Christina Salas PhD Christina Salas PhD

Good as New

Bioprinting Replacements for Worn-Out Ligaments

Like most of us, you probably print out recipes or boarding passes from time to time, but have you ever thought of printing out replacements for worn-out or injured ligaments in your body?

Using a hand-built 3D bioprinter assembled for less than $10,000 from off-the-shelf components, University of New Mexico scientist Christina Salas, PhD, is hard at work developing a method for creating made-to-order ligaments that are as good as new.

Ligaments are tough, stretchy bands of fiber that connect bones to one another and stabilize the joints. But they can fray and tear – and they’re notoriously hard to fix.

“Right now we’re kind of in the investigative phase,” says Salas, an assistant professor in UNM’s Department of Orthopaedics & Rehabilitation and in the School of Engineering. She recently received a two-year $150,000 grant award from the National Institutes of Health that will enable her to spend more time on her research.

The award came as a supplement to UNM’s Clinical & Translational Science Award, says Richard S. Larson, MD, PhD, executive vice chancellor at the UNM Health Sciences Center.

“Dr. Salas brings expertise from multiple domains to bear on a persistent problem in orthopedics,” Larson says. “Her work has real potential to improve the quality of life for many patients who suffer ligament injuries.”

Ligament tears commonly occur with sports injuries, as well as from accidents or the wear and tear that comes with age. Ligaments may heal – slowly – but in many cases, surgical repair is called for.

When surgeons “repair” a torn ligament, what they’re really doing is harvesting a length of tendon from elsewhere in the body, Salas says. They drill holes through the adjoining bones, then thread the ends of the tendon through and secure them.

The transplanted tendon is meant to act as a replacement for the torn ligament. But tendons are not mechanically equivalent to ligaments: they stretch out, and that can cause too much instability in the joint, she says.

Others have tried to develop artificial ligaments, with limited success, Salas says. A major hurdle has been figuring out how to securely attach the ligaments to the bone.

Salas thinks she may have solution. “What we’ve been focused on is developing a scaffold for joint regeneration,” she said.

She has several patents pending on a technique in which a 3-D bio-printer alternates with a device called a near-field electrospinner that can create long, ultrafine fibers that simulate the collagen fibers in ligaments.

The two devices, in a single platform, take turns building a “scaffold” of biodegradable materials that is a perfect replica of the adjacent bones and the ligament that joins them. With the fibers sandwiched between alternating layers of bone deposited by the 3-D printer, a tight connection is created for a stable joint.

Then the scaffold is “seeded” with stem cells that will replicate and develop into the unique interwoven ligament-and-bone structure of the original joint. For a surgeon it would then be a simple matter to graft the new joint onto the ends of the existing bones.

Salas hopes the new NIH grant will allow for the development of a functional prototype suitable for commercialization. If all works out as planned, there may come a time when a patient with a joint injury will come in for a 3-D scan that will be rapidly translated into a print-to-order custom replacement part – and that would be good news for everyone.

Categories: Top Stories, Patient Care, School of Medicine, Research, UNM Clinical & Translational Science Center, Features

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