Analysis of mesenchymal stem cells grown on a three-dimensional HYAFF 11-based prototype ligament scaffold.

Ligaments are complex structures that maintain the mechanical stability of the joint. Healing of injured ligaments involves the interactions of different cell types, local cellular environment, and the use of devices. To gain new information on the complex interactions between mesenchymal stem cells (MSCs) and a specific hyaluronan-based prototype scaffold (HYAFF, useful for ligament tissue engineering, short time-course experiments were performed to analyze the proliferation, vitality, and phenotype of MSCs grown on the scaffold. MSC proliferation was analyzed using the MTT test, during the early time points (2, 4, 6, days). Viability was assessed using calcein/acetyloxymethylester immunofluorescence dye and confocal microscopy analysis. Hyaluronic acid receptor (CD44), typical matrix ligament proteins (collagen type I, type III, laminin, fibronectin, actin), and chondrogenic/osteogenic markers (collagen type II and bone sialoprotein) were evaluated by immunohistochemistry. Our data demonstrated that MSC growth and viability were cell density-dependent. MSCs completely wrapped the fibers of the scaffold, expressed CD44, collagen type I, type III, laminin, fibronectin, and actin, and were negative to collagen type II and bone sialoprotein. These data demonstrate that MSCs survive well in the hyaluronan-based prototype ligament scaffold, as assessed after 2 days from seeding, and express CD44, a receptor important for scaffold interaction, and proteins responsible for the functional characteristics of the ligaments.

A tissue engineering approach to meniscus regeneration in a sheep model.

OBJECTIVE: Regeneration of the meniscal tissue occurs to a limited extent, and the loss of meniscal tissue leads to osteoarthritis. A new biomaterial consisting of hyaluronic acid and polycaprolactone was used as a meniscus substitute in sheep to evaluate the properties of the implant material with regard to size, biomechanical stability, tissue ingrowth, and integration. METHODS: Eight sheep (right stifle joints) were treated with three total and three partial meniscus replacements while two meniscectomies served as empty controls. The animals were euthanized after 6 weeks. The specimens were assessed by gross inspection and histology, and compared with the nonoperated left joints. RESULTS: The surgical technique was found to be feasible. The implants remained in position, did not tear, and showed excellent tissue ingrowth to the capsule. Tissue integration was also observed between the original meniscus and the implant. However, graft compression and extrusion occurred. The histological investigation revealed tissue formation, cellular infiltration and vascularization. Cartilage degeneration was more severe in the operated joints. CONCLUSION: The present study shows promising results concerning the qualities of this biomaterial with regard to implantation technique, stability and tissue ingrowth.