Directional cell elongation through filopodia-steered lamellipodial extension on patterned silk fibroin films

Abstract

Micropatterned biomaterials have been used to direct cell alignment for specific tissue engineering applications. However, the understanding of how cells respond to guidance cues remains limited. Plasticity in protrusion formation has been proposed to enable cells to adapt their motility mode to microenvironment. In this study, the authors investigated the key role of protrusion response in cell guidance on patterned silk fibroin films. The results revealed that the ability to transform between filopodia and small lamellipodia played important roles in directional cell guidance. Filopodia did not show directional extension on patterned substrates prior to spreading, but they transduced topographical cues to the cell to trigger the formation of small lamellipodia along the direction of a microgrooved or parallel nanofiber pattern. The polar lamellipodia formation provided not only a path with directionality, but a driving force for directional cell elongation. Moreover, aligned nanofibers coating provided better mechanical support for the traction of filopodia and lamellipodia, promoting cell attachment, spreading, and migration. This study provides new insight into how cells respond to guidance cues and how filopodia and lamellipodia control cell contact guidance on micropatterned biomaterial surfaces.

Anisotropic Materials for Skeletal‐Muscle‐Tissue Engineering

“…Although substantial research has been performed to characterize the response of skeletal myoblasts to engineered directionality, the mechanisms underlying cellular behavior in response to topographical cues remain to be clarified. [109–112] Creating awareness of and understanding mechanisms underlying the effect of aligned materials on myogenesis is critical to improving our collective approach to skeletal muscle tissue engineering. Furthermore, understanding the mechanisms driving myogenesis within in vitro platforms will allow for design and development of scaffolds that can recruit host cells or initiate endogenous tissue regeneration cascades in situ , which may prove to be a superior approach to the delivery of cells via scaffolds.…”

“…16). [109] Therefore filopodia play an important role in cell spreading and migration. [111] Filopodia have been shown to respond to variation in the diameter (hundreds of nm) of silica beads indicating the ability to identify differences in topographical features.…”

“…[122] On micropatterned substrates, cells align along the pattern direction through periodic extension and retraction of lamellipodia parallel to the grooves/ridges (Figure 16 a–d). [109, 123] This is directly related to alignment of actin filaments and focal adhesions along substrate topographies demonstrating a link between anisotropic topographic features and cell behavior. [124] On aligned nanofiber-coated film substrates or nanopatterned substrates, cells protrusions were positioned along the direction of nanofibers or grooves through actin polymerization (Fig.…”

“…16 e–h) whereas cells on a substrate with nano-columns showed an increased number of filopodia, which guided cell migration via FAK and myosin II activity. [109, 125, 126] Focal adhesion kinase (FAK), is an important cytosolic protein component of focal adhesions because it mediates adhesive signaling by activating integrins and promoting integrin binding. [127, 128] On nanopatterned substrates, the extent of cell adhesion and spreading depends on the distance between nanoscale features, reflecting length scales associated with integrin clustering and focal adhesion signaling.…”

Study of myoblast differentiation using multi-dimensional scaffolds consisting of nano and micropatterns

“…As a result, not only do the cells express elongated morphology, but an end-to-end configuration also appears; an optimal environment for myogenesis, from myocytes to nascent myotubes, can be provided by the given scaffolds. It was known that the ability to transform between filopodia and small lamellipodia played important roles in directional cell guidance [21]. Filopodia did not show directional extension on patterned substrates prior to spreading, but they transduced topographical cues to the cell to trigger the formation of small lamellipodia along the direction of a microgrooved or parallel nanofiber pattern.…”