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

Tissue Engineering of ACL Replacements

“…Obviously, this option may not be available in the human scenario because of either the resorbing of the torn ends of the injured tissue, or their becoming more scar like with time post-injury. However, this approach has been used by Goulet and colleagues in both goats 23,24 and other species such as the dog model (Goulet, Laverty, Hart and Shrive, unpublished findings). In the goat model, there was still tissue present 1 year post-implantation that was partially functional as assessed by biomechanics and was cellular with an organized matrix.…”

“…In the goat model, there was still tissue present 1 year post-implantation that was partially functional as assessed by biomechanics and was cellular with an organized matrix. 24 Therefore, this approach using endogenous cells as a starting point for generating the replacement tissue offers good potential for contributing to a positive outcome.…”

“…24,26 The advantage of this molecule is that ligaments are composed primarily of type I collagen, type 1 collagen from several species is commercially available, and cells can be incorporated into a ligament-like structure by regulating the pH of the collagen solution. 24 Furthermore, recombinant human type 1 collagen can be expressed (Islam and Goulet, in preparation) and thus, would be free of unwanted contaminating proteins and other molecules including infectious agents. An additional advantage of collagen type 1 is that it can be formed in a manner that allows for mechanical loading of the cell-matrix construct during the development of a suitable implant.…”

“…An additional advantage of collagen type 1 is that it can be formed in a manner that allows for mechanical loading of the cell-matrix construct during the development of a suitable implant. 24,26 In the studies by Goulet et al, 24 the collagen 1/cell construct was attached to bone plugs that could be mechanically activated and then the bone plug ends could be used to facilitate the implantation of the construct into experimental models, 24 (F. Goulet, unpublished observations). Whereas the studies by Garvin et al 26 used a smaller cell/matrix construct, it has the potential to be enlarged and adapted to generate a construct suitable for implantation.…”

“…5 The mechanical stimulation of an in vitro generated construct has indeed been shown to lead to enhanced biomechanical and histologic attributes of the tissue. 24,26 Therefore, mechanical loading of the tissue as it matures in vitro is likely critical for improvement in the properties of the engineered tissue. However, whether there are limits to the dynamics of the artificial tissues response to loading in vitro is not yet known, but it is likely that the end point that can be reached is a combination of the biologic and mechanical environments.…”