Fabrication of Bioactive Inverted Colloidal Crystal Scaffolds Using Expanded Polystyrene Beads

Bone Marrow Adipocytes Contribute to Tumor Microenvironment-Driven Chemoresistance via Sequestration of Doxorubicin

Chemoresistance is a significant problem in the effective treatment of bone metastasis. Adipocytes are a major stromal cell type in the bone marrow and may play a crucial role in developing microenvironment-driven chemoresistance. However, detailed investigation remains challenging due to the anatomical inaccessibility and intrinsic tissue complexity of the bone marrow microenvironment. In this study, we developed 2D and 3D in vitro models of bone marrow adipocytes to examine the mechanisms underlying adipocyte-induced chemoresistance. We first established a protocol for the rapid and robust differentiation of human bone marrow stromal cells (hBMSCs) into mature adipocytes in 2D tissue culture plastic using rosiglitazone (10 μM), a PPARγ agonist. Next, we created a 3D adipocyte culture model by inducing aggregation of hBMSCs and adipogenesis to create adipocyte spheroids in porous hydrogel scaffolds that mimic bone marrow sinusoids. Simulated chemotherapy treatment with doxorubicin (2.5 μM) demonstrated that mature adipocytes sequester doxorubicin in lipid droplets, resulting in reduced cytotoxicity. Lastly, we performed direct coculture of human multiple myeloma cells (MM1.S) with the established 3D adipocyte model in the presence of doxorubicin. This resulted in significantly accelerated multiple myeloma proliferation following doxorubicin treatment. Our findings suggest that the sequestration of hydrophobic chemotherapeutics by mature adipocytes represents a potent mechanism of bone marrow microenvironment-driven chemoresistance.

Colloidal systems toward 3D cell culture scaffolds

Three-dimensional porous scaffolds are essential for the development of tissue engineering and regeneration, as biomimetic supports to recreate the microenvironment present in natural tissues. To successfully achieve the growth and development of a specific kind of tissue, porous matrices should be able to influence cell behavior by promoting close cell-cell and cell-matrix interactions. To achieve this goal, the scaffold must fulfil a set of conditions, including ordered interconnected porosity to promote cell diffusion and vascularization, mechanical strength to support the tissue during continuous ingrowth, and biocompatibility to avoid toxicity. Among various building approaches to the construction of porous matrices, selected strategies afford hierarchical scaffolds with such defined properties. The control over porosity, microstructure or morphology, is crucial to the fabrication of high-end, reproducible scaffolds for the target application. In this review, we provide an insight into recent advances toward the colloidal fabrication of hierarchical scaffolds. After identifying the main requirements for scaffolds in biomedical applications, conceptual building processes are introduced. Examples of tissue regeneration applications are provided for different scaffold types, highlighting their versatility and biocompatibility. We finally provide a prospect about the current state of the art and limitations of porous scaffolds, along with challenges that are to be addressed, so these materials consolidate in the fields of tissue engineering and drug delivery.