Sex-stratified osteochondral organ-on-chip model reveals sex-specific responses to inflammatory stimulation.

Osteoarthritis (OA) is a musculoskeletal degenerative disease characterized by alterations in cartilage and subchondral bone leading to impaired joint function. OA disproportionally affects females more than males, yet the molecular mechanisms underlying these biological sex differences remain elusive. Current therapeutic strategies to halt the progression of OA are still lacking, in part due to the limited predictive potential of standard models which often do not account for sex disparities. Herein, an organ-on-chip microfluidic platform was developed to model the osteochondral unit, composed of adjacent bone and cartilage culture chambers, and capture sex-specific hallmarks of OA. Sex-stratified human primary chondrocytes and osteoblasts were compartmentalized within biomimetic hydrogels emulating the bone-cartilage interface, which were subjected to inflammatory triggers to mimic the onset of OA. We confirmed that interleukin-1β and Tumor Necrosis Factor-α stimulation triggered upregulation of pro-inflammatory cytokines and matrix metalloproteinases related genes in all donors, with marginal trends for increased expression in female cells. In addition, metabolic labeling coupled with confocal imaging revealed that inflammatory stimulation modulated extracellular matrix deposition by human chondrocytes in a sex-specific fashion. Not only matrix deposition but also matrix remodeling was altered upon inflammation, leading to a significant reduction in matrix stiffness in both cartilage and bone compartments. Overall, sex-stratified osteochondral unit on-chips offer novel insights into sex-specific cellular responses to inflammatory insults, demonstrating the importance of incorporating sex stratification in emergent organ-on-chip models. Thus, this platform provides a physiologically relevant 3D microenvironment to further investigate sex-specific drivers of OA, paving the way for targeted therapies.