Mechanical regulation of cell function withgeometrically modulated elastomeric

substrates

SUMMARY

Micromolded elastomeric micropost arrays modulate substrate rigidity.

Micropost rigidity affect cell morphology, focal adhesions (FA), cytoskeletal contractility and stem cell differentiation.

Manufacturing micropost

INTRODUCTION

Cell function is regulated primarily by extracellular stimuli.

Recent advances suggest that the rigidity of the extracellular matrix (ECM) can mediate cell signaling, proliferation, differentiation and migration.

Culturing cells on hydrogels based on ECM proteins has a strong impact on cell adhesion, morphology and function.

Substrate rigidity can modulate many cellular functons including stem cell differentiation.

Results

Micromolded elastomeric micropost arrays can decouple substrate rigidity from adhesive and surface properties.

Post height determines the bending degree in response to horizontal traction force. Rigidity characterized by computing the nominal spring constant K (1.31-1.556 nN/m).

a) FEM analysis of bending in response to a horizontal traction force (20 nN).

b) Micropost deflection as function of traction force.c) Nominal spring constant as function of post height L (FEM analysis

(bars) and Euler-Bernouilli beam theory (curve)).

Different behaviour in hMSCs cultured on high/low rigidity microposts: high rigidity leads to well spread cells, with

prominent, highly organized actin stress fibers and large FA.

Low rigidity leads to a rounded morphology with prominent microvilli.

high rigidity: L = 0,97 m, K = 1,556 nN/m; medium rigiditiy:L = 6.1 m, K = 18.16 nN/m low rigidity: L = 12.9 m, K = 1.90 nN /m

Strong correlations between: FA and cell spreading regardless of micropost

rigidity, and Traction force and cell spreading.

Responses similar to those reported on hydrogels of varying rigidities, but with rigidity sensing at a micrometer scale (between focal adhesions).

Measured subcellular traction forces could be attributed to FA. This allows us to map traction forces in individual FA and spatially quantify subcellular distributios of FA area, traction force and FA stress.

Advantages of using micropost over hydrogels

Traction force as a function of FA area for different rigidities; hMSCs (top) and hUVECs (bottom)

FA stress anisotropy for hMSCs and HUVECs. Average FA stress per cell increased with micropost

rigidity, but different for the 2 types.

There may be multiple ways for cells to mechanically adapt to their environment.

FA stress computed as the slope of the linear fit in traction force vs FA area plots.

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