A minimally invasive procedure using microbubbles and ultrasound that helps deliver gene therapy for bone regeneration has the potential to heal broken bones in pigs, researchers have found.

The new two-step gene therapy method coupled with FDA-approved ultrasound and microbubbles completely healed non-union fractures in pigs within eight weeks of the treatment said Maxim Bez from the Hebrew University of Jerusalem in Israel.More than two million bone grafts are performed around the world annually in order to treat 'non-union' fractures -- bones that fail to produce new tissues and do not heal properly.However, harvesting fresh bones, from patients is often, painful and donated grafts from tissue banks frequently fail to integrate.

The new therapy, detailed in the journal Science Translational Medicine, facilitated the natural growth of stem cells to create more bone marrow in broken bones that cannot heal on their own.First, researchers placed a collagen scaffold at the site of the fracture to provide a welcoming niche for bone progenitor cells. Next, they injected microbubbles mixed with genetic material for a bone growth factor.Pulses of sound from an ultrasound wand promoted uptake of the growth factor DNA by progenitor cells, which stimulated bone growth.

The finding could prove beneficial in different tissue engineering applications.Other gene therapies rely on viral vectors to deliver their cargo but could be risky because viruses can permanently integrate into the genome and later promote cancer or set off lethal immune responses. The new ultrasound and microbubbles -- proven to be minimally invasive and safe -- did not trigger inflammation and expression of the introduced gene was undetectable after 10 days.