Abstract
More than 200,000 people are suffering from Anterior Cruciate Ligament (ACL) related injuries each year in the US. There is an unmet clinical demand for improving biological attachment between grafts and the host tissue in addition to providing mechanical support. For biological graft integration, it is important to provide a physiologically feasible environment for the host cells to enable them to perform their duties. However, behavior of cells during ACL healing and the mechanism of ACL healing is not fully understood partly due to the absence of appropriate environment to test cell behavior both in vitro and in vivo. This study aims at (i) investigating the change in fibril diameter of bovine ACL tissue upon injury and (ii) fabricating nanofiber-based scaffolds to represent the morphology and structure of healthy and injured ACL tissues. We hypothesized that distribution and mean diameter of ACL fibrils will be altered upon injury. Findings revealed that the collagen fibril diameter distribution of bovine ACL changed from bimodal to unimodal upon injury with subsequent decrease in mean diameter. Polycaprolactone (PCL) scaffold fiber diameter distribution exhibited similar bimodal and unimodal distribution behavior to qualitatively represent the cases of healthy and injured ACL, respectively. The native ACL tissue demonstrated comparable modulus values only with the aligned bimodal PCL scaffolds. There was significant difference between mechanical properties of aligned bimodal and unaligned unimodal PCL scaffolds. We believe that the results obtained from measurements of diameter of collagen fibrils of native bovine ACL tissue can serve as a benchmark for scaffold design.
Highlights
Anterior cruciate ligament (ACL) injuries have an estimated annual incidence of more than 200,000 in the United States alone [1]
Increased ACL loading stretches the collagen bundles/fibers, a major constituent of the tissue, until partial or complete ligament rupture occurs as a result of disruption of individual collagen fibrils [5,6,7]
Our findings demonstrated that a healthy bovine
Summary
Anterior cruciate ligament (ACL) injuries have an estimated annual incidence of more than 200,000 in the United States alone [1]. ACL injuries cannot regenerate but heal slowly, resulting in scar tissue formation due to their poorly vascularized nature and frequency of motion. Currently available clinical procedures are not able to fully repair ACL injuries, mainly because of the absence of biological integration between grafts and the host tissue [2]. Reports reveal that females carry three to five times higher risk [3] and that more than one-third of the people with injured ligament tissue undergo reconstruction surgery each year [1], with an estimated annual cost of more than 4 billion dollars for nonsurgical management of ACL injuries, and about 3 billion dollars for surgical reconstruction of ACL [4].
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