A collagen-based interface construct for the assessment of cell-dependent mechanical integration of tissue surfaces

Abstract

The interface between any newly engineered tissue and pre-existing tissue is of great importance to tissue engineering; however, this process has so far been largely ignored, with few reports regarding the mechanical strength of newly integrated connective tissues surfaces. A new model system has been developed to generate a well-defined interface between two collagen lattices: one pre-contracted by resident fibroblasts and the other a cell-free wrapping gel. This construct can be cultured for prolonged periods (>2 weeks) and can also be fitted onto a mechanical testing system to measure the interface adhesive strength at the end of the culture time. Interface adhesive strength shows a six-fold increase after 1 week in culture, compared with the time-zero baseline. Observations of cell migration across the interface suggest that cell translocation in the three-dimensional matrix might play an important role in the integration process. In this new controlled geometry, normal and shear stresses at the interface can be analysed by finite element modelling and the areas at which debonding starts can be defined. The current experimental design permits solid multiple (homogeneous or heterogeneous) interface formation in vitro with a well-defined geometry and the possibility of measuring mechanical linkage. This design should enable many other factors affecting cell-driven interface strengthening to be investigated.

Engineering extracellular matrix structure in 3D multiphase tissues

“…The slabs were glued on acrylic platens, and then “bonded” to each other using a small volume of collagen gelled (equivalent to ~50 µm-thick layer of iECM) at two different concentrations and two gelling temperatures. Similar setups have been used previously to measure the bond strength of tissue adhesives and cell-mediated interfacing of collagen-based ECMs [24, 25, 27, 28]. Because we expected the crosslinked alginate in the composite pECM would prevent failure within the pECM slabs (since these composite gels are more robust than pure collagen matrices), we expected failure to always occur in the iECM phase.…”

“…Based on previous setups to study collagen gel adhesion [24, 25], we built a custom mechanical testing apparatus. This device consisted of a media bath container (machined from acrylic) attached to a motorized stage, with a load cell fixed at one end (see Fig.…”

Engineering Hydrogels as Extracellular Matrix Mimics

“…Microscale engineering is a method that can be used to control the cellular microenvironment [48,110–114] and has the potential to construct matrices mimicking the inhomogeneous and anisotropic properties of native tissues [48,115–117]. In addition, this method can also be applied to modify and control cell–cell and cell–ECM interactions [113].…”

Topographical guidance of 3D tumor cell migration at an interface of collagen densities

“…There have been several attempts to generate 3D gels containing a heterogeneous interface, including the use of synthetic gel constructs [16, 17] and nested collagen matrices [18, 19]. However, both methods do present limitations.…”

“…While synthetic constructs are easily tunable, cells are unable to migrate through them [17] unless engineered cleavable sites are introduced [16]. Nested collagen gels can provide an interface, however their fabrication requires both mechanical collagen compaction and significant time in culture [18, 19]. As such, their microarchitecture and mechanical properties are hard to control.…”