Histone Modification of Osteogenesis Related Genes Triggered by Substrate Topography Promotes Human Mesenchymal Stem...

Area of Science:

• Biomaterials Science
• Stem Cell Biology
• Tissue Engineering

Background:

• Orthopedic implant success depends on bone tissue integration, influenced by surface topography.
• Cellular response to artificial microenvironments is crucial for osseointegration.
• Understanding stem cell behavior on different surface structures is key for implant design.

Purpose of the Study:

• To investigate the relationship between surface microstructure and cell instructivity in polycarbonate (PC) substrates.
• To determine how surface topography affects osteogenic differentiation of human bone marrow mesenchymal stem cells (hBMSCs).
• To elucidate the underlying molecular and epigenetic mechanisms of surface-topography-driven stem cell fate determination.

Main Methods:

• Fabrication of PC substrates with varying surface roughness (smooth, moderate, and high peak spacing).
• Culturing hBMSCs on these substrates and evaluating osteogenic differentiation markers.
• Assessing cell adhesion, F-actin assembly, cell contractile force (pMLC expression), YAP nuclear translocation, and nuclear deformation.
• Analyzing epigenetic modifications (H3K27me3, H3K9ac) on osteogenic gene promoters.
• Utilizing inhibitors and siRNAs to probe the roles of key signaling molecules (YAP, integrin, F-actin, myosin).

Main Results:

• A high-roughness PC surface (hPC) with peak spacing similar to trabecular bone significantly improved hBMSC osteogenic differentiation compared to smooth (sPC) and moderate (mPC) surfaces.
• The hPC substrate enhanced cell adhesion, F-actin organization, and contractile force via pMLC upregulation.
• Increased cell contractility induced YAP nuclear translocation, nuclear elongation, and altered histone modifications (decreased H3K27me3, increased H3K9ac) at osteogenic gene loci.
• Mechanism studies confirmed the involvement of YAP, integrin, F-actin, myosin, and nuclear membrane proteins in this process.

Conclusions:

• Surface topography, specifically roughness mimicking trabecular bone, can bioinstruct stem cells towards osteogenic differentiation.
• Cellular mechanotransduction pathways involving YAP, F-actin, and myosin, coupled with epigenetic modifications, mediate the response to surface microstructure.
• These findings provide critical insights for designing advanced, bioinstructive orthopedic implants that promote enhanced osseointegration.