A leading cause of long-term disability, ischemic stroke results in bone loss and higher fracture risk than with typical aging, yet underlying causes remain poorly understood and cannot be explained solely by disuse. Inflammation may contribute, as other inflammatory conditions like arthritis also experience marked bone loss. Circulating inflammatory cytokines are elevated weeks to months following stroke, but whether cytokine dysregulation is a driving factor for altered bone remodeling following stroke is unknown. Microdevices and “organ-on-chip” constructs are effective 3D in vitro platforms for mechanistically probing cell-cell interactions in controlled microenvironments. Such microdevices have enabled study of different bone niches with pharmaceuticals, radiation, and genetic disorders but have not previously been used to examine mineralized bonevascular interactions.

This dissertation aims to examine whether inflammatory factors may contribute to stroke-related bone loss by developing a bone-vascular microdevice platform mimicking the mineralized bone microenvironment. We determined optimal manufacturing conditions for producing a mineralized extracellular matrix scaffold for osteoblast support in the microdevice using a freeze-drying method and passive mineralization. This scaffold was biocompatible with mesenchymal stem cells and promoted alkaline phosphatase activity indicative of osteoblast differentiation. Microdevices were successfully fabricated using polydimethylsiloxane set in 3D-printed molds and supported co-culture of endothelial cells (bottom channel) and mesenchymal stem cells grown on the optimized scaffold (top channel). Using this device, we identified pro-bone remodeling gene expression in static cocultures and quiescent endothelium/pro-bone formation gene expression in dynamic culture in responses to stroke-related inflammatory cytokines. These results highlight differences between in vitro models in investigating complex cell interactions. Finally, we identified several pathways that are dysregulated in bone using a mouse model of stroke and spatial mass spectrometry. Dysregulated pathways exhibited co-localized metabolites, primarily located in the endosteal region of bone, suggesting complex pathway interactions. These results revealed targets to probe mechanistically in future studies to advance understanding of complex bone-vascular interactions in stroke-related bone loss, with the ultimate goal of informing better treatment strategies to mitigate bone fragility.