Tissue Engineering And Nanotheranostics

“9.61x6.69” b2815 Tissue Engineering and Nanotheranostics

Engineering Approaches for Creating Skeletal Muscle 15

nanoscale topography such as electrospun fibers can stimulate the

parallel alignment of C2C12 murine myoblasts, a common model cell

for myoblast culture.^58 Coincident with this alignment was an increase

in proliferation and upregulation of myosin heavy chain (MYH) and

myogenin (MyoG) expression, signaling the beginning of a progres-

sion toward myofiber fusion.^58 When the nanofiber topography was

coupled with microgrooves, it was found that the grooves restricted

myofiber movement and promoted further maturation.^58 Investigations

into ideal substrate stiffness have been performed with murine SCs.

The cells were cultured on polyethylene glycol (PEG) hydrogels of

varying stiffness by controlling the percent weight of the polymer

solution.^59 It was found that gels that mimicked the natural stiffness

of skeletal muscle, roughly 12 kPa in this study, had the best effect on

the SCs in terms of their final engraftment and spread in a murine

wound model.^59 The soft hydrogels were also able to significantly

reduce cell death commonly experienced by this cell type on rigid

polystyrene culture plastic.^59 Keeping these results in mind, it appears

that an ideal substrate for tissue engineering of muscle must provide

stiffness close to that of the native tissue and ideally have a combina-

tion of topographies that lead to improved alignment, proliferation,

and differentiation.

Vascular endothelial cells are the primary components of capillary

beds in the muscle, and their unique mechanobiology must be

addressed in conjunction with that of the myoblasts for formation of

functional muscle. Much like with muscle, it has been determined that

the substrates that most closely mimic the natural environment can

lead to better outcomes in terms of vascularization. It has been shown

that endothelial cell morphology changes drastically when cultured on

substrates of increasing stiffness. Above 3 kPa, endothelial cells lose

their normal shape and begin to elongate drastically.^60 Furthermore,

the presence of thick bundles of stress fibers has been observed.^60

These stress fibers, and the other drastic morphological changes

between the substrate stiffness disappear when the cells reach conflu-

ency.^60 Some authors have noticed that bovine aortic endothelial cells

(BAECs) have stronger attachment and increased spreading on stiff

(1.1 MPa) vs. soft (0.3 MPa) PDMS substrates.^61 Some authors believe

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