| The anterior cruciate ligament (ACL) is a major stabilizer of the knee, and is often injured during sports and exercise. If left untreated, ACL ruptures lead to degeneration of other knee structures. Autogenous and allogenic tissues grafts are currently used for ACL repair. Intrinsic cell removal from allogenic tissues may decrease their antigenicity and disease transmission risks. Tissue engineering offers an alternative to ACL reconstruction by utilizing a bioresorbable scaffold to induce tissue regeneration. The tissue engineered implant can also act as a carrier for viable cells or chemotactic factors. This dissertation describes a tissue engineered device for ACL reconstruction in the rabbit model. This unique approach utilizes allogenic bone-patellar tendon-bone (B-PT-B) matrices processed to decrease their intrinsic cell density, and then seeded with autogenic cells prior to implantation. The results of preliminary work on cell removal from tendon matrices and the in vitro biocompatibility of these matrices is described. The hypothesis of this dissertation is that an hypocellular patellar tendon matrix can be created, and when such a device is seeded with autogenous cells will result in improved ACL reconstruction performance.; First, cell removal protocols for ACL grafts were developed and refined. The solvent tri(n-butyl)phosphate (TBP) and the detergent sodium dodecyl sulfate (SDS) were evaluated on rabbit B-PT-B's in vitro. Both resulted in a hypocellular matrix, but SDS caused matrix disruption. TBP resulted in an aligned matrix, and supported cell growth better than SDS. Prior demineralization increased cell removal from the tendon's bony attachments. Based on these results, demineralization plus TBP was chosen as the cell removal method to stud in vivo for ACL reconstruction grafts.; Next, B-PT-B grafts seeded with autogenous cells were used for ACL reconstructions in the rabbit. This study demonstrated a reduced immune response towards processed grafts relative to control grafts. Decreased mechanical properties and premature graft failure occurred with processed grafts, most likely the result of disruption of the mineral-collagen transition in the graft's bony attachments. Additionally, some seeded cells were detectable at 12 weeks post-implantation. The presence of the seeded cells has the potential to influence graft resorption and regeneration. |
