Mapping the tumor microenvironment response to bone mineral content

Decreased mineral density is a risk factor for skeletal pathologies including bone metastasis, the leading cause of mortality in patients with advanced breast cancer, but the underlying mechanisms are poorly understood. While reduced mineral density can drive pathological bone remodeling via direct effects on select cell types, indirect effects due to broad changes of the microenvironment may be similarly important. However, how bone mineral content affects microenvironmental heterogeneity remains to be elucidated. Here, we leverage decellularized bone matrices with varied mineral content in combination with single-cell RNA-sequencing to study how reduced bone mineral content affects microenvironmental complexity and tumor growth. We performed single-cell RNA sequencing on implanted decellularized bovine bone scaffolds in which the mineral was either maintained at physiological levels or removed to simulate scenarios of impaired bone mineralization as, for example, present during aging. Using this approach, we explored the heterogeneous stromal response to varied bone mineral content in both an immunocompromised and immunocompetent, syngeneic mouse model in the presence and absence of cancer cells.