Development of bone cell microarrays in microfluidic chips for studying osteocyte-osteoblast communication under fluid flow mechanical loading

Bone tissue remodels throughout life in response to mechanical loads. Impaired activities of bone cells (osteocytes, osteoblasts and osteoclasts) result in a disruption of the bone remodelling cycle, which eventually leads to bone disorders such as osteoporosis. To develop efficient therapeutic strategies against bone disorders, new tools are needed to unravel the bone remodelling cycle at the molecular level. Here, we developed a microfluidic platform, which should allow understanding the bone remodelling cycle in much more detail and ultimately be used to discover new therapeutic compounds. We focused specifically on studying cell-cell communication between osteocytes and osteoblasts cells via connexin 43-gap junctions. Therefore, a new cell printing method was developed to create living cellular bone cell arrays in a microfluidic channel. Several cell printing designs where osteocytes and osteoblasts heterotypically interacted at localized interfaces were evaluated. Physical contacts between the bone cells were characterized at high resolution by correlative atomic force microscopy (AFM)-fluorescence microscopy. We demonstrated that the platform is compatible with single-cell mechanostimulation by AFM nanoindentation and subsequent fluorescent analysis of the mechanoresponse. As a proof of concept, we showed the functionality of the platform by analysing the induced in vivo-like Ca++ wave in the printed osteocyte-osteoblast network upon mechanical stimulation by fluid flow shear stress.

Automated summary

Bone tissue constantly remodels in response to mechanical loads, and disruptions in bone cell activities can lead to disorders like osteoporosis. To understand and develop therapeutic strategies for bone disorders, a microfluidic platform was developed to study the bone remodelling cycle at a molecular level. The platform utilized a cell printing method to create living bone cell arrays in a microfluidic channel, enabling the study of cell-cell communication between osteocytes and osteoblasts. High-resolution characterization of physical contacts was achieved using correlative atomic force microscopy (AFM) and fluorescence microscopy. The platform also demonstrated compatibility with single-cell mechanostimulation and analysis of mechanoresponse.