Tissue Engineers Use New Biomaterial to Repair Knee Cartilage


Tissue engineers from Johns Hopkins University School of Medicine’s Translational Tissue Engineering Center (TTEC) have used a biomaterial to stimulate and facilitate the growth of new cartilage in human patients.

An illustration of the cartilage repair surgical procedure. A mini-incision exposes the cartilage defect (top left-hand panel), and any dead tissue is removed from the edges. (B) The adhesive is then applied to the base and walls of the defect, followed by microfracture. (C) Lastly, the hydrogel solution is injected into the defect. (D) Bleeding from the microfracture holes is trapped in and around the hydrogel.Science Translational Medicine/AAAS
An illustration of the cartilage repair surgical procedure. A mini-incision exposes the cartilage defect (top left-hand panel), and any dead tissue is removed from the edges. (B) The adhesive is then applied to the base and walls of the defect, followed by microfracture. (C) Lastly, the hydrogel solution is injected into the defect. (D) Bleeding from the microfracture holes is trapped in and around the hydrogel.
Science Translational Medicine/AAAS

This was a rather small study that only examined 15 patients. All 15 patients had cartilage defects and were scheduled to undergo “microfracture surgery.” Microfracture surgery uses a drill to bore tiny holes in the bone. These small holes allow bone marrow stem cells to leak into the joint space and make new bone and cartilage. In this study, hydrogel scaffolding was troweled into the wound to in order to support and nourish the healing process. The results from this study were published in the Jan. 9 issue of Science Translational Medicine. According to the authors, this study is a proof of concept trial that paves the way for larger trials to test the hydrogel’s safety and effectiveness.

“Our pilot study indicates that the new implant works as well in patients as it does in the lab, so we hope it will become a routine part of care and improve healing,” says Jennifer Elisseeff, the Jules Stein Professor of Ophthalmology and director of the Johns Hopkins University School of Medicine’s TTEC. Cartilage damage results from overuse, injury, disease or faulty genes. Microfracture surgery is a standard of care for cartilage repair, but when holes in cartilage are caused by joint injuries, microfracture surgery often either fails to stimulate new cartilage growth or grows cartilage that is less hardy than the original tissue

To address this problem, tissue engineers, such as Elisseeff, have postulated that the bone marrow mesenchymal stem cells need a nourishing scaffold on which to grow in order to make the right type of cartilage and enough of it. Unfortunately, demonstrating the clinical value of hydrogels has been slow, difficult, and expensive. By experimenting with various materials, Elisseeff and her colleagues have developed a promising hydrogel, and an adhesive that sticks the hydrogel to the bone.

After testing the combination for several years in the lab and in goats, the hydrogel seemed ready for human trials. Elisseeff and her group collaborated with orthopedic surgeons to conduct their first clinical study. 15 patients with holes in the cartilage of their knees received a hydrogel and adhesive implant along in combination with microfracture surgery. In order to compare the efficacy of their hydrogel, another three patients were treated with microfracture surgery alone. After six months, it was clear that the hydrogel implants had caused no major problems. Furthermore, magnetic resonance imaging of these patient’s knees showed that patients with implants had new cartilage filling an average 86% of their defects in their knees, and patients that had received only microfracture surgery had an average of 64% of their tissue replaced. Patients with the implant also reported a greater decrease in knee pain in the six months following surgery, according to the investigators.

As the trial continues, more patients have enrolled. This clinical trial is presently managed by a company called Biomet. These data from this trial is part of an effort to earn European regulatory approval for the device.

Elisseeff and her team have begun developing a next-generation implant in which the hydrogel and adhesive will be combined in a single material. Elisseeff and others are also interested in technologies for joint lubrication that reduce joint pain and inflammation