Regulation of Tendon Tissue Engineered Construct Stiffness by Culture Time, Mesenchymal Stem Cells and Mechanical Stimulation

More than 57.2 million episodes of musculoskeletal injuries were recorded in 2004 in the United States, costing the US economy more than $254 billion [1, 2]. Approximately 45% of these are tendon, ligament and joint capsule related injuries [3]. Tissue engineering approaches have emerged as an attractive alternative to conventional and oftentimes ineffective treatment methods. Implanting MSC-seeded collagen tissue engineered constructs (TECs) in the central defects of patellar tendon (PT) has significantly improved repair biomechanics compared to natural healing as well as acellular repairs in the rabbit model [4, 5]. Mechanically stimulating these MSC-collagen TECs further improved repair outcome, and TEC stiffness at the time of surgery positively correlated with and predicted repair stiffness twelve weeks after surgery [6, 7]. Although these improvements were observed twelve weeks after surgery, repairs were still not strong enough to withstand forces that might arise during more strenuous activities.