Introduction

PIEZO mechanoreceptors are increasingly recognized to play critical roles in fundamental physiological processes like proprioception, touch, or tendon biomechanics. However, their gating mechanisms and downstream signaling are still not completely understood, mainly due to the lack of effective tools to probe these processes. Here, we developed new tailor-made nanoswitches enabling wireless targeted actuation on PIEZO1 by combining molecular imprinting concepts with magnetic systems.

Tendon and ligament tissues are fascinating in their simplistic appearance of tissue architecture coupled with outstanding biomechanical properties. In the last decade, the mechanisms governing their development, degenerative disease progression and step-wise repair process are becoming better understood. In this talk, I will present an overview of our basic research work on these following points. (i) Tendon generation: I will discuss our finding on the role of growth and biomechanical factors influencing tendon stem/progenitor cells; (ii) Tendon degeneration: I will provide evidences how disturbed cell-cell and cell-matrix contacts are involved in loss of tissue integrity; (iii) Tendon regeneration: I will present in vivo data on the application and performance of various cell populations in tendon repair

Summary. 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 interaction of cells with nanotopographical features has proven to be an important signaling modality in controlling MSC differentiation. Introduction. 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

We have developed an animal model to examine the formation of heterotopic ossification using standardised muscular damage and implantation of a beta-tricalcium phosphate block into a hip capsulotomy wound in Wistar rats. The aim was to investigate how cells originating from drilled femoral canals and damaged muscles influence the formation of heterotopic bone. The femoral canal was either drilled or left untouched and a tricalcium phosphate block, immersed either in saline or a rhBMP-2 solution, was implanted. These implants were removed at three and 21 days after the operation and examined histologically, histomorphometrically and immunohistochemically.

Bone formation was seen in all implants in rhBMP-2-immersed, whereas in those immersed in saline the process was minimal, irrespective of drilling of the femoral canals. Bone mineralisation was somewhat greater in the absence of drilling with a mean mineralised volume to mean total volume of 18.2% (sd 4.5) versus 12.7% (sd 2.9, p < 0.019), respectively.

Our findings suggest that osteoinductive signalling is an early event in the formation of ectopic bone. If applicable to man the results indicate that careful tissue handling is more important than the prevention of the dissemination of bone cells in order to avoid heterotopic ossification.

The treatment of bony defects of the tibia at the time of revision total knee replacement is controversial. The place of compacted morsellised bone graft is becoming established, particularly in contained defects. It has previously been shown that the initial stability of impaction-grafted trays in the contained defects is equivalent to that of an uncemented primary knee replacement. However, there is little biomechanical evidence on which to base a decision in the treatment of uncontained defects. We undertook a laboratory-based biomechanical study comparing three methods of graft containment in segmental medial tibial defects and compared them with the use of a modular metal augment to bypass the defect.

Using resin models of the proximal tibia with medial defects representing either 46% or 65% of the medial cortical rim, repair of the defect was accomplished using mesh, cement or a novel bag technique, after which impaction bone grafting was used to fill the contained defects and a tibial component was cemented in place. As a control, a cemented tibial component with modular metal augments was used in identical defects. All specimens were submitted to cyclical mechanical loading, during which cyclical and permanent tray displacement were determined.

The results showed satisfactory stability with all the techniques except the bone bag method. Using metal augments gave the highest initial stability, but obviously lacked any potential for bone restoration.