A team of researchers from Washington University in St. Louis has received a five-year, $3.1 million grant from the National Institutes of Health so that they might discover a better way to improve the outcome of surgical repairs by studying the natural attachment of tendon to bone. An interdisciplinary and multi-institutional group of researchers are reverse-engineering the tendon-to-bone attachment. The work is being led by Stavros Thomopoulous, Ph.D., associate professor of orthopedic surgery in the School of Medicine, and Guy Genin, Ph.D., professor of mechanical engineering in the School of Engineering & Applied Science.
The team will use a variety of imaging methods working with Mark Anastasio, Ph.D., interim chair and professor of biomedical engineering in the School of Engineering & Applied Science. They will use scanning transmission electron microscopy-electron energy loss spectroscopy to determine mineral and collagen distributions at the site of insertion of tendon to bone and perform mechanical testing on the collagen fibers.
In addition, they will use synchrotron X-ray diffraction, Raman spectroscopy and polarized light microscopy to determine the distributions of mineral content and collagen orientation along the tendon-to-bone insertion. They will also use phase contrast X-ray computer tomography to determine the 3-D geometry of tendon and bone and tissue-level testing to determine the mechanics of the tendon-to-bone insertion.
Dr. Thomopoulous told OTW, “The work was motivated by the clinical need. Rotator cuff tears are prevalent in the population and the incidence increases with age. 20% of people over the age of 60 have tears, and this increases to 50% in those over 80. These tears don’t heal, and surgical repair is plagued with high failure rates. We decided to reverse-engineer the young, healthy tissue and figure out what makes that system work so well.”
Asked about their first steps, he noted, “The problem is essentially a mechanical one. A compliant rope-like material (tendon) needs to be re-attached to a stiff cement-like material (bone). We are using cutting-edge imaging and modeling approaches to figure out how the body solves this mechanical problem of attaching two dissimilar materials. Experiments will be done at the nanometer through millimeter length scales to understand how the system works.”
As for where they hope to be one year from now, Dr. Thomopoulous told OTW, “Results from our imaging and modeling experiments will serve as the design criteria for building a tissue engineered replacement for tendon-to-bone attachment, with a particular emphasis on the rotator cuff. We have a five year plan to complete experiments and build mathematical models that describe how the natural tendon-to-bone attachment works. In our first year, we will focus on gaining a nanometer through micrometer scale understanding of how collagen and mineral, the building blocks of this material, interact to produce a tough attachment between tendon and bone.”
