Torn ACL: A New Bioengineered Substitute Brought from the Laboratory to the Knee Joint

Abstract

Anterior cruciate ligament (ACL) injuries occur at an annual rate of 120 000 in the USA, and many need reconstructive surgery. We report successful results at 1-13 months following implantation of bioengineered ACL (bACL) in goats. A bACL has been developed using autologous ACL cells, a collagen matrix and bone plugs. The extremities of the bACL were fully integrated into the femur and tibia of the host. Vascularisation of the grafts was extensive 1 month post-surgery and improved with time. At 6 months postgrafting, histological and ultrastructural observations demonstrated a highly organised ligamentous structure, rich in type I collagen fibres and fibroblasts. At the implants' insertion sites, characteristic fibrocartilage was observed having well aligned chondrocytes and collagen fibrils. After a year, mechanical rupture of the grafts demonstrated a major gain in strength. Eventual applications of this new technology in humans include multiple uses in orthopaedic, dental and reconstructive surgeries.

New ligament healing model based on tissue‐engineered collagen scaffolds

“…16,20 Several bACLs seeded with autologous ligament fibroblasts (LFs) were grafted with success in caprine knee joints. 19 After 1 and 6 months, we have observed an increase in the cells populating the bACLs. However, it is not possible to distinguish fibroblasts seeded in the ACL substitutes before grafting from those that migrate from other structures of the joints to populate the grafts.…”

“…The methods that were developed to produce and graft bACLs in goat knee joints were reported previously. 19 However, all previous animal experimentation involved the grafting of bACLs seeded with autologous goat LFs.…”

“…This bone/thread scaffolding was transferred to a sterile plastic tube and kept extended in a central, suspended position by passing two metal pins across the tube and through the transverse holes in the bone plugs. 19 For casting the bACLs, Dulbecco's modification of Eagle medium (DMEM, Gibco BRL, Life Technologies, Grand Island, NY) containing fetal calf serum (FCS) and 1.0 mg/ mL of bovine type I collagen (isolated in our laboratory from healthy Canadian beef skin (Ferme Bruno Germain, Deschambault, Province of Quebec, Canada), tested for its purity by electrophoresis, and solubilized in acetic acid diluted 1,000 times with sterile water) was quickly mixed. The mixture (total of 10 mL) was poured into 12 mL sterile plastic tubes containing the bone plugs linked by the surgical thread.…”

“…These bACLs were maintained in culture in DMEM supplemented with 10% FCS, 50 mg/mL ascorbic acid, 100 IU/mL penicillin G, and 25 mg/mL gentamicin (Sigma-Aldrich Co., Oakville, ON, Canada). 19 After 24 hours, the bACLs were frozen in petri dishes overnight at À70 1C and lyophilized. They were transferred back into new sterile plastic tubes and fixed again with pins as described previously.…”

“…We have developed a three-dimensional bioengineered ACL substitute (bACL), whose scaffold is entirely made of type I collagen. [16][17][18][19] The scaffold is anchored with two bone plugs integrated at its extremities.…”