Characterization of Total and Active Matrix Metalloproteinases-1, -3, and -13 Synthesized and Secreted by Anterior Cruciate Ligament Fibroblasts in Three-Dimensional Collagen Gels

Abstract

Anterior cruciate ligament (ACL) injury and subsequent reconstructive surgery is increasing with an estimated 200,000 reconstructions performed yearly in the United States. Current treatment requires reconstruction with autograft or allograft tissue with inherent disadvantages. The development of tissue-engineered ligament replacements or scaffolds may provide an alternative treatment method minimizing these issues. The study of ligament fibroblast catabolic and anabolic responses to mechanical and biologic stimuli in three-dimensional (3D) cell culture systems is critical to the development of such therapies. A 3D cell culture system was used to measure the total content and active forms of matrix metalloproteinases (MMPs)-1, -3, and -13 to assess the potential role of the mechanical environment in regulation of matrix turnover by ligament fibroblasts. The production, retention, and secretion of MMPs by ACL fibroblasts in 3D culture were measured over a 14-day period. The total MMP content and MMP activity were determined. The level of all MMPs studied increased over 7-10 days and then reached a steady state or decreased slightly in both the collagen gels and the media. This system will now permit the study of externally applied cyclic and static strains, strain deprivation, and the potential combined role of the cytoskeleton and MMPs in matrix turnover in ligaments. IntroductionA nterior cruciate ligament (ACL) reconstruction is the current gold standard for treatment of ACL rupture. Whereas the outcome of these surgical treatments has generally proven favorable, morbidity and rehabilitation of the graft harvest site (autografts) and immune rejection and disease transmission (allografts) have serious drawbacks. 1 Synthetic ligament replacements made from woven fluorocarbons and polyesters were developed to address the weaknesses of grafts and became popular in the late 1980s to the early 1990s. Their popularity was due to ease of manufacture, excellent tensile strength, elimination of donor-site morbidity, and subsequent pain and rehabilitation. These products failed clinically due to material degradation over time, increased incidence of inflammation, and immune foreign body response.2 Thus, research investigating the potential for development of tissue-engineered ligament constructs or scaffolds, which could harness the potential of the ligament to heal, is warranted.Tissue-engineered ligament replacements can potentially provide constructs which combine the benefits of autografts by using autologous cells or tissues, and the strength of synthetic ligaments through the development of strong biological scaffolds. The availability of three-dimensional (3D) gel culture systems permits the study of the behavior of ligament fibroblasts in a spatial orientation, which more closely resembles their position in situ, 3 providing a valuable tool in the progression to engineered ligament substitutes. In the current study, we characterized the expression and activity of matrix metalloproteinases (MMPs) by ligament fibro...

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The relationship between lateral femoral condyle ratio measured by MRI and anterior cruciate ligament injury

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