Researchers at the University of Iowa have tested a “bio patch” that regenerates missing or damaged bone by inserting DNA into nano-sized particles that deliver bone-making instructions directly into cells.
According to Catherine Paddock, PhD., writing in MNT, the method succeeded in regrowing enough bone to cover skull wounds in live rats.
In test tubes it stimulated new growth in human bone marrow stromal cells. Paddock explained that, by using pieces of DNA that encode for a platelet-derived growth factor called PDGF-B, the researchers were able to deliver genetic instructions directly into living bone cells, causing them to make the proteins that lead to more bone production. They reported their work in the latest issue of the journal Biomaterials.
This study differed from previous ones in that it tackled cells from the inside, causing them to produce proteins that led to more bone growth. Previous work relied on repeated applications that deliver the bone-making proteins from the outside. This is costly, according to Paddock, and has to be done over and over again.
Corresponding author Aliasger Salem, Ph.D., professor at Iowa’s College of Pharmacy, explains: “If you deliver just the protein, you have to keep delivering it with continuous injections to maintain the dose. With our method, you get local, sustained expression over a prolonged period of time without having to give continued doses of protein.”
Paddock explained that to make their bio patch the team made a scaffold from collagen and seeded it with synthetically made, nano-sized plasmids, each carrying DNA pieces of genetic instructions for making bone. They then placed DNA-seeded and unseeded scaffolds onto small 5mm x 2mm holes in the skulls of rats. They found after four weeks that the seeded scaffolds grew 44 times more bone and soft tissue than did the unseeded scaffolds and 14 times more than untreated wounds.
Scans also revealed that the seeded scaffolds resulted in new bone growth that nearly closed the wound. They found that plasmids enter bone cells already present in the body which are located near the wound site and drift over to the scaffold. The researchers found the plasmids transport easily into cells once they are shrunk in size and given a positive electrical charge.
Salem explained that the delivery mechanism is the scaffold loaded with the plasmid. When cells migrate into the scaffold, they meet with the plasmid, take it up and get the encoding to start producing PDGF-B, which enhances bone regeneration.
A potential use for the bio patch could be to repair birth defects where bone is missing. The bio patch could be made in the shape and size of the defect site so when the new bone grows it will be a perfect fit.
