness wounds in the aged pig model. Moreover, significantly higher levels of VEGF expression by Ad-VEGF could lead to impaired wound healing.