Despite the wide variety of existing therapies, multiple myeloma (MM) remains a disease with dismal prognosis. Choosing the right treatment for each patient remains one of the major challenges. A new approach being explored is the use of ex vivo models for personalized medicine. Two-dimensional culture or animal models often fail to predict clinical outcomes. Three-dimensional ex vivo models using patients’ bone marrow (BM) cells may better reproduce the complexity and heterogeneity of the BM microenvironment. Here, we review the strengths and limitations of currently existing patient-derived ex vivo three-dimensional MM models. We analyze their biochemical and biophysical properties, molecular and cellular characteristics, as well as their potential for drug testing and identification of disease biomarkers. Furthermore, we discuss the remaining challenges and give some insight on how to achieve a more biomimetic and accurate MM BM model. Overall, there is still a need for standardized culture methods and refined readout techniques. Including both myeloma and other cells of the BM microenvironment in a simple and reproducible three-dimensional scaffold is the key to faithfully mapping and examining the relationship between these players in MM. This will allow a patient-personalized profile, providing a powerful tool for clinical and research applications.

Multiple myeloma (MM), the third most frequent hematological cancer worldwide, is characterized by the proliferation of neoplastic plasma cells in the bone marrow (BM). One of the hallmarks of MM is a permissive BM microenvironment. Increasing evidence suggests that cell-to-cell communication between myeloma and immune cellsviatumor cell-derived extracellular vesicles (EV) plays a key role in the pathogenesis of MM. Hence, we aimed to explore BM immune alterations induced by MM-derived EV. For this, we inoculated immunocompetent BALB/cByJ mice with a myeloma cell line, MOPC315.BM, inducing a MM phenotype. Upon tumor establishment, characterization of the BM microenvironment revealed the expression of both activation and suppressive markers by lymphocytes, such as granzyme B and PD-1, respectively. In addition, conditioning of the animals with MOPC315.BM-derived EV, before transplantation of the MOPC315.BM tumor cells, did not anticipate the disease phenotype. However, it induced features of suppression in the BM milieu, such as an increase in PD-1 expression by CD4+ T cells. Overall, our findings reveal the involvement of MOPC315.BM-derived EV protein content as promoters of immune niche remodeling, strengthening the importance of assessing the mechanisms by which MM may impact the immune microenvironment.

Preclinical models for multiple myeloma (MM) often fail to recapitulate the complexity of the bone marrow (BM) microenvironment, limiting their utility for drug testing and translational research. There is an urgent need for physiologically relevant, patient-adaptable platforms to support personalized therapeutic evaluation. We developed BioMarrow, a 3D ex vivo BM culture system using unmanipulated patient BM aspirates embedded in Matrigel. Culture conditions were optimized to sustain diverse hematopoietic, stromal and immune populations for up to 7 days. Spatial distribution, cytokine secretion and treatment responses were assessed via flow cytometry, immunohistochemistry, multiplex ELISA and cell viability assays. The model maintained key BM components characteristics of MM, supported stromal network formation and preserved cytokines such as IL-6 and TGF-β. Immune-effector cytokines were reduced, consistent with a tumour-permissive microenvironment. Drug testing with MM cell lines confirmed BioMarrow's ability to discriminate treatment sensitivity. BioMarrow captures essential features of the MM niche and offers a clinically relevant, short-term platform for ex vivo therapeutic screening. Its scalability and immune component preservation support future integration into personalized treatment workflows, including immunotherapy evaluation.