Modeling Inflammaging of the Bone Marrow Microenvironment Stimulates Multiple Myeloma Associated Stem Cells

Abstract

Background: Multiple Myeloma (MM) is a malignancy of mature plasma cells, primarily affecting those over 65, with a 5-year survival rate of ~62%. Aging alters the bone marrow (BM) microenvironment, including remodeling of the extracellular matrix (ECM), which may promote tumor-supportive functions of mesenchymal stromal cells (MSCs) and hematopoietic stem cells (HSCs). However, determining the impact of aging-related matrix remodeling on MM onset/progression remains challenging due to the absence of microphysiological systems that preserve the tumorigenic phenotype of MM cells in vitro. We hypothesize recapitulating aged BM ECM may overcome these limitations by providing a physiologically relevant framework that sustains MM cell behavior and models the tumor-supportive microenvironment. Additionally, interleukin-6 (IL-6), an inflammatory cytokine elevated in both the inflammaging BM microenvironment and MM, preferentially expands MM-associated MSCs without affecting HSCs. Methods: Cryopreserved tumor-associated MSCs and HSCs were cultured on tissue culture plastic (TCP), young ECM (≤25 y/o), or aged ECM (≥60 y/o), in either α-MEM or IMDM media, with some cultures supplemented with IL-6. HSC cluster formation was observed, and cells were analyzed using cytospin with Giemsa-May-Grünwald staining. Results: MM-derived HSCs, cultured on aged ECM, exhibited myelopoietic skewing. In contrast, young ECM with IL-6 promoted MSC expansion, suggesting a synergistic effect in developing patient-derived stromal models. Adherent MSCs were harvested and expanded on TCP for ECM generation. Conclusion: ECM-based microphysiological systems offer a promising platform for scalable, in vitro systems that recapitulate aging- and MM-associated remodeling of the BM microenvironment. Understanding how aged ECM drives myeloid skewing may reveal therapeutic targets to delay/prevent MM progression. The observed myeloid bias in MM-derived HSCs cultured on aged ECM may reflect physiologically relevant disruptions in immunoregulatory cell populations. Future work will test whether ECM from MM patient-derived MSCs preserves tumor-specific phenotypes to advance translational models for MM drug discovery.