MICROENGINEERING OF BONE

Bone tissue exhibits exceptional structural and cellular complexity, rooted in its diverse population of specialized cells, hierarchically organized and dynamic extracellular matrix (ECM), and extensive vascular and neural networks. To faithfully model bone physiology and pathology in vitro, it is essential to integrate the critical components that constitute native bone, and to develop platforms that enable controlled investigation of their interactions. Miniaturized in vitro bone models, or “mini-bones,” have emerged as powerful tools for mimicking native bone tissue, and probing bone regeneration and disease mechanisms under physiologically relevant conditions. These models allow precise recapitulation of physiological conditions, compatibility with high-throughput experimentation, and integration with high-content imaging techniques. In this work, we focus on a subset of mini-bone models based on spheroid formation technology, which enable the formation of three-dimensional bone-like constructs within a controlled microenvironment. Central to this approach is the incorporation of ECM-mimicking biomaterials within the spheroids. These matrices are either formed in situ through mineralization processes driven by the cells themselves, or introduced in the form of designer microparticles. The microparticles are engineered with tunable chemical and physical properties, such as composition, porosity, shape, and topography, to recapitulate the mechanical and biochemical cues of native bone ECM. Such precision-engineered elements enhance the functional relevance of the model and provide a means to systematically study ECM-mediated regulation of bone cell behavior. Another critical aspect of bone physiology is the presence of a vascular network. To address this, we present a microengineering strategy to vascularize spheroid models. Using microwell arrays, we pattern endothelial cells either on the inner or outer surfaces of the microwells to form a vascular bed that interfaces with the spheroids during culture. This configuration supports the establishment of microvasculature, which is vital for nutrient transport, cellular signaling, and tissue maturation. By integrating ECM biomimicry with engineered vascularization, these microengineered mini-bone models offer a miniaturized platform for studying bone biology, disease modeling, and regenerative strategies.