Authors: Xiao Hua, 1, Sang-Hyug Parka, 1, Eun Seok Gila, Xiao-Xia Xiaa, Anthony S. Weissb and David L. Kaplana
Affiliation: a Department of Biomedical Engineering, Tufts University; b School of Molecular Bioscience, The University of Sydney
Being able to precisely control the differentiation of cells is an important tool for researchers wanting to make tissues of a specific function. The differentiation of cells is dependent on the environment in which they are cultured. In this paper the authors investigate tunable silk-tropoelastin biomaterials as a matrix to culture cells. The researchers hope to correlate changes in the mechanical stiffness and surface morphology of these biomaterials to the response of C2C12 mouse myoblasts and human bone marrow stem cells (hMSCs).
In previous work, the researchers have shown they are able to form silk-tropoelastin biomaterials with a variety of properties by controlling the formation of the material and by further processing. In this work they use different ratios of silk to tropoelastin and temperature controlled water vapor annealing to create biomaterials with a variety of surface morphologies and mechanical properties. The authors used atomic force microscopy (AFM) to investigate the surface roughness. Roughness increased with increased tropoelastin content. Tensile stress-strain tests were performed to determine stiffness. The authors found that increasing tropoelastin content decreased stiffness.
In agreement with previous studies, the researchers found that C2C12 cells proliferate and differentiate into myotubes more readily on a film with low roughness and high stiffness. They determined that different micro/nano-porous patterns did not have a large effect on the proliferation and differentiation of the C2C12 cells.
In previous studies hMSCs have been shown to prefer rougher materials with rigidities lower than any of the rigidities studied in this paper. hMSCs have been shown to have increased spreading with increased rigidity up to a certain point, but the rigidities of the materials discussed here had rigidities orders of magnitude higher. The authors did find that the softest material tended to have cells with higher transcript levels and cell-matrix interactions which suggested to them that at this higher range of rigidities the lower stiffness may help proliferation and differentiation, the lower range might favor differentiation, or that other factors such as the biochemical nature of the material may be at play.
This paper is part of a large body of work exploring ways we can use mechanical cues to control cell differentiation. This field will continue to be vitally important as we take biological engineering to the next level.