Papers by Author: Simone Vesentini

Abstract: It is well-known that cellular behavior can be guided by chemical signals and physical interactions at the cell-substrate interface. The patterns that cells encounter in their natural environment include nanometer-to-micrometer-sized topographies comprising extracellular matrix, proteins, and adjacent cells. Whether cells transduce substrate rigidity at the microscopic scale (for example, sensing the rigidity between adhesion sites) or the nanoscopic scale remains an open question. Here we report that micromolded elastomeric micropost arrays can decouple substrate rigidity from adhesive and surface properties. Arrays of poly (dimethylsiloxane) (PDMS) microposts from microfabricated silicon masters have been fabricated. To control substrate rigidity they present the same post heights but different surface area and spacing between posts. The main advantage of micropost arrays over other surface modification solutions (i.e. hydrogels) is that measured subcellular traction forces could be attributed directly to focal adhesions. This would allow to map traction forces to individual focal adhesions and spatially quantify subcellular distributions of focal-adhesion area, traction force and focal-adhesion stress. Moreover, different adhesion intracellular pathways could be used by the cells to differentiate toward a proliferative or a contractile cellular phenotype, for instance. This particular application is advantageous for vascular tissue engineering applications, where mimicking as close as possible the vessels dynamics should be a step forward in this research field.

Abstract: One of the merging methods to produce tissue-engineered vascular substitutes is to process scaffolds to direct the regeneration of vascular tissues. Collagen, as one of the main protein in the vascular extracellular matrix, is one of biopolymers that exhibits a major potential for scaffold technology. However, gels made from reconstituted collagen generally exhibit poor mechanical properties and limited manipulability. Therefore, adding a reinforcement to the scaffold to make the structure resist to the physiological constraints applied during the regeneration represents a valid alternative. Silk fibroin is an interesting reinforcing candidate being a mechanically strong natural fibre, susceptible to proteolytic degradation in vivo and showing acceptable biological performances. Therefore, the aim of this study was to develop a model of a composite scaffold obtained by controlling the filament geometry winding of silk fibroin in the collagen gel. A finite element model taking into account the orthotropic elasticity of arteries has been combined with classic laminate theory applied to the filament winding of a tubular vessel. The design of the small structure susceptible to scaffold the vascular tissue regeneration was optimised by mean of an evolutive algorithm with the imperative to mimic the experimentally measured mechanical properties (compliance) of a native artery.

Abstract: Collagen is the most used naturally occurring scaffold material. It’s a structural protein ubiquitous among mammalian. The ability of collagen type I to host different cell phenotype in vitro and its low antigenecity in vivo are well known. However, the principal drawback of collagenbased materials consists in their low mechanical properties. For vascular tissue engineering this represents a major limit, as the aim is to mimic the structure of a native vessel, which is known to be resistant and viscoelastic. Moreover, vascular cells are known to be susceptible in vivo to reorganize the matrix in which they proliferate. Therefore, the aim of this project is to study the micro structural organization of collagen-based scaffolds, and to assess the interactions between collagen and smooth muscle cells during regeneration. This knowledge will then allow the development of appropriate strategies to tailor the microstructure of the scaffold and its properties. Smooth muscle cells (SMCs) were selected to study the interactions between cells and matrix during the proliferation. Atomic Force Microscopy (AFM) in dry state in tapping mode and Confocal Laser Scanning Microscopy (CLSM) in reflection mode were used to investigate the microstructure of the scaffold. For the former technique cells were seeded on top of the collagen gel after jellification, while for the latter, cells were embedded into the collagen gel and stained with Rhodamine. The contact points between matrix and cells were investigated, as well as the capacity of vascular cells to induce a structural reorganization of collagen fibrils in the scaffold.