Physical, Spatial, and Molecular Aspects of Extracellular Matrix of In Vivo Niches and Artificial Scaffolds Relevant to Stem Cells Research

Table 1

Summary of elastic moduli of mammalian tissues.

Tissue type	Range of stiffness	Testing method	Reference
Bone marrow	<0.3 kPa	Atomic force microscopy	[41]
Brain	0.5–1 kPa	Indentation	[33, 34]
Endothelial basement membrane	2-3 kPa	Atomic force microscopy	[28]
Hypodermis (skin layer)	2 kPa	Millimeter indentation	[29]
Adipose tissue	2–6 kPa	Indentation	[11, 30]
Liver	2–6 kPa	Ultrasound elastography	[44]
Fibrosis (liver)	8–12 kPa	Ultrasound elastography	[44]
Media layer of arterial wall	2–15 kPa	Atomic force microscopy	[61]
Muscle tissue (relaxed)	8–20 kPa	Atomic force microscopy	[11, 43]
Heart tissue (at diastole)	10–20 kPa	Atomic force microscopy	[46]
Chondron (matrix around chondrocytes)	20–30 kPa	Micropipette aspiration	[37]
Precalcified bone (matrix around osteoblasts)	20–50 kPa	Atomic force microscopy	[10]
Fibrous tissue (heart)	20–60 kPa	Atomic force microscopy	[42]
Dermis (skin layer)	35 kPa	Millimeter indentation	[29]
Muscle (skin layer)	80 kPa	Millimeter indentation	[29]
Skin	100 kPa	Optical coherence elastography	[31]
	210 kPa	Millimeter indentation	[30]
Arterial wall	0.3–1 MPa	Tensile tests	[25]
Cartilage	450–800 kPa	Indentation	[38]
	20–50 kPa	Nanoindentation	[39]
Tendon	2–8 GPa	Tensile tests	[36]
Bone (cortical bone)	10–20 GPa	Ultrasonic and microtensile test	[35]
Tissue culture plastic (TCP)	1–10 GPa		[50, 56]

Presented are the values, which have been measured at the lowest strain and lowest strain rate to approximate the elastic behavior of the tissues at rest, that is, at small deformations. The values of Young’s modulus for any given tissue measured using different methods of deformation typically span several orders of magnitude [32]. Results for indentation are typically lower than for tensile tests. For unambiguity, testing methods are mentioned. Mechanical testing methods are summarized in Table 2.