Surface‐Driven Collagen Self‐Assembly Affects Early Osteogenic Stem Cell Signaling

Abstract

This study reports how extracellular matrix (ECM) ligand self-assembly on biomaterial surfaces and the resulting nanoscale architecture can drive stem cell behavior. To isolate the biological effects of surface wettability on protein deposition, folding, and ligand activity, a polydimethylsiloxane (PDMS)-based platform was developed and characterized with the ability to tune wettability of elastomeric substrates with otherwise equivalent topology, ligand loading, and mechanical properties. Using this platform, markedly different assembly of covalently bound type I collagen monomers was observed depending on wettability, with hydrophobic substrates yielding a relatively rough layer of collagen aggregates compared to a smooth collagen layer on more hydrophilic substrates. Cellular and molecular investigations with human bone marrow stromal cells revealed higher osteogenic differentiation and upregulation of focal adhesion-related components on the resulting smooth collagen layer coated substrates. The initial collagen assembly driven by the PDMS surface directly affected α1β1 integrin/discoidin domain receptor 1 signaling, activation of the extracellular signal-regulated kinase/mitogen activated protein kinase pathway, and ultimately markers of osteogenic stem cell differentiation. We demonstrate for the first time that surface-driven ligand assembly on material surfaces, even on materials with otherwise identical starting topographies and mechanical properties, can dominate the biomaterial surface-driven cell response.

Biophysical Regulation of Cell Behavior—Cross Talk between Substrate Stiffness and Nanotopography

“…Substrate surface hydrophilicity also affects protein conformation. Collagen I proteins fold and clump to form aggregates on hydrophobic PDMS surfaces, thus delaying osteogenesis of hMSCs; conversely, the proteins adopt a more extended conformation on hydrophilic PDMS surfaces, which is associated with an increase in activation of α 1 β 1 integrin and enhanced osteogenic behavior [ 253 ].…”

On the biomechanical properties of osteosarcoma cells and their environment

“…Although with slightly different θ values, MG-63 cells respond similarly to surface wettability and attach preferentially to polystyrene surfaces with θ values of approximately 64° (Dowling et al, 2011). Interestingly, primary human MSCs that grow on stiff silicone substrates doped with poly (dimethylsiloxane-ethylene oxide) (PEO) surfactant and have a θ value in the same range (60°), display a tendency of osteogenic differentiation (Razafiarison et al, 2016). Although the regulatory mechanism is not fully understood, a plausible explanation is the hydrophobicity-driven exposure of cell binding sites in the deposited extracellular matrix (ECM), collagen I in this case, which in turn directs the expression of focal adhesion components (Razafiarison et al, 2018).…”

Traction Force Microscopy for Understanding Cellular Mechanotransduction

“…Subsequently, traction forces are calculated using constitutive equations by computational engineering analyses such as standard finite element method (FEM) (33) and Fast Fourier Transform (FFT) (34). Very recently, Razafiarison et al (32,35) utilized the aforementioned PAA hydrogel-based TFM method to unveil the relationship of mechanosensitivity of hMSCs to matrix stiffness with supramolecular self-assembly and topology of ECM ligands on biomaterial surfaces with respect to surface energy. The contribution of such relationship to stem cell lineage commitment was evaluated by TFM (32,35).…”

“…Very recently, Razafiarison et al (32,35) utilized the aforementioned PAA hydrogel-based TFM method to unveil the relationship of mechanosensitivity of hMSCs to matrix stiffness with supramolecular self-assembly and topology of ECM ligands on biomaterial surfaces with respect to surface energy. The contribution of such relationship to stem cell lineage commitment was evaluated by TFM (32,35). To validate the hypothesis that surface energy-driven ligand topology could regulate stem cell fates, they introduced hydrophobic-polydimethylsiloxane (PDMS) and its counterparthttp://bmbreports.org BMB Reports with type I collagen (Fig.…”