Endothelial cell responses in terms of adhesion, proliferation, and morphology to stiffness of polydimethylsiloxane elastomer substrates

Abstract

Extracellular environments can regulate cell behavior because cells can actively sense their mechanical environments. This study evaluated the adhesion, proliferation and morphology of endothelial cells on polydimethylsiloxane (PDMS)/alumina (Al2 O3 ) composites and pure PDMS. The substrates were prepared from pure PDMS and its composites with 2.5, 5, 7.5, and 10 wt % Al2 O3 at a curing temperature of 50°C for 4 h. The substrates were then characterized by mechanical, structural, and morphological analyses. The cell adhesion, proliferation, and morphology of cultured bovine aortic endothelial (BAEC) cells on substrate materials were evaluated by using resazurin assay and 1,1'-dioctadecyl-1,3,3,3',3'-tetramethylindocarbocyanine perchlorate-acetylated LDL (Dil-Ac-LDL) cell staining, respectively. The composites (PDMS/2.5, 5, 7.5, and 10 wt % Al2 O3 ) exhibited higher stiffness than the pure PDMS substrate. The results also revealed that stiffer substrates promoted endothelial cell adhesion and proliferation and also induced spread morphology in the endothelial cells compared with lesser stiff substrates. Statistical analysis showed that the effect of time on cell proliferation depended on stiffness. Therefore, this study concludes that the addition of different Al2 O3 percentages to PDMS elevated substrate stiffness which in turn increased endothelial cell adhesion and proliferation significantly and induced spindle shape morphology in endothelial cells.

Regulation of Endothelial Cell Adherence and Elastic Modulus by Substrate Stiffness

“…Such endothelial cells exhibited rounded to more spread morphologies on soft to hard PAAM substrates, respectively. This is in agreement with previously published data on the morphological dependence of endothelial cells on substrate stiffness, where cells showed rounded to more spread resting shapes, as substrate stiffness was increased (Yeung et al 2005;Ataollahi et al 2015).…”

“…Stiffer substrates cause enhanced cytoskeleton through enrichment of actin structure and generation of new stress fibers (Geiger et al 2001), as an early study suggested that stress fibers represent an increased need for adhesion to the substrate (Sumpio et al 1988). Here, we observed cell stiffening and also enhanced adhesiveness of HUVECs when interacted with stiffer substrates, consistent with a recent study which reported the increased adhesion of endothelial cells with increasing the stiffness of substrates (Ataollahi et al 2015).…”

“…While numerous studies have confirmed the importance of surface chemistry in cell-substrate interaction for successful performance of implants or tissue engineered constructs, the impact of mechanical parameters of substrate, such as stiffness on cellular functions has only been studied in the past 10 years Yeung et al 2005;Saha et al 2008;Byfield et al 2009;Stroka & Aranda-Espinoza 2011a;Yeh et al 2012;Huang et al 2013;Ataollahi et al 2015).…”

“…Some studies have examined cellular responses to the stiffness of different substrates, such as polyacrylamide (PAAM) (Lo et al 2000;Wang et al 2000;Engler et al 2004a;Stroka & Aranda-Espinoza 2011a;Galie et al 2015), Polydimethylsiloxane (PDMS) (Sarkar et al 2005;Ataollahi et al 2015) or alginate (Huang et al 2013), as such materials are biocompatible and can be fabricated using suitable methods to achieve desired stiffness values.…”

Engineering Approaches for Creating Skeletal Muscle

“…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 that the effect of a soft substrate on endothelial cells comes from more emphasis on the cell-cell junctions rather than substrate adhesions. This seems to lead to the beginning of more stable vascular networks.…”