Kazunori Yasuda

Application of Growth Factors for Enhancement of Mechanical Strength of Grafted Tendon Following Anterior Cruciate Ligament Reconstruction

Anterior cruciate ligament (ACL) injury is a relatively common knee injury during sports activities (Uhorchak, 2003). A torn ACL usually occurs through a twisting force being applied to the knee whilst the foot is firmly planted on the ground or upon landing (Boden, 2000). The traditional surgical treatment for ACL rupture is ACL reconstruction by an autogenous tendon graft. However, fibroblasts of the tendon graft are necrotized immediately after transplantation of an autogenous tendon graft, and, then, extrinsic fibroblasts infiltrate in the graft (Amiel, 1986; Arnoczky, 1982; Kleiner 1986). During this process, the grafted tendon weakens in the early phase after ACL reconstruction surgery, even if the grafted tendon is subjected in the mechanically physiological condition (Jackson 1991). In addition, a case report of histology of patellar tendon graft 18 months after ACL reconstruction suggested that the cell infiltration into a core portion of the graft occurs very slowly after ligament reconstruction (Delay, 2002). The slow graft maturation may result in graft failure during the postoperative rehabilitation period. It has been known that growth factors enhance proliferation, migration, and matrix synthesis of cells in vitro (Deie, 1997; DesRosiers, 1996; Kobayashi, 2000; Marui, 1997; Scherping, 1997; Schmidt, 1995). The authors conducted a series of animal experimental studies for the application of growth factors to ligament reconstruction. We will review our recent experimental studies that intended to enhance mechanical strength of grafted tendon after ligament reconstruction using growth factors.

0441 The Influence of Genetic Ablation of Macrophage Migration Inhibitory Factor on Healing of The Medial Collateral Ligament of The Knee : A Biomechanical Study

INTRODUCTION: Ligament healing is composed of several phases, including acute inflammation and reaction phase, repair and regeneration phase, and remodeling phase. At the molecular level, these phases are regulated by a complex interplay among inflammatory cells, fibroblasts, and the molecules, such as inflammatory cytokines, proteinases, extracellular matrices, and etc, which are produced by these cells. Macrophage migration inhibitory factor (MIF), which was discovered in 1966 as the first lymphokine, has been recognized as a pivotal mediator of inflammation in various pathological conditions including sepsis, arthritis, ARDS, and etc. Recent studies have shown that MIF plays an important role in proliferation and differentiation of cells, generation of organs, and wound healing. However, a role of MIF on the ligament healing process has not been elucidated as of yet. Based on the abovedescribed knowledge, we have hypothesized that MIF may enhance healing of the injured medial collateral ligament (MCL). Recently, a murine MCL injury model has attracted much notice because it is useful to clarify the effect of specific factor ablation on MCL healing by using genetically altered mice. A specific hypothesis to be tested in this study using MIF gene-deficient (MIF KO) mice is that the genetic ablation of MIF may inhibit natural improvement of the structural and mechanical properties of the injured MCL.