Substrate properties
Cells interact with their environment what manifests in the morphological, structural, and also mechanical alterations. The interaction is cell- and substrate-type specific. In one of the first papers [67], the effect of substrate properties was studied in the context of surface suitability in tissue engineering. Osteoblasts cultured on various substrates (CoCr, Ti, TiV, glass and tissue culture polystyrene) revealed the elasticity range from 2 Pa (observed for CoCr and TiV substrates) to 9 kPa for Ti surface. The latter modulus was comparable for that obtained for osteoblasts cultured in polysterene surface used for cell culture [67]. These results were related to the non-specific cell adhesion.
There are many studies focused on the role of extracellular matrix in cell functioning, including cancer progression [68, 69]. To assess the role of integrins in the interaction with ECM, glass or plastic surfaces are coated with the ECM protein, like fibronectin or collagen. Next, cells are cultured on such prepared surfaces and elastic properties are measured. Various results show that depending on the type of the ECM proteins cells exhibit distinct mechanical properties. One example of such studies has been reported by Docheva et al. [64]. The elastic properties and cytoskeleton organization of prostate cancer cells (less invasive LNCaP and more invasive PC-3 cell lines) have been studied in search of the answer whether collagen I produced in bones is responsible for cancer invasion and metastasis to bone. The PC-3 cells changed their elastic properties when they were cultured on surfaces coated with collagen I, what was accompanied by alterations in the cytoskeletal actin network [64]. The change of mechanical properties in the presence of ECM proteins is observed also for other cell types, e.g., for bladder cancer cells (Fig. 4.26).
Figure 4.26 Elastic modulus to indentation depth relations, determined for human bladder cells (HCV29—non-malignant cell cancer of ureter, and HT1376—transitional cell carcinoma) cultured on a glass surface without and with laminin coating. Stars indicate statistical significance carried out using the Student t-test. Unpublished data of the author.
The results presented in Fig. 4.26 show clearly that the presence of laminin (one of the ECM proteins) changes mechanical properties of bladder cells, in particular, in the case of non-malignant HCV29 ones. The effect was independent on the indentation depth chosen for the analysis. Surprisingly, the presence of laminin is not influencing the cancerous HT1376 cells, probably indicating their large capability to adapt to various conditions.
Recently, the analysis of mechanical properties of cells as a function of surface properties started to be applied in the studies on the influence of extracellular matrix stiffness and structure on properties of cancerous cells aiming at the understanding the ECM role in cancer progression [65].
