Printed Implant Helps Regenerate the Meniscus

Researchers at Columbia University (New York, NY, USA), the Hospital for Special Surgery (HSS; New York, NY, USA), and Cornell University (Ithaca, NY, USA) first performed magnetic resonance imaging (MRI) scans of an intact meniscus in an undamaged knee. The scans were then converted into a 3-D image which was used to drive a 3-D printer, producing a scaffold in the exact shape of the meniscus, down to a resolution of 10 microns. The scaffold was made of polycaprolactone, a biodegradable polymer that is also used to make surgical sutures.

The scaffold was then infused with two recombinant human proteins: connective growth factor (CTGF) and transforming growth factor β3 (TGFβ3); the delivery of the two proteins attracted existing stem cells from the body and induced them to form meniscal tissue, when released in specific areas of the scaffold in a specific sequential order. This was accomplished by encapsulating the proteins in slow-dissolving polymeric microspheres, first releasing CTGF (to stimulate production of the outer meniscus) and then TGFβ3 (to stimulate production of the inner meniscus).

Finally, the protein-infused scaffold was tested by inserting the scaffold in 11 sheep (whose knee closely resembles that of humans). The animals were randomized to have their meniscus replaced with a protein-infused 3-D scaffold, replacing the surgically removed natural meniscus. The meniscus regenerated in about four to six weeks, and after three months, the treated animals were walking normally. In a postmortem analysis, the regenerated meniscus had structural and mechanical properties very similar to those of natural meniscus. The study was published online on December 10, 2014, in Science Translational Medicine.

“This is a departure from classic tissue engineering, in which stems cells are harvested from the body, manipulated in the laboratory, and then returned to the patient, an approach that has met with limited success,” said lead author Jeremy Mao, DDS, PhD. “In contrast, we're jumpstarting the process within the body, using factors that promote endogenous stem cells for tissue regeneration. We envision that personalized meniscus scaffolds, from initial MRI to 3-D printing, could be completed within days.”

According to the researchers, the therapy could provide the first effective and long-lasting repair of damaged menisci, which occur in millions of people each year and can lead to debilitating osteoarthritis.

Related Links:
Columbia University
Hospital for Special Surgery
Cornell University