Michael J. Smietana

Morphological and Functional Characteristics of Three- Dimensional Engineered Bone-Ligament-Bone Constructs Following Implantation

The incidence of ligament injury has recently been estimated at 400,000/year. The preferred treatment is reconstruction using an allograft, but outcomes are limited by donor availability, biomechanical incompatibility, and immune rejection. The creation of an engineered ligament in vitro solely from patient bone marrow stromal cells (has the potential to greatly enhance outcomes in knee reconstructions. Our laboratory has developed a scaffoldless method to engineer three-dimensional (3D) ligament and bone constructs from rat bone marrow stem cells in vitro. Coculture of these two engineered constructs results in a 3D bone-ligament-bone (BLB) construct with viable entheses, which was successfully used for medial collateral ligament (MCL) replacement in a rat model. 1 month and 2 month implantations were applied to the engineered BLBs. Implantation of 3D BLBs in a MCL replacement application demonstrated that our in vitro engineered tissues grew and remodeled quickly in vivo to an advanced phenotype and partially restored function of the knee. The explanted 3D BLB ligament region stained positively for type I collagen and elastin and was well vascularized after 1 and 2 months in vivo. Tangent moduli of the ligament portion of the 3D BLB 1 month explants increased by a factor of 2.4 over in vitro controls, to a value equivalent to those observed in 14-day-old neonatal rat MCLs. The 3D BLB 1 month explants also exhibited a functionally graded response that closely matched native MCL inhomogeneity, indicating the constructs functionally adapted in vivo.

Reactive oxygen species on bone mineral density and mechanics in Cu,Zn superoxide dismutase (Sod1) knockout mice

Reactive oxygen species (ROS) play a role in a number of degenerative conditions including osteoporosis. Mice deficient in Cu,Zn-superoxide dismutase (Sod1) (Sod1(-/-) mice) have elevated oxidative stress and decreased muscle mass and strength compared to wild-type mice (WT) and appear to have an accelerated muscular aging phenotype. Thus, Sod1(-/-) mice may be a good model for evaluating the effects of free radical generation on diseases associated with aging. In this experiment, we tested the hypothesis that the structural integrity of bone as measured by bending stiffness (EI; N/mm(2)) and strength (MPa) is diminished in Sod1(-/-) compared to WT mice. Femurs were obtained from male and female WT and Sod1(-/-) mice at 8months of age and three-point bending tests were used to determine bending stiffness and strength. Bones were also analyzed for bone mineral density (BMD; mg/cc) using micro-computed tomography. Femurs were approximately equal in length across all groups, and there were no significant differences in BMD or EI with respect to gender in either genotype. Although male and female mice demonstrated similar properties within each genotype, Sod1(-/-) mice exhibited lower BMD and EI of femurs from both males and females compared with gender matched WT mice. Strength of femurs was also lower in Sod1(-/-) mice compared to WT as well as between genders. These data indicate that increased oxidative stress, due to the deficiency of Sod1 is associated with decreased bone stiffness and strength and Sod1(-/-) mice may represent an appropriate model for studying disease processes in aging bone.

Mechanical Characteristics of Tissue Engineered Bone-Ligament-Bone Constructs Following ACL Replacement in Sheep

With approximately 400,000 reported each year, anterior crucial ligament (ACL) injuries are the most common injury in the US. Unfortunately current ACL replacement strategies, which involve using either allografts from cadavers or autografts from patients’ own patellar tendons (PT) or hamstring tendons as a replacement, have several limitations including graft availability, risk of rejection, increased morbidity and, more importantly, unmatched intra-articular biomechanical properties of grafts and ACL. The objective of this study is to use self-assembling, scaffold-less bone-ligament-bone (BLB) engineered tissue constructs as grafts in a sheep ACL repair model to characterize the biomechanical behaviors of native ACL, PT, and tissue engineered ligament and subsequently present a viable option of using tissue engineered ligament graft for ACL repair.Copyright

Erratum to: The effect of implantation on scaffoldless three-dimensional engineered bone constructs

E. M. ArrudaMechanical Engineering, University of Michigan,2250 GG Brown, 2350 Hayward,Ann Arbor, MI 48109, USAE. M. ArrudaProgram in Macromolecular Science and Engineering,University of Michigan,2250 GG Brown, 2350 Hayward,Ann Arbor, MI 48109, USAT. KostrominovaDepartment of Anatomy and Cell Biology,Indiana University School of Medicine-Northwest,Gary, IN 46409-1008, USAIn Vitro Cell.Dev.Biol.—Animal (2010) 46:82DOI 10.1007/s11626-009-9251-0