Developing a Novel Vascularized Bone Microdevice for Investigating the Post-Stroke Bone Microenvironment

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PROJECT SUMMARY Ischemic stroke is a serious condition affecting nearly 800,000 people in the United States annually and is a leading cause of long-term disability. Although stroke survivors commonly experience accelerated bone loss and higher fracture risk compared to typically aging adults, the underlying causes remain poorly understood and cannot be explained solely by bedrest. Inflammatory cytokines are present in serum post-stroke, but whether cytokine dysregulation is a driving factor for altered bone remodeling following stroke – as seen in inflammatory- related bone loss in other conditions like arthritis – is unknown. Our primary hypothesis is that the inflammatory environment seen post-stroke stimulates a pro-inflammatory response in bone vasculature that acts to suppress osteoblast activity and drive an increase in secreted proteins to activate bone resorptive programs. Microdevices and “organ-on-chip” constructs are effective 3D in vitro platforms for mechanistically probing different cell-cell interactions in controlled microenvironments. Such microdevices have been used successfully to examine the response of different niches within bone to pharmaceuticals, radiation, and genetic disorders, but they have not yet been used to examine mineralized bone and vascular interactions. The overall goal of this project is to expand understanding of underlying factors contributing to stroke-related bone loss, specifically inflammatory factors, by developing and implementing a bone-vascular microdevice platform that mimics the mineralized bone microenvironment. Aim 1 will determine optimal manufacturing conditions for producing a mineralized extracellular matrix (ECM) scaffold for osteoblast support in the microdevice. Aim 2 will develop the novel bone- vascular microdevice platform and investigate osteoblast-endothelial cell interactions under homeostatic conditions. Aim 3 will determine the effects of inflammatory cytokines interleukin-6, interleukin-1β, and interferon- γ on osteoblast-endothelial paracrine signaling using the microdevice platform. We will accomplish these aims by leveraging traditional ECM scaffold fabrication techniques with passive mineral deposition, computational fluid dynamics modeling of fluidic shear and nutrient transport, and biological assays of osteoblast activity and vascular barrier function. This work will create a new in vitro platform that enables mechanistic probing of complex bone-vascular interactions and advance understanding of inflammatory regulation of bone loss post- stroke, thereby providing a framework that may inform better treatment strategies to mitigate stroke-related bone fragility.