Myoblast adhesion, proliferation and differentiation on human elastin-like polypeptide (HELP) hydrogels

The biochemical, mechanical and topographic properties of extracellular matrix are crucially involved in determining skeletal muscle cell morphogenesis, proliferation and differentiation. Human elastin-like polypeptides (HELPs) are recombinant biomimetic proteins designed to mimic some properties of the native matrix protein; when employed as myoblast adhesion substrates, they stimulate in vitro myogenesis. Given the influence that the biophysical properties of extracellular matrix have on skeletal muscle cells, the aim of this work was to investigate the effects of HELP hydrogels on myoblasts' viability and functions.

We recently synthesized a novel polypeptide, HELPc, by fusing the elastin-like backbone to a 41aa sequence present in the α2 chain of type IV collagen, containing two arginyl-glycyl-aspartic acid (RGD) motifs. To obtain hydrogels, the enzymatic cross-linking of the HELPc was accomplished by transglutaminase. Here, we employed both non-cross-linked HELPc glass coatings and cross-linked HELPc hydrogels at different monomer densities, as adhesion substrates for C2C12 cells, used as a myoblast model.

By comparing cell adhesion, proliferation and differentiation, we revealed several striking differences. Depending on support rigidity, adhesion to HELPc substrates dictated cell morphology, spreading, focal adhesion formation and cytoskeletal organization. Hydrogels greatly stimulated cell proliferation, particularly in low-serum medium, and partially inhibited myogenic differentiation.

On the whole, the results underline the potential of these genetically engineered polypeptides as a tool for dissecting crucial steps in myogenesis.