Tendon injuries represent an important clinical challenge, partly due to the mechanical constraints that occur at the junctions with muscle and bone. Biomimetic models could provide cues for efficient tissue repair. In-vitro engineered tendons can already be obtained using stem cells cultured under uniaxial tension in a fibrin gel. Here such tendon-like structures were developed using collagen, the main structural protein of tendons, and mixtures of collagen and fibrin. Total protein concentrations ranged from 2 to 7 mg/mL with various ratios between the two proteins. Ultrastructural studies showed that in the hybrid constructs cells coexisted with two different phases, one of which is primarily composed of fibrillated collagen. The physical dimensions of the tendon constructs varied with protein composition, suggesting a tendency for more prominent compaction in the presence of fibrin and larger diameters for the hybrid constructs. Traction tests showed that the Young’s modulus and Ultimate Tensile Stress were strongly dependent on the final diameter, independently from the proteins involved (higher values recorded corresponding to tubular structures with smaller diameter). In order to better understand the behavior of protein mixtures at high concentrations, the gelation procedure for fibrin and collagen mixtures, without the use of cells, was studied by varying protein ratios and concentrations, solvents, and thrombin and calcium concentrations. Rheological studies showed a higher storage modulus in gels using fibrin only, and an increased modulus of the mixtures as compared to collagen only. Both approaches indicate that introduction of fibrin to collagen gels improve their elastic properties.

Producing collagen-fibrin matrices to investigate tendon engineering strategies

251st National Meeting (2016)

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