Stem cells are powerful tools that could one day unlock new frontiers in regenerative medicine. Now, a new study has shown that a certain type of stem cell can be delivered into injured tissues with dissolvable microneedles, to heal wounds.
Mesenchymal stem cells (MSCs) are responsible for replenishing bone, cartilage, muscle and fat cells in the body. But more recently, scientists have found that they have broader healing potential. If introduced to injured tissue, MSCs have been found to boost the formation of new blood vessels, reduce inflammation, and keep cells alive.
But there are a few problems. For one, injecting MSCs into the tissue with regular needles can cause further damage and scarring. Plus, it takes huge amounts of the cells to make sure that enough of them stick around to do their job.
So for the new study, researchers at the Terasaki Institute and the University of California Los Angeles (UCLA) set out to find a less invasive, more effective way to deliver MSCs. Rather than introduce them in bulk, the team wanted to find a way to keep MSCs healthy, so that they could stay there and function for longer.
To do so, the researchers looked to recreate the kind of environment that MSCs naturally live in. A matrix of gelatin fibers did the trick, allowing the MSCs to take hold, absorb nutrients, and begin healing damaged tissue.
The next step was effectively delivering the stem cells into tissues, and microneedles stepped up for this part. As the name suggests, microneedles are so tiny that they can penetrate skin or tissue painlessly. They’re usually arranged in a patch of thousands, and they don’t just pass a payload on – they’re actually made of the drug they’re delivering. Once in the skin they dissolve over time, releasing the drug slowly.
In this case, the researchers made microneedles out of the gelatin matrix, complete with MSCs. These were then encased in a shell made of a tougher biomaterial called PLGA. Once embedded in a wound, the PLGA dissolves first, and as it does the microneedles begin to poke out between the cracks, allowing them to deliver their payloads. In lab tests, 90 percent of the MSCs were still alive and functioning 24 hours later.
The team moved onto tests in mice that had had small sections of skin removed. The PLGA-coated microneedles were embedded into the wound using plain old scotch tape, which can be peeled away to leave them behind. The team called the system Detachable Hybrid Microneedle Depot (d-HMND).
And it seemed to work. Measuring a number of different markers, the team observed that the technique sped up the contraction of the wound, regrowth of skin and hair, reduced inflammation, and stimulated remodeling of tissue and the formation of new blood vessels. In all of these factors, the treatment worked better than injecting MSCs directly into the wound or using microneedles with no MSCs.
“In future scenarios, d-HMNDs could be rapidly fabricated in clinical laboratories shortly before use, applied to treat skin injuries, and explored more broadly as treatments for a variety of other disorders, including melanoma and other dermatological disorders that could benefit from the power of MSC cells,” says Ali Khademhosseini, co-corresponding author of the study. “The concept would even be compatible with using patient-derived cells in more personalized device approaches.”
The research was published in the journal Advanced Functional Materials.
Source: Terasaki Institute