Ohio State University researchers have developed a novel technology that was capable of directly transforming skin cells into other cell types in vivo.

In a paper published in the Aug. 7, 2017, issue of Nature Nanotechnology, the team showed that they were able to restore vascular and muscle function in injured pigs and improve brain function in mice using the technology, which they have called Tissue Nanotransfection (TNT).

TNT is designed to avoid known difficulties with induced pluripotent stem cell (iPSC) approaches such as immune system rejection, genomic integration and increased cancer risk.

"Our goal was to come up with a technology that could switch the function of cells – not in a petri dish, not in the laboratory but in the live body – and to do that without a virus. That is exactly what we have achieved," Chanden Sen, director of the Center for Regenerative Medicine and Cell-Based Therapies at The Ohio State University Wexner Medical Center and executive director of Ohio State's Comprehensive Wound Center, told BioWorld. "We demonstrated that when you transect the major blood supply of the mouse supplied by the femoral artery . . . and then use our chip, we reprogrammed the skin cells to become blood vessels.

"So, not only are we making these cells in vitro, we are reprogramming the skin to actually form vessel structures that are . . . carrying blood to the leg. Functionally, it's quite different than just making a blood vessel-related cell or an actual vessel that carries blood," he added. "We are achieving this with a process that is less than a second long and requires no laboratory intervention."

Potential applications range from battlefield wounds to the battle of the bulge. A point-of-care device (POC) is expected to enter a first-in-human trial next year in U.S. military personnel with injured extremities, and co-corresponding author L. James Lee, professor of chemical and biomolecular engineering with Ohio State's College of Engineering in collaboration with Ohio State's Nanoscale Science and Engineering Center, told BioWorld that one of the applications they are working on is converting energy-storing white fat cells to energy-burning brown fat cells.

Lee said that when his team started the experiments now described in Nature Nanotechnology, he was not actually expecting them to work.

Several years ago, after Lee's team published work describing the nanotransfection process in cell culture, he received multiple inquiries from other researchers as to whether the procedure could be done in vivo to repair damaged organs.

"In the beginning, I actually told them, 'It's probably not possible,' because we only transfect one layer of cells, and organs have many layers," he said.

But as requests for adapting the method to in vivo use kept coming in, he told first author Daniel Gallego-Perez, "Why don't we give it a try, because there is such a strong need and interest. If we don't try, we won't know."

When the team did try, by now collaborating with Sen's lab, at first it looked like Lee's skepticism was vindicated.

Initially, "we only saw transfection of one layer of skin" using TNT, he said. "But to our surprise, within 24 hours, when we took the skin from the mouse, we found that transfection could propagate."

The skin cell alterations were taken up by deeper tissues, traveling from the epidermis into the dermis, muscle and fat to create functional vascular repair. And, in normal animals, early vascular growth soon ended and withered away, signaling that perhaps the technology may work in conjunction with the body to minimize off-target effects.

In work with a mouse model, the researchers also created nerve cells from skin cells; those were subsequently injected into brain-injured mice to aid stroke recovery. In both the pig vasculature and the mouse brain, they were able to demonstrate restored function with the use of the cells. The measures to assess function included MR spectroscopy to show regeneration of phosphates in the muscle, as well as MRI to demonstrate brain activity improvement.

Genetic implications

The TNT technology includes both a nanotech-based chip to deliver biological cargo into the skin cells, and the DNA or RNA itself. The biological material is delivered into the body via a small electrical charge.

Compared to bulk electroporation, which is a common method for introducing genetic material into cells, the targeted electroporation used by the team "only affects about 2 percent of the cell surface," Lee said.

Because one of the side effects of bulk electroporation is to reduce plasticity of cells, "only a fraction of the cells listen to you and go to the intended fate," Lee said. Using nanotransfection enabled the team to "maximize the plasticity outcome of the cell."

The process was reported to work successfully 98 percent of the time.

Sen underscored that the process can work with RNA alone, which would virtually eliminate the potential for unintended genetic effects caused by DNA integrating into the host cell genome. No issues of uncontrolled or pathological growth have emerged thus far, with healthy animal models seeing some small vascular growth that subsequently diminishes and dissipates.

What's next?

Given the somewhat outlandish nature of the initial exploratory work, the researchers opted not to seek public funding for the preclinical studies, which were supported by the private family group the Wexner Foundation. But now, military and corporate interest has been piqued by early results.

The researchers are already in talks with an undisclosed multibillion-dollar corporation, and hope to work in conjunction with one or more corporate partners to get the technology to market in a number of applications.

Sen said he expects that POC injury devices will be the first application to make it to market, perhaps within the next decade.

"I would like to see the technology for point of care to use on the field," he said. "I think that we'll be taking this into practical use, because it does not need a lot of sophisticated laboratories. I'd like to see this used in say a 911 situation and in the military field – in situations like that."