NANOSTRUCTURED MATERIALS: A NEW APPROACH TO DESIGN INNOVATIVE SCAFFOLDS FOR THE TREATMENT OF BONE DEFECTS

ntroduction The wide bone defects, caused by trauma, tumor, infectious, periprosthetic osteolysis, need to be surgically treated because their low potential of repair. Nowadays the bone allograft and autograft represent 80% of all transplantation done in the world. However this technique shows many disadvantages, such as the risk of infections, the immunological rejection, the low bone availability and the high costs. These reasons have motivated extensive research to find alternative strategies. As shown in literature, the future strategies are based on the synergic combination of different methodologies: use of biomimetic scaffold in order to support bone regeneration, use of mesenchymal stromal cells (MSCs) and growth factors. Successful regeneration necessitates the development of tissue-inducing scaffolds that mimic the hierarchical architecture of native tissue extracellular matrix (ECM). Cells in nature recognise and interact with the surface topography they are exposed to via ECM proteins. Here we are going to show the guidelines recently published for the design and development of nanostructured scaffolds for the bone regeneration, and the morphofunctional changing of MSCs interacting with nanogratings. Methods Aim of this study is to design, develop and preclinical test PET nanostructured scaffolds for the transplantation and differentiation of MSCs in the treatment of bone defects. The first step of our study was the extraction of patient's bone marrow and the isolation of MSCs. After characterizing (demonstrating the typical cell surface markers) and isolating the MSCs were cultivated on the PET substrates. The PET nanosubstrates were obtained by a low temperature embossing lithography (HEL) achieving low-damage nanotopographic surface modifications. After MSC cultivation on PET substrates we made a cytotoxicity evaluation, an optic and confocal microscopic evaluation (cells adhesion, cells polarization…) and tests to optimise cell differentiation towards osteogenic fate. Results PET is a highly suitable thermo-plastic material, able to sustain the necessary methods to obtain nanostructured substrates. MSCs cultivated on nanostructured PET rapidly align with the direction of the nanostructure itself without any cytotoxic effects. After the cultivation on the nanostructures, MSCs sustained cytoskeleton changes suggesting the activation of intracellular signaling (mechanotrasduction) promoting osteogenesis. Discussion The mechanisms by which nanotopographic cues influence stem cell proliferation and differentiation appear to involve changes in cytoskeletal organization and structure, potentially in response to the geometry and size of the underlying features of the ECM by a process called mechanotrasduction. The interaction of cells with nanotopographical features such as pores, ridges, groves, fibers, nodes, and their combinations has proven to be an important signaling modality in controlling cellular processes. Integrating nanotopographical cues is especially important in engineering complex tissues that have multiple cell types and require precisely defined cell-cell and cell-matrix interactions at the nanoscale. Thus, in the next-generation regenerative engineering approaches, nanoscale materials/scaffolds are expected to play a parimary role in controlling MSC fate and the consequent regenerative capacity. We believe that the continuous development of nanotechnology and deeply comprehension of how mechanical inputs can affect cell biology is fundamental to design the future scaffold for orthopedic application