Substrate topography-induced osteogenesis of bone marrow stem cells by reducing the chromatin accessibility of YBX1

Stem cell fate is profoundly influenced by a complex interplay of biochemical and biophysical cues, with the latter increasingly recognized for its roles in cellular processes, yet the mechanisms are unclear. Since chromatin accessibility is a critical determinant in the processes of osteogenesis and bone repair, investigating the contributions of open chromatin regions (OCRs) to the intracellular signaling pathways triggered by topographical cues, which lead to osteogenic differentiation is highly valuable. This study explores the impact of the nanotopography of biomaterials on the osteogenic differentiation of human bone marrow stem cells (hBMSCs). By utilizing electrospun poly-L-lactide (PLLA) membranes with random fiber arrangements, we mimic the natural extracellular matrix (ECM) topography to study its effects on hBMSCs, contrasting them with flat PLLA controls. Through high-throughput Assay for Transposase-Accessible Chromatin with sequencing (ATAC-seq) and RNA sequencing (RNA-seq), we reveal that the nanotopography of electrospun surfaces promotes osteogenic differentiation by modulating the chromatin accessibility of the <i>YBX1</i> gene promoter, leading to its upregulation. Lentiviral knockdown experiments further confirm the crucial role of YBX1, revealing a reversal of the osteogenic effects induced by nanotopography. This study emphasizes the importance of YBX1 in the osteogenic response to the surface topography of biomaterials and suggests that nanotopographical cues could be harnessed to direct stem cell fate. These findings are important for developing biomaterials that promote specific stem cell outcomes in regenerative medicine. Our results further contribute to a deeper understanding of the mechanisms underlying stem cell differentiation in response to environmental cues and pave the way for the rational design of biomaterials with enhanced osteogenic potential. By elucidating the role of chromatin accessibility and specific transcription factors such as YBX1, this study highlights the intricate interplay between cell-material interactions and the intracellular signaling pathways that govern stem cell fate.