Fibrin network adaptation to cell-generated forces

Fransisca A S Van Esterik,Stephen L Flores,Arianne V Vega,Daniel R Cuizon,Jenneke Klein-Nulend,Michelle E Velayo,Kristian A T Pajanonot,Jahazel Dejito,Rommel G Bacabac

doi:10.1007/s00397-018-1099-3

Abstract

Fibrin promotes wound healing by serving as provisional extracellular matrix for fibroblasts that realign and degrade fibrin fibers, and sense and respond to surrounding substrate in a mechanical-feedback loop. We aimed to study mechanical adaptation of fibrin networks due to cell-generated forces at the micron-scale. Fibroblasts were elongated-shaped in networks with ≤ 2 mg/ml fibrinogen, or cobblestone-shaped with 3 mg/ml fibrinogen at 24 h. At frequencies f < 102 Hz, G′ of fibroblast-seeded fibrin networks with ≥ 1 mg/ml fibrinogen increased compared to that of fibrin networks. At frequencies f > 103 Hz, G″ of fibrin networks decreased with increasing concentration following the power-law in frequency with exponents ranging from 0.75 ± 0.03 to 0.43 ± 0.03 at 3 h, and of fibroblast-seeded fibrin networks with exponents ranging from 0.56 ± 0.08 to 0.28 ± 0.06. In conclusion, fibroblasts actively contributed to a change in viscoelastic properties of fibrin networks at the micron-scale, suggesting that the cells and fibrin network mechanically interact. This provides better understanding of, e.g., cellular migration in wound healing.Graphical abstract

Highlights

Fibrin is a resilient naturally occurring biopolymer and the main structural protein in blood clots, which stops bleeding, and promotes wound healing by serving as a provisional extracellular matrix for cells such as fibroblasts (Laurens et al 2006; Jansen et al 2013)
Fibroblasts were incubated at 37 °C in a humidified atmosphere with 5% CO2, and subcultured until passage 3 to be used in fibroblast-seeded fibrin networks to perform one-particle passive microrheology
For visualizing the dynamics of cell spreading in fibrin networks, fibroblast-seeded fibrin networks were imaged using a TCM400 inverted bright field microscope (LaboMed America, Inc., Fremont, CA, USA) immediately after seeding, and at 1, 2, and 24 h after cell seeding

Summary

Introduction

Fibrin is a resilient naturally occurring biopolymer and the main structural protein in blood clots, which stops bleeding, and promotes wound healing by serving as a provisional extracellular matrix for cells such as fibroblasts (Laurens et al 2006; Jansen et al 2013). Rheology is used to measure the viscoelastic properties of fibrin networks using different rheological techniques (Ferry et al 1997; Jansen et al 2013; Kurniawan et al 2016; Piechocka et al 2016). Passive microrheology by using optical tweezers is non-invasive and can access the high-frequency domain, and can be used to characterize polymer network behavior (Morse 1998). Passive and active microrheology are suitable to obtain information about the local micromechanical properties of extracellular matrix networks at the scale relevant to cells, as well as the network and fiber response (Jansen et al 2013)

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Results