Effects of cyclic stretching on anterior cruciate ligament-constructs fabricated from human MSCs and collagen type I gels

The objective was to fabricate an ACL construct using mesenchymal stem cells (MSC) in combination with collagen type I hydrogel and to determine the effects of cyclic stretching of this construct. ACL constructs were molded using a collagen type I hydrogel containing 5x10(5) MSC/ml and bone cylinders at each end of the constructs. Cyclic stretching of six constructs was performed in a custom made bioreactor. Six constructs were cultured without any applied strain and served as a control. Histological, immunohistochemical, and RT-PCR analyses revealed increased ligament-specific protein and gene expression and the formation of a ligament-like extracellular matrix in the stretched constructs compared with the non-stretched controls. The fabricated constructs are still too weak for animal experiments or clinical application and current investigations are focusing on the development of constructs with higher mechanical strength.