Localized, direct plasmid gene delivery in vivo: prolonged therapy results in reproducible tissue regeneration

Abstract

The inability to deliver growth factors locally in a transient but sustained manner is a substantial barrier to tissue regeneration. Systems capable of localized plasmid gene delivery for prolonged times may offer lower toxicity and should be well-suited for growth factor therapeutics. We investigated the potency of plasmid gene delivery from genes physically entrapped in a polymer matrix (gene activated matrix) using bone regeneration as the endpoint in vivo. Implantation of gene activated matrices at sites of bone injury was associated with retention and expression of plasmid DNA for at least 6 weeks, and with the induction of centimeters of normal new bone in a stable, reproducible, dose- and time-dependent manner.

Poly (D, L-lactide-co-glycolide)/DNA microspheres to facilitate prolonged transgene expression in airway epithelium in vitro, ex vivo and in vivo

“…Sheep trachea 16 2 ) and transported to the laboratory on ice. To remove the mucus, the noncartilaginous sections were cut longitudinally to leave horse-shoe-shaped segments that were placed in 10 mm Petri dishes containing MEM with 50 mg/ml gentamycin and 1 Â antibiotic/antimycotic solution (MEM-A) with the tips of the cartilage submerged in the media.…”

Robust and prolonged gene expression from injectable polymeric implants

“…These DNA-containing implants have been fabricated from biodegradable polymers in a range of shapes and sizes: from microcapsules and microspheres to rods, films, and three-dimensional matrices. [2][3][4][5] All of these implants are solids that are formed outside the body to precise dimensions, and then inserted into the body for gene delivery. An alternative to ex vivo matrix formation has been proposed for protein delivery, [6][7][8][9] where the biodegradable implant forms in situ upon injection.…”

Realizing the potential of gene-based molecular therapies in bone repair

“…(48) Delivery of a PTH1-34 plasmid on a collagen sponge implanted at a beagle tibial defect model was successful without the use of a carrier. (49) Bone formation at the critical-size defect increased by 25% after 4 weeks with 40 mg, but 100 mg pDNA was required for union within 6 weeks. Although effective, it appears that excessive amounts of pDNA may be required for significant bone induction, making this approach not clinically feasible.…”

“…(47,49) Based on estimated defect volumes, the concentration of pDNA required for efficacy borders that of protein in clinical therapies (0.9 to 1.5 mg/mL). The need for more effective synthetic carriers calls for a better understanding of pharmacokinetic and pharmacodynamic issues affecting gene medicines.…”