Megakaryocytes (MK) in the bone marrow (BM) are immersed in a network of extracellular matrix components that regulates platelet release into the circulation. Combining biological and bioengineering approaches, we found that the activation of transient receptor potential cation channel subfamily V member 4 (TRPV4), a mechano-sensitive ion channel, is induced upon MK adhesion on softer matrices. This response promoted platelet production by triggering a cascade of events that lead to calcium influx, β1 integrin activation and internalization, and Akt phosphorylation, responses not found on stiffer matrices. Lysyl oxidase (LOX) is a physiological modulator of BM matrix stiffness via collagen crosslinking. In vivo inhibition of LOX and consequent matrix softening lead to TRPV4 activation cascade and increased platelet levels. At the same time, in vitro proplatelet formation was reduced on a recombinant enzyme-mediated stiffer collagen. These results suggest a novel mechanism by which MKs, through TRPV4, sense extracellular matrix environmental rigidity and release platelets accordingly

Developing green and nontoxic biomaterials, derived from renewable sources and processable through 3D bioprinting technologies, is an emerging challenge of sustainable tissue engineering. Here, pectin from citrus peels was cross-linked for the first time with (3-glycidyloxypropyl)­trimethoxysilane (GPTMS) through a one-pot procedure. Freeze-dried porous pectin sponges, with tunable properties in terms of porosity, water uptake, and compressive modulus, were obtained by controlling GPTMS content. Cell experiments showed that GPTMS did not affect the cytocompatibility of pectin. The addition of GPTMS improved the printability of pectin due to an increase of viscosity and yield stress. Three-dimensional woodpile and complex anatomical-shaped scaffolds with interconnected micro- and macropores were, therefore, bioprinted without the use of any additional support material. These results show the great potential of using pectin cross-linked with GPTMS as biomaterial ink to fabricate patient-specific scaffolds, which could be used to promote tissue regeneration in vivo.

The aim of this study is the analysis and characterization of a hydrolyzed keratin-based biomaterial and its processing using electrospinning technology to develop in vitro tissue models. This biomaterial, extracted from poultry feathers, was mixed with type A porcine gelatin and cross-linked with γ-glycidyloxy-propyl-trimethoxy-silane (GPTMS) to be casted initially in the form of film and characterized in terms of swelling, contact angle, mechanical properties, and surface charge density. After these chemical-physical characterizations, electrospun nanofibers structures were manufactured and their mechanical properties were evaluated. Finally, cell response was analyzed by testing the efficacy of keratin-based structures in sustaining cell vitality and proliferation over 4 days of human epithelial, rat neuronal and human primary skin fibroblast cells.