3D fractal topography attenuates inflammation and confers resilience to glomerular podocytes

In vivo, podocytes wrap around a looping capillary forming interdigitations required to establish a barrier function in kidney filtration. Cultured human podocytes can mimic key in vivo disease-associated changes—such as junctional and cytoskeletal remodeling, but their intricate, self-similar 3D branching structure remains poorly understood and technically difficult to replicate in vitro, especially in the context of inflammatory injury. Here, we established 3D fractal hemispheres capturing key features of glomerular architecture using nanoscale two-photon polymerization (2PP), enabling a detailed investigation into the effects of 3D topographies with various fractal indices on podocyte morphology and function. Podocytes cultured on intermediate fractal hemispheres, exhibited enhanced cytoskeletal branching, increased expression of slit diaphragm markers, and upregulation of nephrogenesis-related genes. To explore cellular responses to inflammatory stimuli by TNF-α and IL-6, we established a culture of fluorescently labelled podocytes within otherwise optically silent monolayer. The changes of single podocyte structure, fractal dimension and RNA sequencing revealed that podocytes grown on intermediate fractal hemispheres exhibited an enhanced immunosuppressive response, highlighting the potential of fractal topological structures in mitigating inflammation induced podocyte damage and kidney disease progression. A co-culture system with reporter THP-1-derived macrophages demonstrated a pronounced shift toward the M1 macrophage phenotype and heightened activation of inflammation pathways when podocytes were co-cultured on smooth hemispheres, compared to those on intermediate fractal hemispheres. These findings suggest that fractal microenvironments may play a crucial role in modulating podocyte-macrophage interactions and inflammatory responses in kidney disease.