Tissue Engineering And Nanotheranostics

b2815 Tissue Engineering and Nanotheranostics “9.61x6.69”

14 Tissue Engineering and Nanotheranostics

recovery of grip strength.^55 A similar study using a variety of cells,

including fibroblasts, endothelial cells, and myoblasts, also showed

similar results in terms of vascularization.^56 It is possible that the use

of multiple cell types, or at least prior induction of stem cells along

different lineages, may be necessary to obtain the complexity needed

for formation of both vasculature and myofibers.

All of these approaches, both in vitro and in vivo, show some

promise. However, to precisely control the outcomes of these types of

experiments, many engineering factors must be considered. Cells are

responsive to both chemical and physical stimuli, opening many pos-

sible routes to modifying their behavior. These engineering factors are

summarized in Table 1 and also described below.

4.2.2. Scaffolding materials

Fully formed myofibers are very specifically arranged with a high

degree of alignment within skeletal muscle tissue, so it comes as no

surprise that beneficial effects can be generated by providing the cells

with a patterned substrate.^57 It has been discovered that aligned

Table 1. Over view of engineering factors for tissue engineering of skeletal muscle.

Various factors leading to improved differentiation or function are highlighted.

Myoblasts Endothelial cells Neurons

Substrate

properties

12 kPa stiffness

nanofibers +

microchannels →

alignment and

differentiation58,59

200 Pa → vasculature

2500 Pa →

proliferation^60

7 kPa stiffness +

microchannels →

proliferation^63

Mechanical

stimulation

Cyclic stretching or

static strain →

alignment and

differentiation64,66

Cyclic stretching →

perpendicular

alignment and

angiogenesis^67

Equibiaxial stretching

→ neurite out-

growth^70

Electrical

stimulation

0.2 V/m 1 Hz

4 ms → increasing

contractility^71

100–300 mV/mm

DC field →

perpendicular

alignment and

angiogenesis^72

NGF necessary + 100–

200 mV/mm at 100

Hz (sinusoid) →

neurite elongation^73

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