AFM mapping of the elastic properties of brain tissue reveals kPa μm⁻¹gradients of rigidity

Abstract

It is now well established that the mechanical environment of the cells in tissues deeply impacts cellular fate, including life cycle, differentiation and tumor progression. Designs of biomaterials already include the control of mechanical parameters, and in general, their main focus is to control the rheological properties of the biomaterials at a macroscopic scale. However, recent studies have demonstrated that cells can stress their environment below the micron scale, and therefore could possibly respond to the rheological properties of their environment at this micron scale. In this context, probing the mechanical properties of physiological cellular environments at subcellular scales is becoming critical. To this aim, we performed in vitro indentation measurements using AFM on sliced human pituitary gland tissues. A robust methodology was implemented using elasto-adhesive models, which shows that accounting for the adhesion of the probe on the tissue is critical for the reliability of the measurement. In addition to quantifying for the first time the rigidity of normal pituitary gland tissue, with a geometric mean of 9.5 kPa, our measurements demonstrated that the mechanical properties of this tissue are far from uniform at subcellular scales. Gradients of rigidity as large as 12 kPa μm(-1) were observed. This observation suggests that physiological rigidity can be highly non-uniform at the micron-scale.

Predicting calvarial growth in normal and craniosynostotic mice using a computational approach

“…; Gefen & Margulies, ; Bouchonville et al. ), therefore the baseline value of 150 MPa was altered within the range from 1 to 1500 MPa; (iii) suture properties: our previous experimental measurements (Moazen et al. ) showed a large standard deviation for the suture properties, therefore the baseline value of 30 MPa was varied between 3 and 300 MPa.…”

“…The elastic modulus of the brain is reported to be in the range of 1–30 kPa (Bouchonville et al. ). This is three to four orders of magnitude lower than the baseline value of 150 MPa used in this study.…”

“…Three sensitivity tests were carried out on the WT model to investigate the sensitivity of the results to some of the key input parameters, in particular: (i) boundary condition: the baseline model in this study was constrained at the presphenoid bone; this was altered to basisphenoid or both presphenoid and basisphenoid; (ii) brain properties: there is a large range of data reported in the literature for brain properties (e.g. Miller et al 2000;Gefen & Margulies, 2004;Bouchonville et al 2016), therefore the baseline value of 150 MPa was altered within the range from 1 to 1500 MPa; (iii) suture properties: our previous experimental measurements ( Moazen et al 2015) showed a large standard deviation for the suture properties, therefore the baseline value of 30 MPa was varied between 3 and 300 MPa.…”

Role of mechanical cues in shaping neuronal morphology and connectivity

“…Several studies shed light on the role of substrate stiffness in axonal extension, growth pattern and branching in vitro [Balgude et al, 2001;Flanagan et al, 2002;Jiang et al, 2010;Koch et al, 2012;Lantoine et al, 2016]. In vivo, neurons encounter environments with heterogeneous rigidities [Elkin et al, 2010;Franze et al, 2011;Iwashita et al, 2014;Bouchonville et al, 2016] which likely act as cues instructing axon navigation. Indeed, a recent work reported that axon pathfinding is influenced by the stiffness of the environment ex vivo and in vivo, in the optic pathway of Xenopus embryos ( Figure 1c) [Koser et al, 2016].…”

Dynamic bioengineered hydrogels as scaffolds for advanced stem cell and organoid culture

“…Using an advanced atomic force microscopy mapping technique, Bouchonville et al revealed that brain tissue rigidity changes as steeply as 12 kPa/μm. [6] While the mean elasticity of the human-derived pituitary gland tissue was 9.5 kPa, areas with moduli as high as 25.9 kPa and as low as 3.5 kPa were detected. Organs and tissues also receive and interpret a range of biochemical signals that vary in space and time; presentation and removal of biologically relevant molecules affect cell differentiation and morphology.…”