Torn ACL: a new bioengineered substitute brought from the laboratory to the knee joint

A Roadmap for the Design of Bioreactors in Mechanobiological Research and Engineering of Load-Bearing Tissues

In the field of tissue engineering, a bioreactor is a valuable instrument that mimics a physiological environment to maintain live tissues in vitro. Although bioreactors are conceptually relatively simple, the vast majority of current bioreactors (commercial and custom-built) are not fully adapted to current research needs. Designing the optimal bioreactor requires a very thorough approach to a series of steps in the product development process. These four basic steps are: (1) identifying the needs and technical requirements, (2) defining and evaluating the related concepts, (3) designing the apparatus and drawing up the blueprints, and (4) building and validating the apparatus. Furthermore, the design has to be adapted to the specific purpose of the research and how the tissues will be used. In the emerging field of bioreactor research, roadmaps are needed to assist tissue engineering researchers as they embark on this process. The necessary multidisciplinary expertise covering micromechanical design, mechatronics, viscoelasticity, tissue culture, and human ergonomics is not necessarily available to all research teams. Therefore, the challenge of adapting and conducting each step in the product development process is significant. This paper details our proposal for a roadmap to accompany researchers in identifying their needs and technical requirements: step one in the product development process. Our roadmap proposal is set up in two phases. Phase 1 is based on the analysis of the bioreactor use cycle and phase 2 is based on the analysis of one specific and critical step in the use cycle: conducting stimulation and characterization protocols with the bioreactor. A meticulous approach to these two phases minimizes the risk of forgetting important requirements and strengthens the probability of acquiring or designing a high performance bioreactor.

Potential of Skin Fibroblasts for Application to Anterior Cruciate Ligament Tissue Engineering

Fibroblasts isolated from skin and from anterior cruciate ligament (ACL) secrete type I and type III collagens in vivo and in vitro. However, it is much easier and practical to obtain a small skin biopsy than an ACL sample to isolate fibroblasts for tissue engineering applications. Various tissue engineering strategies have been proposed for torn ACL replacement. We report here the results of the implantation of bioengineered ACLs (bACLs), reconstructed in vitro using a type I collagen scaffold, anchored with two porous bone plugs to allow bone–ligament–bone surgical engraftment. The bACLs were seeded with autologous living dermal fibroblasts, and grafted for 6 months in goat knee joints. Histological and ultrastructural observations ex vivo demonstrated a highly organized ligamentous structure, rich in type I collagen fibers and cells. Grafts' vascularization and innervation were observed in all bACLs that were entirely reconstructed in vitro. Organized Sharpey's fibers and fibrocartilage, including chondrocytes, were present at the osseous insertion sites of the grafts. They showed remodeling and matrix synthesis postimplantation. Our tissue engineering approach may eventually provide a new solution to replace torn ACL in humans.