Biomechanical, Biochemical, and Cell Biological Evaluation of Different Collagen Scaffolds for Tendon Augmentation

Abstract

Tendon augmentation is increasingly clinically relevant due to rising amount of tendon ruptures because of the aging and more demanding population. Therefore, newly developed scaffolds based on bovine epoxide stabilized collagen maintaining the native fibril-like collagen structure were characterized and compared to two commercially available porcine collagen scaffolds. For biomechanical testing (ultimate load, ultimate stress, stiffness, and elastic modulus), bovine collagen scaffolds were hydrated and compared to reference products. Cell viability and proliferation were assessed by seeding human primary fibroblasts on each collagen-based scaffold and cultured over various time periods (3 d, 7 d, and 14 d). Live/dead staining was performed and metabolic cell activity (WST-1 assay) was measured. Biochemical degradability was investigated by enzymatic digestion. The bovine collagen scaffold showed significantly enhanced biomechanical properties. These persisted over different rehydration times. Cell biological tests revealed that the bovine collagen scaffolds support reproducible cell colonization and a significant increase in the number of viable cells during cultivation. The results are comparable with the viability and proliferation rate of cells grown on porcine reference materials. With regard to biochemical degradability, all tested materials showed comparable resistance to enzymatic degradation in vitro. Due to imitating the natural tendon structure the new scaffold material is supposed to provide beneficial effects in future clinical application.

In Vivo Evaluation of Different Collagen Scaffolds in an Achilles Tendon Defect Model

“…Before animal testing, the scaffold material was tested in vitro, showing promising biomechanical and cell biological properties [ 25 ]. The biomechanical data of the test material used in the present study were superior to the DX Reinforcement Matrix material and were in the range of the GraftJacket allograft [ 8 ].…”

“…In the present study, we used two patches of the control material which differed in their mechanical properties, resulting in high standard deviations in vitro. Also the means of stiffness and tensile modulus were about three times higher compared to the control material [ 25 ]. Due to high costs and long delivery times of the commercial control material, the patches were used for both in vitro and in vivo trials to save time and material.…”

“…Two collagen scaffold materials were evaluated. As the test material, a newly developed scaffold based on bovine collagen was used, as described previously [ 25 ]. Briefly, for scaffold preparation, bovine dermal collagen was treated chemically with NaOH, H 2 O 2 , and HCl in order to remove noncollagenous proteins, fatty acids, and cells and to inactivate viruses.…”

“…As we used samples from new charges, we repeated the initial biomechanical testing [ 25 ] according to Barber and Aziz-Jacobo [ 8 ]. Before animal testing, additionally a suture retention test was performed according to Barber and Aziz-Jacobo [ 8 ].…”

“…Therefore, we have developed a new scaffold material, based on bovine collagen and a chemical cross-linking process. The material has been already tested in vitro and showed favorable biomechanical, biochemical, and cell biological properties [ 25 ]. In the present pilot animal study, the newly introduced bovine collagen scaffold was investigated with regard to functional outcomes and remodeling using an Achilles tendon defect model in rats.…”