Development of solvent-casting particulate leaching (SCPL) polymer scaffolds as improved three-dimensional supports to mimic the bone marrow niche.

The need for new approaches to investigate ex vivo the causes and effects of tumor and to achieve improved cancer treatments and medical therapies is particularly urgent for malignant pathologies such as lymphomas and leukemias, whose tissue initiator cells interact with the stroma creating a three-dimensional (3D) protective environment that conventional mono- and bi-dimensional (2D) models are not able to simulate realistically. The solvent-casting particulate leaching (SCPL) technique, that is already a standard method to produce polymer-based scaffolds for bone tissue repair, is proposed here to fabricate innovative 3D porous structures to mimic the bone marrow niche in vitro. Two different polymers, namely a rigid polymethyl methacrylate (PMMA) and a flexible polyurethane (PU), were evaluated to the purpose, whereas NaCl, in the form of common salt table, resulted to be an efficient porogen. The adoption of an appropriate polymer-to-salt ratio, experimentally defined as 1:4 for both PMMA and PU, gave place to a rich and interconnected porosity, ranging between 82.1 vol% and 91.3 vol%, and the choice of admixing fine-grained or coarse-grained salt powders allowed to control the final pore size. The mechanical properties under compression load were affected both by the polymer matrix and by the scaffold's architecture, with values of the elastic modulus indicatively varying between 29 kPa and 1283 kPa. Preliminary tests performed with human stromal HS-5 cells co-cultured with leukemic cells allowed us to conclude that stromal cells grown associated to the supports keep their well-known protective and pro-survival effect on cancer cells, indicating that these devices can be very useful to mimic the bone marrow microenvironment and therefore to assess the efficacy of novel therapies in pre-clinical studies.

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