Biomechanics of biomaterial have broadly been shown to influence differentiation of progenitor and stem cells in both, 2D and 3D conditions. Little attention has so far been drawn on the effect of material stiffness on cellular infiltration into dense materials. However, migration into a matrix is important for tissue engineering using scaffolds or hydrogels to fill defects and support tissue formation and regeneration.

We have recently developed a biomaterial for focal articular cartilage regeneration (AuriScaff [1]) fulfilling the requirements of the highly loaded environment inside the joint. The material is based on bovine auricular cartilage and is dense but porous due to the removal of elastic fibers using a combination of enzymes including elastase. Chondrocytes as well as adipose derived stromal cells (ASCs) were able to infiltrate the 400µm thick material within a few day. The cells were further stimulated towards the chondrogenic lineage within an animal model, revealing that the material provides optimal preconditions for cartilage regeneration.

By using different treatment protocols based on a graded series of enzymes, we were able to generate scaffolds of varying stiffness and glycosaminoglycan content. Despite all of the scaffold versions had the same porous structure, the infiltration of cells varied according to the matrix treatment with higher infiltration in the softer materials. Differences between the cell types were found, whereas ASCs were penetrating the material faster than chondrocytes. Different mechanical tests (e.g. compression tests) and cell imaging tools (cell transduction, cell tracking and live cell imaging) were used to characterize the relation between material properties and cellular behavior.

The auricular cartilage scaffold, AuriScaff, is a mechanically tunable matrix with constant porosity that allows to investigate the influence of material stiffness on cellular infiltration into a dense collagen matrix.

[1] S. Nürnberger et al., 'Repopulation of an auricular cartilage scaffold, AuriScaff, perforated with an enzyme combination', Acta Biomater., vol. 86, pp. 207–222, 2019.