For years, stem cell-based therapies have promised myriad breakthroughs in healthcare—from cancer treatments and re-growing teeth to preventing brain damage and degeneration. While some therapies have met with much more success than others, they all face the same challenge of working with live cells. This work can be tricky. Getting some types of cells can pose ethical issues; a patient’s immune system can attack those cells once they're used; and stem cells can sometimes go haywire and generate tumors.

But for one promising stem cell therapy—one that thwarts brain damage—scientists may have found a way around the problems.

By extracting molecular bundles called microvesicles from stem cells, scientists can harness the same neuro-protective and healing properties seen with whole stem cell treatments. Microvesicles normally act like cell-to-cell mail, and they bud from one cell, bearing proteins and snippets of genetic material that tame the immune system and coordinate neighboring cells. In rats with irradiated brains, the bundles safeguarded brain structures, reduced inflammation, and preserved cognitive functions compared with rats that didn’t get the cellular cargo, researchers report.

The findings, published Monday in the Proceedings of the National Academy of Sciences, offer a proof-of-principle that microvesicle therapies could one day sidestep the challenges of cell-based treatments for brain damage, injury, or degeneration.

Those researchers, all based at the University of California, Irvine, began looking into microvesicles as a way to treat patients with brain cancer—particularly child patients. Current treatments to zap tumors in the brain can include powerful irradiation, which can be effective but comes with weighty side effects such as lifelong cognitive dysfunction.

In previous studies, the authors found that treatments with stem cells can dodge those effects, yet they came with the standard concerns of using whole cells. But, they noticed that other studies had hinted that stem cell microvesicles can help heal brains, too. In those studies the packages helped heal the damage from stroke and traumatic injuries.

To see if the microvesicles could shield against the effects of radiation, the researchers set up a study in rats with and without head-only radiation exposure. For some of the irradiated rats, the researchers injected microvesicles from human neural stem cells into their brains two days after the exposure. Then they put all the rats through cognitive tests that evaluated memory and learning. The rats with stem cell packages performed just as well as rats that weren’t exposed to radiation at all, while the irradiated rats showed cognitive decline.

When the researchers looked more closely at the rodents' brains, they found that the microvesicles had dispersed through their noggins. That dispersal protected their nerve cells and brain tissue from damage, the researchers found. The irradiated rats injected with microvesicles also had less brain inflammation than their irradiated counterparts.

If the data holds up in further testing, the results suggest that stem cell microvesicles could deliver on the promises of stem cell treatments to protect the brain from a host of injuries and traumas—without the fuss of cells.

Proceedings of the National Academy of Sciences, 2015. DOI: 10.1073/pnas.1521668113 (About DOIs).