Gene therapy of skull injury
The gene restores bones
Nadezhda Markina, <url>Russian scientists have created a transplant to restore bone tissue.
In an interview with the Newspaper.En" the researchers told the details of their work (in rabbits with a transplant, skull defects healed better and faster) and about the problems that arise during it (in Russia it is very difficult to get permission for a clinical trial of a gene-activated medical device).
The method of bone restoration using a gene therapy approach was developed by Russian specialists from the Institute of Human Stem Cells (ISC) and presented it at the annual international symposium "Topical Issues of Gene and Cell Technologies".
"The problem of bone tissue reconstruction is quite urgent," he tells the newspaper.Ru" Deputy Director of the ISKCH for Science Roman Deev. – Of course, if an adult patient needs to close the defect of the integumentary bones of the skull, no one will suffer with biotechnologies – put a titanium plate, and that's it. Another thing is in a child, on the growing bones of the skull. Or if you need to make up for a defect in the maxillofacial bones. There is no adequate solution to this problem. There are some defects that can't be repaired, do whatever you want with them."
These defects can occur with injuries, inflammatory diseases, oncological diseases. It is for such bone defects that researchers are developing high-tech approaches.
A lot of different materials, synthetic and natural, have been developed for simple replacement of bone tissue. But all these materials serve only as a matrix, they cannot start the growth of bone tissue, as experts say, they do not have osteoinduction. In order to give them this property, you need to add something to them, activate them. More advanced materials consist of a carrier and this active component.
"There are three options for what can be added,– explains Deev. – These are genes, growth factors (proteins) and cells. It doesn't work out very well with factors, although there are already drugs on the market that cost crazy money, because recombinant proteins are very expensive. But as soon as they start to come into contact with wound fluid, they largely lose their properties due to the action of enzymes."
Making a bone graft with cells is also very difficult. One of the main difficulties is to ensure the blood supply to the cells, otherwise they will die.
The third option – to add genes – is being implemented by the ISC researchers. They received the so-called gene-activated bone graft (GACG).
It consists of a collagen–based carrier and hydroxyapatite, which carries the VEGF gene - the human vascular endothelial growth factor gene.
In order to insert a gene construct, experts used not a virus, but another method – the ring DNA of a bacterium (plasmid).
Such a gene-activated bone graft was tested on Chinchilla rabbits. For experimental purposes, defects of the parietal bones were inflicted on them. Each rabbit had two holes made in the parietal bones of the skull – on the right and on the left. A GACG was inserted into the right hole, and a control carrier graft without the VEGF gene was inserted into the left one.
After 15 and 30 days, the results were compared. In order to objectively assess the quality of bone tissue restoration, computed tomography was used, and then histology. After 15 days, the difference between simple and gene transplants was not noticeable. But after 30 days it became obvious that GABA restores bone much better – clear signs of osteogenesis were noticeable on histological preparations. During this time, almost 29% of the bone defect was restored in the case of GACG, and only 14% in the case of a simple transplant. In the future, the scientists traced the action of GACG to 120 days.
The researchers tested the effect of the genetic construct by combining the VEGF gene with the GFP gene, a green fluorescent protein. So they made the gene's work visible. Penetrating into the target cells, the VEGF gene began to produce a protein - vascular endothelial growth factor. It would seem, how does the protein of blood vessels help the growth of bone tissue? But scientists have shown that it stimulated vascular growth – angiogenesis, and it, in turn, turned out to be a critical condition for bone regeneration
Russian specialists have developed the first domestic prototype of GACG and proved that bone regeneration can be induced by a gene construct. The authors of the study emphasize that they used a proven gene design, since it works in the already registered Neovasculgen drug for the treatment of lower limb ischemia.
"We have received approval of our clinical protocol," says Roman Deev, "and are now waiting for permission to conduct clinical trials from the Federal Service for Supervision of Healthcare."
Portal "Eternal youth" http://vechnayamolodost.ru29.10.2013