[In vitro fabrication of tendon substitutes using human mesenchymal stem cells and a collagen type I gel]

Reconstruction of tendon tissue is problematic in many cases. Since direct tendon suture is often impossible, major reconstruction with the use of free tendon transplants or tendon transposition is necessary. Important motor units often have to be sacrificed for reconstructive purposes. In this study we investigated whether long tendon-like substitutes can be fabricated in vitro from human mesenchymal stem cells (MSCs) and a collagen type I gel when cultured under cyclic stretching conditions.

MSCs were obtained from bone marrow aspirates of the iliac crest. Cells were suspended in a collagen type I gel and polymerized in a glass-cylinder with defined size. The fabricated tendon substitutes underwent static stretching for 14 days followed by cyclic stretching for 21 days in a special manufactured bioreactor. Non-stretched substitutes served as a control.

Macroscopically the stretched tendon substitutes showed an increased opacity and a smoother surface structure compared to the non-stretched control. The stretched substitutes displayed more spindle-shaped, longitudinal orientated cells, a tendon-like organization of the collagen matrix, and a parallel organization of the collagen fibers when stained with Hematoxylin/Eosin and Elastica.

Long tendon substitutes could be fabricated from MSCs and a collagen type I gel by cyclic stretching and showed tendon-like parallel collagen fibers and spindle-shaped cells. The use of MSCs in combination with adequate scaffold materials has great therapeutic potential for the development of autologous transplantable tendon substitutes.