Magnetic resonance imaging monitoring of cartilage tissue engineering in vivo

Mrignayani Kotecha

University of Illinois at Chicago, Chicago, IL, United States

I ntroduction

Cartilage injury and damage are the major causes of disability in the United States [1,2]. Arthritis, sports injuries, trauma, and developmental issues frequently cause damage in the articular cartilage of joints such as knees, hips, wrists, etc. [2-4]. Cartilage is a highly specialized connective tissue covering the bones of these joints, and its main function is to provide a frictionless smooth movement of these joints. Cartilage has an inadequate self-healing capacity in adults; therefore it often requires a surgical intervention if the tissue is damaged. Some current available surgical treatment options for the repair and restoration of damaged cartilage are microfracture, osteochondral autograft implantation, osteochondral allograft transfer, and autologous chondrocyte implantation [5-7]. However, these treatments are often inadequate in restoring the full load-bearing capabilities of joints, and they have a high failure rate [7]. The regenerated tissues often do not match the biological composition and biomechanical properties of native cartilage, thus defeating the purpose of intervention [8,9]. It is believed that cartilage tissue engineering can overcome these deficits by creating a neocartilage tissue in the lab that matches the desired properties and can be implanted at the damaged site.

Cartilage tissue engineering utilizes a typical “tissue-engineering” approach by using a combination of biomaterial-based scaffolds, appropriate cells, and growth strategies to create a neocartilage tissue that expresses a high amount of cartilage extracellular matrix proteins, proteoglycans, and collagen, type II [10]. The flexibility of choosing biopolymers with suitable mechanical properties, increasingly complex tissue growth strategies involving cells and suitable growth conditions, and an ability to print a custom tissue design are all too attractive choices for targeting patient-specific cartilage therapies. This promise has led to an explosion of research in cartilage tissue engineering. However, there is still a gap in translating these techniques from bench to bedside. Promising in vitro techniques are tested and tweaked at many stages before they can reach patients. Here the animal models are an important middle step to validate promising tissue-engineering strategies from bench to bedside. A number of animal models such as mice, rats, rabbits, sheep, dogs, and horses have been used for the purpose of validating new and developing tissue-engineering technologies and moving the promising ones to the next level of hierarchy.

Monitoring and Evaluation of Biomaterials and their Performance in vivo.

Copyright © 2017 Elsevier Ltd. All rights reserved.

One important issue in cartilage tissue engineering is how engineered cartilage tissues are evaluated. At each stage of validation, engineered tissues are typically assessed using a variety of biochemical assays, histological staining, and gene expression analysis. Once authenticated, the process moves to the next level of validation using higher animal models. Increasingly, MRI is added as an additional criterion of assessment. Because of the available contrast mechanisms and because of the depth and breadth of information produced, MRI can provide a multiscale window in tissue assessment both in vitro and in vivo [11]. There has been tremendous progress in the MRI assessment of tissue-engineered cartilage in small and large animal models and in clinics. It is expected that in the near future, MRI will be widespread and acceptable in the tissue-engineering community as a sole method to provide universal tissue assessment, thus removing the need for destructive assessment techniques.

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